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, 2004, 2005
4 @c Free Software Foundation, Inc.
7 @c makeinfo ignores cmds prev to setfilename, so its arg cannot make use
8 @c of @set vars. However, you can override filename with makeinfo -o.
13 @settitle Debugging with @value{GDBN}
14 @setchapternewpage odd
25 @c readline appendices use @vindex, @findex and @ftable,
26 @c annotate.texi and gdbmi use @findex.
30 @c !!set GDB manual's edition---not the same as GDB version!
31 @c This is updated by GNU Press.
34 @c !!set GDB edit command default editor
37 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
39 @c This is a dir.info fragment to support semi-automated addition of
40 @c manuals to an info tree.
41 @dircategory Software development
43 * Gdb: (gdb). The GNU debugger.
47 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, 2004, 2005@*
56 Free Software Foundation, Inc.
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.1 or
60 any later version published by the Free Software Foundation; with the
61 Invariant Sections being ``Free Software'' and ``Free Software Needs
62 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
63 and with the Back-Cover Texts as in (a) below.
65 (a) The Free Software Foundation's Back-Cover Text is: ``You have
66 freedom to copy and modify this GNU Manual, like GNU software. Copies
67 published by the Free Software Foundation raise funds for GNU
72 @title Debugging with @value{GDBN}
73 @subtitle The @sc{gnu} Source-Level Debugger
75 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
76 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
80 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
81 \hfill {\it Debugging with @value{GDBN}}\par
82 \hfill \TeX{}info \texinfoversion\par
86 @vskip 0pt plus 1filll
87 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
88 1996, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005
89 Free Software Foundation, Inc.
91 Published by the Free Software Foundation @*
92 59 Temple Place - Suite 330, @*
93 Boston, MA 02111-1307 USA @*
96 Permission is granted to copy, distribute and/or modify this document
97 under the terms of the GNU Free Documentation License, Version 1.1 or
98 any later version published by the Free Software Foundation; with the
99 Invariant Sections being ``Free Software'' and ``Free Software Needs
100 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
101 and with the Back-Cover Texts as in (a) below.
103 (a) The Free Software Foundation's Back-Cover Text is: ``You have
104 freedom to copy and modify this GNU Manual, like GNU software. Copies
105 published by the Free Software Foundation raise funds for GNU
111 @node Top, Summary, (dir), (dir)
113 @top Debugging with @value{GDBN}
115 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
117 This is the @value{EDITION} Edition, for @value{GDBN} Version
120 Copyright (C) 1988-2005 Free Software Foundation, Inc.
123 * Summary:: Summary of @value{GDBN}
124 * Sample Session:: A sample @value{GDBN} session
126 * Invocation:: Getting in and out of @value{GDBN}
127 * Commands:: @value{GDBN} commands
128 * Running:: Running programs under @value{GDBN}
129 * Stopping:: Stopping and continuing
130 * Stack:: Examining the stack
131 * Source:: Examining source files
132 * Data:: Examining data
133 * Macros:: Preprocessor Macros
134 * Tracepoints:: Debugging remote targets non-intrusively
135 * Overlays:: Debugging programs that use overlays
137 * Languages:: Using @value{GDBN} with different languages
139 * Symbols:: Examining the symbol table
140 * Altering:: Altering execution
141 * GDB Files:: @value{GDBN} files
142 * Targets:: Specifying a debugging target
143 * Remote Debugging:: Debugging remote programs
144 * Configurations:: Configuration-specific information
145 * Controlling GDB:: Controlling @value{GDBN}
146 * Sequences:: Canned sequences of commands
147 * TUI:: @value{GDBN} Text User Interface
148 * Interpreters:: Command Interpreters
149 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
150 * Annotations:: @value{GDBN}'s annotation interface.
151 * GDB/MI:: @value{GDBN}'s Machine Interface.
153 * GDB Bugs:: Reporting bugs in @value{GDBN}
154 * Formatting Documentation:: How to format and print @value{GDBN} documentation
156 * Command Line Editing:: Command Line Editing
157 * Using History Interactively:: Using History Interactively
158 * Installing GDB:: Installing GDB
159 * Maintenance Commands:: Maintenance Commands
160 * Remote Protocol:: GDB Remote Serial Protocol
161 * Agent Expressions:: The GDB Agent Expression Mechanism
162 * Copying:: GNU General Public License says
163 how you can copy and share GDB
164 * GNU Free Documentation License:: The license for this documentation
173 @unnumbered Summary of @value{GDBN}
175 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
176 going on ``inside'' another program while it executes---or what another
177 program was doing at the moment it crashed.
179 @value{GDBN} can do four main kinds of things (plus other things in support of
180 these) to help you catch bugs in the act:
184 Start your program, specifying anything that might affect its behavior.
187 Make your program stop on specified conditions.
190 Examine what has happened, when your program has stopped.
193 Change things in your program, so you can experiment with correcting the
194 effects of one bug and go on to learn about another.
197 You can use @value{GDBN} to debug programs written in C and C@t{++}.
198 For more information, see @ref{Supported languages,,Supported languages}.
199 For more information, see @ref{C,,C and C++}.
202 Support for Modula-2 is partial. For information on Modula-2, see
203 @ref{Modula-2,,Modula-2}.
206 Debugging Pascal programs which use sets, subranges, file variables, or
207 nested functions does not currently work. @value{GDBN} does not support
208 entering expressions, printing values, or similar features using Pascal
212 @value{GDBN} can be used to debug programs written in Fortran, although
213 it may be necessary to refer to some variables with a trailing
216 @value{GDBN} can be used to debug programs written in Objective-C,
217 using either the Apple/NeXT or the GNU Objective-C runtime.
220 * Free Software:: Freely redistributable software
221 * Contributors:: Contributors to GDB
225 @unnumberedsec Free software
227 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
228 General Public License
229 (GPL). The GPL gives you the freedom to copy or adapt a licensed
230 program---but every person getting a copy also gets with it the
231 freedom to modify that copy (which means that they must get access to
232 the source code), and the freedom to distribute further copies.
233 Typical software companies use copyrights to limit your freedoms; the
234 Free Software Foundation uses the GPL to preserve these freedoms.
236 Fundamentally, the General Public License is a license which says that
237 you have these freedoms and that you cannot take these freedoms away
240 @unnumberedsec Free Software Needs Free Documentation
242 The biggest deficiency in the free software community today is not in
243 the software---it is the lack of good free documentation that we can
244 include with the free software. Many of our most important
245 programs do not come with free reference manuals and free introductory
246 texts. Documentation is an essential part of any software package;
247 when an important free software package does not come with a free
248 manual and a free tutorial, that is a major gap. We have many such
251 Consider Perl, for instance. The tutorial manuals that people
252 normally use are non-free. How did this come about? Because the
253 authors of those manuals published them with restrictive terms---no
254 copying, no modification, source files not available---which exclude
255 them from the free software world.
257 That wasn't the first time this sort of thing happened, and it was far
258 from the last. Many times we have heard a GNU user eagerly describe a
259 manual that he is writing, his intended contribution to the community,
260 only to learn that he had ruined everything by signing a publication
261 contract to make it non-free.
263 Free documentation, like free software, is a matter of freedom, not
264 price. The problem with the non-free manual is not that publishers
265 charge a price for printed copies---that in itself is fine. (The Free
266 Software Foundation sells printed copies of manuals, too.) The
267 problem is the restrictions on the use of the manual. Free manuals
268 are available in source code form, and give you permission to copy and
269 modify. Non-free manuals do not allow this.
271 The criteria of freedom for a free manual are roughly the same as for
272 free software. Redistribution (including the normal kinds of
273 commercial redistribution) must be permitted, so that the manual can
274 accompany every copy of the program, both on-line and on paper.
276 Permission for modification of the technical content is crucial too.
277 When people modify the software, adding or changing features, if they
278 are conscientious they will change the manual too---so they can
279 provide accurate and clear documentation for the modified program. A
280 manual that leaves you no choice but to write a new manual to document
281 a changed version of the program is not really available to our
284 Some kinds of limits on the way modification is handled are
285 acceptable. For example, requirements to preserve the original
286 author's copyright notice, the distribution terms, or the list of
287 authors, are ok. It is also no problem to require modified versions
288 to include notice that they were modified. Even entire sections that
289 may not be deleted or changed are acceptable, as long as they deal
290 with nontechnical topics (like this one). These kinds of restrictions
291 are acceptable because they don't obstruct the community's normal use
294 However, it must be possible to modify all the @emph{technical}
295 content of the manual, and then distribute the result in all the usual
296 media, through all the usual channels. Otherwise, the restrictions
297 obstruct the use of the manual, it is not free, and we need another
298 manual to replace it.
300 Please spread the word about this issue. Our community continues to
301 lose manuals to proprietary publishing. If we spread the word that
302 free software needs free reference manuals and free tutorials, perhaps
303 the next person who wants to contribute by writing documentation will
304 realize, before it is too late, that only free manuals contribute to
305 the free software community.
307 If you are writing documentation, please insist on publishing it under
308 the GNU Free Documentation License or another free documentation
309 license. Remember that this decision requires your approval---you
310 don't have to let the publisher decide. Some commercial publishers
311 will use a free license if you insist, but they will not propose the
312 option; it is up to you to raise the issue and say firmly that this is
313 what you want. If the publisher you are dealing with refuses, please
314 try other publishers. If you're not sure whether a proposed license
315 is free, write to @email{licensing@@gnu.org}.
317 You can encourage commercial publishers to sell more free, copylefted
318 manuals and tutorials by buying them, and particularly by buying
319 copies from the publishers that paid for their writing or for major
320 improvements. Meanwhile, try to avoid buying non-free documentation
321 at all. Check the distribution terms of a manual before you buy it,
322 and insist that whoever seeks your business must respect your freedom.
323 Check the history of the book, and try to reward the publishers that
324 have paid or pay the authors to work on it.
326 The Free Software Foundation maintains a list of free documentation
327 published by other publishers, at
328 @url{http://www.fsf.org/doc/other-free-books.html}.
331 @unnumberedsec Contributors to @value{GDBN}
333 Richard Stallman was the original author of @value{GDBN}, and of many
334 other @sc{gnu} programs. Many others have contributed to its
335 development. This section attempts to credit major contributors. One
336 of the virtues of free software is that everyone is free to contribute
337 to it; with regret, we cannot actually acknowledge everyone here. The
338 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
339 blow-by-blow account.
341 Changes much prior to version 2.0 are lost in the mists of time.
344 @emph{Plea:} Additions to this section are particularly welcome. If you
345 or your friends (or enemies, to be evenhanded) have been unfairly
346 omitted from this list, we would like to add your names!
349 So that they may not regard their many labors as thankless, we
350 particularly thank those who shepherded @value{GDBN} through major
352 Andrew Cagney (releases 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
353 Jim Blandy (release 4.18);
354 Jason Molenda (release 4.17);
355 Stan Shebs (release 4.14);
356 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
357 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
358 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
359 Jim Kingdon (releases 3.5, 3.4, and 3.3);
360 and Randy Smith (releases 3.2, 3.1, and 3.0).
362 Richard Stallman, assisted at various times by Peter TerMaat, Chris
363 Hanson, and Richard Mlynarik, handled releases through 2.8.
365 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
366 in @value{GDBN}, with significant additional contributions from Per
367 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
368 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
369 much general update work leading to release 3.0).
371 @value{GDBN} uses the BFD subroutine library to examine multiple
372 object-file formats; BFD was a joint project of David V.
373 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
375 David Johnson wrote the original COFF support; Pace Willison did
376 the original support for encapsulated COFF.
378 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
380 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
381 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
383 Jean-Daniel Fekete contributed Sun 386i support.
384 Chris Hanson improved the HP9000 support.
385 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
386 David Johnson contributed Encore Umax support.
387 Jyrki Kuoppala contributed Altos 3068 support.
388 Jeff Law contributed HP PA and SOM support.
389 Keith Packard contributed NS32K support.
390 Doug Rabson contributed Acorn Risc Machine support.
391 Bob Rusk contributed Harris Nighthawk CX-UX support.
392 Chris Smith contributed Convex support (and Fortran debugging).
393 Jonathan Stone contributed Pyramid support.
394 Michael Tiemann contributed SPARC support.
395 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
396 Pace Willison contributed Intel 386 support.
397 Jay Vosburgh contributed Symmetry support.
398 Marko Mlinar contributed OpenRISC 1000 support.
400 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
402 Rich Schaefer and Peter Schauer helped with support of SunOS shared
405 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
406 about several machine instruction sets.
408 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
409 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
410 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
411 and RDI targets, respectively.
413 Brian Fox is the author of the readline libraries providing
414 command-line editing and command history.
416 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
417 Modula-2 support, and contributed the Languages chapter of this manual.
419 Fred Fish wrote most of the support for Unix System Vr4.
420 He also enhanced the command-completion support to cover C@t{++} overloaded
423 Hitachi America (now Renesas America), Ltd. sponsored the support for
424 H8/300, H8/500, and Super-H processors.
426 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
428 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
431 Toshiba sponsored the support for the TX39 Mips processor.
433 Matsushita sponsored the support for the MN10200 and MN10300 processors.
435 Fujitsu sponsored the support for SPARClite and FR30 processors.
437 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
440 Michael Snyder added support for tracepoints.
442 Stu Grossman wrote gdbserver.
444 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
445 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
447 The following people at the Hewlett-Packard Company contributed
448 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
449 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
450 compiler, and the Text User Interface (nee Terminal User Interface):
451 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
452 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
453 provided HP-specific information in this manual.
455 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
456 Robert Hoehne made significant contributions to the DJGPP port.
458 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
459 development since 1991. Cygnus engineers who have worked on @value{GDBN}
460 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
461 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
462 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
463 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
464 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
465 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
466 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
467 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
468 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
469 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
470 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
471 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
472 Zuhn have made contributions both large and small.
474 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
475 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
477 Jim Blandy added support for preprocessor macros, while working for Red
481 @chapter A Sample @value{GDBN} Session
483 You can use this manual at your leisure to read all about @value{GDBN}.
484 However, a handful of commands are enough to get started using the
485 debugger. This chapter illustrates those commands.
488 In this sample session, we emphasize user input like this: @b{input},
489 to make it easier to pick out from the surrounding output.
492 @c FIXME: this example may not be appropriate for some configs, where
493 @c FIXME...primary interest is in remote use.
495 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
496 processor) exhibits the following bug: sometimes, when we change its
497 quote strings from the default, the commands used to capture one macro
498 definition within another stop working. In the following short @code{m4}
499 session, we define a macro @code{foo} which expands to @code{0000}; we
500 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
501 same thing. However, when we change the open quote string to
502 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
503 procedure fails to define a new synonym @code{baz}:
512 @b{define(bar,defn(`foo'))}
516 @b{changequote(<QUOTE>,<UNQUOTE>)}
518 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
521 m4: End of input: 0: fatal error: EOF in string
525 Let us use @value{GDBN} to try to see what is going on.
528 $ @b{@value{GDBP} m4}
529 @c FIXME: this falsifies the exact text played out, to permit smallbook
530 @c FIXME... format to come out better.
531 @value{GDBN} is free software and you are welcome to distribute copies
532 of it under certain conditions; type "show copying" to see
534 There is absolutely no warranty for @value{GDBN}; type "show warranty"
537 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
542 @value{GDBN} reads only enough symbol data to know where to find the
543 rest when needed; as a result, the first prompt comes up very quickly.
544 We now tell @value{GDBN} to use a narrower display width than usual, so
545 that examples fit in this manual.
548 (@value{GDBP}) @b{set width 70}
552 We need to see how the @code{m4} built-in @code{changequote} works.
553 Having looked at the source, we know the relevant subroutine is
554 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
555 @code{break} command.
558 (@value{GDBP}) @b{break m4_changequote}
559 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
563 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
564 control; as long as control does not reach the @code{m4_changequote}
565 subroutine, the program runs as usual:
568 (@value{GDBP}) @b{run}
569 Starting program: /work/Editorial/gdb/gnu/m4/m4
577 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
578 suspends execution of @code{m4}, displaying information about the
579 context where it stops.
582 @b{changequote(<QUOTE>,<UNQUOTE>)}
584 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
586 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
590 Now we use the command @code{n} (@code{next}) to advance execution to
591 the next line of the current function.
595 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
600 @code{set_quotes} looks like a promising subroutine. We can go into it
601 by using the command @code{s} (@code{step}) instead of @code{next}.
602 @code{step} goes to the next line to be executed in @emph{any}
603 subroutine, so it steps into @code{set_quotes}.
607 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
609 530 if (lquote != def_lquote)
613 The display that shows the subroutine where @code{m4} is now
614 suspended (and its arguments) is called a stack frame display. It
615 shows a summary of the stack. We can use the @code{backtrace}
616 command (which can also be spelled @code{bt}), to see where we are
617 in the stack as a whole: the @code{backtrace} command displays a
618 stack frame for each active subroutine.
621 (@value{GDBP}) @b{bt}
622 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
624 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
626 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
627 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
629 #4 0x79dc in expand_input () at macro.c:40
630 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
634 We step through a few more lines to see what happens. The first two
635 times, we can use @samp{s}; the next two times we use @code{n} to avoid
636 falling into the @code{xstrdup} subroutine.
640 0x3b5c 532 if (rquote != def_rquote)
642 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
643 def_lquote : xstrdup(lq);
645 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
648 538 len_lquote = strlen(rquote);
652 The last line displayed looks a little odd; we can examine the variables
653 @code{lquote} and @code{rquote} to see if they are in fact the new left
654 and right quotes we specified. We use the command @code{p}
655 (@code{print}) to see their values.
658 (@value{GDBP}) @b{p lquote}
659 $1 = 0x35d40 "<QUOTE>"
660 (@value{GDBP}) @b{p rquote}
661 $2 = 0x35d50 "<UNQUOTE>"
665 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
666 To look at some context, we can display ten lines of source
667 surrounding the current line with the @code{l} (@code{list}) command.
673 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
675 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
678 538 len_lquote = strlen(rquote);
679 539 len_rquote = strlen(lquote);
686 Let us step past the two lines that set @code{len_lquote} and
687 @code{len_rquote}, and then examine the values of those variables.
691 539 len_rquote = strlen(lquote);
694 (@value{GDBP}) @b{p len_lquote}
696 (@value{GDBP}) @b{p len_rquote}
701 That certainly looks wrong, assuming @code{len_lquote} and
702 @code{len_rquote} are meant to be the lengths of @code{lquote} and
703 @code{rquote} respectively. We can set them to better values using
704 the @code{p} command, since it can print the value of
705 any expression---and that expression can include subroutine calls and
709 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
711 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
716 Is that enough to fix the problem of using the new quotes with the
717 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
718 executing with the @code{c} (@code{continue}) command, and then try the
719 example that caused trouble initially:
725 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
732 Success! The new quotes now work just as well as the default ones. The
733 problem seems to have been just the two typos defining the wrong
734 lengths. We allow @code{m4} exit by giving it an EOF as input:
738 Program exited normally.
742 The message @samp{Program exited normally.} is from @value{GDBN}; it
743 indicates @code{m4} has finished executing. We can end our @value{GDBN}
744 session with the @value{GDBN} @code{quit} command.
747 (@value{GDBP}) @b{quit}
751 @chapter Getting In and Out of @value{GDBN}
753 This chapter discusses how to start @value{GDBN}, and how to get out of it.
757 type @samp{@value{GDBP}} to start @value{GDBN}.
759 type @kbd{quit} or @kbd{C-d} to exit.
763 * Invoking GDB:: How to start @value{GDBN}
764 * Quitting GDB:: How to quit @value{GDBN}
765 * Shell Commands:: How to use shell commands inside @value{GDBN}
766 * Logging output:: How to log @value{GDBN}'s output to a file
770 @section Invoking @value{GDBN}
772 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
773 @value{GDBN} reads commands from the terminal until you tell it to exit.
775 You can also run @code{@value{GDBP}} with a variety of arguments and options,
776 to specify more of your debugging environment at the outset.
778 The command-line options described here are designed
779 to cover a variety of situations; in some environments, some of these
780 options may effectively be unavailable.
782 The most usual way to start @value{GDBN} is with one argument,
783 specifying an executable program:
786 @value{GDBP} @var{program}
790 You can also start with both an executable program and a core file
794 @value{GDBP} @var{program} @var{core}
797 You can, instead, specify a process ID as a second argument, if you want
798 to debug a running process:
801 @value{GDBP} @var{program} 1234
805 would attach @value{GDBN} to process @code{1234} (unless you also have a file
806 named @file{1234}; @value{GDBN} does check for a core file first).
808 Taking advantage of the second command-line argument requires a fairly
809 complete operating system; when you use @value{GDBN} as a remote
810 debugger attached to a bare board, there may not be any notion of
811 ``process'', and there is often no way to get a core dump. @value{GDBN}
812 will warn you if it is unable to attach or to read core dumps.
814 You can optionally have @code{@value{GDBP}} pass any arguments after the
815 executable file to the inferior using @code{--args}. This option stops
818 gdb --args gcc -O2 -c foo.c
820 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
821 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
823 You can run @code{@value{GDBP}} without printing the front material, which describes
824 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
831 You can further control how @value{GDBN} starts up by using command-line
832 options. @value{GDBN} itself can remind you of the options available.
842 to display all available options and briefly describe their use
843 (@samp{@value{GDBP} -h} is a shorter equivalent).
845 All options and command line arguments you give are processed
846 in sequential order. The order makes a difference when the
847 @samp{-x} option is used.
851 * File Options:: Choosing files
852 * Mode Options:: Choosing modes
853 * Startup:: What @value{GDBN} does during startup
857 @subsection Choosing files
859 When @value{GDBN} starts, it reads any arguments other than options as
860 specifying an executable file and core file (or process ID). This is
861 the same as if the arguments were specified by the @samp{-se} and
862 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
863 first argument that does not have an associated option flag as
864 equivalent to the @samp{-se} option followed by that argument; and the
865 second argument that does not have an associated option flag, if any, as
866 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
867 If the second argument begins with a decimal digit, @value{GDBN} will
868 first attempt to attach to it as a process, and if that fails, attempt
869 to open it as a corefile. If you have a corefile whose name begins with
870 a digit, you can prevent @value{GDBN} from treating it as a pid by
871 prefixing it with @file{./}, eg. @file{./12345}.
873 If @value{GDBN} has not been configured to included core file support,
874 such as for most embedded targets, then it will complain about a second
875 argument and ignore it.
877 Many options have both long and short forms; both are shown in the
878 following list. @value{GDBN} also recognizes the long forms if you truncate
879 them, so long as enough of the option is present to be unambiguous.
880 (If you prefer, you can flag option arguments with @samp{--} rather
881 than @samp{-}, though we illustrate the more usual convention.)
883 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
884 @c way, both those who look for -foo and --foo in the index, will find
888 @item -symbols @var{file}
890 @cindex @code{--symbols}
892 Read symbol table from file @var{file}.
894 @item -exec @var{file}
896 @cindex @code{--exec}
898 Use file @var{file} as the executable file to execute when appropriate,
899 and for examining pure data in conjunction with a core dump.
903 Read symbol table from file @var{file} and use it as the executable
906 @item -core @var{file}
908 @cindex @code{--core}
910 Use file @var{file} as a core dump to examine.
912 @item -c @var{number}
913 @item -pid @var{number}
914 @itemx -p @var{number}
917 Connect to process ID @var{number}, as with the @code{attach} command.
918 If there is no such process, @value{GDBN} will attempt to open a core
919 file named @var{number}.
921 @item -command @var{file}
923 @cindex @code{--command}
925 Execute @value{GDBN} commands from file @var{file}. @xref{Command
926 Files,, Command files}.
928 @item -directory @var{directory}
929 @itemx -d @var{directory}
930 @cindex @code{--directory}
932 Add @var{directory} to the path to search for source files.
936 @cindex @code{--mapped}
938 @emph{Warning: this option depends on operating system facilities that are not
939 supported on all systems.}@*
940 If memory-mapped files are available on your system through the @code{mmap}
941 system call, you can use this option
942 to have @value{GDBN} write the symbols from your
943 program into a reusable file in the current directory. If the program you are debugging is
944 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
945 Future @value{GDBN} debugging sessions notice the presence of this file,
946 and can quickly map in symbol information from it, rather than reading
947 the symbol table from the executable program.
949 The @file{.syms} file is specific to the host machine where @value{GDBN}
950 is run. It holds an exact image of the internal @value{GDBN} symbol
951 table. It cannot be shared across multiple host platforms.
955 @cindex @code{--readnow}
957 Read each symbol file's entire symbol table immediately, rather than
958 the default, which is to read it incrementally as it is needed.
959 This makes startup slower, but makes future operations faster.
963 You typically combine the @code{-mapped} and @code{-readnow} options in
964 order to build a @file{.syms} file that contains complete symbol
965 information. (@xref{Files,,Commands to specify files}, for information
966 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
967 but build a @file{.syms} file for future use is:
970 gdb -batch -nx -mapped -readnow programname
974 @subsection Choosing modes
976 You can run @value{GDBN} in various alternative modes---for example, in
977 batch mode or quiet mode.
984 Do not execute commands found in any initialization files. Normally,
985 @value{GDBN} executes the commands in these files after all the command
986 options and arguments have been processed. @xref{Command Files,,Command
992 @cindex @code{--quiet}
993 @cindex @code{--silent}
995 ``Quiet''. Do not print the introductory and copyright messages. These
996 messages are also suppressed in batch mode.
999 @cindex @code{--batch}
1000 Run in batch mode. Exit with status @code{0} after processing all the
1001 command files specified with @samp{-x} (and all commands from
1002 initialization files, if not inhibited with @samp{-n}). Exit with
1003 nonzero status if an error occurs in executing the @value{GDBN} commands
1004 in the command files.
1006 Batch mode may be useful for running @value{GDBN} as a filter, for
1007 example to download and run a program on another computer; in order to
1008 make this more useful, the message
1011 Program exited normally.
1015 (which is ordinarily issued whenever a program running under
1016 @value{GDBN} control terminates) is not issued when running in batch
1021 @cindex @code{--nowindows}
1023 ``No windows''. If @value{GDBN} comes with a graphical user interface
1024 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1025 interface. If no GUI is available, this option has no effect.
1029 @cindex @code{--windows}
1031 If @value{GDBN} includes a GUI, then this option requires it to be
1034 @item -cd @var{directory}
1036 Run @value{GDBN} using @var{directory} as its working directory,
1037 instead of the current directory.
1041 @cindex @code{--fullname}
1043 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1044 subprocess. It tells @value{GDBN} to output the full file name and line
1045 number in a standard, recognizable fashion each time a stack frame is
1046 displayed (which includes each time your program stops). This
1047 recognizable format looks like two @samp{\032} characters, followed by
1048 the file name, line number and character position separated by colons,
1049 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1050 @samp{\032} characters as a signal to display the source code for the
1054 @cindex @code{--epoch}
1055 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1056 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1057 routines so as to allow Epoch to display values of expressions in a
1060 @item -annotate @var{level}
1061 @cindex @code{--annotate}
1062 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1063 effect is identical to using @samp{set annotate @var{level}}
1064 (@pxref{Annotations}). The annotation @var{level} controls how much
1065 information @value{GDBN} prints together with its prompt, values of
1066 expressions, source lines, and other types of output. Level 0 is the
1067 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1068 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1069 that control @value{GDBN}, and level 2 has been deprecated.
1071 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
1075 @cindex @code{--args}
1076 Change interpretation of command line so that arguments following the
1077 executable file are passed as command line arguments to the inferior.
1078 This option stops option processing.
1080 @item -baud @var{bps}
1082 @cindex @code{--baud}
1084 Set the line speed (baud rate or bits per second) of any serial
1085 interface used by @value{GDBN} for remote debugging.
1087 @item -l @var{timeout}
1089 Set the timeout (in seconds) of any communication used by @value{GDBN}
1090 for remote debugging.
1092 @item -tty @var{device}
1093 @itemx -t @var{device}
1094 @cindex @code{--tty}
1096 Run using @var{device} for your program's standard input and output.
1097 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1099 @c resolve the situation of these eventually
1101 @cindex @code{--tui}
1102 Activate the @dfn{Text User Interface} when starting. The Text User
1103 Interface manages several text windows on the terminal, showing
1104 source, assembly, registers and @value{GDBN} command outputs
1105 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Alternatively, the
1106 Text User Interface can be enabled by invoking the program
1107 @samp{gdbtui}. Do not use this option if you run @value{GDBN} from
1108 Emacs (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1111 @c @cindex @code{--xdb}
1112 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1113 @c For information, see the file @file{xdb_trans.html}, which is usually
1114 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1117 @item -interpreter @var{interp}
1118 @cindex @code{--interpreter}
1119 Use the interpreter @var{interp} for interface with the controlling
1120 program or device. This option is meant to be set by programs which
1121 communicate with @value{GDBN} using it as a back end.
1122 @xref{Interpreters, , Command Interpreters}.
1124 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1125 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1126 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1127 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1128 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1129 @sc{gdb/mi} interfaces are no longer supported.
1132 @cindex @code{--write}
1133 Open the executable and core files for both reading and writing. This
1134 is equivalent to the @samp{set write on} command inside @value{GDBN}
1138 @cindex @code{--statistics}
1139 This option causes @value{GDBN} to print statistics about time and
1140 memory usage after it completes each command and returns to the prompt.
1143 @cindex @code{--version}
1144 This option causes @value{GDBN} to print its version number and
1145 no-warranty blurb, and exit.
1150 @subsection What @value{GDBN} does during startup
1151 @cindex @value{GDBN} startup
1153 Here's the description of what @value{GDBN} does during session startup:
1157 Sets up the command interpreter as specified by the command line
1158 (@pxref{Mode Options, interpreter}).
1162 Reads the @dfn{init file} (if any) in your home directory@footnote{On
1163 DOS/Windows systems, the home directory is the one pointed to by the
1164 @code{HOME} environment variable.} and executes all the commands in
1168 Processes command line options and operands.
1171 Reads and executes the commands from init file (if any) in the current
1172 working directory. This is only done if the current directory is
1173 different from your home directory. Thus, you can have more than one
1174 init file, one generic in your home directory, and another, specific
1175 to the program you are debugging, in the directory where you invoke
1179 Reads command files specified by the @samp{-x} option. @xref{Command
1180 Files}, for more details about @value{GDBN} command files.
1183 Reads the command history recorded in the @dfn{history file}.
1184 @xref{History}, for more details about the command history and the
1185 files where @value{GDBN} records it.
1188 Init files use the same syntax as @dfn{command files} (@pxref{Command
1189 Files}) and are processed by @value{GDBN} in the same way. The init
1190 file in your home directory can set options (such as @samp{set
1191 complaints}) that affect subsequent processing of command line options
1192 and operands. Init files are not executed if you use the @samp{-nx}
1193 option (@pxref{Mode Options, ,Choosing modes}).
1195 @cindex init file name
1196 @cindex @file{.gdbinit}
1197 The @value{GDBN} init files are normally called @file{.gdbinit}.
1198 On some configurations of @value{GDBN}, the init file is known by a
1199 different name (these are typically environments where a specialized
1200 form of @value{GDBN} may need to coexist with other forms, hence a
1201 different name for the specialized version's init file). These are the
1202 environments with special init file names:
1205 @cindex @file{gdb.ini}
1207 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1208 the limitations of file names imposed by DOS filesystems. The Windows
1209 ports of @value{GDBN} use the standard name, but if they find a
1210 @file{gdb.ini} file, they warn you about that and suggest to rename
1211 the file to the standard name.
1213 @cindex @file{.vxgdbinit}
1215 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
1217 @cindex @file{.os68gdbinit}
1219 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
1221 @cindex @file{.esgdbinit}
1223 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
1226 CISCO 68k: @file{.cisco-gdbinit}
1231 @section Quitting @value{GDBN}
1232 @cindex exiting @value{GDBN}
1233 @cindex leaving @value{GDBN}
1236 @kindex quit @r{[}@var{expression}@r{]}
1237 @kindex q @r{(@code{quit})}
1238 @item quit @r{[}@var{expression}@r{]}
1240 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1241 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1242 do not supply @var{expression}, @value{GDBN} will terminate normally;
1243 otherwise it will terminate using the result of @var{expression} as the
1248 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1249 terminates the action of any @value{GDBN} command that is in progress and
1250 returns to @value{GDBN} command level. It is safe to type the interrupt
1251 character at any time because @value{GDBN} does not allow it to take effect
1252 until a time when it is safe.
1254 If you have been using @value{GDBN} to control an attached process or
1255 device, you can release it with the @code{detach} command
1256 (@pxref{Attach, ,Debugging an already-running process}).
1258 @node Shell Commands
1259 @section Shell commands
1261 If you need to execute occasional shell commands during your
1262 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1263 just use the @code{shell} command.
1267 @cindex shell escape
1268 @item shell @var{command string}
1269 Invoke a standard shell to execute @var{command string}.
1270 If it exists, the environment variable @code{SHELL} determines which
1271 shell to run. Otherwise @value{GDBN} uses the default shell
1272 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1275 The utility @code{make} is often needed in development environments.
1276 You do not have to use the @code{shell} command for this purpose in
1281 @cindex calling make
1282 @item make @var{make-args}
1283 Execute the @code{make} program with the specified
1284 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1287 @node Logging output
1288 @section Logging output
1289 @cindex logging @value{GDBN} output
1290 @cindex save @value{GDBN} output to a file
1292 You may want to save the output of @value{GDBN} commands to a file.
1293 There are several commands to control @value{GDBN}'s logging.
1297 @item set logging on
1299 @item set logging off
1301 @cindex logging file name
1302 @item set logging file @var{file}
1303 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1304 @item set logging overwrite [on|off]
1305 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1306 you want @code{set logging on} to overwrite the logfile instead.
1307 @item set logging redirect [on|off]
1308 By default, @value{GDBN} output will go to both the terminal and the logfile.
1309 Set @code{redirect} if you want output to go only to the log file.
1310 @kindex show logging
1312 Show the current values of the logging settings.
1316 @chapter @value{GDBN} Commands
1318 You can abbreviate a @value{GDBN} command to the first few letters of the command
1319 name, if that abbreviation is unambiguous; and you can repeat certain
1320 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1321 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1322 show you the alternatives available, if there is more than one possibility).
1325 * Command Syntax:: How to give commands to @value{GDBN}
1326 * Completion:: Command completion
1327 * Help:: How to ask @value{GDBN} for help
1330 @node Command Syntax
1331 @section Command syntax
1333 A @value{GDBN} command is a single line of input. There is no limit on
1334 how long it can be. It starts with a command name, which is followed by
1335 arguments whose meaning depends on the command name. For example, the
1336 command @code{step} accepts an argument which is the number of times to
1337 step, as in @samp{step 5}. You can also use the @code{step} command
1338 with no arguments. Some commands do not allow any arguments.
1340 @cindex abbreviation
1341 @value{GDBN} command names may always be truncated if that abbreviation is
1342 unambiguous. Other possible command abbreviations are listed in the
1343 documentation for individual commands. In some cases, even ambiguous
1344 abbreviations are allowed; for example, @code{s} is specially defined as
1345 equivalent to @code{step} even though there are other commands whose
1346 names start with @code{s}. You can test abbreviations by using them as
1347 arguments to the @code{help} command.
1349 @cindex repeating commands
1350 @kindex RET @r{(repeat last command)}
1351 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1352 repeat the previous command. Certain commands (for example, @code{run})
1353 will not repeat this way; these are commands whose unintentional
1354 repetition might cause trouble and which you are unlikely to want to
1355 repeat. User-defined commands can disable this feature; see
1356 @ref{Define, dont-repeat}.
1358 The @code{list} and @code{x} commands, when you repeat them with
1359 @key{RET}, construct new arguments rather than repeating
1360 exactly as typed. This permits easy scanning of source or memory.
1362 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1363 output, in a way similar to the common utility @code{more}
1364 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1365 @key{RET} too many in this situation, @value{GDBN} disables command
1366 repetition after any command that generates this sort of display.
1368 @kindex # @r{(a comment)}
1370 Any text from a @kbd{#} to the end of the line is a comment; it does
1371 nothing. This is useful mainly in command files (@pxref{Command
1372 Files,,Command files}).
1374 @cindex repeating command sequences
1375 @kindex C-o @r{(operate-and-get-next)}
1376 The @kbd{C-o} binding is useful for repeating a complex sequence of
1377 commands. This command accepts the current line, like @kbd{RET}, and
1378 then fetches the next line relative to the current line from the history
1382 @section Command completion
1385 @cindex word completion
1386 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1387 only one possibility; it can also show you what the valid possibilities
1388 are for the next word in a command, at any time. This works for @value{GDBN}
1389 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1391 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1392 of a word. If there is only one possibility, @value{GDBN} fills in the
1393 word, and waits for you to finish the command (or press @key{RET} to
1394 enter it). For example, if you type
1396 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1397 @c complete accuracy in these examples; space introduced for clarity.
1398 @c If texinfo enhancements make it unnecessary, it would be nice to
1399 @c replace " @key" by "@key" in the following...
1401 (@value{GDBP}) info bre @key{TAB}
1405 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1406 the only @code{info} subcommand beginning with @samp{bre}:
1409 (@value{GDBP}) info breakpoints
1413 You can either press @key{RET} at this point, to run the @code{info
1414 breakpoints} command, or backspace and enter something else, if
1415 @samp{breakpoints} does not look like the command you expected. (If you
1416 were sure you wanted @code{info breakpoints} in the first place, you
1417 might as well just type @key{RET} immediately after @samp{info bre},
1418 to exploit command abbreviations rather than command completion).
1420 If there is more than one possibility for the next word when you press
1421 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1422 characters and try again, or just press @key{TAB} a second time;
1423 @value{GDBN} displays all the possible completions for that word. For
1424 example, you might want to set a breakpoint on a subroutine whose name
1425 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1426 just sounds the bell. Typing @key{TAB} again displays all the
1427 function names in your program that begin with those characters, for
1431 (@value{GDBP}) b make_ @key{TAB}
1432 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1433 make_a_section_from_file make_environ
1434 make_abs_section make_function_type
1435 make_blockvector make_pointer_type
1436 make_cleanup make_reference_type
1437 make_command make_symbol_completion_list
1438 (@value{GDBP}) b make_
1442 After displaying the available possibilities, @value{GDBN} copies your
1443 partial input (@samp{b make_} in the example) so you can finish the
1446 If you just want to see the list of alternatives in the first place, you
1447 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1448 means @kbd{@key{META} ?}. You can type this either by holding down a
1449 key designated as the @key{META} shift on your keyboard (if there is
1450 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1452 @cindex quotes in commands
1453 @cindex completion of quoted strings
1454 Sometimes the string you need, while logically a ``word'', may contain
1455 parentheses or other characters that @value{GDBN} normally excludes from
1456 its notion of a word. To permit word completion to work in this
1457 situation, you may enclose words in @code{'} (single quote marks) in
1458 @value{GDBN} commands.
1460 The most likely situation where you might need this is in typing the
1461 name of a C@t{++} function. This is because C@t{++} allows function
1462 overloading (multiple definitions of the same function, distinguished
1463 by argument type). For example, when you want to set a breakpoint you
1464 may need to distinguish whether you mean the version of @code{name}
1465 that takes an @code{int} parameter, @code{name(int)}, or the version
1466 that takes a @code{float} parameter, @code{name(float)}. To use the
1467 word-completion facilities in this situation, type a single quote
1468 @code{'} at the beginning of the function name. This alerts
1469 @value{GDBN} that it may need to consider more information than usual
1470 when you press @key{TAB} or @kbd{M-?} to request word completion:
1473 (@value{GDBP}) b 'bubble( @kbd{M-?}
1474 bubble(double,double) bubble(int,int)
1475 (@value{GDBP}) b 'bubble(
1478 In some cases, @value{GDBN} can tell that completing a name requires using
1479 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1480 completing as much as it can) if you do not type the quote in the first
1484 (@value{GDBP}) b bub @key{TAB}
1485 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1486 (@value{GDBP}) b 'bubble(
1490 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1491 you have not yet started typing the argument list when you ask for
1492 completion on an overloaded symbol.
1494 For more information about overloaded functions, see @ref{C plus plus
1495 expressions, ,C@t{++} expressions}. You can use the command @code{set
1496 overload-resolution off} to disable overload resolution;
1497 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1501 @section Getting help
1502 @cindex online documentation
1505 You can always ask @value{GDBN} itself for information on its commands,
1506 using the command @code{help}.
1509 @kindex h @r{(@code{help})}
1512 You can use @code{help} (abbreviated @code{h}) with no arguments to
1513 display a short list of named classes of commands:
1517 List of classes of commands:
1519 aliases -- Aliases of other commands
1520 breakpoints -- Making program stop at certain points
1521 data -- Examining data
1522 files -- Specifying and examining files
1523 internals -- Maintenance commands
1524 obscure -- Obscure features
1525 running -- Running the program
1526 stack -- Examining the stack
1527 status -- Status inquiries
1528 support -- Support facilities
1529 tracepoints -- Tracing of program execution without@*
1530 stopping the program
1531 user-defined -- User-defined commands
1533 Type "help" followed by a class name for a list of
1534 commands in that class.
1535 Type "help" followed by command name for full
1537 Command name abbreviations are allowed if unambiguous.
1540 @c the above line break eliminates huge line overfull...
1542 @item help @var{class}
1543 Using one of the general help classes as an argument, you can get a
1544 list of the individual commands in that class. For example, here is the
1545 help display for the class @code{status}:
1548 (@value{GDBP}) help status
1553 @c Line break in "show" line falsifies real output, but needed
1554 @c to fit in smallbook page size.
1555 info -- Generic command for showing things
1556 about the program being debugged
1557 show -- Generic command for showing things
1560 Type "help" followed by command name for full
1562 Command name abbreviations are allowed if unambiguous.
1566 @item help @var{command}
1567 With a command name as @code{help} argument, @value{GDBN} displays a
1568 short paragraph on how to use that command.
1571 @item apropos @var{args}
1572 The @code{apropos} command searches through all of the @value{GDBN}
1573 commands, and their documentation, for the regular expression specified in
1574 @var{args}. It prints out all matches found. For example:
1585 set symbol-reloading -- Set dynamic symbol table reloading
1586 multiple times in one run
1587 show symbol-reloading -- Show dynamic symbol table reloading
1588 multiple times in one run
1593 @item complete @var{args}
1594 The @code{complete @var{args}} command lists all the possible completions
1595 for the beginning of a command. Use @var{args} to specify the beginning of the
1596 command you want completed. For example:
1602 @noindent results in:
1613 @noindent This is intended for use by @sc{gnu} Emacs.
1616 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1617 and @code{show} to inquire about the state of your program, or the state
1618 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1619 manual introduces each of them in the appropriate context. The listings
1620 under @code{info} and under @code{show} in the Index point to
1621 all the sub-commands. @xref{Index}.
1626 @kindex i @r{(@code{info})}
1628 This command (abbreviated @code{i}) is for describing the state of your
1629 program. For example, you can list the arguments given to your program
1630 with @code{info args}, list the registers currently in use with @code{info
1631 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1632 You can get a complete list of the @code{info} sub-commands with
1633 @w{@code{help info}}.
1637 You can assign the result of an expression to an environment variable with
1638 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1639 @code{set prompt $}.
1643 In contrast to @code{info}, @code{show} is for describing the state of
1644 @value{GDBN} itself.
1645 You can change most of the things you can @code{show}, by using the
1646 related command @code{set}; for example, you can control what number
1647 system is used for displays with @code{set radix}, or simply inquire
1648 which is currently in use with @code{show radix}.
1651 To display all the settable parameters and their current
1652 values, you can use @code{show} with no arguments; you may also use
1653 @code{info set}. Both commands produce the same display.
1654 @c FIXME: "info set" violates the rule that "info" is for state of
1655 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1656 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1660 Here are three miscellaneous @code{show} subcommands, all of which are
1661 exceptional in lacking corresponding @code{set} commands:
1664 @kindex show version
1665 @cindex @value{GDBN} version number
1667 Show what version of @value{GDBN} is running. You should include this
1668 information in @value{GDBN} bug-reports. If multiple versions of
1669 @value{GDBN} are in use at your site, you may need to determine which
1670 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1671 commands are introduced, and old ones may wither away. Also, many
1672 system vendors ship variant versions of @value{GDBN}, and there are
1673 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1674 The version number is the same as the one announced when you start
1677 @kindex show copying
1678 @kindex info copying
1679 @cindex display @value{GDBN} copyright
1682 Display information about permission for copying @value{GDBN}.
1684 @kindex show warranty
1685 @kindex info warranty
1687 @itemx info warranty
1688 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1689 if your version of @value{GDBN} comes with one.
1694 @chapter Running Programs Under @value{GDBN}
1696 When you run a program under @value{GDBN}, you must first generate
1697 debugging information when you compile it.
1699 You may start @value{GDBN} with its arguments, if any, in an environment
1700 of your choice. If you are doing native debugging, you may redirect
1701 your program's input and output, debug an already running process, or
1702 kill a child process.
1705 * Compilation:: Compiling for debugging
1706 * Starting:: Starting your program
1707 * Arguments:: Your program's arguments
1708 * Environment:: Your program's environment
1710 * Working Directory:: Your program's working directory
1711 * Input/Output:: Your program's input and output
1712 * Attach:: Debugging an already-running process
1713 * Kill Process:: Killing the child process
1715 * Threads:: Debugging programs with multiple threads
1716 * Processes:: Debugging programs with multiple processes
1720 @section Compiling for debugging
1722 In order to debug a program effectively, you need to generate
1723 debugging information when you compile it. This debugging information
1724 is stored in the object file; it describes the data type of each
1725 variable or function and the correspondence between source line numbers
1726 and addresses in the executable code.
1728 To request debugging information, specify the @samp{-g} option when you run
1731 Programs that are to be shipped to your customers are compiled with
1732 optimizations, using the @samp{-O} compiler option. However, many
1733 compilers are unable to handle the @samp{-g} and @samp{-O} options
1734 together. Using those compilers, you cannot generate optimized
1735 executables containing debugging information.
1737 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1738 without @samp{-O}, making it possible to debug optimized code. We
1739 recommend that you @emph{always} use @samp{-g} whenever you compile a
1740 program. You may think your program is correct, but there is no sense
1741 in pushing your luck.
1743 @cindex optimized code, debugging
1744 @cindex debugging optimized code
1745 When you debug a program compiled with @samp{-g -O}, remember that the
1746 optimizer is rearranging your code; the debugger shows you what is
1747 really there. Do not be too surprised when the execution path does not
1748 exactly match your source file! An extreme example: if you define a
1749 variable, but never use it, @value{GDBN} never sees that
1750 variable---because the compiler optimizes it out of existence.
1752 Some things do not work as well with @samp{-g -O} as with just
1753 @samp{-g}, particularly on machines with instruction scheduling. If in
1754 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1755 please report it to us as a bug (including a test case!).
1756 @xref{Variables}, for more information about debugging optimized code.
1758 Older versions of the @sc{gnu} C compiler permitted a variant option
1759 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1760 format; if your @sc{gnu} C compiler has this option, do not use it.
1762 @value{GDBN} knows about preprocessor macros and can show you their
1763 expansion (@pxref{Macros}). Most compilers do not include information
1764 about preprocessor macros in the debugging information if you specify
1765 the @option{-g} flag alone, because this information is rather large.
1766 Version 3.1 and later of @value{NGCC}, the @sc{gnu} C compiler,
1767 provides macro information if you specify the options
1768 @option{-gdwarf-2} and @option{-g3}; the former option requests
1769 debugging information in the Dwarf 2 format, and the latter requests
1770 ``extra information''. In the future, we hope to find more compact
1771 ways to represent macro information, so that it can be included with
1776 @section Starting your program
1782 @kindex r @r{(@code{run})}
1785 Use the @code{run} command to start your program under @value{GDBN}.
1786 You must first specify the program name (except on VxWorks) with an
1787 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1788 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1789 (@pxref{Files, ,Commands to specify files}).
1793 If you are running your program in an execution environment that
1794 supports processes, @code{run} creates an inferior process and makes
1795 that process run your program. (In environments without processes,
1796 @code{run} jumps to the start of your program.)
1798 The execution of a program is affected by certain information it
1799 receives from its superior. @value{GDBN} provides ways to specify this
1800 information, which you must do @emph{before} starting your program. (You
1801 can change it after starting your program, but such changes only affect
1802 your program the next time you start it.) This information may be
1803 divided into four categories:
1806 @item The @emph{arguments.}
1807 Specify the arguments to give your program as the arguments of the
1808 @code{run} command. If a shell is available on your target, the shell
1809 is used to pass the arguments, so that you may use normal conventions
1810 (such as wildcard expansion or variable substitution) in describing
1812 In Unix systems, you can control which shell is used with the
1813 @code{SHELL} environment variable.
1814 @xref{Arguments, ,Your program's arguments}.
1816 @item The @emph{environment.}
1817 Your program normally inherits its environment from @value{GDBN}, but you can
1818 use the @value{GDBN} commands @code{set environment} and @code{unset
1819 environment} to change parts of the environment that affect
1820 your program. @xref{Environment, ,Your program's environment}.
1822 @item The @emph{working directory.}
1823 Your program inherits its working directory from @value{GDBN}. You can set
1824 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1825 @xref{Working Directory, ,Your program's working directory}.
1827 @item The @emph{standard input and output.}
1828 Your program normally uses the same device for standard input and
1829 standard output as @value{GDBN} is using. You can redirect input and output
1830 in the @code{run} command line, or you can use the @code{tty} command to
1831 set a different device for your program.
1832 @xref{Input/Output, ,Your program's input and output}.
1835 @emph{Warning:} While input and output redirection work, you cannot use
1836 pipes to pass the output of the program you are debugging to another
1837 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1841 When you issue the @code{run} command, your program begins to execute
1842 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1843 of how to arrange for your program to stop. Once your program has
1844 stopped, you may call functions in your program, using the @code{print}
1845 or @code{call} commands. @xref{Data, ,Examining Data}.
1847 If the modification time of your symbol file has changed since the last
1848 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1849 table, and reads it again. When it does this, @value{GDBN} tries to retain
1850 your current breakpoints.
1855 @cindex run to main procedure
1856 The name of the main procedure can vary from language to language.
1857 With C or C@t{++}, the main procedure name is always @code{main}, but
1858 other languages such as Ada do not require a specific name for their
1859 main procedure. The debugger provides a convenient way to start the
1860 execution of the program and to stop at the beginning of the main
1861 procedure, depending on the language used.
1863 The @samp{start} command does the equivalent of setting a temporary
1864 breakpoint at the beginning of the main procedure and then invoking
1865 the @samp{run} command.
1867 @cindex elaboration phase
1868 Some programs contain an @dfn{elaboration} phase where some startup code is
1869 executed before the main procedure is called. This depends on the
1870 languages used to write your program. In C@t{++}, for instance,
1871 constructors for static and global objects are executed before
1872 @code{main} is called. It is therefore possible that the debugger stops
1873 before reaching the main procedure. However, the temporary breakpoint
1874 will remain to halt execution.
1876 Specify the arguments to give to your program as arguments to the
1877 @samp{start} command. These arguments will be given verbatim to the
1878 underlying @samp{run} command. Note that the same arguments will be
1879 reused if no argument is provided during subsequent calls to
1880 @samp{start} or @samp{run}.
1882 It is sometimes necessary to debug the program during elaboration. In
1883 these cases, using the @code{start} command would stop the execution of
1884 your program too late, as the program would have already completed the
1885 elaboration phase. Under these circumstances, insert breakpoints in your
1886 elaboration code before running your program.
1890 @section Your program's arguments
1892 @cindex arguments (to your program)
1893 The arguments to your program can be specified by the arguments of the
1895 They are passed to a shell, which expands wildcard characters and
1896 performs redirection of I/O, and thence to your program. Your
1897 @code{SHELL} environment variable (if it exists) specifies what shell
1898 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1899 the default shell (@file{/bin/sh} on Unix).
1901 On non-Unix systems, the program is usually invoked directly by
1902 @value{GDBN}, which emulates I/O redirection via the appropriate system
1903 calls, and the wildcard characters are expanded by the startup code of
1904 the program, not by the shell.
1906 @code{run} with no arguments uses the same arguments used by the previous
1907 @code{run}, or those set by the @code{set args} command.
1912 Specify the arguments to be used the next time your program is run. If
1913 @code{set args} has no arguments, @code{run} executes your program
1914 with no arguments. Once you have run your program with arguments,
1915 using @code{set args} before the next @code{run} is the only way to run
1916 it again without arguments.
1920 Show the arguments to give your program when it is started.
1924 @section Your program's environment
1926 @cindex environment (of your program)
1927 The @dfn{environment} consists of a set of environment variables and
1928 their values. Environment variables conventionally record such things as
1929 your user name, your home directory, your terminal type, and your search
1930 path for programs to run. Usually you set up environment variables with
1931 the shell and they are inherited by all the other programs you run. When
1932 debugging, it can be useful to try running your program with a modified
1933 environment without having to start @value{GDBN} over again.
1937 @item path @var{directory}
1938 Add @var{directory} to the front of the @code{PATH} environment variable
1939 (the search path for executables) that will be passed to your program.
1940 The value of @code{PATH} used by @value{GDBN} does not change.
1941 You may specify several directory names, separated by whitespace or by a
1942 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1943 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1944 is moved to the front, so it is searched sooner.
1946 You can use the string @samp{$cwd} to refer to whatever is the current
1947 working directory at the time @value{GDBN} searches the path. If you
1948 use @samp{.} instead, it refers to the directory where you executed the
1949 @code{path} command. @value{GDBN} replaces @samp{.} in the
1950 @var{directory} argument (with the current path) before adding
1951 @var{directory} to the search path.
1952 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1953 @c document that, since repeating it would be a no-op.
1957 Display the list of search paths for executables (the @code{PATH}
1958 environment variable).
1960 @kindex show environment
1961 @item show environment @r{[}@var{varname}@r{]}
1962 Print the value of environment variable @var{varname} to be given to
1963 your program when it starts. If you do not supply @var{varname},
1964 print the names and values of all environment variables to be given to
1965 your program. You can abbreviate @code{environment} as @code{env}.
1967 @kindex set environment
1968 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1969 Set environment variable @var{varname} to @var{value}. The value
1970 changes for your program only, not for @value{GDBN} itself. @var{value} may
1971 be any string; the values of environment variables are just strings, and
1972 any interpretation is supplied by your program itself. The @var{value}
1973 parameter is optional; if it is eliminated, the variable is set to a
1975 @c "any string" here does not include leading, trailing
1976 @c blanks. Gnu asks: does anyone care?
1978 For example, this command:
1985 tells the debugged program, when subsequently run, that its user is named
1986 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1987 are not actually required.)
1989 @kindex unset environment
1990 @item unset environment @var{varname}
1991 Remove variable @var{varname} from the environment to be passed to your
1992 program. This is different from @samp{set env @var{varname} =};
1993 @code{unset environment} removes the variable from the environment,
1994 rather than assigning it an empty value.
1997 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1999 by your @code{SHELL} environment variable if it exists (or
2000 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2001 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2002 @file{.bashrc} for BASH---any variables you set in that file affect
2003 your program. You may wish to move setting of environment variables to
2004 files that are only run when you sign on, such as @file{.login} or
2007 @node Working Directory
2008 @section Your program's working directory
2010 @cindex working directory (of your program)
2011 Each time you start your program with @code{run}, it inherits its
2012 working directory from the current working directory of @value{GDBN}.
2013 The @value{GDBN} working directory is initially whatever it inherited
2014 from its parent process (typically the shell), but you can specify a new
2015 working directory in @value{GDBN} with the @code{cd} command.
2017 The @value{GDBN} working directory also serves as a default for the commands
2018 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2023 @cindex change working directory
2024 @item cd @var{directory}
2025 Set the @value{GDBN} working directory to @var{directory}.
2029 Print the @value{GDBN} working directory.
2032 It is generally impossible to find the current working directory of
2033 the process being debugged (since a program can change its directory
2034 during its run). If you work on a system where @value{GDBN} is
2035 configured with the @file{/proc} support, you can use the @code{info
2036 proc} command (@pxref{SVR4 Process Information}) to find out the
2037 current working directory of the debuggee.
2040 @section Your program's input and output
2045 By default, the program you run under @value{GDBN} does input and output to
2046 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2047 to its own terminal modes to interact with you, but it records the terminal
2048 modes your program was using and switches back to them when you continue
2049 running your program.
2052 @kindex info terminal
2054 Displays information recorded by @value{GDBN} about the terminal modes your
2058 You can redirect your program's input and/or output using shell
2059 redirection with the @code{run} command. For example,
2066 starts your program, diverting its output to the file @file{outfile}.
2069 @cindex controlling terminal
2070 Another way to specify where your program should do input and output is
2071 with the @code{tty} command. This command accepts a file name as
2072 argument, and causes this file to be the default for future @code{run}
2073 commands. It also resets the controlling terminal for the child
2074 process, for future @code{run} commands. For example,
2081 directs that processes started with subsequent @code{run} commands
2082 default to do input and output on the terminal @file{/dev/ttyb} and have
2083 that as their controlling terminal.
2085 An explicit redirection in @code{run} overrides the @code{tty} command's
2086 effect on the input/output device, but not its effect on the controlling
2089 When you use the @code{tty} command or redirect input in the @code{run}
2090 command, only the input @emph{for your program} is affected. The input
2091 for @value{GDBN} still comes from your terminal.
2094 @section Debugging an already-running process
2099 @item attach @var{process-id}
2100 This command attaches to a running process---one that was started
2101 outside @value{GDBN}. (@code{info files} shows your active
2102 targets.) The command takes as argument a process ID. The usual way to
2103 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2104 or with the @samp{jobs -l} shell command.
2106 @code{attach} does not repeat if you press @key{RET} a second time after
2107 executing the command.
2110 To use @code{attach}, your program must be running in an environment
2111 which supports processes; for example, @code{attach} does not work for
2112 programs on bare-board targets that lack an operating system. You must
2113 also have permission to send the process a signal.
2115 When you use @code{attach}, the debugger finds the program running in
2116 the process first by looking in the current working directory, then (if
2117 the program is not found) by using the source file search path
2118 (@pxref{Source Path, ,Specifying source directories}). You can also use
2119 the @code{file} command to load the program. @xref{Files, ,Commands to
2122 The first thing @value{GDBN} does after arranging to debug the specified
2123 process is to stop it. You can examine and modify an attached process
2124 with all the @value{GDBN} commands that are ordinarily available when
2125 you start processes with @code{run}. You can insert breakpoints; you
2126 can step and continue; you can modify storage. If you would rather the
2127 process continue running, you may use the @code{continue} command after
2128 attaching @value{GDBN} to the process.
2133 When you have finished debugging the attached process, you can use the
2134 @code{detach} command to release it from @value{GDBN} control. Detaching
2135 the process continues its execution. After the @code{detach} command,
2136 that process and @value{GDBN} become completely independent once more, and you
2137 are ready to @code{attach} another process or start one with @code{run}.
2138 @code{detach} does not repeat if you press @key{RET} again after
2139 executing the command.
2142 If you exit @value{GDBN} or use the @code{run} command while you have an
2143 attached process, you kill that process. By default, @value{GDBN} asks
2144 for confirmation if you try to do either of these things; you can
2145 control whether or not you need to confirm by using the @code{set
2146 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
2150 @section Killing the child process
2155 Kill the child process in which your program is running under @value{GDBN}.
2158 This command is useful if you wish to debug a core dump instead of a
2159 running process. @value{GDBN} ignores any core dump file while your program
2162 On some operating systems, a program cannot be executed outside @value{GDBN}
2163 while you have breakpoints set on it inside @value{GDBN}. You can use the
2164 @code{kill} command in this situation to permit running your program
2165 outside the debugger.
2167 The @code{kill} command is also useful if you wish to recompile and
2168 relink your program, since on many systems it is impossible to modify an
2169 executable file while it is running in a process. In this case, when you
2170 next type @code{run}, @value{GDBN} notices that the file has changed, and
2171 reads the symbol table again (while trying to preserve your current
2172 breakpoint settings).
2175 @section Debugging programs with multiple threads
2177 @cindex threads of execution
2178 @cindex multiple threads
2179 @cindex switching threads
2180 In some operating systems, such as HP-UX and Solaris, a single program
2181 may have more than one @dfn{thread} of execution. The precise semantics
2182 of threads differ from one operating system to another, but in general
2183 the threads of a single program are akin to multiple processes---except
2184 that they share one address space (that is, they can all examine and
2185 modify the same variables). On the other hand, each thread has its own
2186 registers and execution stack, and perhaps private memory.
2188 @value{GDBN} provides these facilities for debugging multi-thread
2192 @item automatic notification of new threads
2193 @item @samp{thread @var{threadno}}, a command to switch among threads
2194 @item @samp{info threads}, a command to inquire about existing threads
2195 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2196 a command to apply a command to a list of threads
2197 @item thread-specific breakpoints
2201 @emph{Warning:} These facilities are not yet available on every
2202 @value{GDBN} configuration where the operating system supports threads.
2203 If your @value{GDBN} does not support threads, these commands have no
2204 effect. For example, a system without thread support shows no output
2205 from @samp{info threads}, and always rejects the @code{thread} command,
2209 (@value{GDBP}) info threads
2210 (@value{GDBP}) thread 1
2211 Thread ID 1 not known. Use the "info threads" command to
2212 see the IDs of currently known threads.
2214 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2215 @c doesn't support threads"?
2218 @cindex focus of debugging
2219 @cindex current thread
2220 The @value{GDBN} thread debugging facility allows you to observe all
2221 threads while your program runs---but whenever @value{GDBN} takes
2222 control, one thread in particular is always the focus of debugging.
2223 This thread is called the @dfn{current thread}. Debugging commands show
2224 program information from the perspective of the current thread.
2226 @cindex @code{New} @var{systag} message
2227 @cindex thread identifier (system)
2228 @c FIXME-implementors!! It would be more helpful if the [New...] message
2229 @c included GDB's numeric thread handle, so you could just go to that
2230 @c thread without first checking `info threads'.
2231 Whenever @value{GDBN} detects a new thread in your program, it displays
2232 the target system's identification for the thread with a message in the
2233 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2234 whose form varies depending on the particular system. For example, on
2235 LynxOS, you might see
2238 [New process 35 thread 27]
2242 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2243 the @var{systag} is simply something like @samp{process 368}, with no
2246 @c FIXME!! (1) Does the [New...] message appear even for the very first
2247 @c thread of a program, or does it only appear for the
2248 @c second---i.e.@: when it becomes obvious we have a multithread
2250 @c (2) *Is* there necessarily a first thread always? Or do some
2251 @c multithread systems permit starting a program with multiple
2252 @c threads ab initio?
2254 @cindex thread number
2255 @cindex thread identifier (GDB)
2256 For debugging purposes, @value{GDBN} associates its own thread
2257 number---always a single integer---with each thread in your program.
2260 @kindex info threads
2262 Display a summary of all threads currently in your
2263 program. @value{GDBN} displays for each thread (in this order):
2267 the thread number assigned by @value{GDBN}
2270 the target system's thread identifier (@var{systag})
2273 the current stack frame summary for that thread
2277 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2278 indicates the current thread.
2282 @c end table here to get a little more width for example
2285 (@value{GDBP}) info threads
2286 3 process 35 thread 27 0x34e5 in sigpause ()
2287 2 process 35 thread 23 0x34e5 in sigpause ()
2288 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2294 @cindex debugging multithreaded programs (on HP-UX)
2295 @cindex thread identifier (GDB), on HP-UX
2296 For debugging purposes, @value{GDBN} associates its own thread
2297 number---a small integer assigned in thread-creation order---with each
2298 thread in your program.
2300 @cindex @code{New} @var{systag} message, on HP-UX
2301 @cindex thread identifier (system), on HP-UX
2302 @c FIXME-implementors!! It would be more helpful if the [New...] message
2303 @c included GDB's numeric thread handle, so you could just go to that
2304 @c thread without first checking `info threads'.
2305 Whenever @value{GDBN} detects a new thread in your program, it displays
2306 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2307 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2308 whose form varies depending on the particular system. For example, on
2312 [New thread 2 (system thread 26594)]
2316 when @value{GDBN} notices a new thread.
2319 @kindex info threads (HP-UX)
2321 Display a summary of all threads currently in your
2322 program. @value{GDBN} displays for each thread (in this order):
2325 @item the thread number assigned by @value{GDBN}
2327 @item the target system's thread identifier (@var{systag})
2329 @item the current stack frame summary for that thread
2333 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2334 indicates the current thread.
2338 @c end table here to get a little more width for example
2341 (@value{GDBP}) info threads
2342 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2344 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2345 from /usr/lib/libc.2
2346 1 system thread 27905 0x7b003498 in _brk () \@*
2347 from /usr/lib/libc.2
2350 On Solaris, you can display more information about user threads with a
2351 Solaris-specific command:
2354 @item maint info sol-threads
2355 @kindex maint info sol-threads
2356 @cindex thread info (Solaris)
2357 Display info on Solaris user threads.
2361 @kindex thread @var{threadno}
2362 @item thread @var{threadno}
2363 Make thread number @var{threadno} the current thread. The command
2364 argument @var{threadno} is the internal @value{GDBN} thread number, as
2365 shown in the first field of the @samp{info threads} display.
2366 @value{GDBN} responds by displaying the system identifier of the thread
2367 you selected, and its current stack frame summary:
2370 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2371 (@value{GDBP}) thread 2
2372 [Switching to process 35 thread 23]
2373 0x34e5 in sigpause ()
2377 As with the @samp{[New @dots{}]} message, the form of the text after
2378 @samp{Switching to} depends on your system's conventions for identifying
2381 @kindex thread apply
2382 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2383 The @code{thread apply} command allows you to apply a command to one or
2384 more threads. Specify the numbers of the threads that you want affected
2385 with the command argument @var{threadno}. @var{threadno} is the internal
2386 @value{GDBN} thread number, as shown in the first field of the @samp{info
2387 threads} display. To apply a command to all threads, use
2388 @code{thread apply all} @var{args}.
2391 @cindex automatic thread selection
2392 @cindex switching threads automatically
2393 @cindex threads, automatic switching
2394 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2395 signal, it automatically selects the thread where that breakpoint or
2396 signal happened. @value{GDBN} alerts you to the context switch with a
2397 message of the form @samp{[Switching to @var{systag}]} to identify the
2400 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2401 more information about how @value{GDBN} behaves when you stop and start
2402 programs with multiple threads.
2404 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2405 watchpoints in programs with multiple threads.
2408 @section Debugging programs with multiple processes
2410 @cindex fork, debugging programs which call
2411 @cindex multiple processes
2412 @cindex processes, multiple
2413 On most systems, @value{GDBN} has no special support for debugging
2414 programs which create additional processes using the @code{fork}
2415 function. When a program forks, @value{GDBN} will continue to debug the
2416 parent process and the child process will run unimpeded. If you have
2417 set a breakpoint in any code which the child then executes, the child
2418 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2419 will cause it to terminate.
2421 However, if you want to debug the child process there is a workaround
2422 which isn't too painful. Put a call to @code{sleep} in the code which
2423 the child process executes after the fork. It may be useful to sleep
2424 only if a certain environment variable is set, or a certain file exists,
2425 so that the delay need not occur when you don't want to run @value{GDBN}
2426 on the child. While the child is sleeping, use the @code{ps} program to
2427 get its process ID. Then tell @value{GDBN} (a new invocation of
2428 @value{GDBN} if you are also debugging the parent process) to attach to
2429 the child process (@pxref{Attach}). From that point on you can debug
2430 the child process just like any other process which you attached to.
2432 On some systems, @value{GDBN} provides support for debugging programs that
2433 create additional processes using the @code{fork} or @code{vfork} functions.
2434 Currently, the only platforms with this feature are HP-UX (11.x and later
2435 only?) and GNU/Linux (kernel version 2.5.60 and later).
2437 By default, when a program forks, @value{GDBN} will continue to debug
2438 the parent process and the child process will run unimpeded.
2440 If you want to follow the child process instead of the parent process,
2441 use the command @w{@code{set follow-fork-mode}}.
2444 @kindex set follow-fork-mode
2445 @item set follow-fork-mode @var{mode}
2446 Set the debugger response to a program call of @code{fork} or
2447 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2448 process. The @var{mode} argument can be:
2452 The original process is debugged after a fork. The child process runs
2453 unimpeded. This is the default.
2456 The new process is debugged after a fork. The parent process runs
2461 @kindex show follow-fork-mode
2462 @item show follow-fork-mode
2463 Display the current debugger response to a @code{fork} or @code{vfork} call.
2466 If you ask to debug a child process and a @code{vfork} is followed by an
2467 @code{exec}, @value{GDBN} executes the new target up to the first
2468 breakpoint in the new target. If you have a breakpoint set on
2469 @code{main} in your original program, the breakpoint will also be set on
2470 the child process's @code{main}.
2472 When a child process is spawned by @code{vfork}, you cannot debug the
2473 child or parent until an @code{exec} call completes.
2475 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2476 call executes, the new target restarts. To restart the parent process,
2477 use the @code{file} command with the parent executable name as its
2480 You can use the @code{catch} command to make @value{GDBN} stop whenever
2481 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2482 Catchpoints, ,Setting catchpoints}.
2485 @chapter Stopping and Continuing
2487 The principal purposes of using a debugger are so that you can stop your
2488 program before it terminates; or so that, if your program runs into
2489 trouble, you can investigate and find out why.
2491 Inside @value{GDBN}, your program may stop for any of several reasons,
2492 such as a signal, a breakpoint, or reaching a new line after a
2493 @value{GDBN} command such as @code{step}. You may then examine and
2494 change variables, set new breakpoints or remove old ones, and then
2495 continue execution. Usually, the messages shown by @value{GDBN} provide
2496 ample explanation of the status of your program---but you can also
2497 explicitly request this information at any time.
2500 @kindex info program
2502 Display information about the status of your program: whether it is
2503 running or not, what process it is, and why it stopped.
2507 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2508 * Continuing and Stepping:: Resuming execution
2510 * Thread Stops:: Stopping and starting multi-thread programs
2514 @section Breakpoints, watchpoints, and catchpoints
2517 A @dfn{breakpoint} makes your program stop whenever a certain point in
2518 the program is reached. For each breakpoint, you can add conditions to
2519 control in finer detail whether your program stops. You can set
2520 breakpoints with the @code{break} command and its variants (@pxref{Set
2521 Breaks, ,Setting breakpoints}), to specify the place where your program
2522 should stop by line number, function name or exact address in the
2525 On some systems, you can set breakpoints in shared libraries before
2526 the executable is run. There is a minor limitation on HP-UX systems:
2527 you must wait until the executable is run in order to set breakpoints
2528 in shared library routines that are not called directly by the program
2529 (for example, routines that are arguments in a @code{pthread_create}
2533 @cindex memory tracing
2534 @cindex breakpoint on memory address
2535 @cindex breakpoint on variable modification
2536 A @dfn{watchpoint} is a special breakpoint that stops your program
2537 when the value of an expression changes. You must use a different
2538 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2539 watchpoints}), but aside from that, you can manage a watchpoint like
2540 any other breakpoint: you enable, disable, and delete both breakpoints
2541 and watchpoints using the same commands.
2543 You can arrange to have values from your program displayed automatically
2544 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2548 @cindex breakpoint on events
2549 A @dfn{catchpoint} is another special breakpoint that stops your program
2550 when a certain kind of event occurs, such as the throwing of a C@t{++}
2551 exception or the loading of a library. As with watchpoints, you use a
2552 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2553 catchpoints}), but aside from that, you can manage a catchpoint like any
2554 other breakpoint. (To stop when your program receives a signal, use the
2555 @code{handle} command; see @ref{Signals, ,Signals}.)
2557 @cindex breakpoint numbers
2558 @cindex numbers for breakpoints
2559 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2560 catchpoint when you create it; these numbers are successive integers
2561 starting with one. In many of the commands for controlling various
2562 features of breakpoints you use the breakpoint number to say which
2563 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2564 @dfn{disabled}; if disabled, it has no effect on your program until you
2567 @cindex breakpoint ranges
2568 @cindex ranges of breakpoints
2569 Some @value{GDBN} commands accept a range of breakpoints on which to
2570 operate. A breakpoint range is either a single breakpoint number, like
2571 @samp{5}, or two such numbers, in increasing order, separated by a
2572 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2573 all breakpoint in that range are operated on.
2576 * Set Breaks:: Setting breakpoints
2577 * Set Watchpoints:: Setting watchpoints
2578 * Set Catchpoints:: Setting catchpoints
2579 * Delete Breaks:: Deleting breakpoints
2580 * Disabling:: Disabling breakpoints
2581 * Conditions:: Break conditions
2582 * Break Commands:: Breakpoint command lists
2583 * Breakpoint Menus:: Breakpoint menus
2584 * Error in Breakpoints:: ``Cannot insert breakpoints''
2585 * Breakpoint related warnings:: ``Breakpoint address adjusted...''
2589 @subsection Setting breakpoints
2591 @c FIXME LMB what does GDB do if no code on line of breakpt?
2592 @c consider in particular declaration with/without initialization.
2594 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2597 @kindex b @r{(@code{break})}
2598 @vindex $bpnum@r{, convenience variable}
2599 @cindex latest breakpoint
2600 Breakpoints are set with the @code{break} command (abbreviated
2601 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2602 number of the breakpoint you've set most recently; see @ref{Convenience
2603 Vars,, Convenience variables}, for a discussion of what you can do with
2604 convenience variables.
2606 You have several ways to say where the breakpoint should go.
2609 @item break @var{function}
2610 Set a breakpoint at entry to function @var{function}.
2611 When using source languages that permit overloading of symbols, such as
2612 C@t{++}, @var{function} may refer to more than one possible place to break.
2613 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2615 @item break +@var{offset}
2616 @itemx break -@var{offset}
2617 Set a breakpoint some number of lines forward or back from the position
2618 at which execution stopped in the currently selected @dfn{stack frame}.
2619 (@xref{Frames, ,Frames}, for a description of stack frames.)
2621 @item break @var{linenum}
2622 Set a breakpoint at line @var{linenum} in the current source file.
2623 The current source file is the last file whose source text was printed.
2624 The breakpoint will stop your program just before it executes any of the
2627 @item break @var{filename}:@var{linenum}
2628 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2630 @item break @var{filename}:@var{function}
2631 Set a breakpoint at entry to function @var{function} found in file
2632 @var{filename}. Specifying a file name as well as a function name is
2633 superfluous except when multiple files contain similarly named
2636 @item break *@var{address}
2637 Set a breakpoint at address @var{address}. You can use this to set
2638 breakpoints in parts of your program which do not have debugging
2639 information or source files.
2642 When called without any arguments, @code{break} sets a breakpoint at
2643 the next instruction to be executed in the selected stack frame
2644 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2645 innermost, this makes your program stop as soon as control
2646 returns to that frame. This is similar to the effect of a
2647 @code{finish} command in the frame inside the selected frame---except
2648 that @code{finish} does not leave an active breakpoint. If you use
2649 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2650 the next time it reaches the current location; this may be useful
2653 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2654 least one instruction has been executed. If it did not do this, you
2655 would be unable to proceed past a breakpoint without first disabling the
2656 breakpoint. This rule applies whether or not the breakpoint already
2657 existed when your program stopped.
2659 @item break @dots{} if @var{cond}
2660 Set a breakpoint with condition @var{cond}; evaluate the expression
2661 @var{cond} each time the breakpoint is reached, and stop only if the
2662 value is nonzero---that is, if @var{cond} evaluates as true.
2663 @samp{@dots{}} stands for one of the possible arguments described
2664 above (or no argument) specifying where to break. @xref{Conditions,
2665 ,Break conditions}, for more information on breakpoint conditions.
2668 @item tbreak @var{args}
2669 Set a breakpoint enabled only for one stop. @var{args} are the
2670 same as for the @code{break} command, and the breakpoint is set in the same
2671 way, but the breakpoint is automatically deleted after the first time your
2672 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2675 @cindex hardware breakpoints
2676 @item hbreak @var{args}
2677 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2678 @code{break} command and the breakpoint is set in the same way, but the
2679 breakpoint requires hardware support and some target hardware may not
2680 have this support. The main purpose of this is EPROM/ROM code
2681 debugging, so you can set a breakpoint at an instruction without
2682 changing the instruction. This can be used with the new trap-generation
2683 provided by SPARClite DSU and most x86-based targets. These targets
2684 will generate traps when a program accesses some data or instruction
2685 address that is assigned to the debug registers. However the hardware
2686 breakpoint registers can take a limited number of breakpoints. For
2687 example, on the DSU, only two data breakpoints can be set at a time, and
2688 @value{GDBN} will reject this command if more than two are used. Delete
2689 or disable unused hardware breakpoints before setting new ones
2690 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2691 For remote targets, you can restrict the number of hardware
2692 breakpoints @value{GDBN} will use, see @ref{set remote
2693 hardware-breakpoint-limit}.
2697 @item thbreak @var{args}
2698 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2699 are the same as for the @code{hbreak} command and the breakpoint is set in
2700 the same way. However, like the @code{tbreak} command,
2701 the breakpoint is automatically deleted after the
2702 first time your program stops there. Also, like the @code{hbreak}
2703 command, the breakpoint requires hardware support and some target hardware
2704 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2705 See also @ref{Conditions, ,Break conditions}.
2708 @cindex regular expression
2709 @cindex breakpoints in functions matching a regexp
2710 @cindex set breakpoints in many functions
2711 @item rbreak @var{regex}
2712 Set breakpoints on all functions matching the regular expression
2713 @var{regex}. This command sets an unconditional breakpoint on all
2714 matches, printing a list of all breakpoints it set. Once these
2715 breakpoints are set, they are treated just like the breakpoints set with
2716 the @code{break} command. You can delete them, disable them, or make
2717 them conditional the same way as any other breakpoint.
2719 The syntax of the regular expression is the standard one used with tools
2720 like @file{grep}. Note that this is different from the syntax used by
2721 shells, so for instance @code{foo*} matches all functions that include
2722 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2723 @code{.*} leading and trailing the regular expression you supply, so to
2724 match only functions that begin with @code{foo}, use @code{^foo}.
2726 @cindex non-member C@t{++} functions, set breakpoint in
2727 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2728 breakpoints on overloaded functions that are not members of any special
2731 @cindex set breakpoints on all functions
2732 The @code{rbreak} command can be used to set breakpoints in
2733 @strong{all} the functions in a program, like this:
2736 (@value{GDBP}) rbreak .
2739 @kindex info breakpoints
2740 @cindex @code{$_} and @code{info breakpoints}
2741 @item info breakpoints @r{[}@var{n}@r{]}
2742 @itemx info break @r{[}@var{n}@r{]}
2743 @itemx info watchpoints @r{[}@var{n}@r{]}
2744 Print a table of all breakpoints, watchpoints, and catchpoints set and
2745 not deleted, with the following columns for each breakpoint:
2748 @item Breakpoint Numbers
2750 Breakpoint, watchpoint, or catchpoint.
2752 Whether the breakpoint is marked to be disabled or deleted when hit.
2753 @item Enabled or Disabled
2754 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2755 that are not enabled.
2757 Where the breakpoint is in your program, as a memory address. If the
2758 breakpoint is pending (see below for details) on a future load of a shared library, the address
2759 will be listed as @samp{<PENDING>}.
2761 Where the breakpoint is in the source for your program, as a file and
2762 line number. For a pending breakpoint, the original string passed to
2763 the breakpoint command will be listed as it cannot be resolved until
2764 the appropriate shared library is loaded in the future.
2768 If a breakpoint is conditional, @code{info break} shows the condition on
2769 the line following the affected breakpoint; breakpoint commands, if any,
2770 are listed after that. A pending breakpoint is allowed to have a condition
2771 specified for it. The condition is not parsed for validity until a shared
2772 library is loaded that allows the pending breakpoint to resolve to a
2776 @code{info break} with a breakpoint
2777 number @var{n} as argument lists only that breakpoint. The
2778 convenience variable @code{$_} and the default examining-address for
2779 the @code{x} command are set to the address of the last breakpoint
2780 listed (@pxref{Memory, ,Examining memory}).
2783 @code{info break} displays a count of the number of times the breakpoint
2784 has been hit. This is especially useful in conjunction with the
2785 @code{ignore} command. You can ignore a large number of breakpoint
2786 hits, look at the breakpoint info to see how many times the breakpoint
2787 was hit, and then run again, ignoring one less than that number. This
2788 will get you quickly to the last hit of that breakpoint.
2791 @value{GDBN} allows you to set any number of breakpoints at the same place in
2792 your program. There is nothing silly or meaningless about this. When
2793 the breakpoints are conditional, this is even useful
2794 (@pxref{Conditions, ,Break conditions}).
2796 @cindex pending breakpoints
2797 If a specified breakpoint location cannot be found, it may be due to the fact
2798 that the location is in a shared library that is yet to be loaded. In such
2799 a case, you may want @value{GDBN} to create a special breakpoint (known as
2800 a @dfn{pending breakpoint}) that
2801 attempts to resolve itself in the future when an appropriate shared library
2804 Pending breakpoints are useful to set at the start of your
2805 @value{GDBN} session for locations that you know will be dynamically loaded
2806 later by the program being debugged. When shared libraries are loaded,
2807 a check is made to see if the load resolves any pending breakpoint locations.
2808 If a pending breakpoint location gets resolved,
2809 a regular breakpoint is created and the original pending breakpoint is removed.
2811 @value{GDBN} provides some additional commands for controlling pending
2814 @kindex set breakpoint pending
2815 @kindex show breakpoint pending
2817 @item set breakpoint pending auto
2818 This is the default behavior. When @value{GDBN} cannot find the breakpoint
2819 location, it queries you whether a pending breakpoint should be created.
2821 @item set breakpoint pending on
2822 This indicates that an unrecognized breakpoint location should automatically
2823 result in a pending breakpoint being created.
2825 @item set breakpoint pending off
2826 This indicates that pending breakpoints are not to be created. Any
2827 unrecognized breakpoint location results in an error. This setting does
2828 not affect any pending breakpoints previously created.
2830 @item show breakpoint pending
2831 Show the current behavior setting for creating pending breakpoints.
2834 @cindex operations allowed on pending breakpoints
2835 Normal breakpoint operations apply to pending breakpoints as well. You may
2836 specify a condition for a pending breakpoint and/or commands to run when the
2837 breakpoint is reached. You can also enable or disable
2838 the pending breakpoint. When you specify a condition for a pending breakpoint,
2839 the parsing of the condition will be deferred until the point where the
2840 pending breakpoint location is resolved. Disabling a pending breakpoint
2841 tells @value{GDBN} to not attempt to resolve the breakpoint on any subsequent
2842 shared library load. When a pending breakpoint is re-enabled,
2843 @value{GDBN} checks to see if the location is already resolved.
2844 This is done because any number of shared library loads could have
2845 occurred since the time the breakpoint was disabled and one or more
2846 of these loads could resolve the location.
2848 @cindex negative breakpoint numbers
2849 @cindex internal @value{GDBN} breakpoints
2850 @value{GDBN} itself sometimes sets breakpoints in your program for
2851 special purposes, such as proper handling of @code{longjmp} (in C
2852 programs). These internal breakpoints are assigned negative numbers,
2853 starting with @code{-1}; @samp{info breakpoints} does not display them.
2854 You can see these breakpoints with the @value{GDBN} maintenance command
2855 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2858 @node Set Watchpoints
2859 @subsection Setting watchpoints
2861 @cindex setting watchpoints
2862 You can use a watchpoint to stop execution whenever the value of an
2863 expression changes, without having to predict a particular place where
2866 @cindex software watchpoints
2867 @cindex hardware watchpoints
2868 Depending on your system, watchpoints may be implemented in software or
2869 hardware. @value{GDBN} does software watchpointing by single-stepping your
2870 program and testing the variable's value each time, which is hundreds of
2871 times slower than normal execution. (But this may still be worth it, to
2872 catch errors where you have no clue what part of your program is the
2875 On some systems, such as HP-UX, @sc{gnu}/Linux and most other
2876 x86-based targets, @value{GDBN} includes support for hardware
2877 watchpoints, which do not slow down the running of your program.
2881 @item watch @var{expr}
2882 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2883 is written into by the program and its value changes.
2886 @item rwatch @var{expr}
2887 Set a watchpoint that will break when the value of @var{expr} is read
2891 @item awatch @var{expr}
2892 Set a watchpoint that will break when @var{expr} is either read from
2893 or written into by the program.
2895 @kindex info watchpoints
2896 @item info watchpoints
2897 This command prints a list of watchpoints, breakpoints, and catchpoints;
2898 it is the same as @code{info break} (@pxref{Set Breaks}).
2901 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2902 watchpoints execute very quickly, and the debugger reports a change in
2903 value at the exact instruction where the change occurs. If @value{GDBN}
2904 cannot set a hardware watchpoint, it sets a software watchpoint, which
2905 executes more slowly and reports the change in value at the next
2906 @emph{statement}, not the instruction, after the change occurs.
2908 @vindex can-use-hw-watchpoints
2909 @cindex use only software watchpoints
2910 You can force @value{GDBN} to use only software watchpoints with the
2911 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
2912 zero, @value{GDBN} will never try to use hardware watchpoints, even if
2913 the underlying system supports them. (Note that hardware-assisted
2914 watchpoints that were set @emph{before} setting
2915 @code{can-use-hw-watchpoints} to zero will still use the hardware
2916 mechanism of watching expressiion values.)
2919 @item set can-use-hw-watchpoints
2920 @kindex set can-use-hw-watchpoints
2921 Set whether or not to use hardware watchpoints.
2923 @item show can-use-hw-watchpoints
2924 @kindex show can-use-hw-watchpoints
2925 Show the current mode of using hardware watchpoints.
2928 For remote targets, you can restrict the number of hardware
2929 watchpoints @value{GDBN} will use, see @ref{set remote
2930 hardware-breakpoint-limit}.
2932 When you issue the @code{watch} command, @value{GDBN} reports
2935 Hardware watchpoint @var{num}: @var{expr}
2939 if it was able to set a hardware watchpoint.
2941 Currently, the @code{awatch} and @code{rwatch} commands can only set
2942 hardware watchpoints, because accesses to data that don't change the
2943 value of the watched expression cannot be detected without examining
2944 every instruction as it is being executed, and @value{GDBN} does not do
2945 that currently. If @value{GDBN} finds that it is unable to set a
2946 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2947 will print a message like this:
2950 Expression cannot be implemented with read/access watchpoint.
2953 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2954 data type of the watched expression is wider than what a hardware
2955 watchpoint on the target machine can handle. For example, some systems
2956 can only watch regions that are up to 4 bytes wide; on such systems you
2957 cannot set hardware watchpoints for an expression that yields a
2958 double-precision floating-point number (which is typically 8 bytes
2959 wide). As a work-around, it might be possible to break the large region
2960 into a series of smaller ones and watch them with separate watchpoints.
2962 If you set too many hardware watchpoints, @value{GDBN} might be unable
2963 to insert all of them when you resume the execution of your program.
2964 Since the precise number of active watchpoints is unknown until such
2965 time as the program is about to be resumed, @value{GDBN} might not be
2966 able to warn you about this when you set the watchpoints, and the
2967 warning will be printed only when the program is resumed:
2970 Hardware watchpoint @var{num}: Could not insert watchpoint
2974 If this happens, delete or disable some of the watchpoints.
2976 The SPARClite DSU will generate traps when a program accesses some data
2977 or instruction address that is assigned to the debug registers. For the
2978 data addresses, DSU facilitates the @code{watch} command. However the
2979 hardware breakpoint registers can only take two data watchpoints, and
2980 both watchpoints must be the same kind. For example, you can set two
2981 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2982 @strong{or} two with @code{awatch} commands, but you cannot set one
2983 watchpoint with one command and the other with a different command.
2984 @value{GDBN} will reject the command if you try to mix watchpoints.
2985 Delete or disable unused watchpoint commands before setting new ones.
2987 If you call a function interactively using @code{print} or @code{call},
2988 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2989 kind of breakpoint or the call completes.
2991 @value{GDBN} automatically deletes watchpoints that watch local
2992 (automatic) variables, or expressions that involve such variables, when
2993 they go out of scope, that is, when the execution leaves the block in
2994 which these variables were defined. In particular, when the program
2995 being debugged terminates, @emph{all} local variables go out of scope,
2996 and so only watchpoints that watch global variables remain set. If you
2997 rerun the program, you will need to set all such watchpoints again. One
2998 way of doing that would be to set a code breakpoint at the entry to the
2999 @code{main} function and when it breaks, set all the watchpoints.
3002 @cindex watchpoints and threads
3003 @cindex threads and watchpoints
3004 @emph{Warning:} In multi-thread programs, watchpoints have only limited
3005 usefulness. With the current watchpoint implementation, @value{GDBN}
3006 can only watch the value of an expression @emph{in a single thread}. If
3007 you are confident that the expression can only change due to the current
3008 thread's activity (and if you are also confident that no other thread
3009 can become current), then you can use watchpoints as usual. However,
3010 @value{GDBN} may not notice when a non-current thread's activity changes
3013 @c FIXME: this is almost identical to the previous paragraph.
3014 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
3015 have only limited usefulness. If @value{GDBN} creates a software
3016 watchpoint, it can only watch the value of an expression @emph{in a
3017 single thread}. If you are confident that the expression can only
3018 change due to the current thread's activity (and if you are also
3019 confident that no other thread can become current), then you can use
3020 software watchpoints as usual. However, @value{GDBN} may not notice
3021 when a non-current thread's activity changes the expression. (Hardware
3022 watchpoints, in contrast, watch an expression in all threads.)
3025 @xref{set remote hardware-watchpoint-limit}.
3027 @node Set Catchpoints
3028 @subsection Setting catchpoints
3029 @cindex catchpoints, setting
3030 @cindex exception handlers
3031 @cindex event handling
3033 You can use @dfn{catchpoints} to cause the debugger to stop for certain
3034 kinds of program events, such as C@t{++} exceptions or the loading of a
3035 shared library. Use the @code{catch} command to set a catchpoint.
3039 @item catch @var{event}
3040 Stop when @var{event} occurs. @var{event} can be any of the following:
3043 @cindex stop on C@t{++} exceptions
3044 The throwing of a C@t{++} exception.
3047 The catching of a C@t{++} exception.
3050 @cindex break on fork/exec
3051 A call to @code{exec}. This is currently only available for HP-UX.
3054 A call to @code{fork}. This is currently only available for HP-UX.
3057 A call to @code{vfork}. This is currently only available for HP-UX.
3060 @itemx load @var{libname}
3061 @cindex break on load/unload of shared library
3062 The dynamic loading of any shared library, or the loading of the library
3063 @var{libname}. This is currently only available for HP-UX.
3066 @itemx unload @var{libname}
3067 The unloading of any dynamically loaded shared library, or the unloading
3068 of the library @var{libname}. This is currently only available for HP-UX.
3071 @item tcatch @var{event}
3072 Set a catchpoint that is enabled only for one stop. The catchpoint is
3073 automatically deleted after the first time the event is caught.
3077 Use the @code{info break} command to list the current catchpoints.
3079 There are currently some limitations to C@t{++} exception handling
3080 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
3084 If you call a function interactively, @value{GDBN} normally returns
3085 control to you when the function has finished executing. If the call
3086 raises an exception, however, the call may bypass the mechanism that
3087 returns control to you and cause your program either to abort or to
3088 simply continue running until it hits a breakpoint, catches a signal
3089 that @value{GDBN} is listening for, or exits. This is the case even if
3090 you set a catchpoint for the exception; catchpoints on exceptions are
3091 disabled within interactive calls.
3094 You cannot raise an exception interactively.
3097 You cannot install an exception handler interactively.
3100 @cindex raise exceptions
3101 Sometimes @code{catch} is not the best way to debug exception handling:
3102 if you need to know exactly where an exception is raised, it is better to
3103 stop @emph{before} the exception handler is called, since that way you
3104 can see the stack before any unwinding takes place. If you set a
3105 breakpoint in an exception handler instead, it may not be easy to find
3106 out where the exception was raised.
3108 To stop just before an exception handler is called, you need some
3109 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
3110 raised by calling a library function named @code{__raise_exception}
3111 which has the following ANSI C interface:
3114 /* @var{addr} is where the exception identifier is stored.
3115 @var{id} is the exception identifier. */
3116 void __raise_exception (void **addr, void *id);
3120 To make the debugger catch all exceptions before any stack
3121 unwinding takes place, set a breakpoint on @code{__raise_exception}
3122 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
3124 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
3125 that depends on the value of @var{id}, you can stop your program when
3126 a specific exception is raised. You can use multiple conditional
3127 breakpoints to stop your program when any of a number of exceptions are
3132 @subsection Deleting breakpoints
3134 @cindex clearing breakpoints, watchpoints, catchpoints
3135 @cindex deleting breakpoints, watchpoints, catchpoints
3136 It is often necessary to eliminate a breakpoint, watchpoint, or
3137 catchpoint once it has done its job and you no longer want your program
3138 to stop there. This is called @dfn{deleting} the breakpoint. A
3139 breakpoint that has been deleted no longer exists; it is forgotten.
3141 With the @code{clear} command you can delete breakpoints according to
3142 where they are in your program. With the @code{delete} command you can
3143 delete individual breakpoints, watchpoints, or catchpoints by specifying
3144 their breakpoint numbers.
3146 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
3147 automatically ignores breakpoints on the first instruction to be executed
3148 when you continue execution without changing the execution address.
3153 Delete any breakpoints at the next instruction to be executed in the
3154 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
3155 the innermost frame is selected, this is a good way to delete a
3156 breakpoint where your program just stopped.
3158 @item clear @var{function}
3159 @itemx clear @var{filename}:@var{function}
3160 Delete any breakpoints set at entry to the named @var{function}.
3162 @item clear @var{linenum}
3163 @itemx clear @var{filename}:@var{linenum}
3164 Delete any breakpoints set at or within the code of the specified
3165 @var{linenum} of the specified @var{filename}.
3167 @cindex delete breakpoints
3169 @kindex d @r{(@code{delete})}
3170 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3171 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
3172 ranges specified as arguments. If no argument is specified, delete all
3173 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
3174 confirm off}). You can abbreviate this command as @code{d}.
3178 @subsection Disabling breakpoints
3180 @cindex enable/disable a breakpoint
3181 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
3182 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
3183 it had been deleted, but remembers the information on the breakpoint so
3184 that you can @dfn{enable} it again later.
3186 You disable and enable breakpoints, watchpoints, and catchpoints with
3187 the @code{enable} and @code{disable} commands, optionally specifying one
3188 or more breakpoint numbers as arguments. Use @code{info break} or
3189 @code{info watch} to print a list of breakpoints, watchpoints, and
3190 catchpoints if you do not know which numbers to use.
3192 A breakpoint, watchpoint, or catchpoint can have any of four different
3193 states of enablement:
3197 Enabled. The breakpoint stops your program. A breakpoint set
3198 with the @code{break} command starts out in this state.
3200 Disabled. The breakpoint has no effect on your program.
3202 Enabled once. The breakpoint stops your program, but then becomes
3205 Enabled for deletion. The breakpoint stops your program, but
3206 immediately after it does so it is deleted permanently. A breakpoint
3207 set with the @code{tbreak} command starts out in this state.
3210 You can use the following commands to enable or disable breakpoints,
3211 watchpoints, and catchpoints:
3215 @kindex dis @r{(@code{disable})}
3216 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3217 Disable the specified breakpoints---or all breakpoints, if none are
3218 listed. A disabled breakpoint has no effect but is not forgotten. All
3219 options such as ignore-counts, conditions and commands are remembered in
3220 case the breakpoint is enabled again later. You may abbreviate
3221 @code{disable} as @code{dis}.
3224 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
3225 Enable the specified breakpoints (or all defined breakpoints). They
3226 become effective once again in stopping your program.
3228 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
3229 Enable the specified breakpoints temporarily. @value{GDBN} disables any
3230 of these breakpoints immediately after stopping your program.
3232 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
3233 Enable the specified breakpoints to work once, then die. @value{GDBN}
3234 deletes any of these breakpoints as soon as your program stops there.
3235 Breakpoints set by the @code{tbreak} command start out in this state.
3238 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
3239 @c confusing: tbreak is also initially enabled.
3240 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
3241 ,Setting breakpoints}), breakpoints that you set are initially enabled;
3242 subsequently, they become disabled or enabled only when you use one of
3243 the commands above. (The command @code{until} can set and delete a
3244 breakpoint of its own, but it does not change the state of your other
3245 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
3249 @subsection Break conditions
3250 @cindex conditional breakpoints
3251 @cindex breakpoint conditions
3253 @c FIXME what is scope of break condition expr? Context where wanted?
3254 @c in particular for a watchpoint?
3255 The simplest sort of breakpoint breaks every time your program reaches a
3256 specified place. You can also specify a @dfn{condition} for a
3257 breakpoint. A condition is just a Boolean expression in your
3258 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
3259 a condition evaluates the expression each time your program reaches it,
3260 and your program stops only if the condition is @emph{true}.
3262 This is the converse of using assertions for program validation; in that
3263 situation, you want to stop when the assertion is violated---that is,
3264 when the condition is false. In C, if you want to test an assertion expressed
3265 by the condition @var{assert}, you should set the condition
3266 @samp{! @var{assert}} on the appropriate breakpoint.
3268 Conditions are also accepted for watchpoints; you may not need them,
3269 since a watchpoint is inspecting the value of an expression anyhow---but
3270 it might be simpler, say, to just set a watchpoint on a variable name,
3271 and specify a condition that tests whether the new value is an interesting
3274 Break conditions can have side effects, and may even call functions in
3275 your program. This can be useful, for example, to activate functions
3276 that log program progress, or to use your own print functions to
3277 format special data structures. The effects are completely predictable
3278 unless there is another enabled breakpoint at the same address. (In
3279 that case, @value{GDBN} might see the other breakpoint first and stop your
3280 program without checking the condition of this one.) Note that
3281 breakpoint commands are usually more convenient and flexible than break
3283 purpose of performing side effects when a breakpoint is reached
3284 (@pxref{Break Commands, ,Breakpoint command lists}).
3286 Break conditions can be specified when a breakpoint is set, by using
3287 @samp{if} in the arguments to the @code{break} command. @xref{Set
3288 Breaks, ,Setting breakpoints}. They can also be changed at any time
3289 with the @code{condition} command.
3291 You can also use the @code{if} keyword with the @code{watch} command.
3292 The @code{catch} command does not recognize the @code{if} keyword;
3293 @code{condition} is the only way to impose a further condition on a
3298 @item condition @var{bnum} @var{expression}
3299 Specify @var{expression} as the break condition for breakpoint,
3300 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3301 breakpoint @var{bnum} stops your program only if the value of
3302 @var{expression} is true (nonzero, in C). When you use
3303 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3304 syntactic correctness, and to determine whether symbols in it have
3305 referents in the context of your breakpoint. If @var{expression} uses
3306 symbols not referenced in the context of the breakpoint, @value{GDBN}
3307 prints an error message:
3310 No symbol "foo" in current context.
3315 not actually evaluate @var{expression} at the time the @code{condition}
3316 command (or a command that sets a breakpoint with a condition, like
3317 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3319 @item condition @var{bnum}
3320 Remove the condition from breakpoint number @var{bnum}. It becomes
3321 an ordinary unconditional breakpoint.
3324 @cindex ignore count (of breakpoint)
3325 A special case of a breakpoint condition is to stop only when the
3326 breakpoint has been reached a certain number of times. This is so
3327 useful that there is a special way to do it, using the @dfn{ignore
3328 count} of the breakpoint. Every breakpoint has an ignore count, which
3329 is an integer. Most of the time, the ignore count is zero, and
3330 therefore has no effect. But if your program reaches a breakpoint whose
3331 ignore count is positive, then instead of stopping, it just decrements
3332 the ignore count by one and continues. As a result, if the ignore count
3333 value is @var{n}, the breakpoint does not stop the next @var{n} times
3334 your program reaches it.
3338 @item ignore @var{bnum} @var{count}
3339 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3340 The next @var{count} times the breakpoint is reached, your program's
3341 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3344 To make the breakpoint stop the next time it is reached, specify
3347 When you use @code{continue} to resume execution of your program from a
3348 breakpoint, you can specify an ignore count directly as an argument to
3349 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3350 Stepping,,Continuing and stepping}.
3352 If a breakpoint has a positive ignore count and a condition, the
3353 condition is not checked. Once the ignore count reaches zero,
3354 @value{GDBN} resumes checking the condition.
3356 You could achieve the effect of the ignore count with a condition such
3357 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3358 is decremented each time. @xref{Convenience Vars, ,Convenience
3362 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3365 @node Break Commands
3366 @subsection Breakpoint command lists
3368 @cindex breakpoint commands
3369 You can give any breakpoint (or watchpoint or catchpoint) a series of
3370 commands to execute when your program stops due to that breakpoint. For
3371 example, you might want to print the values of certain expressions, or
3372 enable other breakpoints.
3377 @item commands @r{[}@var{bnum}@r{]}
3378 @itemx @dots{} @var{command-list} @dots{}
3380 Specify a list of commands for breakpoint number @var{bnum}. The commands
3381 themselves appear on the following lines. Type a line containing just
3382 @code{end} to terminate the commands.
3384 To remove all commands from a breakpoint, type @code{commands} and
3385 follow it immediately with @code{end}; that is, give no commands.
3387 With no @var{bnum} argument, @code{commands} refers to the last
3388 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3389 recently encountered).
3392 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3393 disabled within a @var{command-list}.
3395 You can use breakpoint commands to start your program up again. Simply
3396 use the @code{continue} command, or @code{step}, or any other command
3397 that resumes execution.
3399 Any other commands in the command list, after a command that resumes
3400 execution, are ignored. This is because any time you resume execution
3401 (even with a simple @code{next} or @code{step}), you may encounter
3402 another breakpoint---which could have its own command list, leading to
3403 ambiguities about which list to execute.
3406 If the first command you specify in a command list is @code{silent}, the
3407 usual message about stopping at a breakpoint is not printed. This may
3408 be desirable for breakpoints that are to print a specific message and
3409 then continue. If none of the remaining commands print anything, you
3410 see no sign that the breakpoint was reached. @code{silent} is
3411 meaningful only at the beginning of a breakpoint command list.
3413 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3414 print precisely controlled output, and are often useful in silent
3415 breakpoints. @xref{Output, ,Commands for controlled output}.
3417 For example, here is how you could use breakpoint commands to print the
3418 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3424 printf "x is %d\n",x
3429 One application for breakpoint commands is to compensate for one bug so
3430 you can test for another. Put a breakpoint just after the erroneous line
3431 of code, give it a condition to detect the case in which something
3432 erroneous has been done, and give it commands to assign correct values
3433 to any variables that need them. End with the @code{continue} command
3434 so that your program does not stop, and start with the @code{silent}
3435 command so that no output is produced. Here is an example:
3446 @node Breakpoint Menus
3447 @subsection Breakpoint menus
3449 @cindex symbol overloading
3451 Some programming languages (notably C@t{++} and Objective-C) permit a
3452 single function name
3453 to be defined several times, for application in different contexts.
3454 This is called @dfn{overloading}. When a function name is overloaded,
3455 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3456 a breakpoint. If you realize this is a problem, you can use
3457 something like @samp{break @var{function}(@var{types})} to specify which
3458 particular version of the function you want. Otherwise, @value{GDBN} offers
3459 you a menu of numbered choices for different possible breakpoints, and
3460 waits for your selection with the prompt @samp{>}. The first two
3461 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3462 sets a breakpoint at each definition of @var{function}, and typing
3463 @kbd{0} aborts the @code{break} command without setting any new
3466 For example, the following session excerpt shows an attempt to set a
3467 breakpoint at the overloaded symbol @code{String::after}.
3468 We choose three particular definitions of that function name:
3470 @c FIXME! This is likely to change to show arg type lists, at least
3473 (@value{GDBP}) b String::after
3476 [2] file:String.cc; line number:867
3477 [3] file:String.cc; line number:860
3478 [4] file:String.cc; line number:875
3479 [5] file:String.cc; line number:853
3480 [6] file:String.cc; line number:846
3481 [7] file:String.cc; line number:735
3483 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3484 Breakpoint 2 at 0xb344: file String.cc, line 875.
3485 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3486 Multiple breakpoints were set.
3487 Use the "delete" command to delete unwanted
3493 @c @ifclear BARETARGET
3494 @node Error in Breakpoints
3495 @subsection ``Cannot insert breakpoints''
3497 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3499 Under some operating systems, breakpoints cannot be used in a program if
3500 any other process is running that program. In this situation,
3501 attempting to run or continue a program with a breakpoint causes
3502 @value{GDBN} to print an error message:
3505 Cannot insert breakpoints.
3506 The same program may be running in another process.
3509 When this happens, you have three ways to proceed:
3513 Remove or disable the breakpoints, then continue.
3516 Suspend @value{GDBN}, and copy the file containing your program to a new
3517 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3518 that @value{GDBN} should run your program under that name.
3519 Then start your program again.
3522 Relink your program so that the text segment is nonsharable, using the
3523 linker option @samp{-N}. The operating system limitation may not apply
3524 to nonsharable executables.
3528 A similar message can be printed if you request too many active
3529 hardware-assisted breakpoints and watchpoints:
3531 @c FIXME: the precise wording of this message may change; the relevant
3532 @c source change is not committed yet (Sep 3, 1999).
3534 Stopped; cannot insert breakpoints.
3535 You may have requested too many hardware breakpoints and watchpoints.
3539 This message is printed when you attempt to resume the program, since
3540 only then @value{GDBN} knows exactly how many hardware breakpoints and
3541 watchpoints it needs to insert.
3543 When this message is printed, you need to disable or remove some of the
3544 hardware-assisted breakpoints and watchpoints, and then continue.
3546 @node Breakpoint related warnings
3547 @subsection ``Breakpoint address adjusted...''
3548 @cindex breakpoint address adjusted
3550 Some processor architectures place constraints on the addresses at
3551 which breakpoints may be placed. For architectures thus constrained,
3552 @value{GDBN} will attempt to adjust the breakpoint's address to comply
3553 with the constraints dictated by the architecture.
3555 One example of such an architecture is the Fujitsu FR-V. The FR-V is
3556 a VLIW architecture in which a number of RISC-like instructions may be
3557 bundled together for parallel execution. The FR-V architecture
3558 constrains the location of a breakpoint instruction within such a
3559 bundle to the instruction with the lowest address. @value{GDBN}
3560 honors this constraint by adjusting a breakpoint's address to the
3561 first in the bundle.
3563 It is not uncommon for optimized code to have bundles which contain
3564 instructions from different source statements, thus it may happen that
3565 a breakpoint's address will be adjusted from one source statement to
3566 another. Since this adjustment may significantly alter @value{GDBN}'s
3567 breakpoint related behavior from what the user expects, a warning is
3568 printed when the breakpoint is first set and also when the breakpoint
3571 A warning like the one below is printed when setting a breakpoint
3572 that's been subject to address adjustment:
3575 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
3578 Such warnings are printed both for user settable and @value{GDBN}'s
3579 internal breakpoints. If you see one of these warnings, you should
3580 verify that a breakpoint set at the adjusted address will have the
3581 desired affect. If not, the breakpoint in question may be removed and
3582 other breakpoints may be set which will have the desired behavior.
3583 E.g., it may be sufficient to place the breakpoint at a later
3584 instruction. A conditional breakpoint may also be useful in some
3585 cases to prevent the breakpoint from triggering too often.
3587 @value{GDBN} will also issue a warning when stopping at one of these
3588 adjusted breakpoints:
3591 warning: Breakpoint 1 address previously adjusted from 0x00010414
3595 When this warning is encountered, it may be too late to take remedial
3596 action except in cases where the breakpoint is hit earlier or more
3597 frequently than expected.
3599 @node Continuing and Stepping
3600 @section Continuing and stepping
3604 @cindex resuming execution
3605 @dfn{Continuing} means resuming program execution until your program
3606 completes normally. In contrast, @dfn{stepping} means executing just
3607 one more ``step'' of your program, where ``step'' may mean either one
3608 line of source code, or one machine instruction (depending on what
3609 particular command you use). Either when continuing or when stepping,
3610 your program may stop even sooner, due to a breakpoint or a signal. (If
3611 it stops due to a signal, you may want to use @code{handle}, or use
3612 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3616 @kindex c @r{(@code{continue})}
3617 @kindex fg @r{(resume foreground execution)}
3618 @item continue @r{[}@var{ignore-count}@r{]}
3619 @itemx c @r{[}@var{ignore-count}@r{]}
3620 @itemx fg @r{[}@var{ignore-count}@r{]}
3621 Resume program execution, at the address where your program last stopped;
3622 any breakpoints set at that address are bypassed. The optional argument
3623 @var{ignore-count} allows you to specify a further number of times to
3624 ignore a breakpoint at this location; its effect is like that of
3625 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3627 The argument @var{ignore-count} is meaningful only when your program
3628 stopped due to a breakpoint. At other times, the argument to
3629 @code{continue} is ignored.
3631 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3632 debugged program is deemed to be the foreground program) are provided
3633 purely for convenience, and have exactly the same behavior as
3637 To resume execution at a different place, you can use @code{return}
3638 (@pxref{Returning, ,Returning from a function}) to go back to the
3639 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3640 different address}) to go to an arbitrary location in your program.
3642 A typical technique for using stepping is to set a breakpoint
3643 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3644 beginning of the function or the section of your program where a problem
3645 is believed to lie, run your program until it stops at that breakpoint,
3646 and then step through the suspect area, examining the variables that are
3647 interesting, until you see the problem happen.
3651 @kindex s @r{(@code{step})}
3653 Continue running your program until control reaches a different source
3654 line, then stop it and return control to @value{GDBN}. This command is
3655 abbreviated @code{s}.
3658 @c "without debugging information" is imprecise; actually "without line
3659 @c numbers in the debugging information". (gcc -g1 has debugging info but
3660 @c not line numbers). But it seems complex to try to make that
3661 @c distinction here.
3662 @emph{Warning:} If you use the @code{step} command while control is
3663 within a function that was compiled without debugging information,
3664 execution proceeds until control reaches a function that does have
3665 debugging information. Likewise, it will not step into a function which
3666 is compiled without debugging information. To step through functions
3667 without debugging information, use the @code{stepi} command, described
3671 The @code{step} command only stops at the first instruction of a source
3672 line. This prevents the multiple stops that could otherwise occur in
3673 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3674 to stop if a function that has debugging information is called within
3675 the line. In other words, @code{step} @emph{steps inside} any functions
3676 called within the line.
3678 Also, the @code{step} command only enters a function if there is line
3679 number information for the function. Otherwise it acts like the
3680 @code{next} command. This avoids problems when using @code{cc -gl}
3681 on MIPS machines. Previously, @code{step} entered subroutines if there
3682 was any debugging information about the routine.
3684 @item step @var{count}
3685 Continue running as in @code{step}, but do so @var{count} times. If a
3686 breakpoint is reached, or a signal not related to stepping occurs before
3687 @var{count} steps, stepping stops right away.
3690 @kindex n @r{(@code{next})}
3691 @item next @r{[}@var{count}@r{]}
3692 Continue to the next source line in the current (innermost) stack frame.
3693 This is similar to @code{step}, but function calls that appear within
3694 the line of code are executed without stopping. Execution stops when
3695 control reaches a different line of code at the original stack level
3696 that was executing when you gave the @code{next} command. This command
3697 is abbreviated @code{n}.
3699 An argument @var{count} is a repeat count, as for @code{step}.
3702 @c FIX ME!! Do we delete this, or is there a way it fits in with
3703 @c the following paragraph? --- Vctoria
3705 @c @code{next} within a function that lacks debugging information acts like
3706 @c @code{step}, but any function calls appearing within the code of the
3707 @c function are executed without stopping.
3709 The @code{next} command only stops at the first instruction of a
3710 source line. This prevents multiple stops that could otherwise occur in
3711 @code{switch} statements, @code{for} loops, etc.
3713 @kindex set step-mode
3715 @cindex functions without line info, and stepping
3716 @cindex stepping into functions with no line info
3717 @itemx set step-mode on
3718 The @code{set step-mode on} command causes the @code{step} command to
3719 stop at the first instruction of a function which contains no debug line
3720 information rather than stepping over it.
3722 This is useful in cases where you may be interested in inspecting the
3723 machine instructions of a function which has no symbolic info and do not
3724 want @value{GDBN} to automatically skip over this function.
3726 @item set step-mode off
3727 Causes the @code{step} command to step over any functions which contains no
3728 debug information. This is the default.
3730 @item show step-mode
3731 Show whether @value{GDBN} will stop in or step over functions without
3732 source line debug information.
3736 Continue running until just after function in the selected stack frame
3737 returns. Print the returned value (if any).
3739 Contrast this with the @code{return} command (@pxref{Returning,
3740 ,Returning from a function}).
3743 @kindex u @r{(@code{until})}
3744 @cindex run until specified location
3747 Continue running until a source line past the current line, in the
3748 current stack frame, is reached. This command is used to avoid single
3749 stepping through a loop more than once. It is like the @code{next}
3750 command, except that when @code{until} encounters a jump, it
3751 automatically continues execution until the program counter is greater
3752 than the address of the jump.
3754 This means that when you reach the end of a loop after single stepping
3755 though it, @code{until} makes your program continue execution until it
3756 exits the loop. In contrast, a @code{next} command at the end of a loop
3757 simply steps back to the beginning of the loop, which forces you to step
3758 through the next iteration.
3760 @code{until} always stops your program if it attempts to exit the current
3763 @code{until} may produce somewhat counterintuitive results if the order
3764 of machine code does not match the order of the source lines. For
3765 example, in the following excerpt from a debugging session, the @code{f}
3766 (@code{frame}) command shows that execution is stopped at line
3767 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3771 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3773 (@value{GDBP}) until
3774 195 for ( ; argc > 0; NEXTARG) @{
3777 This happened because, for execution efficiency, the compiler had
3778 generated code for the loop closure test at the end, rather than the
3779 start, of the loop---even though the test in a C @code{for}-loop is
3780 written before the body of the loop. The @code{until} command appeared
3781 to step back to the beginning of the loop when it advanced to this
3782 expression; however, it has not really gone to an earlier
3783 statement---not in terms of the actual machine code.
3785 @code{until} with no argument works by means of single
3786 instruction stepping, and hence is slower than @code{until} with an
3789 @item until @var{location}
3790 @itemx u @var{location}
3791 Continue running your program until either the specified location is
3792 reached, or the current stack frame returns. @var{location} is any of
3793 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3794 ,Setting breakpoints}). This form of the command uses breakpoints, and
3795 hence is quicker than @code{until} without an argument. The specified
3796 location is actually reached only if it is in the current frame. This
3797 implies that @code{until} can be used to skip over recursive function
3798 invocations. For instance in the code below, if the current location is
3799 line @code{96}, issuing @code{until 99} will execute the program up to
3800 line @code{99} in the same invocation of factorial, i.e. after the inner
3801 invocations have returned.
3804 94 int factorial (int value)
3806 96 if (value > 1) @{
3807 97 value *= factorial (value - 1);
3814 @kindex advance @var{location}
3815 @itemx advance @var{location}
3816 Continue running the program up to the given @var{location}. An argument is
3817 required, which should be of the same form as arguments for the @code{break}
3818 command. Execution will also stop upon exit from the current stack
3819 frame. This command is similar to @code{until}, but @code{advance} will
3820 not skip over recursive function calls, and the target location doesn't
3821 have to be in the same frame as the current one.
3825 @kindex si @r{(@code{stepi})}
3827 @itemx stepi @var{arg}
3829 Execute one machine instruction, then stop and return to the debugger.
3831 It is often useful to do @samp{display/i $pc} when stepping by machine
3832 instructions. This makes @value{GDBN} automatically display the next
3833 instruction to be executed, each time your program stops. @xref{Auto
3834 Display,, Automatic display}.
3836 An argument is a repeat count, as in @code{step}.
3840 @kindex ni @r{(@code{nexti})}
3842 @itemx nexti @var{arg}
3844 Execute one machine instruction, but if it is a function call,
3845 proceed until the function returns.
3847 An argument is a repeat count, as in @code{next}.
3854 A signal is an asynchronous event that can happen in a program. The
3855 operating system defines the possible kinds of signals, and gives each
3856 kind a name and a number. For example, in Unix @code{SIGINT} is the
3857 signal a program gets when you type an interrupt character (often @kbd{C-c});
3858 @code{SIGSEGV} is the signal a program gets from referencing a place in
3859 memory far away from all the areas in use; @code{SIGALRM} occurs when
3860 the alarm clock timer goes off (which happens only if your program has
3861 requested an alarm).
3863 @cindex fatal signals
3864 Some signals, including @code{SIGALRM}, are a normal part of the
3865 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3866 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3867 program has not specified in advance some other way to handle the signal.
3868 @code{SIGINT} does not indicate an error in your program, but it is normally
3869 fatal so it can carry out the purpose of the interrupt: to kill the program.
3871 @value{GDBN} has the ability to detect any occurrence of a signal in your
3872 program. You can tell @value{GDBN} in advance what to do for each kind of
3875 @cindex handling signals
3876 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3877 @code{SIGALRM} be silently passed to your program
3878 (so as not to interfere with their role in the program's functioning)
3879 but to stop your program immediately whenever an error signal happens.
3880 You can change these settings with the @code{handle} command.
3883 @kindex info signals
3887 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3888 handle each one. You can use this to see the signal numbers of all
3889 the defined types of signals.
3891 @code{info handle} is an alias for @code{info signals}.
3894 @item handle @var{signal} @var{keywords}@dots{}
3895 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3896 can be the number of a signal or its name (with or without the
3897 @samp{SIG} at the beginning); a list of signal numbers of the form
3898 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3899 known signals. The @var{keywords} say what change to make.
3903 The keywords allowed by the @code{handle} command can be abbreviated.
3904 Their full names are:
3908 @value{GDBN} should not stop your program when this signal happens. It may
3909 still print a message telling you that the signal has come in.
3912 @value{GDBN} should stop your program when this signal happens. This implies
3913 the @code{print} keyword as well.
3916 @value{GDBN} should print a message when this signal happens.
3919 @value{GDBN} should not mention the occurrence of the signal at all. This
3920 implies the @code{nostop} keyword as well.
3924 @value{GDBN} should allow your program to see this signal; your program
3925 can handle the signal, or else it may terminate if the signal is fatal
3926 and not handled. @code{pass} and @code{noignore} are synonyms.
3930 @value{GDBN} should not allow your program to see this signal.
3931 @code{nopass} and @code{ignore} are synonyms.
3935 When a signal stops your program, the signal is not visible to the
3937 continue. Your program sees the signal then, if @code{pass} is in
3938 effect for the signal in question @emph{at that time}. In other words,
3939 after @value{GDBN} reports a signal, you can use the @code{handle}
3940 command with @code{pass} or @code{nopass} to control whether your
3941 program sees that signal when you continue.
3943 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3944 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3945 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3948 You can also use the @code{signal} command to prevent your program from
3949 seeing a signal, or cause it to see a signal it normally would not see,
3950 or to give it any signal at any time. For example, if your program stopped
3951 due to some sort of memory reference error, you might store correct
3952 values into the erroneous variables and continue, hoping to see more
3953 execution; but your program would probably terminate immediately as
3954 a result of the fatal signal once it saw the signal. To prevent this,
3955 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3959 @section Stopping and starting multi-thread programs
3961 When your program has multiple threads (@pxref{Threads,, Debugging
3962 programs with multiple threads}), you can choose whether to set
3963 breakpoints on all threads, or on a particular thread.
3966 @cindex breakpoints and threads
3967 @cindex thread breakpoints
3968 @kindex break @dots{} thread @var{threadno}
3969 @item break @var{linespec} thread @var{threadno}
3970 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3971 @var{linespec} specifies source lines; there are several ways of
3972 writing them, but the effect is always to specify some source line.
3974 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3975 to specify that you only want @value{GDBN} to stop the program when a
3976 particular thread reaches this breakpoint. @var{threadno} is one of the
3977 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3978 column of the @samp{info threads} display.
3980 If you do not specify @samp{thread @var{threadno}} when you set a
3981 breakpoint, the breakpoint applies to @emph{all} threads of your
3984 You can use the @code{thread} qualifier on conditional breakpoints as
3985 well; in this case, place @samp{thread @var{threadno}} before the
3986 breakpoint condition, like this:
3989 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3994 @cindex stopped threads
3995 @cindex threads, stopped
3996 Whenever your program stops under @value{GDBN} for any reason,
3997 @emph{all} threads of execution stop, not just the current thread. This
3998 allows you to examine the overall state of the program, including
3999 switching between threads, without worrying that things may change
4002 @cindex thread breakpoints and system calls
4003 @cindex system calls and thread breakpoints
4004 @cindex premature return from system calls
4005 There is an unfortunate side effect. If one thread stops for a
4006 breakpoint, or for some other reason, and another thread is blocked in a
4007 system call, then the system call may return prematurely. This is a
4008 consequence of the interaction between multiple threads and the signals
4009 that @value{GDBN} uses to implement breakpoints and other events that
4012 To handle this problem, your program should check the return value of
4013 each system call and react appropriately. This is good programming
4016 For example, do not write code like this:
4022 The call to @code{sleep} will return early if a different thread stops
4023 at a breakpoint or for some other reason.
4025 Instead, write this:
4030 unslept = sleep (unslept);
4033 A system call is allowed to return early, so the system is still
4034 conforming to its specification. But @value{GDBN} does cause your
4035 multi-threaded program to behave differently than it would without
4038 Also, @value{GDBN} uses internal breakpoints in the thread library to
4039 monitor certain events such as thread creation and thread destruction.
4040 When such an event happens, a system call in another thread may return
4041 prematurely, even though your program does not appear to stop.
4043 @cindex continuing threads
4044 @cindex threads, continuing
4045 Conversely, whenever you restart the program, @emph{all} threads start
4046 executing. @emph{This is true even when single-stepping} with commands
4047 like @code{step} or @code{next}.
4049 In particular, @value{GDBN} cannot single-step all threads in lockstep.
4050 Since thread scheduling is up to your debugging target's operating
4051 system (not controlled by @value{GDBN}), other threads may
4052 execute more than one statement while the current thread completes a
4053 single step. Moreover, in general other threads stop in the middle of a
4054 statement, rather than at a clean statement boundary, when the program
4057 You might even find your program stopped in another thread after
4058 continuing or even single-stepping. This happens whenever some other
4059 thread runs into a breakpoint, a signal, or an exception before the
4060 first thread completes whatever you requested.
4062 On some OSes, you can lock the OS scheduler and thus allow only a single
4066 @item set scheduler-locking @var{mode}
4067 @cindex scheduler locking mode
4068 @cindex lock scheduler
4069 Set the scheduler locking mode. If it is @code{off}, then there is no
4070 locking and any thread may run at any time. If @code{on}, then only the
4071 current thread may run when the inferior is resumed. The @code{step}
4072 mode optimizes for single-stepping. It stops other threads from
4073 ``seizing the prompt'' by preempting the current thread while you are
4074 stepping. Other threads will only rarely (or never) get a chance to run
4075 when you step. They are more likely to run when you @samp{next} over a
4076 function call, and they are completely free to run when you use commands
4077 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
4078 thread hits a breakpoint during its timeslice, they will never steal the
4079 @value{GDBN} prompt away from the thread that you are debugging.
4081 @item show scheduler-locking
4082 Display the current scheduler locking mode.
4087 @chapter Examining the Stack
4089 When your program has stopped, the first thing you need to know is where it
4090 stopped and how it got there.
4093 Each time your program performs a function call, information about the call
4095 That information includes the location of the call in your program,
4096 the arguments of the call,
4097 and the local variables of the function being called.
4098 The information is saved in a block of data called a @dfn{stack frame}.
4099 The stack frames are allocated in a region of memory called the @dfn{call
4102 When your program stops, the @value{GDBN} commands for examining the
4103 stack allow you to see all of this information.
4105 @cindex selected frame
4106 One of the stack frames is @dfn{selected} by @value{GDBN} and many
4107 @value{GDBN} commands refer implicitly to the selected frame. In
4108 particular, whenever you ask @value{GDBN} for the value of a variable in
4109 your program, the value is found in the selected frame. There are
4110 special @value{GDBN} commands to select whichever frame you are
4111 interested in. @xref{Selection, ,Selecting a frame}.
4113 When your program stops, @value{GDBN} automatically selects the
4114 currently executing frame and describes it briefly, similar to the
4115 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
4118 * Frames:: Stack frames
4119 * Backtrace:: Backtraces
4120 * Selection:: Selecting a frame
4121 * Frame Info:: Information on a frame
4126 @section Stack frames
4128 @cindex frame, definition
4130 The call stack is divided up into contiguous pieces called @dfn{stack
4131 frames}, or @dfn{frames} for short; each frame is the data associated
4132 with one call to one function. The frame contains the arguments given
4133 to the function, the function's local variables, and the address at
4134 which the function is executing.
4136 @cindex initial frame
4137 @cindex outermost frame
4138 @cindex innermost frame
4139 When your program is started, the stack has only one frame, that of the
4140 function @code{main}. This is called the @dfn{initial} frame or the
4141 @dfn{outermost} frame. Each time a function is called, a new frame is
4142 made. Each time a function returns, the frame for that function invocation
4143 is eliminated. If a function is recursive, there can be many frames for
4144 the same function. The frame for the function in which execution is
4145 actually occurring is called the @dfn{innermost} frame. This is the most
4146 recently created of all the stack frames that still exist.
4148 @cindex frame pointer
4149 Inside your program, stack frames are identified by their addresses. A
4150 stack frame consists of many bytes, each of which has its own address; each
4151 kind of computer has a convention for choosing one byte whose
4152 address serves as the address of the frame. Usually this address is kept
4153 in a register called the @dfn{frame pointer register} while execution is
4154 going on in that frame.
4156 @cindex frame number
4157 @value{GDBN} assigns numbers to all existing stack frames, starting with
4158 zero for the innermost frame, one for the frame that called it,
4159 and so on upward. These numbers do not really exist in your program;
4160 they are assigned by @value{GDBN} to give you a way of designating stack
4161 frames in @value{GDBN} commands.
4163 @c The -fomit-frame-pointer below perennially causes hbox overflow
4164 @c underflow problems.
4165 @cindex frameless execution
4166 Some compilers provide a way to compile functions so that they operate
4167 without stack frames. (For example, the @value{GCC} option
4169 @samp{-fomit-frame-pointer}
4171 generates functions without a frame.)
4172 This is occasionally done with heavily used library functions to save
4173 the frame setup time. @value{GDBN} has limited facilities for dealing
4174 with these function invocations. If the innermost function invocation
4175 has no stack frame, @value{GDBN} nevertheless regards it as though
4176 it had a separate frame, which is numbered zero as usual, allowing
4177 correct tracing of the function call chain. However, @value{GDBN} has
4178 no provision for frameless functions elsewhere in the stack.
4181 @kindex frame@r{, command}
4182 @cindex current stack frame
4183 @item frame @var{args}
4184 The @code{frame} command allows you to move from one stack frame to another,
4185 and to print the stack frame you select. @var{args} may be either the
4186 address of the frame or the stack frame number. Without an argument,
4187 @code{frame} prints the current stack frame.
4189 @kindex select-frame
4190 @cindex selecting frame silently
4192 The @code{select-frame} command allows you to move from one stack frame
4193 to another without printing the frame. This is the silent version of
4201 @cindex call stack traces
4202 A backtrace is a summary of how your program got where it is. It shows one
4203 line per frame, for many frames, starting with the currently executing
4204 frame (frame zero), followed by its caller (frame one), and on up the
4209 @kindex bt @r{(@code{backtrace})}
4212 Print a backtrace of the entire stack: one line per frame for all
4213 frames in the stack.
4215 You can stop the backtrace at any time by typing the system interrupt
4216 character, normally @kbd{C-c}.
4218 @item backtrace @var{n}
4220 Similar, but print only the innermost @var{n} frames.
4222 @item backtrace -@var{n}
4224 Similar, but print only the outermost @var{n} frames.
4226 @item backtrace full
4227 Print the values of the local variables also.
4233 The names @code{where} and @code{info stack} (abbreviated @code{info s})
4234 are additional aliases for @code{backtrace}.
4236 Each line in the backtrace shows the frame number and the function name.
4237 The program counter value is also shown---unless you use @code{set
4238 print address off}. The backtrace also shows the source file name and
4239 line number, as well as the arguments to the function. The program
4240 counter value is omitted if it is at the beginning of the code for that
4243 Here is an example of a backtrace. It was made with the command
4244 @samp{bt 3}, so it shows the innermost three frames.
4248 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4250 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
4251 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
4253 (More stack frames follow...)
4258 The display for frame zero does not begin with a program counter
4259 value, indicating that your program has stopped at the beginning of the
4260 code for line @code{993} of @code{builtin.c}.
4262 @cindex value optimized out, in backtrace
4263 @cindex function call arguments, optimized out
4264 If your program was compiled with optimizations, some compilers will
4265 optimize away arguments passed to functions if those arguments are
4266 never used after the call. Such optimizations generate code that
4267 passes arguments through registers, but doesn't store those arguments
4268 in the stack frame. @value{GDBN} has no way of displaying such
4269 arguments in stack frames other than the innermost one. Here's what
4270 such a backtrace might look like:
4274 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
4276 #1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242
4277 #2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08)
4279 (More stack frames follow...)
4284 The values of arguments that were not saved in their stack frames are
4285 shown as @samp{<value optimized out>}.
4287 If you need to display the values of such optimized-out arguments,
4288 either deduce that from other variables whose values depend on the one
4289 you are interested in, or recompile without optimizations.
4291 @cindex backtrace beyond @code{main} function
4292 @cindex program entry point
4293 @cindex startup code, and backtrace
4294 Most programs have a standard user entry point---a place where system
4295 libraries and startup code transition into user code. For C this is
4296 @code{main}. When @value{GDBN} finds the entry function in a backtrace
4297 it will terminate the backtrace, to avoid tracing into highly
4298 system-specific (and generally uninteresting) code.
4300 If you need to examine the startup code, or limit the number of levels
4301 in a backtrace, you can change this behavior:
4304 @item set backtrace past-main
4305 @itemx set backtrace past-main on
4306 @kindex set backtrace
4307 Backtraces will continue past the user entry point.
4309 @item set backtrace past-main off
4310 Backtraces will stop when they encounter the user entry point. This is the
4313 @item show backtrace past-main
4314 @kindex show backtrace
4315 Display the current user entry point backtrace policy.
4317 @item set backtrace past-entry
4318 @itemx set backtrace past-entry on
4319 Backtraces will continue past the internal entry point of an application.
4320 This entry point is encoded by the linker when the application is built,
4321 and is likely before the user entry point @code{main} (or equivalent) is called.
4323 @item set backtrace past-entry off
4324 Backtraces will stop when they encouter the internal entry point of an
4325 application. This is the default.
4327 @item show backtrace past-entry
4328 Display the current internal entry point backtrace policy.
4330 @item set backtrace limit @var{n}
4331 @itemx set backtrace limit 0
4332 @cindex backtrace limit
4333 Limit the backtrace to @var{n} levels. A value of zero means
4336 @item show backtrace limit
4337 Display the current limit on backtrace levels.
4341 @section Selecting a frame
4343 Most commands for examining the stack and other data in your program work on
4344 whichever stack frame is selected at the moment. Here are the commands for
4345 selecting a stack frame; all of them finish by printing a brief description
4346 of the stack frame just selected.
4349 @kindex frame@r{, selecting}
4350 @kindex f @r{(@code{frame})}
4353 Select frame number @var{n}. Recall that frame zero is the innermost
4354 (currently executing) frame, frame one is the frame that called the
4355 innermost one, and so on. The highest-numbered frame is the one for
4358 @item frame @var{addr}
4360 Select the frame at address @var{addr}. This is useful mainly if the
4361 chaining of stack frames has been damaged by a bug, making it
4362 impossible for @value{GDBN} to assign numbers properly to all frames. In
4363 addition, this can be useful when your program has multiple stacks and
4364 switches between them.
4366 On the SPARC architecture, @code{frame} needs two addresses to
4367 select an arbitrary frame: a frame pointer and a stack pointer.
4369 On the MIPS and Alpha architecture, it needs two addresses: a stack
4370 pointer and a program counter.
4372 On the 29k architecture, it needs three addresses: a register stack
4373 pointer, a program counter, and a memory stack pointer.
4374 @c note to future updaters: this is conditioned on a flag
4375 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
4376 @c as of 27 Jan 1994.
4380 Move @var{n} frames up the stack. For positive numbers @var{n}, this
4381 advances toward the outermost frame, to higher frame numbers, to frames
4382 that have existed longer. @var{n} defaults to one.
4385 @kindex do @r{(@code{down})}
4387 Move @var{n} frames down the stack. For positive numbers @var{n}, this
4388 advances toward the innermost frame, to lower frame numbers, to frames
4389 that were created more recently. @var{n} defaults to one. You may
4390 abbreviate @code{down} as @code{do}.
4393 All of these commands end by printing two lines of output describing the
4394 frame. The first line shows the frame number, the function name, the
4395 arguments, and the source file and line number of execution in that
4396 frame. The second line shows the text of that source line.
4404 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
4406 10 read_input_file (argv[i]);
4410 After such a printout, the @code{list} command with no arguments
4411 prints ten lines centered on the point of execution in the frame.
4412 You can also edit the program at the point of execution with your favorite
4413 editing program by typing @code{edit}.
4414 @xref{List, ,Printing source lines},
4418 @kindex down-silently
4420 @item up-silently @var{n}
4421 @itemx down-silently @var{n}
4422 These two commands are variants of @code{up} and @code{down},
4423 respectively; they differ in that they do their work silently, without
4424 causing display of the new frame. They are intended primarily for use
4425 in @value{GDBN} command scripts, where the output might be unnecessary and
4430 @section Information about a frame
4432 There are several other commands to print information about the selected
4438 When used without any argument, this command does not change which
4439 frame is selected, but prints a brief description of the currently
4440 selected stack frame. It can be abbreviated @code{f}. With an
4441 argument, this command is used to select a stack frame.
4442 @xref{Selection, ,Selecting a frame}.
4445 @kindex info f @r{(@code{info frame})}
4448 This command prints a verbose description of the selected stack frame,
4453 the address of the frame
4455 the address of the next frame down (called by this frame)
4457 the address of the next frame up (caller of this frame)
4459 the language in which the source code corresponding to this frame is written
4461 the address of the frame's arguments
4463 the address of the frame's local variables
4465 the program counter saved in it (the address of execution in the caller frame)
4467 which registers were saved in the frame
4470 @noindent The verbose description is useful when
4471 something has gone wrong that has made the stack format fail to fit
4472 the usual conventions.
4474 @item info frame @var{addr}
4475 @itemx info f @var{addr}
4476 Print a verbose description of the frame at address @var{addr}, without
4477 selecting that frame. The selected frame remains unchanged by this
4478 command. This requires the same kind of address (more than one for some
4479 architectures) that you specify in the @code{frame} command.
4480 @xref{Selection, ,Selecting a frame}.
4484 Print the arguments of the selected frame, each on a separate line.
4488 Print the local variables of the selected frame, each on a separate
4489 line. These are all variables (declared either static or automatic)
4490 accessible at the point of execution of the selected frame.
4493 @cindex catch exceptions, list active handlers
4494 @cindex exception handlers, how to list
4496 Print a list of all the exception handlers that are active in the
4497 current stack frame at the current point of execution. To see other
4498 exception handlers, visit the associated frame (using the @code{up},
4499 @code{down}, or @code{frame} commands); then type @code{info catch}.
4500 @xref{Set Catchpoints, , Setting catchpoints}.
4506 @chapter Examining Source Files
4508 @value{GDBN} can print parts of your program's source, since the debugging
4509 information recorded in the program tells @value{GDBN} what source files were
4510 used to build it. When your program stops, @value{GDBN} spontaneously prints
4511 the line where it stopped. Likewise, when you select a stack frame
4512 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4513 execution in that frame has stopped. You can print other portions of
4514 source files by explicit command.
4516 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4517 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4518 @value{GDBN} under @sc{gnu} Emacs}.
4521 * List:: Printing source lines
4522 * Edit:: Editing source files
4523 * Search:: Searching source files
4524 * Source Path:: Specifying source directories
4525 * Machine Code:: Source and machine code
4529 @section Printing source lines
4532 @kindex l @r{(@code{list})}
4533 To print lines from a source file, use the @code{list} command
4534 (abbreviated @code{l}). By default, ten lines are printed.
4535 There are several ways to specify what part of the file you want to print.
4537 Here are the forms of the @code{list} command most commonly used:
4540 @item list @var{linenum}
4541 Print lines centered around line number @var{linenum} in the
4542 current source file.
4544 @item list @var{function}
4545 Print lines centered around the beginning of function
4549 Print more lines. If the last lines printed were printed with a
4550 @code{list} command, this prints lines following the last lines
4551 printed; however, if the last line printed was a solitary line printed
4552 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4553 Stack}), this prints lines centered around that line.
4556 Print lines just before the lines last printed.
4559 @cindex @code{list}, how many lines to display
4560 By default, @value{GDBN} prints ten source lines with any of these forms of
4561 the @code{list} command. You can change this using @code{set listsize}:
4564 @kindex set listsize
4565 @item set listsize @var{count}
4566 Make the @code{list} command display @var{count} source lines (unless
4567 the @code{list} argument explicitly specifies some other number).
4569 @kindex show listsize
4571 Display the number of lines that @code{list} prints.
4574 Repeating a @code{list} command with @key{RET} discards the argument,
4575 so it is equivalent to typing just @code{list}. This is more useful
4576 than listing the same lines again. An exception is made for an
4577 argument of @samp{-}; that argument is preserved in repetition so that
4578 each repetition moves up in the source file.
4581 In general, the @code{list} command expects you to supply zero, one or two
4582 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4583 of writing them, but the effect is always to specify some source line.
4584 Here is a complete description of the possible arguments for @code{list}:
4587 @item list @var{linespec}
4588 Print lines centered around the line specified by @var{linespec}.
4590 @item list @var{first},@var{last}
4591 Print lines from @var{first} to @var{last}. Both arguments are
4594 @item list ,@var{last}
4595 Print lines ending with @var{last}.
4597 @item list @var{first},
4598 Print lines starting with @var{first}.
4601 Print lines just after the lines last printed.
4604 Print lines just before the lines last printed.
4607 As described in the preceding table.
4610 Here are the ways of specifying a single source line---all the
4615 Specifies line @var{number} of the current source file.
4616 When a @code{list} command has two linespecs, this refers to
4617 the same source file as the first linespec.
4620 Specifies the line @var{offset} lines after the last line printed.
4621 When used as the second linespec in a @code{list} command that has
4622 two, this specifies the line @var{offset} lines down from the
4626 Specifies the line @var{offset} lines before the last line printed.
4628 @item @var{filename}:@var{number}
4629 Specifies line @var{number} in the source file @var{filename}.
4631 @item @var{function}
4632 Specifies the line that begins the body of the function @var{function}.
4633 For example: in C, this is the line with the open brace.
4635 @item @var{filename}:@var{function}
4636 Specifies the line of the open-brace that begins the body of the
4637 function @var{function} in the file @var{filename}. You only need the
4638 file name with a function name to avoid ambiguity when there are
4639 identically named functions in different source files.
4641 @item *@var{address}
4642 Specifies the line containing the program address @var{address}.
4643 @var{address} may be any expression.
4647 @section Editing source files
4648 @cindex editing source files
4651 @kindex e @r{(@code{edit})}
4652 To edit the lines in a source file, use the @code{edit} command.
4653 The editing program of your choice
4654 is invoked with the current line set to
4655 the active line in the program.
4656 Alternatively, there are several ways to specify what part of the file you
4657 want to print if you want to see other parts of the program.
4659 Here are the forms of the @code{edit} command most commonly used:
4663 Edit the current source file at the active line number in the program.
4665 @item edit @var{number}
4666 Edit the current source file with @var{number} as the active line number.
4668 @item edit @var{function}
4669 Edit the file containing @var{function} at the beginning of its definition.
4671 @item edit @var{filename}:@var{number}
4672 Specifies line @var{number} in the source file @var{filename}.
4674 @item edit @var{filename}:@var{function}
4675 Specifies the line that begins the body of the
4676 function @var{function} in the file @var{filename}. You only need the
4677 file name with a function name to avoid ambiguity when there are
4678 identically named functions in different source files.
4680 @item edit *@var{address}
4681 Specifies the line containing the program address @var{address}.
4682 @var{address} may be any expression.
4685 @subsection Choosing your editor
4686 You can customize @value{GDBN} to use any editor you want
4688 The only restriction is that your editor (say @code{ex}), recognizes the
4689 following command-line syntax:
4691 ex +@var{number} file
4693 The optional numeric value +@var{number} specifies the number of the line in
4694 the file where to start editing.}.
4695 By default, it is @file{@value{EDITOR}}, but you can change this
4696 by setting the environment variable @code{EDITOR} before using
4697 @value{GDBN}. For example, to configure @value{GDBN} to use the
4698 @code{vi} editor, you could use these commands with the @code{sh} shell:
4704 or in the @code{csh} shell,
4706 setenv EDITOR /usr/bin/vi
4711 @section Searching source files
4712 @cindex searching source files
4714 There are two commands for searching through the current source file for a
4719 @kindex forward-search
4720 @item forward-search @var{regexp}
4721 @itemx search @var{regexp}
4722 The command @samp{forward-search @var{regexp}} checks each line,
4723 starting with the one following the last line listed, for a match for
4724 @var{regexp}. It lists the line that is found. You can use the
4725 synonym @samp{search @var{regexp}} or abbreviate the command name as
4728 @kindex reverse-search
4729 @item reverse-search @var{regexp}
4730 The command @samp{reverse-search @var{regexp}} checks each line, starting
4731 with the one before the last line listed and going backward, for a match
4732 for @var{regexp}. It lists the line that is found. You can abbreviate
4733 this command as @code{rev}.
4737 @section Specifying source directories
4740 @cindex directories for source files
4741 Executable programs sometimes do not record the directories of the source
4742 files from which they were compiled, just the names. Even when they do,
4743 the directories could be moved between the compilation and your debugging
4744 session. @value{GDBN} has a list of directories to search for source files;
4745 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4746 it tries all the directories in the list, in the order they are present
4747 in the list, until it finds a file with the desired name.
4749 For example, suppose an executable references the file
4750 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
4751 @file{/mnt/cross}. The file is first looked up literally; if this
4752 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
4753 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
4754 message is printed. @value{GDBN} does not look up the parts of the
4755 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
4756 Likewise, the subdirectories of the source path are not searched: if
4757 the source path is @file{/mnt/cross}, and the binary refers to
4758 @file{foo.c}, @value{GDBN} would not find it under
4759 @file{/mnt/cross/usr/src/foo-1.0/lib}.
4761 Plain file names, relative file names with leading directories, file
4762 names containing dots, etc.@: are all treated as described above; for
4763 instance, if the source path is @file{/mnt/cross}, and the source file
4764 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
4765 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
4766 that---@file{/mnt/cross/foo.c}.
4768 Note that the executable search path is @emph{not} used to locate the
4769 source files. Neither is the current working directory, unless it
4770 happens to be in the source path.
4772 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4773 any information it has cached about where source files are found and where
4774 each line is in the file.
4778 When you start @value{GDBN}, its source path includes only @samp{cdir}
4779 and @samp{cwd}, in that order.
4780 To add other directories, use the @code{directory} command.
4783 @item directory @var{dirname} @dots{}
4784 @item dir @var{dirname} @dots{}
4785 Add directory @var{dirname} to the front of the source path. Several
4786 directory names may be given to this command, separated by @samp{:}
4787 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4788 part of absolute file names) or
4789 whitespace. You may specify a directory that is already in the source
4790 path; this moves it forward, so @value{GDBN} searches it sooner.
4794 @vindex $cdir@r{, convenience variable}
4795 @vindex $cwdr@r{, convenience variable}
4796 @cindex compilation directory
4797 @cindex current directory
4798 @cindex working directory
4799 @cindex directory, current
4800 @cindex directory, compilation
4801 You can use the string @samp{$cdir} to refer to the compilation
4802 directory (if one is recorded), and @samp{$cwd} to refer to the current
4803 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4804 tracks the current working directory as it changes during your @value{GDBN}
4805 session, while the latter is immediately expanded to the current
4806 directory at the time you add an entry to the source path.
4809 Reset the source path to empty again. This requires confirmation.
4811 @c RET-repeat for @code{directory} is explicitly disabled, but since
4812 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4814 @item show directories
4815 @kindex show directories
4816 Print the source path: show which directories it contains.
4819 If your source path is cluttered with directories that are no longer of
4820 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4821 versions of source. You can correct the situation as follows:
4825 Use @code{directory} with no argument to reset the source path to empty.
4828 Use @code{directory} with suitable arguments to reinstall the
4829 directories you want in the source path. You can add all the
4830 directories in one command.
4834 @section Source and machine code
4835 @cindex source line and its code address
4837 You can use the command @code{info line} to map source lines to program
4838 addresses (and vice versa), and the command @code{disassemble} to display
4839 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4840 mode, the @code{info line} command causes the arrow to point to the
4841 line specified. Also, @code{info line} prints addresses in symbolic form as
4846 @item info line @var{linespec}
4847 Print the starting and ending addresses of the compiled code for
4848 source line @var{linespec}. You can specify source lines in any of
4849 the ways understood by the @code{list} command (@pxref{List, ,Printing
4853 For example, we can use @code{info line} to discover the location of
4854 the object code for the first line of function
4855 @code{m4_changequote}:
4857 @c FIXME: I think this example should also show the addresses in
4858 @c symbolic form, as they usually would be displayed.
4860 (@value{GDBP}) info line m4_changequote
4861 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4865 @cindex code address and its source line
4866 We can also inquire (using @code{*@var{addr}} as the form for
4867 @var{linespec}) what source line covers a particular address:
4869 (@value{GDBP}) info line *0x63ff
4870 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4873 @cindex @code{$_} and @code{info line}
4874 @cindex @code{x} command, default address
4875 @kindex x@r{(examine), and} info line
4876 After @code{info line}, the default address for the @code{x} command
4877 is changed to the starting address of the line, so that @samp{x/i} is
4878 sufficient to begin examining the machine code (@pxref{Memory,
4879 ,Examining memory}). Also, this address is saved as the value of the
4880 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4885 @cindex assembly instructions
4886 @cindex instructions, assembly
4887 @cindex machine instructions
4888 @cindex listing machine instructions
4890 This specialized command dumps a range of memory as machine
4891 instructions. The default memory range is the function surrounding the
4892 program counter of the selected frame. A single argument to this
4893 command is a program counter value; @value{GDBN} dumps the function
4894 surrounding this value. Two arguments specify a range of addresses
4895 (first inclusive, second exclusive) to dump.
4898 The following example shows the disassembly of a range of addresses of
4899 HP PA-RISC 2.0 code:
4902 (@value{GDBP}) disas 0x32c4 0x32e4
4903 Dump of assembler code from 0x32c4 to 0x32e4:
4904 0x32c4 <main+204>: addil 0,dp
4905 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4906 0x32cc <main+212>: ldil 0x3000,r31
4907 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4908 0x32d4 <main+220>: ldo 0(r31),rp
4909 0x32d8 <main+224>: addil -0x800,dp
4910 0x32dc <main+228>: ldo 0x588(r1),r26
4911 0x32e0 <main+232>: ldil 0x3000,r31
4912 End of assembler dump.
4915 Some architectures have more than one commonly-used set of instruction
4916 mnemonics or other syntax.
4919 @kindex set disassembly-flavor
4920 @cindex Intel disassembly flavor
4921 @cindex AT&T disassembly flavor
4922 @item set disassembly-flavor @var{instruction-set}
4923 Select the instruction set to use when disassembling the
4924 program via the @code{disassemble} or @code{x/i} commands.
4926 Currently this command is only defined for the Intel x86 family. You
4927 can set @var{instruction-set} to either @code{intel} or @code{att}.
4928 The default is @code{att}, the AT&T flavor used by default by Unix
4929 assemblers for x86-based targets.
4931 @kindex show disassembly-flavor
4932 @item show disassembly-flavor
4933 Show the current setting of the disassembly flavor.
4938 @chapter Examining Data
4940 @cindex printing data
4941 @cindex examining data
4944 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4945 @c document because it is nonstandard... Under Epoch it displays in a
4946 @c different window or something like that.
4947 The usual way to examine data in your program is with the @code{print}
4948 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4949 evaluates and prints the value of an expression of the language your
4950 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4951 Different Languages}).
4954 @item print @var{expr}
4955 @itemx print /@var{f} @var{expr}
4956 @var{expr} is an expression (in the source language). By default the
4957 value of @var{expr} is printed in a format appropriate to its data type;
4958 you can choose a different format by specifying @samp{/@var{f}}, where
4959 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4963 @itemx print /@var{f}
4964 @cindex reprint the last value
4965 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4966 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4967 conveniently inspect the same value in an alternative format.
4970 A more low-level way of examining data is with the @code{x} command.
4971 It examines data in memory at a specified address and prints it in a
4972 specified format. @xref{Memory, ,Examining memory}.
4974 If you are interested in information about types, or about how the
4975 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4976 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4980 * Expressions:: Expressions
4981 * Variables:: Program variables
4982 * Arrays:: Artificial arrays
4983 * Output Formats:: Output formats
4984 * Memory:: Examining memory
4985 * Auto Display:: Automatic display
4986 * Print Settings:: Print settings
4987 * Value History:: Value history
4988 * Convenience Vars:: Convenience variables
4989 * Registers:: Registers
4990 * Floating Point Hardware:: Floating point hardware
4991 * Vector Unit:: Vector Unit
4992 * OS Information:: Auxiliary data provided by operating system
4993 * Memory Region Attributes:: Memory region attributes
4994 * Dump/Restore Files:: Copy between memory and a file
4995 * Core File Generation:: Cause a program dump its core
4996 * Character Sets:: Debugging programs that use a different
4997 character set than GDB does
4998 * Caching Remote Data:: Data caching for remote targets
5002 @section Expressions
5005 @code{print} and many other @value{GDBN} commands accept an expression and
5006 compute its value. Any kind of constant, variable or operator defined
5007 by the programming language you are using is valid in an expression in
5008 @value{GDBN}. This includes conditional expressions, function calls,
5009 casts, and string constants. It also includes preprocessor macros, if
5010 you compiled your program to include this information; see
5013 @cindex arrays in expressions
5014 @value{GDBN} supports array constants in expressions input by
5015 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
5016 you can use the command @code{print @{1, 2, 3@}} to build up an array in
5017 memory that is @code{malloc}ed in the target program.
5019 Because C is so widespread, most of the expressions shown in examples in
5020 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
5021 Languages}, for information on how to use expressions in other
5024 In this section, we discuss operators that you can use in @value{GDBN}
5025 expressions regardless of your programming language.
5027 @cindex casts, in expressions
5028 Casts are supported in all languages, not just in C, because it is so
5029 useful to cast a number into a pointer in order to examine a structure
5030 at that address in memory.
5031 @c FIXME: casts supported---Mod2 true?
5033 @value{GDBN} supports these operators, in addition to those common
5034 to programming languages:
5038 @samp{@@} is a binary operator for treating parts of memory as arrays.
5039 @xref{Arrays, ,Artificial arrays}, for more information.
5042 @samp{::} allows you to specify a variable in terms of the file or
5043 function where it is defined. @xref{Variables, ,Program variables}.
5045 @cindex @{@var{type}@}
5046 @cindex type casting memory
5047 @cindex memory, viewing as typed object
5048 @cindex casts, to view memory
5049 @item @{@var{type}@} @var{addr}
5050 Refers to an object of type @var{type} stored at address @var{addr} in
5051 memory. @var{addr} may be any expression whose value is an integer or
5052 pointer (but parentheses are required around binary operators, just as in
5053 a cast). This construct is allowed regardless of what kind of data is
5054 normally supposed to reside at @var{addr}.
5058 @section Program variables
5060 The most common kind of expression to use is the name of a variable
5063 Variables in expressions are understood in the selected stack frame
5064 (@pxref{Selection, ,Selecting a frame}); they must be either:
5068 global (or file-static)
5075 visible according to the scope rules of the
5076 programming language from the point of execution in that frame
5079 @noindent This means that in the function
5094 you can examine and use the variable @code{a} whenever your program is
5095 executing within the function @code{foo}, but you can only use or
5096 examine the variable @code{b} while your program is executing inside
5097 the block where @code{b} is declared.
5099 @cindex variable name conflict
5100 There is an exception: you can refer to a variable or function whose
5101 scope is a single source file even if the current execution point is not
5102 in this file. But it is possible to have more than one such variable or
5103 function with the same name (in different source files). If that
5104 happens, referring to that name has unpredictable effects. If you wish,
5105 you can specify a static variable in a particular function or file,
5106 using the colon-colon (@code{::}) notation:
5108 @cindex colon-colon, context for variables/functions
5110 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
5111 @cindex @code{::}, context for variables/functions
5114 @var{file}::@var{variable}
5115 @var{function}::@var{variable}
5119 Here @var{file} or @var{function} is the name of the context for the
5120 static @var{variable}. In the case of file names, you can use quotes to
5121 make sure @value{GDBN} parses the file name as a single word---for example,
5122 to print a global value of @code{x} defined in @file{f2.c}:
5125 (@value{GDBP}) p 'f2.c'::x
5128 @cindex C@t{++} scope resolution
5129 This use of @samp{::} is very rarely in conflict with the very similar
5130 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
5131 scope resolution operator in @value{GDBN} expressions.
5132 @c FIXME: Um, so what happens in one of those rare cases where it's in
5135 @cindex wrong values
5136 @cindex variable values, wrong
5137 @cindex function entry/exit, wrong values of variables
5138 @cindex optimized code, wrong values of variables
5140 @emph{Warning:} Occasionally, a local variable may appear to have the
5141 wrong value at certain points in a function---just after entry to a new
5142 scope, and just before exit.
5144 You may see this problem when you are stepping by machine instructions.
5145 This is because, on most machines, it takes more than one instruction to
5146 set up a stack frame (including local variable definitions); if you are
5147 stepping by machine instructions, variables may appear to have the wrong
5148 values until the stack frame is completely built. On exit, it usually
5149 also takes more than one machine instruction to destroy a stack frame;
5150 after you begin stepping through that group of instructions, local
5151 variable definitions may be gone.
5153 This may also happen when the compiler does significant optimizations.
5154 To be sure of always seeing accurate values, turn off all optimization
5157 @cindex ``No symbol "foo" in current context''
5158 Another possible effect of compiler optimizations is to optimize
5159 unused variables out of existence, or assign variables to registers (as
5160 opposed to memory addresses). Depending on the support for such cases
5161 offered by the debug info format used by the compiler, @value{GDBN}
5162 might not be able to display values for such local variables. If that
5163 happens, @value{GDBN} will print a message like this:
5166 No symbol "foo" in current context.
5169 To solve such problems, either recompile without optimizations, or use a
5170 different debug info format, if the compiler supports several such
5171 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler,
5172 usually supports the @option{-gstabs+} option. @option{-gstabs+}
5173 produces debug info in a format that is superior to formats such as
5174 COFF. You may be able to use DWARF 2 (@option{-gdwarf-2}), which is also
5175 an effective form for debug info. @xref{Debugging Options,,Options
5176 for Debugging Your Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}.
5177 @xref{C, , Debugging C++}, for more info about debug info formats
5178 that are best suited to C@t{++} programs.
5181 @section Artificial arrays
5183 @cindex artificial array
5185 @kindex @@@r{, referencing memory as an array}
5186 It is often useful to print out several successive objects of the
5187 same type in memory; a section of an array, or an array of
5188 dynamically determined size for which only a pointer exists in the
5191 You can do this by referring to a contiguous span of memory as an
5192 @dfn{artificial array}, using the binary operator @samp{@@}. The left
5193 operand of @samp{@@} should be the first element of the desired array
5194 and be an individual object. The right operand should be the desired length
5195 of the array. The result is an array value whose elements are all of
5196 the type of the left argument. The first element is actually the left
5197 argument; the second element comes from bytes of memory immediately
5198 following those that hold the first element, and so on. Here is an
5199 example. If a program says
5202 int *array = (int *) malloc (len * sizeof (int));
5206 you can print the contents of @code{array} with
5212 The left operand of @samp{@@} must reside in memory. Array values made
5213 with @samp{@@} in this way behave just like other arrays in terms of
5214 subscripting, and are coerced to pointers when used in expressions.
5215 Artificial arrays most often appear in expressions via the value history
5216 (@pxref{Value History, ,Value history}), after printing one out.
5218 Another way to create an artificial array is to use a cast.
5219 This re-interprets a value as if it were an array.
5220 The value need not be in memory:
5222 (@value{GDBP}) p/x (short[2])0x12345678
5223 $1 = @{0x1234, 0x5678@}
5226 As a convenience, if you leave the array length out (as in
5227 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
5228 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
5230 (@value{GDBP}) p/x (short[])0x12345678
5231 $2 = @{0x1234, 0x5678@}
5234 Sometimes the artificial array mechanism is not quite enough; in
5235 moderately complex data structures, the elements of interest may not
5236 actually be adjacent---for example, if you are interested in the values
5237 of pointers in an array. One useful work-around in this situation is
5238 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
5239 variables}) as a counter in an expression that prints the first
5240 interesting value, and then repeat that expression via @key{RET}. For
5241 instance, suppose you have an array @code{dtab} of pointers to
5242 structures, and you are interested in the values of a field @code{fv}
5243 in each structure. Here is an example of what you might type:
5253 @node Output Formats
5254 @section Output formats
5256 @cindex formatted output
5257 @cindex output formats
5258 By default, @value{GDBN} prints a value according to its data type. Sometimes
5259 this is not what you want. For example, you might want to print a number
5260 in hex, or a pointer in decimal. Or you might want to view data in memory
5261 at a certain address as a character string or as an instruction. To do
5262 these things, specify an @dfn{output format} when you print a value.
5264 The simplest use of output formats is to say how to print a value
5265 already computed. This is done by starting the arguments of the
5266 @code{print} command with a slash and a format letter. The format
5267 letters supported are:
5271 Regard the bits of the value as an integer, and print the integer in
5275 Print as integer in signed decimal.
5278 Print as integer in unsigned decimal.
5281 Print as integer in octal.
5284 Print as integer in binary. The letter @samp{t} stands for ``two''.
5285 @footnote{@samp{b} cannot be used because these format letters are also
5286 used with the @code{x} command, where @samp{b} stands for ``byte'';
5287 see @ref{Memory,,Examining memory}.}
5290 @cindex unknown address, locating
5291 @cindex locate address
5292 Print as an address, both absolute in hexadecimal and as an offset from
5293 the nearest preceding symbol. You can use this format used to discover
5294 where (in what function) an unknown address is located:
5297 (@value{GDBP}) p/a 0x54320
5298 $3 = 0x54320 <_initialize_vx+396>
5302 The command @code{info symbol 0x54320} yields similar results.
5303 @xref{Symbols, info symbol}.
5306 Regard as an integer and print it as a character constant.
5309 Regard the bits of the value as a floating point number and print
5310 using typical floating point syntax.
5313 For example, to print the program counter in hex (@pxref{Registers}), type
5320 Note that no space is required before the slash; this is because command
5321 names in @value{GDBN} cannot contain a slash.
5323 To reprint the last value in the value history with a different format,
5324 you can use the @code{print} command with just a format and no
5325 expression. For example, @samp{p/x} reprints the last value in hex.
5328 @section Examining memory
5330 You can use the command @code{x} (for ``examine'') to examine memory in
5331 any of several formats, independently of your program's data types.
5333 @cindex examining memory
5335 @kindex x @r{(examine memory)}
5336 @item x/@var{nfu} @var{addr}
5339 Use the @code{x} command to examine memory.
5342 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
5343 much memory to display and how to format it; @var{addr} is an
5344 expression giving the address where you want to start displaying memory.
5345 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
5346 Several commands set convenient defaults for @var{addr}.
5349 @item @var{n}, the repeat count
5350 The repeat count is a decimal integer; the default is 1. It specifies
5351 how much memory (counting by units @var{u}) to display.
5352 @c This really is **decimal**; unaffected by 'set radix' as of GDB
5355 @item @var{f}, the display format
5356 The display format is one of the formats used by @code{print},
5357 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
5358 The default is @samp{x} (hexadecimal) initially.
5359 The default changes each time you use either @code{x} or @code{print}.
5361 @item @var{u}, the unit size
5362 The unit size is any of
5368 Halfwords (two bytes).
5370 Words (four bytes). This is the initial default.
5372 Giant words (eight bytes).
5375 Each time you specify a unit size with @code{x}, that size becomes the
5376 default unit the next time you use @code{x}. (For the @samp{s} and
5377 @samp{i} formats, the unit size is ignored and is normally not written.)
5379 @item @var{addr}, starting display address
5380 @var{addr} is the address where you want @value{GDBN} to begin displaying
5381 memory. The expression need not have a pointer value (though it may);
5382 it is always interpreted as an integer address of a byte of memory.
5383 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
5384 @var{addr} is usually just after the last address examined---but several
5385 other commands also set the default address: @code{info breakpoints} (to
5386 the address of the last breakpoint listed), @code{info line} (to the
5387 starting address of a line), and @code{print} (if you use it to display
5388 a value from memory).
5391 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
5392 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
5393 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
5394 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
5395 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
5397 Since the letters indicating unit sizes are all distinct from the
5398 letters specifying output formats, you do not have to remember whether
5399 unit size or format comes first; either order works. The output
5400 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
5401 (However, the count @var{n} must come first; @samp{wx4} does not work.)
5403 Even though the unit size @var{u} is ignored for the formats @samp{s}
5404 and @samp{i}, you might still want to use a count @var{n}; for example,
5405 @samp{3i} specifies that you want to see three machine instructions,
5406 including any operands. The command @code{disassemble} gives an
5407 alternative way of inspecting machine instructions; see @ref{Machine
5408 Code,,Source and machine code}.
5410 All the defaults for the arguments to @code{x} are designed to make it
5411 easy to continue scanning memory with minimal specifications each time
5412 you use @code{x}. For example, after you have inspected three machine
5413 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
5414 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
5415 the repeat count @var{n} is used again; the other arguments default as
5416 for successive uses of @code{x}.
5418 @cindex @code{$_}, @code{$__}, and value history
5419 The addresses and contents printed by the @code{x} command are not saved
5420 in the value history because there is often too much of them and they
5421 would get in the way. Instead, @value{GDBN} makes these values available for
5422 subsequent use in expressions as values of the convenience variables
5423 @code{$_} and @code{$__}. After an @code{x} command, the last address
5424 examined is available for use in expressions in the convenience variable
5425 @code{$_}. The contents of that address, as examined, are available in
5426 the convenience variable @code{$__}.
5428 If the @code{x} command has a repeat count, the address and contents saved
5429 are from the last memory unit printed; this is not the same as the last
5430 address printed if several units were printed on the last line of output.
5432 @cindex remote memory comparison
5433 @cindex verify remote memory image
5434 When you are debugging a program running on a remote target machine
5435 (@pxref{Remote}), you may wish to verify the program's image in the
5436 remote machine's memory against the executable file you downloaded to
5437 the target. The @code{compare-sections} command is provided for such
5441 @kindex compare-sections
5442 @item compare-sections @r{[}@var{section-name}@r{]}
5443 Compare the data of a loadable section @var{section-name} in the
5444 executable file of the program being debugged with the same section in
5445 the remote machine's memory, and report any mismatches. With no
5446 arguments, compares all loadable sections. This command's
5447 availability depends on the target's support for the @code{"qCRC"}
5452 @section Automatic display
5453 @cindex automatic display
5454 @cindex display of expressions
5456 If you find that you want to print the value of an expression frequently
5457 (to see how it changes), you might want to add it to the @dfn{automatic
5458 display list} so that @value{GDBN} prints its value each time your program stops.
5459 Each expression added to the list is given a number to identify it;
5460 to remove an expression from the list, you specify that number.
5461 The automatic display looks like this:
5465 3: bar[5] = (struct hack *) 0x3804
5469 This display shows item numbers, expressions and their current values. As with
5470 displays you request manually using @code{x} or @code{print}, you can
5471 specify the output format you prefer; in fact, @code{display} decides
5472 whether to use @code{print} or @code{x} depending on how elaborate your
5473 format specification is---it uses @code{x} if you specify a unit size,
5474 or one of the two formats (@samp{i} and @samp{s}) that are only
5475 supported by @code{x}; otherwise it uses @code{print}.
5479 @item display @var{expr}
5480 Add the expression @var{expr} to the list of expressions to display
5481 each time your program stops. @xref{Expressions, ,Expressions}.
5483 @code{display} does not repeat if you press @key{RET} again after using it.
5485 @item display/@var{fmt} @var{expr}
5486 For @var{fmt} specifying only a display format and not a size or
5487 count, add the expression @var{expr} to the auto-display list but
5488 arrange to display it each time in the specified format @var{fmt}.
5489 @xref{Output Formats,,Output formats}.
5491 @item display/@var{fmt} @var{addr}
5492 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
5493 number of units, add the expression @var{addr} as a memory address to
5494 be examined each time your program stops. Examining means in effect
5495 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
5498 For example, @samp{display/i $pc} can be helpful, to see the machine
5499 instruction about to be executed each time execution stops (@samp{$pc}
5500 is a common name for the program counter; @pxref{Registers, ,Registers}).
5503 @kindex delete display
5505 @item undisplay @var{dnums}@dots{}
5506 @itemx delete display @var{dnums}@dots{}
5507 Remove item numbers @var{dnums} from the list of expressions to display.
5509 @code{undisplay} does not repeat if you press @key{RET} after using it.
5510 (Otherwise you would just get the error @samp{No display number @dots{}}.)
5512 @kindex disable display
5513 @item disable display @var{dnums}@dots{}
5514 Disable the display of item numbers @var{dnums}. A disabled display
5515 item is not printed automatically, but is not forgotten. It may be
5516 enabled again later.
5518 @kindex enable display
5519 @item enable display @var{dnums}@dots{}
5520 Enable display of item numbers @var{dnums}. It becomes effective once
5521 again in auto display of its expression, until you specify otherwise.
5524 Display the current values of the expressions on the list, just as is
5525 done when your program stops.
5527 @kindex info display
5529 Print the list of expressions previously set up to display
5530 automatically, each one with its item number, but without showing the
5531 values. This includes disabled expressions, which are marked as such.
5532 It also includes expressions which would not be displayed right now
5533 because they refer to automatic variables not currently available.
5536 @cindex display disabled out of scope
5537 If a display expression refers to local variables, then it does not make
5538 sense outside the lexical context for which it was set up. Such an
5539 expression is disabled when execution enters a context where one of its
5540 variables is not defined. For example, if you give the command
5541 @code{display last_char} while inside a function with an argument
5542 @code{last_char}, @value{GDBN} displays this argument while your program
5543 continues to stop inside that function. When it stops elsewhere---where
5544 there is no variable @code{last_char}---the display is disabled
5545 automatically. The next time your program stops where @code{last_char}
5546 is meaningful, you can enable the display expression once again.
5548 @node Print Settings
5549 @section Print settings
5551 @cindex format options
5552 @cindex print settings
5553 @value{GDBN} provides the following ways to control how arrays, structures,
5554 and symbols are printed.
5557 These settings are useful for debugging programs in any language:
5561 @item set print address
5562 @itemx set print address on
5563 @cindex print/don't print memory addresses
5564 @value{GDBN} prints memory addresses showing the location of stack
5565 traces, structure values, pointer values, breakpoints, and so forth,
5566 even when it also displays the contents of those addresses. The default
5567 is @code{on}. For example, this is what a stack frame display looks like with
5568 @code{set print address on}:
5573 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5575 530 if (lquote != def_lquote)
5579 @item set print address off
5580 Do not print addresses when displaying their contents. For example,
5581 this is the same stack frame displayed with @code{set print address off}:
5585 (@value{GDBP}) set print addr off
5587 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5588 530 if (lquote != def_lquote)
5592 You can use @samp{set print address off} to eliminate all machine
5593 dependent displays from the @value{GDBN} interface. For example, with
5594 @code{print address off}, you should get the same text for backtraces on
5595 all machines---whether or not they involve pointer arguments.
5598 @item show print address
5599 Show whether or not addresses are to be printed.
5602 When @value{GDBN} prints a symbolic address, it normally prints the
5603 closest earlier symbol plus an offset. If that symbol does not uniquely
5604 identify the address (for example, it is a name whose scope is a single
5605 source file), you may need to clarify. One way to do this is with
5606 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5607 you can set @value{GDBN} to print the source file and line number when
5608 it prints a symbolic address:
5611 @item set print symbol-filename on
5612 @cindex source file and line of a symbol
5613 @cindex symbol, source file and line
5614 Tell @value{GDBN} to print the source file name and line number of a
5615 symbol in the symbolic form of an address.
5617 @item set print symbol-filename off
5618 Do not print source file name and line number of a symbol. This is the
5621 @item show print symbol-filename
5622 Show whether or not @value{GDBN} will print the source file name and
5623 line number of a symbol in the symbolic form of an address.
5626 Another situation where it is helpful to show symbol filenames and line
5627 numbers is when disassembling code; @value{GDBN} shows you the line
5628 number and source file that corresponds to each instruction.
5630 Also, you may wish to see the symbolic form only if the address being
5631 printed is reasonably close to the closest earlier symbol:
5634 @item set print max-symbolic-offset @var{max-offset}
5635 @cindex maximum value for offset of closest symbol
5636 Tell @value{GDBN} to only display the symbolic form of an address if the
5637 offset between the closest earlier symbol and the address is less than
5638 @var{max-offset}. The default is 0, which tells @value{GDBN}
5639 to always print the symbolic form of an address if any symbol precedes it.
5641 @item show print max-symbolic-offset
5642 Ask how large the maximum offset is that @value{GDBN} prints in a
5646 @cindex wild pointer, interpreting
5647 @cindex pointer, finding referent
5648 If you have a pointer and you are not sure where it points, try
5649 @samp{set print symbol-filename on}. Then you can determine the name
5650 and source file location of the variable where it points, using
5651 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5652 For example, here @value{GDBN} shows that a variable @code{ptt} points
5653 at another variable @code{t}, defined in @file{hi2.c}:
5656 (@value{GDBP}) set print symbol-filename on
5657 (@value{GDBP}) p/a ptt
5658 $4 = 0xe008 <t in hi2.c>
5662 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5663 does not show the symbol name and filename of the referent, even with
5664 the appropriate @code{set print} options turned on.
5667 Other settings control how different kinds of objects are printed:
5670 @item set print array
5671 @itemx set print array on
5672 @cindex pretty print arrays
5673 Pretty print arrays. This format is more convenient to read,
5674 but uses more space. The default is off.
5676 @item set print array off
5677 Return to compressed format for arrays.
5679 @item show print array
5680 Show whether compressed or pretty format is selected for displaying
5683 @item set print elements @var{number-of-elements}
5684 @cindex number of array elements to print
5685 @cindex limit on number of printed array elements
5686 Set a limit on how many elements of an array @value{GDBN} will print.
5687 If @value{GDBN} is printing a large array, it stops printing after it has
5688 printed the number of elements set by the @code{set print elements} command.
5689 This limit also applies to the display of strings.
5690 When @value{GDBN} starts, this limit is set to 200.
5691 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5693 @item show print elements
5694 Display the number of elements of a large array that @value{GDBN} will print.
5695 If the number is 0, then the printing is unlimited.
5697 @item set print repeats
5698 @cindex repeated array elements
5699 Set the threshold for suppressing display of repeated array
5700 elelments. When the number of consecutive identical elements of an
5701 array exceeds the threshold, @value{GDBN} prints the string
5702 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
5703 identical repetitions, instead of displaying the identical elements
5704 themselves. Setting the threshold to zero will cause all elements to
5705 be individually printed. The default threshold is 10.
5707 @item show print repeats
5708 Display the current threshold for printing repeated identical
5711 @item set print null-stop
5712 @cindex @sc{null} elements in arrays
5713 Cause @value{GDBN} to stop printing the characters of an array when the first
5714 @sc{null} is encountered. This is useful when large arrays actually
5715 contain only short strings.
5718 @item show print null-stop
5719 Show whether @value{GDBN} stops printing an array on the first
5720 @sc{null} character.
5722 @item set print pretty on
5723 @cindex print structures in indented form
5724 @cindex indentation in structure display
5725 Cause @value{GDBN} to print structures in an indented format with one member
5726 per line, like this:
5741 @item set print pretty off
5742 Cause @value{GDBN} to print structures in a compact format, like this:
5746 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5747 meat = 0x54 "Pork"@}
5752 This is the default format.
5754 @item show print pretty
5755 Show which format @value{GDBN} is using to print structures.
5757 @item set print sevenbit-strings on
5758 @cindex eight-bit characters in strings
5759 @cindex octal escapes in strings
5760 Print using only seven-bit characters; if this option is set,
5761 @value{GDBN} displays any eight-bit characters (in strings or
5762 character values) using the notation @code{\}@var{nnn}. This setting is
5763 best if you are working in English (@sc{ascii}) and you use the
5764 high-order bit of characters as a marker or ``meta'' bit.
5766 @item set print sevenbit-strings off
5767 Print full eight-bit characters. This allows the use of more
5768 international character sets, and is the default.
5770 @item show print sevenbit-strings
5771 Show whether or not @value{GDBN} is printing only seven-bit characters.
5773 @item set print union on
5774 @cindex unions in structures, printing
5775 Tell @value{GDBN} to print unions which are contained in structures
5776 and other unions. This is the default setting.
5778 @item set print union off
5779 Tell @value{GDBN} not to print unions which are contained in
5780 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
5783 @item show print union
5784 Ask @value{GDBN} whether or not it will print unions which are contained in
5785 structures and other unions.
5787 For example, given the declarations
5790 typedef enum @{Tree, Bug@} Species;
5791 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5792 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5803 struct thing foo = @{Tree, @{Acorn@}@};
5807 with @code{set print union on} in effect @samp{p foo} would print
5810 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5814 and with @code{set print union off} in effect it would print
5817 $1 = @{it = Tree, form = @{...@}@}
5821 @code{set print union} affects programs written in C-like languages
5827 These settings are of interest when debugging C@t{++} programs:
5830 @cindex demangling C@t{++} names
5831 @item set print demangle
5832 @itemx set print demangle on
5833 Print C@t{++} names in their source form rather than in the encoded
5834 (``mangled'') form passed to the assembler and linker for type-safe
5835 linkage. The default is on.
5837 @item show print demangle
5838 Show whether C@t{++} names are printed in mangled or demangled form.
5840 @item set print asm-demangle
5841 @itemx set print asm-demangle on
5842 Print C@t{++} names in their source form rather than their mangled form, even
5843 in assembler code printouts such as instruction disassemblies.
5846 @item show print asm-demangle
5847 Show whether C@t{++} names in assembly listings are printed in mangled
5850 @cindex C@t{++} symbol decoding style
5851 @cindex symbol decoding style, C@t{++}
5852 @kindex set demangle-style
5853 @item set demangle-style @var{style}
5854 Choose among several encoding schemes used by different compilers to
5855 represent C@t{++} names. The choices for @var{style} are currently:
5859 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5862 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5863 This is the default.
5866 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5869 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5872 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5873 @strong{Warning:} this setting alone is not sufficient to allow
5874 debugging @code{cfront}-generated executables. @value{GDBN} would
5875 require further enhancement to permit that.
5878 If you omit @var{style}, you will see a list of possible formats.
5880 @item show demangle-style
5881 Display the encoding style currently in use for decoding C@t{++} symbols.
5883 @item set print object
5884 @itemx set print object on
5885 @cindex derived type of an object, printing
5886 @cindex display derived types
5887 When displaying a pointer to an object, identify the @emph{actual}
5888 (derived) type of the object rather than the @emph{declared} type, using
5889 the virtual function table.
5891 @item set print object off
5892 Display only the declared type of objects, without reference to the
5893 virtual function table. This is the default setting.
5895 @item show print object
5896 Show whether actual, or declared, object types are displayed.
5898 @item set print static-members
5899 @itemx set print static-members on
5900 @cindex static members of C@t{++} objects
5901 Print static members when displaying a C@t{++} object. The default is on.
5903 @item set print static-members off
5904 Do not print static members when displaying a C@t{++} object.
5906 @item show print static-members
5907 Show whether C@t{++} static members are printed or not.
5909 @item set print pascal_static-members
5910 @itemx set print pascal_static-members on
5911 @cindex static members of Pacal objects
5912 @cindex Pacal objects, static members display
5913 Print static members when displaying a Pascal object. The default is on.
5915 @item set print pascal_static-members off
5916 Do not print static members when displaying a Pascal object.
5918 @item show print pascal_static-members
5919 Show whether Pascal static members are printed or not.
5921 @c These don't work with HP ANSI C++ yet.
5922 @item set print vtbl
5923 @itemx set print vtbl on
5924 @cindex pretty print C@t{++} virtual function tables
5925 @cindex virtual functions (C@t{++}) display
5926 @cindex VTBL display
5927 Pretty print C@t{++} virtual function tables. The default is off.
5928 (The @code{vtbl} commands do not work on programs compiled with the HP
5929 ANSI C@t{++} compiler (@code{aCC}).)
5931 @item set print vtbl off
5932 Do not pretty print C@t{++} virtual function tables.
5934 @item show print vtbl
5935 Show whether C@t{++} virtual function tables are pretty printed, or not.
5939 @section Value history
5941 @cindex value history
5942 @cindex history of values printed by @value{GDBN}
5943 Values printed by the @code{print} command are saved in the @value{GDBN}
5944 @dfn{value history}. This allows you to refer to them in other expressions.
5945 Values are kept until the symbol table is re-read or discarded
5946 (for example with the @code{file} or @code{symbol-file} commands).
5947 When the symbol table changes, the value history is discarded,
5948 since the values may contain pointers back to the types defined in the
5953 @cindex history number
5954 The values printed are given @dfn{history numbers} by which you can
5955 refer to them. These are successive integers starting with one.
5956 @code{print} shows you the history number assigned to a value by
5957 printing @samp{$@var{num} = } before the value; here @var{num} is the
5960 To refer to any previous value, use @samp{$} followed by the value's
5961 history number. The way @code{print} labels its output is designed to
5962 remind you of this. Just @code{$} refers to the most recent value in
5963 the history, and @code{$$} refers to the value before that.
5964 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5965 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5966 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5968 For example, suppose you have just printed a pointer to a structure and
5969 want to see the contents of the structure. It suffices to type
5975 If you have a chain of structures where the component @code{next} points
5976 to the next one, you can print the contents of the next one with this:
5983 You can print successive links in the chain by repeating this
5984 command---which you can do by just typing @key{RET}.
5986 Note that the history records values, not expressions. If the value of
5987 @code{x} is 4 and you type these commands:
5995 then the value recorded in the value history by the @code{print} command
5996 remains 4 even though the value of @code{x} has changed.
6001 Print the last ten values in the value history, with their item numbers.
6002 This is like @samp{p@ $$9} repeated ten times, except that @code{show
6003 values} does not change the history.
6005 @item show values @var{n}
6006 Print ten history values centered on history item number @var{n}.
6009 Print ten history values just after the values last printed. If no more
6010 values are available, @code{show values +} produces no display.
6013 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
6014 same effect as @samp{show values +}.
6016 @node Convenience Vars
6017 @section Convenience variables
6019 @cindex convenience variables
6020 @cindex user-defined variables
6021 @value{GDBN} provides @dfn{convenience variables} that you can use within
6022 @value{GDBN} to hold on to a value and refer to it later. These variables
6023 exist entirely within @value{GDBN}; they are not part of your program, and
6024 setting a convenience variable has no direct effect on further execution
6025 of your program. That is why you can use them freely.
6027 Convenience variables are prefixed with @samp{$}. Any name preceded by
6028 @samp{$} can be used for a convenience variable, unless it is one of
6029 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
6030 (Value history references, in contrast, are @emph{numbers} preceded
6031 by @samp{$}. @xref{Value History, ,Value history}.)
6033 You can save a value in a convenience variable with an assignment
6034 expression, just as you would set a variable in your program.
6038 set $foo = *object_ptr
6042 would save in @code{$foo} the value contained in the object pointed to by
6045 Using a convenience variable for the first time creates it, but its
6046 value is @code{void} until you assign a new value. You can alter the
6047 value with another assignment at any time.
6049 Convenience variables have no fixed types. You can assign a convenience
6050 variable any type of value, including structures and arrays, even if
6051 that variable already has a value of a different type. The convenience
6052 variable, when used as an expression, has the type of its current value.
6055 @kindex show convenience
6056 @cindex show all user variables
6057 @item show convenience
6058 Print a list of convenience variables used so far, and their values.
6059 Abbreviated @code{show conv}.
6062 One of the ways to use a convenience variable is as a counter to be
6063 incremented or a pointer to be advanced. For example, to print
6064 a field from successive elements of an array of structures:
6068 print bar[$i++]->contents
6072 Repeat that command by typing @key{RET}.
6074 Some convenience variables are created automatically by @value{GDBN} and given
6075 values likely to be useful.
6078 @vindex $_@r{, convenience variable}
6080 The variable @code{$_} is automatically set by the @code{x} command to
6081 the last address examined (@pxref{Memory, ,Examining memory}). Other
6082 commands which provide a default address for @code{x} to examine also
6083 set @code{$_} to that address; these commands include @code{info line}
6084 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
6085 except when set by the @code{x} command, in which case it is a pointer
6086 to the type of @code{$__}.
6088 @vindex $__@r{, convenience variable}
6090 The variable @code{$__} is automatically set by the @code{x} command
6091 to the value found in the last address examined. Its type is chosen
6092 to match the format in which the data was printed.
6095 @vindex $_exitcode@r{, convenience variable}
6096 The variable @code{$_exitcode} is automatically set to the exit code when
6097 the program being debugged terminates.
6100 On HP-UX systems, if you refer to a function or variable name that
6101 begins with a dollar sign, @value{GDBN} searches for a user or system
6102 name first, before it searches for a convenience variable.
6108 You can refer to machine register contents, in expressions, as variables
6109 with names starting with @samp{$}. The names of registers are different
6110 for each machine; use @code{info registers} to see the names used on
6114 @kindex info registers
6115 @item info registers
6116 Print the names and values of all registers except floating-point
6117 and vector registers (in the selected stack frame).
6119 @kindex info all-registers
6120 @cindex floating point registers
6121 @item info all-registers
6122 Print the names and values of all registers, including floating-point
6123 and vector registers (in the selected stack frame).
6125 @item info registers @var{regname} @dots{}
6126 Print the @dfn{relativized} value of each specified register @var{regname}.
6127 As discussed in detail below, register values are normally relative to
6128 the selected stack frame. @var{regname} may be any register name valid on
6129 the machine you are using, with or without the initial @samp{$}.
6132 @value{GDBN} has four ``standard'' register names that are available (in
6133 expressions) on most machines---whenever they do not conflict with an
6134 architecture's canonical mnemonics for registers. The register names
6135 @code{$pc} and @code{$sp} are used for the program counter register and
6136 the stack pointer. @code{$fp} is used for a register that contains a
6137 pointer to the current stack frame, and @code{$ps} is used for a
6138 register that contains the processor status. For example,
6139 you could print the program counter in hex with
6146 or print the instruction to be executed next with
6153 or add four to the stack pointer@footnote{This is a way of removing
6154 one word from the stack, on machines where stacks grow downward in
6155 memory (most machines, nowadays). This assumes that the innermost
6156 stack frame is selected; setting @code{$sp} is not allowed when other
6157 stack frames are selected. To pop entire frames off the stack,
6158 regardless of machine architecture, use @code{return};
6159 see @ref{Returning, ,Returning from a function}.} with
6165 Whenever possible, these four standard register names are available on
6166 your machine even though the machine has different canonical mnemonics,
6167 so long as there is no conflict. The @code{info registers} command
6168 shows the canonical names. For example, on the SPARC, @code{info
6169 registers} displays the processor status register as @code{$psr} but you
6170 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
6171 is an alias for the @sc{eflags} register.
6173 @value{GDBN} always considers the contents of an ordinary register as an
6174 integer when the register is examined in this way. Some machines have
6175 special registers which can hold nothing but floating point; these
6176 registers are considered to have floating point values. There is no way
6177 to refer to the contents of an ordinary register as floating point value
6178 (although you can @emph{print} it as a floating point value with
6179 @samp{print/f $@var{regname}}).
6181 Some registers have distinct ``raw'' and ``virtual'' data formats. This
6182 means that the data format in which the register contents are saved by
6183 the operating system is not the same one that your program normally
6184 sees. For example, the registers of the 68881 floating point
6185 coprocessor are always saved in ``extended'' (raw) format, but all C
6186 programs expect to work with ``double'' (virtual) format. In such
6187 cases, @value{GDBN} normally works with the virtual format only (the format
6188 that makes sense for your program), but the @code{info registers} command
6189 prints the data in both formats.
6191 Normally, register values are relative to the selected stack frame
6192 (@pxref{Selection, ,Selecting a frame}). This means that you get the
6193 value that the register would contain if all stack frames farther in
6194 were exited and their saved registers restored. In order to see the
6195 true contents of hardware registers, you must select the innermost
6196 frame (with @samp{frame 0}).
6198 However, @value{GDBN} must deduce where registers are saved, from the machine
6199 code generated by your compiler. If some registers are not saved, or if
6200 @value{GDBN} is unable to locate the saved registers, the selected stack
6201 frame makes no difference.
6203 @node Floating Point Hardware
6204 @section Floating point hardware
6205 @cindex floating point
6207 Depending on the configuration, @value{GDBN} may be able to give
6208 you more information about the status of the floating point hardware.
6213 Display hardware-dependent information about the floating
6214 point unit. The exact contents and layout vary depending on the
6215 floating point chip. Currently, @samp{info float} is supported on
6216 the ARM and x86 machines.
6220 @section Vector Unit
6223 Depending on the configuration, @value{GDBN} may be able to give you
6224 more information about the status of the vector unit.
6229 Display information about the vector unit. The exact contents and
6230 layout vary depending on the hardware.
6233 @node OS Information
6234 @section Operating system auxiliary information
6235 @cindex OS information
6237 @value{GDBN} provides interfaces to useful OS facilities that can help
6238 you debug your program.
6240 @cindex @code{ptrace} system call
6241 @cindex @code{struct user} contents
6242 When @value{GDBN} runs on a @dfn{Posix system} (such as GNU or Unix
6243 machines), it interfaces with the inferior via the @code{ptrace}
6244 system call. The operating system creates a special sata structure,
6245 called @code{struct user}, for this interface. You can use the
6246 command @code{info udot} to display the contents of this data
6252 Display the contents of the @code{struct user} maintained by the OS
6253 kernel for the program being debugged. @value{GDBN} displays the
6254 contents of @code{struct user} as a list of hex numbers, similar to
6255 the @code{examine} command.
6258 @cindex auxiliary vector
6259 @cindex vector, auxiliary
6260 Some operating systems supply an @dfn{auxiliary vector} to programs at
6261 startup. This is akin to the arguments and environment that you
6262 specify for a program, but contains a system-dependent variety of
6263 binary values that tell system libraries important details about the
6264 hardware, operating system, and process. Each value's purpose is
6265 identified by an integer tag; the meanings are well-known but system-specific.
6266 Depending on the configuration and operating system facilities,
6267 @value{GDBN} may be able to show you this information. For remote
6268 targets, this functionality may further depend on the remote stub's
6269 support of the @samp{qPart:auxv:read} packet, see @ref{Remote
6270 configuration, auxiliary vector}.
6275 Display the auxiliary vector of the inferior, which can be either a
6276 live process or a core dump file. @value{GDBN} prints each tag value
6277 numerically, and also shows names and text descriptions for recognized
6278 tags. Some values in the vector are numbers, some bit masks, and some
6279 pointers to strings or other data. @value{GDBN} displays each value in the
6280 most appropriate form for a recognized tag, and in hexadecimal for
6281 an unrecognized tag.
6285 @node Memory Region Attributes
6286 @section Memory region attributes
6287 @cindex memory region attributes
6289 @dfn{Memory region attributes} allow you to describe special handling
6290 required by regions of your target's memory. @value{GDBN} uses attributes
6291 to determine whether to allow certain types of memory accesses; whether to
6292 use specific width accesses; and whether to cache target memory.
6294 Defined memory regions can be individually enabled and disabled. When a
6295 memory region is disabled, @value{GDBN} uses the default attributes when
6296 accessing memory in that region. Similarly, if no memory regions have
6297 been defined, @value{GDBN} uses the default attributes when accessing
6300 When a memory region is defined, it is given a number to identify it;
6301 to enable, disable, or remove a memory region, you specify that number.
6305 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
6306 Define a memory region bounded by @var{lower} and @var{upper} with
6307 attributes @var{attributes}@dots{}, and add it to the list of regions
6308 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
6309 case: it is treated as the the target's maximum memory address.
6310 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
6313 @item delete mem @var{nums}@dots{}
6314 Remove memory regions @var{nums}@dots{} from the list of regions
6315 monitored by @value{GDBN}.
6318 @item disable mem @var{nums}@dots{}
6319 Disable monitoring of memory regions @var{nums}@dots{}.
6320 A disabled memory region is not forgotten.
6321 It may be enabled again later.
6324 @item enable mem @var{nums}@dots{}
6325 Enable monitoring of memory regions @var{nums}@dots{}.
6329 Print a table of all defined memory regions, with the following columns
6333 @item Memory Region Number
6334 @item Enabled or Disabled.
6335 Enabled memory regions are marked with @samp{y}.
6336 Disabled memory regions are marked with @samp{n}.
6339 The address defining the inclusive lower bound of the memory region.
6342 The address defining the exclusive upper bound of the memory region.
6345 The list of attributes set for this memory region.
6350 @subsection Attributes
6352 @subsubsection Memory Access Mode
6353 The access mode attributes set whether @value{GDBN} may make read or
6354 write accesses to a memory region.
6356 While these attributes prevent @value{GDBN} from performing invalid
6357 memory accesses, they do nothing to prevent the target system, I/O DMA,
6358 etc. from accessing memory.
6362 Memory is read only.
6364 Memory is write only.
6366 Memory is read/write. This is the default.
6369 @subsubsection Memory Access Size
6370 The acccess size attributes tells @value{GDBN} to use specific sized
6371 accesses in the memory region. Often memory mapped device registers
6372 require specific sized accesses. If no access size attribute is
6373 specified, @value{GDBN} may use accesses of any size.
6377 Use 8 bit memory accesses.
6379 Use 16 bit memory accesses.
6381 Use 32 bit memory accesses.
6383 Use 64 bit memory accesses.
6386 @c @subsubsection Hardware/Software Breakpoints
6387 @c The hardware/software breakpoint attributes set whether @value{GDBN}
6388 @c will use hardware or software breakpoints for the internal breakpoints
6389 @c used by the step, next, finish, until, etc. commands.
6393 @c Always use hardware breakpoints
6394 @c @item swbreak (default)
6397 @subsubsection Data Cache
6398 The data cache attributes set whether @value{GDBN} will cache target
6399 memory. While this generally improves performance by reducing debug
6400 protocol overhead, it can lead to incorrect results because @value{GDBN}
6401 does not know about volatile variables or memory mapped device
6406 Enable @value{GDBN} to cache target memory.
6408 Disable @value{GDBN} from caching target memory. This is the default.
6411 @c @subsubsection Memory Write Verification
6412 @c The memory write verification attributes set whether @value{GDBN}
6413 @c will re-reads data after each write to verify the write was successful.
6417 @c @item noverify (default)
6420 @node Dump/Restore Files
6421 @section Copy between memory and a file
6422 @cindex dump/restore files
6423 @cindex append data to a file
6424 @cindex dump data to a file
6425 @cindex restore data from a file
6427 You can use the commands @code{dump}, @code{append}, and
6428 @code{restore} to copy data between target memory and a file. The
6429 @code{dump} and @code{append} commands write data to a file, and the
6430 @code{restore} command reads data from a file back into the inferior's
6431 memory. Files may be in binary, Motorola S-record, Intel hex, or
6432 Tektronix Hex format; however, @value{GDBN} can only append to binary
6438 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6439 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
6440 Dump the contents of memory from @var{start_addr} to @var{end_addr},
6441 or the value of @var{expr}, to @var{filename} in the given format.
6443 The @var{format} parameter may be any one of:
6450 Motorola S-record format.
6452 Tektronix Hex format.
6455 @value{GDBN} uses the same definitions of these formats as the
6456 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
6457 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
6461 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
6462 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
6463 Append the contents of memory from @var{start_addr} to @var{end_addr},
6464 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
6465 (@value{GDBN} can only append data to files in raw binary form.)
6468 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
6469 Restore the contents of file @var{filename} into memory. The
6470 @code{restore} command can automatically recognize any known @sc{bfd}
6471 file format, except for raw binary. To restore a raw binary file you
6472 must specify the optional keyword @code{binary} after the filename.
6474 If @var{bias} is non-zero, its value will be added to the addresses
6475 contained in the file. Binary files always start at address zero, so
6476 they will be restored at address @var{bias}. Other bfd files have
6477 a built-in location; they will be restored at offset @var{bias}
6480 If @var{start} and/or @var{end} are non-zero, then only data between
6481 file offset @var{start} and file offset @var{end} will be restored.
6482 These offsets are relative to the addresses in the file, before
6483 the @var{bias} argument is applied.
6487 @node Core File Generation
6488 @section How to Produce a Core File from Your Program
6489 @cindex dump core from inferior
6491 A @dfn{core file} or @dfn{core dump} is a file that records the memory
6492 image of a running process and its process status (register values
6493 etc.). Its primary use is post-mortem debugging of a program that
6494 crashed while it ran outside a debugger. A program that crashes
6495 automatically produces a core file, unless this feature is disabled by
6496 the user. @xref{Files}, for information on invoking @value{GDBN} in
6497 the post-mortem debugging mode.
6499 Occasionally, you may wish to produce a core file of the program you
6500 are debugging in order to preserve a snapshot of its state.
6501 @value{GDBN} has a special command for that.
6505 @kindex generate-core-file
6506 @item generate-core-file [@var{file}]
6507 @itemx gcore [@var{file}]
6508 Produce a core dump of the inferior process. The optional argument
6509 @var{file} specifies the file name where to put the core dump. If not
6510 specified, the file name defaults to @file{core.@var{pid}}, where
6511 @var{pid} is the inferior process ID.
6513 Note that this command is implemented only for some systems (as of
6514 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, Unixware, and S390).
6517 @node Character Sets
6518 @section Character Sets
6519 @cindex character sets
6521 @cindex translating between character sets
6522 @cindex host character set
6523 @cindex target character set
6525 If the program you are debugging uses a different character set to
6526 represent characters and strings than the one @value{GDBN} uses itself,
6527 @value{GDBN} can automatically translate between the character sets for
6528 you. The character set @value{GDBN} uses we call the @dfn{host
6529 character set}; the one the inferior program uses we call the
6530 @dfn{target character set}.
6532 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
6533 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
6534 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
6535 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
6536 then the host character set is Latin-1, and the target character set is
6537 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
6538 target-charset EBCDIC-US}, then @value{GDBN} translates between
6539 @sc{ebcdic} and Latin 1 as you print character or string values, or use
6540 character and string literals in expressions.
6542 @value{GDBN} has no way to automatically recognize which character set
6543 the inferior program uses; you must tell it, using the @code{set
6544 target-charset} command, described below.
6546 Here are the commands for controlling @value{GDBN}'s character set
6550 @item set target-charset @var{charset}
6551 @kindex set target-charset
6552 Set the current target character set to @var{charset}. We list the
6553 character set names @value{GDBN} recognizes below, but if you type
6554 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6555 list the target character sets it supports.
6559 @item set host-charset @var{charset}
6560 @kindex set host-charset
6561 Set the current host character set to @var{charset}.
6563 By default, @value{GDBN} uses a host character set appropriate to the
6564 system it is running on; you can override that default using the
6565 @code{set host-charset} command.
6567 @value{GDBN} can only use certain character sets as its host character
6568 set. We list the character set names @value{GDBN} recognizes below, and
6569 indicate which can be host character sets, but if you type
6570 @code{set target-charset} followed by @key{TAB}@key{TAB}, @value{GDBN} will
6571 list the host character sets it supports.
6573 @item set charset @var{charset}
6575 Set the current host and target character sets to @var{charset}. As
6576 above, if you type @code{set charset} followed by @key{TAB}@key{TAB},
6577 @value{GDBN} will list the name of the character sets that can be used
6578 for both host and target.
6582 @kindex show charset
6583 Show the names of the current host and target charsets.
6585 @itemx show host-charset
6586 @kindex show host-charset
6587 Show the name of the current host charset.
6589 @itemx show target-charset
6590 @kindex show target-charset
6591 Show the name of the current target charset.
6595 @value{GDBN} currently includes support for the following character
6601 @cindex ASCII character set
6602 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
6606 @cindex ISO 8859-1 character set
6607 @cindex ISO Latin 1 character set
6608 The ISO Latin 1 character set. This extends @sc{ascii} with accented
6609 characters needed for French, German, and Spanish. @value{GDBN} can use
6610 this as its host character set.
6614 @cindex EBCDIC character set
6615 @cindex IBM1047 character set
6616 Variants of the @sc{ebcdic} character set, used on some of IBM's
6617 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
6618 @value{GDBN} cannot use these as its host character set.
6622 Note that these are all single-byte character sets. More work inside
6623 GDB is needed to support multi-byte or variable-width character
6624 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
6626 Here is an example of @value{GDBN}'s character set support in action.
6627 Assume that the following source code has been placed in the file
6628 @file{charset-test.c}:
6634 = @{72, 101, 108, 108, 111, 44, 32, 119,
6635 111, 114, 108, 100, 33, 10, 0@};
6636 char ibm1047_hello[]
6637 = @{200, 133, 147, 147, 150, 107, 64, 166,
6638 150, 153, 147, 132, 90, 37, 0@};
6642 printf ("Hello, world!\n");
6646 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6647 containing the string @samp{Hello, world!} followed by a newline,
6648 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6650 We compile the program, and invoke the debugger on it:
6653 $ gcc -g charset-test.c -o charset-test
6654 $ gdb -nw charset-test
6655 GNU gdb 2001-12-19-cvs
6656 Copyright 2001 Free Software Foundation, Inc.
6661 We can use the @code{show charset} command to see what character sets
6662 @value{GDBN} is currently using to interpret and display characters and
6666 (@value{GDBP}) show charset
6667 The current host and target character set is `ISO-8859-1'.
6671 For the sake of printing this manual, let's use @sc{ascii} as our
6672 initial character set:
6674 (@value{GDBP}) set charset ASCII
6675 (@value{GDBP}) show charset
6676 The current host and target character set is `ASCII'.
6680 Let's assume that @sc{ascii} is indeed the correct character set for our
6681 host system --- in other words, let's assume that if @value{GDBN} prints
6682 characters using the @sc{ascii} character set, our terminal will display
6683 them properly. Since our current target character set is also
6684 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6687 (@value{GDBP}) print ascii_hello
6688 $1 = 0x401698 "Hello, world!\n"
6689 (@value{GDBP}) print ascii_hello[0]
6694 @value{GDBN} uses the target character set for character and string
6695 literals you use in expressions:
6698 (@value{GDBP}) print '+'
6703 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6706 @value{GDBN} relies on the user to tell it which character set the
6707 target program uses. If we print @code{ibm1047_hello} while our target
6708 character set is still @sc{ascii}, we get jibberish:
6711 (@value{GDBP}) print ibm1047_hello
6712 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6713 (@value{GDBP}) print ibm1047_hello[0]
6718 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
6719 @value{GDBN} tells us the character sets it supports:
6722 (@value{GDBP}) set target-charset
6723 ASCII EBCDIC-US IBM1047 ISO-8859-1
6724 (@value{GDBP}) set target-charset
6727 We can select @sc{ibm1047} as our target character set, and examine the
6728 program's strings again. Now the @sc{ascii} string is wrong, but
6729 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6730 target character set, @sc{ibm1047}, to the host character set,
6731 @sc{ascii}, and they display correctly:
6734 (@value{GDBP}) set target-charset IBM1047
6735 (@value{GDBP}) show charset
6736 The current host character set is `ASCII'.
6737 The current target character set is `IBM1047'.
6738 (@value{GDBP}) print ascii_hello
6739 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6740 (@value{GDBP}) print ascii_hello[0]
6742 (@value{GDBP}) print ibm1047_hello
6743 $8 = 0x4016a8 "Hello, world!\n"
6744 (@value{GDBP}) print ibm1047_hello[0]
6749 As above, @value{GDBN} uses the target character set for character and
6750 string literals you use in expressions:
6753 (@value{GDBP}) print '+'
6758 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
6761 @node Caching Remote Data
6762 @section Caching Data of Remote Targets
6763 @cindex caching data of remote targets
6765 @value{GDBN} can cache data exchanged between the debugger and a
6766 remote target (@pxref{Remote}). Such caching generally improves
6767 performance, because it reduces the overhead of the remote protocol by
6768 bundling memory reads and writes into large chunks. Unfortunately,
6769 @value{GDBN} does not currently know anything about volatile
6770 registers, and thus data caching will produce incorrect results when
6771 volatile registers are in use.
6774 @kindex set remotecache
6775 @item set remotecache on
6776 @itemx set remotecache off
6777 Set caching state for remote targets. When @code{ON}, use data
6778 caching. By default, this option is @code{OFF}.
6780 @kindex show remotecache
6781 @item show remotecache
6782 Show the current state of data caching for remote targets.
6786 Print the information about the data cache performance. The
6787 information displayed includes: the dcache width and depth; and for
6788 each cache line, how many times it was referenced, and its data and
6789 state (dirty, bad, ok, etc.). This command is useful for debugging
6790 the data cache operation.
6795 @chapter C Preprocessor Macros
6797 Some languages, such as C and C@t{++}, provide a way to define and invoke
6798 ``preprocessor macros'' which expand into strings of tokens.
6799 @value{GDBN} can evaluate expressions containing macro invocations, show
6800 the result of macro expansion, and show a macro's definition, including
6801 where it was defined.
6803 You may need to compile your program specially to provide @value{GDBN}
6804 with information about preprocessor macros. Most compilers do not
6805 include macros in their debugging information, even when you compile
6806 with the @option{-g} flag. @xref{Compilation}.
6808 A program may define a macro at one point, remove that definition later,
6809 and then provide a different definition after that. Thus, at different
6810 points in the program, a macro may have different definitions, or have
6811 no definition at all. If there is a current stack frame, @value{GDBN}
6812 uses the macros in scope at that frame's source code line. Otherwise,
6813 @value{GDBN} uses the macros in scope at the current listing location;
6816 At the moment, @value{GDBN} does not support the @code{##}
6817 token-splicing operator, the @code{#} stringification operator, or
6818 variable-arity macros.
6820 Whenever @value{GDBN} evaluates an expression, it always expands any
6821 macro invocations present in the expression. @value{GDBN} also provides
6822 the following commands for working with macros explicitly.
6826 @kindex macro expand
6827 @cindex macro expansion, showing the results of preprocessor
6828 @cindex preprocessor macro expansion, showing the results of
6829 @cindex expanding preprocessor macros
6830 @item macro expand @var{expression}
6831 @itemx macro exp @var{expression}
6832 Show the results of expanding all preprocessor macro invocations in
6833 @var{expression}. Since @value{GDBN} simply expands macros, but does
6834 not parse the result, @var{expression} need not be a valid expression;
6835 it can be any string of tokens.
6838 @item macro expand-once @var{expression}
6839 @itemx macro exp1 @var{expression}
6840 @cindex expand macro once
6841 @i{(This command is not yet implemented.)} Show the results of
6842 expanding those preprocessor macro invocations that appear explicitly in
6843 @var{expression}. Macro invocations appearing in that expansion are
6844 left unchanged. This command allows you to see the effect of a
6845 particular macro more clearly, without being confused by further
6846 expansions. Since @value{GDBN} simply expands macros, but does not
6847 parse the result, @var{expression} need not be a valid expression; it
6848 can be any string of tokens.
6851 @cindex macro definition, showing
6852 @cindex definition, showing a macro's
6853 @item info macro @var{macro}
6854 Show the definition of the macro named @var{macro}, and describe the
6855 source location where that definition was established.
6857 @kindex macro define
6858 @cindex user-defined macros
6859 @cindex defining macros interactively
6860 @cindex macros, user-defined
6861 @item macro define @var{macro} @var{replacement-list}
6862 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6863 @i{(This command is not yet implemented.)} Introduce a definition for a
6864 preprocessor macro named @var{macro}, invocations of which are replaced
6865 by the tokens given in @var{replacement-list}. The first form of this
6866 command defines an ``object-like'' macro, which takes no arguments; the
6867 second form defines a ``function-like'' macro, which takes the arguments
6868 given in @var{arglist}.
6870 A definition introduced by this command is in scope in every expression
6871 evaluated in @value{GDBN}, until it is removed with the @command{macro
6872 undef} command, described below. The definition overrides all
6873 definitions for @var{macro} present in the program being debugged, as
6874 well as any previous user-supplied definition.
6877 @item macro undef @var{macro}
6878 @i{(This command is not yet implemented.)} Remove any user-supplied
6879 definition for the macro named @var{macro}. This command only affects
6880 definitions provided with the @command{macro define} command, described
6881 above; it cannot remove definitions present in the program being
6886 @i{(This command is not yet implemented.)} List all the macros
6887 defined using the @code{macro define} command.
6890 @cindex macros, example of debugging with
6891 Here is a transcript showing the above commands in action. First, we
6892 show our source files:
6900 #define ADD(x) (M + x)
6905 printf ("Hello, world!\n");
6907 printf ("We're so creative.\n");
6909 printf ("Goodbye, world!\n");
6916 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6917 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6918 compiler includes information about preprocessor macros in the debugging
6922 $ gcc -gdwarf-2 -g3 sample.c -o sample
6926 Now, we start @value{GDBN} on our sample program:
6930 GNU gdb 2002-05-06-cvs
6931 Copyright 2002 Free Software Foundation, Inc.
6932 GDB is free software, @dots{}
6936 We can expand macros and examine their definitions, even when the
6937 program is not running. @value{GDBN} uses the current listing position
6938 to decide which macro definitions are in scope:
6941 (@value{GDBP}) list main
6944 5 #define ADD(x) (M + x)
6949 10 printf ("Hello, world!\n");
6951 12 printf ("We're so creative.\n");
6952 (@value{GDBP}) info macro ADD
6953 Defined at /home/jimb/gdb/macros/play/sample.c:5
6954 #define ADD(x) (M + x)
6955 (@value{GDBP}) info macro Q
6956 Defined at /home/jimb/gdb/macros/play/sample.h:1
6957 included at /home/jimb/gdb/macros/play/sample.c:2
6959 (@value{GDBP}) macro expand ADD(1)
6960 expands to: (42 + 1)
6961 (@value{GDBP}) macro expand-once ADD(1)
6962 expands to: once (M + 1)
6966 In the example above, note that @command{macro expand-once} expands only
6967 the macro invocation explicit in the original text --- the invocation of
6968 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6969 which was introduced by @code{ADD}.
6971 Once the program is running, GDB uses the macro definitions in force at
6972 the source line of the current stack frame:
6975 (@value{GDBP}) break main
6976 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6978 Starting program: /home/jimb/gdb/macros/play/sample
6980 Breakpoint 1, main () at sample.c:10
6981 10 printf ("Hello, world!\n");
6985 At line 10, the definition of the macro @code{N} at line 9 is in force:
6988 (@value{GDBP}) info macro N
6989 Defined at /home/jimb/gdb/macros/play/sample.c:9
6991 (@value{GDBP}) macro expand N Q M
6993 (@value{GDBP}) print N Q M
6998 As we step over directives that remove @code{N}'s definition, and then
6999 give it a new definition, @value{GDBN} finds the definition (or lack
7000 thereof) in force at each point:
7005 12 printf ("We're so creative.\n");
7006 (@value{GDBP}) info macro N
7007 The symbol `N' has no definition as a C/C++ preprocessor macro
7008 at /home/jimb/gdb/macros/play/sample.c:12
7011 14 printf ("Goodbye, world!\n");
7012 (@value{GDBP}) info macro N
7013 Defined at /home/jimb/gdb/macros/play/sample.c:13
7015 (@value{GDBP}) macro expand N Q M
7016 expands to: 1729 < 42
7017 (@value{GDBP}) print N Q M
7024 @chapter Tracepoints
7025 @c This chapter is based on the documentation written by Michael
7026 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
7029 In some applications, it is not feasible for the debugger to interrupt
7030 the program's execution long enough for the developer to learn
7031 anything helpful about its behavior. If the program's correctness
7032 depends on its real-time behavior, delays introduced by a debugger
7033 might cause the program to change its behavior drastically, or perhaps
7034 fail, even when the code itself is correct. It is useful to be able
7035 to observe the program's behavior without interrupting it.
7037 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
7038 specify locations in the program, called @dfn{tracepoints}, and
7039 arbitrary expressions to evaluate when those tracepoints are reached.
7040 Later, using the @code{tfind} command, you can examine the values
7041 those expressions had when the program hit the tracepoints. The
7042 expressions may also denote objects in memory---structures or arrays,
7043 for example---whose values @value{GDBN} should record; while visiting
7044 a particular tracepoint, you may inspect those objects as if they were
7045 in memory at that moment. However, because @value{GDBN} records these
7046 values without interacting with you, it can do so quickly and
7047 unobtrusively, hopefully not disturbing the program's behavior.
7049 The tracepoint facility is currently available only for remote
7050 targets. @xref{Targets}. In addition, your remote target must know how
7051 to collect trace data. This functionality is implemented in the remote
7052 stub; however, none of the stubs distributed with @value{GDBN} support
7053 tracepoints as of this writing.
7055 This chapter describes the tracepoint commands and features.
7059 * Analyze Collected Data::
7060 * Tracepoint Variables::
7063 @node Set Tracepoints
7064 @section Commands to Set Tracepoints
7066 Before running such a @dfn{trace experiment}, an arbitrary number of
7067 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
7068 tracepoint has a number assigned to it by @value{GDBN}. Like with
7069 breakpoints, tracepoint numbers are successive integers starting from
7070 one. Many of the commands associated with tracepoints take the
7071 tracepoint number as their argument, to identify which tracepoint to
7074 For each tracepoint, you can specify, in advance, some arbitrary set
7075 of data that you want the target to collect in the trace buffer when
7076 it hits that tracepoint. The collected data can include registers,
7077 local variables, or global data. Later, you can use @value{GDBN}
7078 commands to examine the values these data had at the time the
7081 This section describes commands to set tracepoints and associated
7082 conditions and actions.
7085 * Create and Delete Tracepoints::
7086 * Enable and Disable Tracepoints::
7087 * Tracepoint Passcounts::
7088 * Tracepoint Actions::
7089 * Listing Tracepoints::
7090 * Starting and Stopping Trace Experiment::
7093 @node Create and Delete Tracepoints
7094 @subsection Create and Delete Tracepoints
7097 @cindex set tracepoint
7100 The @code{trace} command is very similar to the @code{break} command.
7101 Its argument can be a source line, a function name, or an address in
7102 the target program. @xref{Set Breaks}. The @code{trace} command
7103 defines a tracepoint, which is a point in the target program where the
7104 debugger will briefly stop, collect some data, and then allow the
7105 program to continue. Setting a tracepoint or changing its commands
7106 doesn't take effect until the next @code{tstart} command; thus, you
7107 cannot change the tracepoint attributes once a trace experiment is
7110 Here are some examples of using the @code{trace} command:
7113 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
7115 (@value{GDBP}) @b{trace +2} // 2 lines forward
7117 (@value{GDBP}) @b{trace my_function} // first source line of function
7119 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
7121 (@value{GDBP}) @b{trace *0x2117c4} // an address
7125 You can abbreviate @code{trace} as @code{tr}.
7128 @cindex last tracepoint number
7129 @cindex recent tracepoint number
7130 @cindex tracepoint number
7131 The convenience variable @code{$tpnum} records the tracepoint number
7132 of the most recently set tracepoint.
7134 @kindex delete tracepoint
7135 @cindex tracepoint deletion
7136 @item delete tracepoint @r{[}@var{num}@r{]}
7137 Permanently delete one or more tracepoints. With no argument, the
7138 default is to delete all tracepoints.
7143 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
7145 (@value{GDBP}) @b{delete trace} // remove all tracepoints
7149 You can abbreviate this command as @code{del tr}.
7152 @node Enable and Disable Tracepoints
7153 @subsection Enable and Disable Tracepoints
7156 @kindex disable tracepoint
7157 @item disable tracepoint @r{[}@var{num}@r{]}
7158 Disable tracepoint @var{num}, or all tracepoints if no argument
7159 @var{num} is given. A disabled tracepoint will have no effect during
7160 the next trace experiment, but it is not forgotten. You can re-enable
7161 a disabled tracepoint using the @code{enable tracepoint} command.
7163 @kindex enable tracepoint
7164 @item enable tracepoint @r{[}@var{num}@r{]}
7165 Enable tracepoint @var{num}, or all tracepoints. The enabled
7166 tracepoints will become effective the next time a trace experiment is
7170 @node Tracepoint Passcounts
7171 @subsection Tracepoint Passcounts
7175 @cindex tracepoint pass count
7176 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
7177 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
7178 automatically stop a trace experiment. If a tracepoint's passcount is
7179 @var{n}, then the trace experiment will be automatically stopped on
7180 the @var{n}'th time that tracepoint is hit. If the tracepoint number
7181 @var{num} is not specified, the @code{passcount} command sets the
7182 passcount of the most recently defined tracepoint. If no passcount is
7183 given, the trace experiment will run until stopped explicitly by the
7189 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
7190 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
7192 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
7193 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
7194 (@value{GDBP}) @b{trace foo}
7195 (@value{GDBP}) @b{pass 3}
7196 (@value{GDBP}) @b{trace bar}
7197 (@value{GDBP}) @b{pass 2}
7198 (@value{GDBP}) @b{trace baz}
7199 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
7200 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
7201 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
7202 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
7206 @node Tracepoint Actions
7207 @subsection Tracepoint Action Lists
7211 @cindex tracepoint actions
7212 @item actions @r{[}@var{num}@r{]}
7213 This command will prompt for a list of actions to be taken when the
7214 tracepoint is hit. If the tracepoint number @var{num} is not
7215 specified, this command sets the actions for the one that was most
7216 recently defined (so that you can define a tracepoint and then say
7217 @code{actions} without bothering about its number). You specify the
7218 actions themselves on the following lines, one action at a time, and
7219 terminate the actions list with a line containing just @code{end}. So
7220 far, the only defined actions are @code{collect} and
7221 @code{while-stepping}.
7223 @cindex remove actions from a tracepoint
7224 To remove all actions from a tracepoint, type @samp{actions @var{num}}
7225 and follow it immediately with @samp{end}.
7228 (@value{GDBP}) @b{collect @var{data}} // collect some data
7230 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
7232 (@value{GDBP}) @b{end} // signals the end of actions.
7235 In the following example, the action list begins with @code{collect}
7236 commands indicating the things to be collected when the tracepoint is
7237 hit. Then, in order to single-step and collect additional data
7238 following the tracepoint, a @code{while-stepping} command is used,
7239 followed by the list of things to be collected while stepping. The
7240 @code{while-stepping} command is terminated by its own separate
7241 @code{end} command. Lastly, the action list is terminated by an
7245 (@value{GDBP}) @b{trace foo}
7246 (@value{GDBP}) @b{actions}
7247 Enter actions for tracepoint 1, one per line:
7256 @kindex collect @r{(tracepoints)}
7257 @item collect @var{expr1}, @var{expr2}, @dots{}
7258 Collect values of the given expressions when the tracepoint is hit.
7259 This command accepts a comma-separated list of any valid expressions.
7260 In addition to global, static, or local variables, the following
7261 special arguments are supported:
7265 collect all registers
7268 collect all function arguments
7271 collect all local variables.
7274 You can give several consecutive @code{collect} commands, each one
7275 with a single argument, or one @code{collect} command with several
7276 arguments separated by commas: the effect is the same.
7278 The command @code{info scope} (@pxref{Symbols, info scope}) is
7279 particularly useful for figuring out what data to collect.
7281 @kindex while-stepping @r{(tracepoints)}
7282 @item while-stepping @var{n}
7283 Perform @var{n} single-step traces after the tracepoint, collecting
7284 new data at each step. The @code{while-stepping} command is
7285 followed by the list of what to collect while stepping (followed by
7286 its own @code{end} command):
7290 > collect $regs, myglobal
7296 You may abbreviate @code{while-stepping} as @code{ws} or
7300 @node Listing Tracepoints
7301 @subsection Listing Tracepoints
7304 @kindex info tracepoints
7306 @cindex information about tracepoints
7307 @item info tracepoints @r{[}@var{num}@r{]}
7308 Display information about the tracepoint @var{num}. If you don't specify
7309 a tracepoint number, displays information about all the tracepoints
7310 defined so far. For each tracepoint, the following information is
7317 whether it is enabled or disabled
7321 its passcount as given by the @code{passcount @var{n}} command
7323 its step count as given by the @code{while-stepping @var{n}} command
7325 where in the source files is the tracepoint set
7327 its action list as given by the @code{actions} command
7331 (@value{GDBP}) @b{info trace}
7332 Num Enb Address PassC StepC What
7333 1 y 0x002117c4 0 0 <gdb_asm>
7334 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
7335 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
7340 This command can be abbreviated @code{info tp}.
7343 @node Starting and Stopping Trace Experiment
7344 @subsection Starting and Stopping Trace Experiment
7348 @cindex start a new trace experiment
7349 @cindex collected data discarded
7351 This command takes no arguments. It starts the trace experiment, and
7352 begins collecting data. This has the side effect of discarding all
7353 the data collected in the trace buffer during the previous trace
7357 @cindex stop a running trace experiment
7359 This command takes no arguments. It ends the trace experiment, and
7360 stops collecting data.
7362 @strong{Note}: a trace experiment and data collection may stop
7363 automatically if any tracepoint's passcount is reached
7364 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
7367 @cindex status of trace data collection
7368 @cindex trace experiment, status of
7370 This command displays the status of the current trace data
7374 Here is an example of the commands we described so far:
7377 (@value{GDBP}) @b{trace gdb_c_test}
7378 (@value{GDBP}) @b{actions}
7379 Enter actions for tracepoint #1, one per line.
7380 > collect $regs,$locals,$args
7385 (@value{GDBP}) @b{tstart}
7386 [time passes @dots{}]
7387 (@value{GDBP}) @b{tstop}
7391 @node Analyze Collected Data
7392 @section Using the collected data
7394 After the tracepoint experiment ends, you use @value{GDBN} commands
7395 for examining the trace data. The basic idea is that each tracepoint
7396 collects a trace @dfn{snapshot} every time it is hit and another
7397 snapshot every time it single-steps. All these snapshots are
7398 consecutively numbered from zero and go into a buffer, and you can
7399 examine them later. The way you examine them is to @dfn{focus} on a
7400 specific trace snapshot. When the remote stub is focused on a trace
7401 snapshot, it will respond to all @value{GDBN} requests for memory and
7402 registers by reading from the buffer which belongs to that snapshot,
7403 rather than from @emph{real} memory or registers of the program being
7404 debugged. This means that @strong{all} @value{GDBN} commands
7405 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
7406 behave as if we were currently debugging the program state as it was
7407 when the tracepoint occurred. Any requests for data that are not in
7408 the buffer will fail.
7411 * tfind:: How to select a trace snapshot
7412 * tdump:: How to display all data for a snapshot
7413 * save-tracepoints:: How to save tracepoints for a future run
7417 @subsection @code{tfind @var{n}}
7420 @cindex select trace snapshot
7421 @cindex find trace snapshot
7422 The basic command for selecting a trace snapshot from the buffer is
7423 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
7424 counting from zero. If no argument @var{n} is given, the next
7425 snapshot is selected.
7427 Here are the various forms of using the @code{tfind} command.
7431 Find the first snapshot in the buffer. This is a synonym for
7432 @code{tfind 0} (since 0 is the number of the first snapshot).
7435 Stop debugging trace snapshots, resume @emph{live} debugging.
7438 Same as @samp{tfind none}.
7441 No argument means find the next trace snapshot.
7444 Find the previous trace snapshot before the current one. This permits
7445 retracing earlier steps.
7447 @item tfind tracepoint @var{num}
7448 Find the next snapshot associated with tracepoint @var{num}. Search
7449 proceeds forward from the last examined trace snapshot. If no
7450 argument @var{num} is given, it means find the next snapshot collected
7451 for the same tracepoint as the current snapshot.
7453 @item tfind pc @var{addr}
7454 Find the next snapshot associated with the value @var{addr} of the
7455 program counter. Search proceeds forward from the last examined trace
7456 snapshot. If no argument @var{addr} is given, it means find the next
7457 snapshot with the same value of PC as the current snapshot.
7459 @item tfind outside @var{addr1}, @var{addr2}
7460 Find the next snapshot whose PC is outside the given range of
7463 @item tfind range @var{addr1}, @var{addr2}
7464 Find the next snapshot whose PC is between @var{addr1} and
7465 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
7467 @item tfind line @r{[}@var{file}:@r{]}@var{n}
7468 Find the next snapshot associated with the source line @var{n}. If
7469 the optional argument @var{file} is given, refer to line @var{n} in
7470 that source file. Search proceeds forward from the last examined
7471 trace snapshot. If no argument @var{n} is given, it means find the
7472 next line other than the one currently being examined; thus saying
7473 @code{tfind line} repeatedly can appear to have the same effect as
7474 stepping from line to line in a @emph{live} debugging session.
7477 The default arguments for the @code{tfind} commands are specifically
7478 designed to make it easy to scan through the trace buffer. For
7479 instance, @code{tfind} with no argument selects the next trace
7480 snapshot, and @code{tfind -} with no argument selects the previous
7481 trace snapshot. So, by giving one @code{tfind} command, and then
7482 simply hitting @key{RET} repeatedly you can examine all the trace
7483 snapshots in order. Or, by saying @code{tfind -} and then hitting
7484 @key{RET} repeatedly you can examine the snapshots in reverse order.
7485 The @code{tfind line} command with no argument selects the snapshot
7486 for the next source line executed. The @code{tfind pc} command with
7487 no argument selects the next snapshot with the same program counter
7488 (PC) as the current frame. The @code{tfind tracepoint} command with
7489 no argument selects the next trace snapshot collected by the same
7490 tracepoint as the current one.
7492 In addition to letting you scan through the trace buffer manually,
7493 these commands make it easy to construct @value{GDBN} scripts that
7494 scan through the trace buffer and print out whatever collected data
7495 you are interested in. Thus, if we want to examine the PC, FP, and SP
7496 registers from each trace frame in the buffer, we can say this:
7499 (@value{GDBP}) @b{tfind start}
7500 (@value{GDBP}) @b{while ($trace_frame != -1)}
7501 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
7502 $trace_frame, $pc, $sp, $fp
7506 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
7507 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
7508 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
7509 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
7510 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
7511 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
7512 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
7513 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
7514 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
7515 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
7516 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
7519 Or, if we want to examine the variable @code{X} at each source line in
7523 (@value{GDBP}) @b{tfind start}
7524 (@value{GDBP}) @b{while ($trace_frame != -1)}
7525 > printf "Frame %d, X == %d\n", $trace_frame, X
7535 @subsection @code{tdump}
7537 @cindex dump all data collected at tracepoint
7538 @cindex tracepoint data, display
7540 This command takes no arguments. It prints all the data collected at
7541 the current trace snapshot.
7544 (@value{GDBP}) @b{trace 444}
7545 (@value{GDBP}) @b{actions}
7546 Enter actions for tracepoint #2, one per line:
7547 > collect $regs, $locals, $args, gdb_long_test
7550 (@value{GDBP}) @b{tstart}
7552 (@value{GDBP}) @b{tfind line 444}
7553 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
7555 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
7557 (@value{GDBP}) @b{tdump}
7558 Data collected at tracepoint 2, trace frame 1:
7559 d0 0xc4aa0085 -995491707
7563 d4 0x71aea3d 119204413
7568 a1 0x3000668 50333288
7571 a4 0x3000698 50333336
7573 fp 0x30bf3c 0x30bf3c
7574 sp 0x30bf34 0x30bf34
7576 pc 0x20b2c8 0x20b2c8
7580 p = 0x20e5b4 "gdb-test"
7587 gdb_long_test = 17 '\021'
7592 @node save-tracepoints
7593 @subsection @code{save-tracepoints @var{filename}}
7594 @kindex save-tracepoints
7595 @cindex save tracepoints for future sessions
7597 This command saves all current tracepoint definitions together with
7598 their actions and passcounts, into a file @file{@var{filename}}
7599 suitable for use in a later debugging session. To read the saved
7600 tracepoint definitions, use the @code{source} command (@pxref{Command
7603 @node Tracepoint Variables
7604 @section Convenience Variables for Tracepoints
7605 @cindex tracepoint variables
7606 @cindex convenience variables for tracepoints
7609 @vindex $trace_frame
7610 @item (int) $trace_frame
7611 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
7612 snapshot is selected.
7615 @item (int) $tracepoint
7616 The tracepoint for the current trace snapshot.
7619 @item (int) $trace_line
7620 The line number for the current trace snapshot.
7623 @item (char []) $trace_file
7624 The source file for the current trace snapshot.
7627 @item (char []) $trace_func
7628 The name of the function containing @code{$tracepoint}.
7631 Note: @code{$trace_file} is not suitable for use in @code{printf},
7632 use @code{output} instead.
7634 Here's a simple example of using these convenience variables for
7635 stepping through all the trace snapshots and printing some of their
7639 (@value{GDBP}) @b{tfind start}
7641 (@value{GDBP}) @b{while $trace_frame != -1}
7642 > output $trace_file
7643 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
7649 @chapter Debugging Programs That Use Overlays
7652 If your program is too large to fit completely in your target system's
7653 memory, you can sometimes use @dfn{overlays} to work around this
7654 problem. @value{GDBN} provides some support for debugging programs that
7658 * How Overlays Work:: A general explanation of overlays.
7659 * Overlay Commands:: Managing overlays in @value{GDBN}.
7660 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
7661 mapped by asking the inferior.
7662 * Overlay Sample Program:: A sample program using overlays.
7665 @node How Overlays Work
7666 @section How Overlays Work
7667 @cindex mapped overlays
7668 @cindex unmapped overlays
7669 @cindex load address, overlay's
7670 @cindex mapped address
7671 @cindex overlay area
7673 Suppose you have a computer whose instruction address space is only 64
7674 kilobytes long, but which has much more memory which can be accessed by
7675 other means: special instructions, segment registers, or memory
7676 management hardware, for example. Suppose further that you want to
7677 adapt a program which is larger than 64 kilobytes to run on this system.
7679 One solution is to identify modules of your program which are relatively
7680 independent, and need not call each other directly; call these modules
7681 @dfn{overlays}. Separate the overlays from the main program, and place
7682 their machine code in the larger memory. Place your main program in
7683 instruction memory, but leave at least enough space there to hold the
7684 largest overlay as well.
7686 Now, to call a function located in an overlay, you must first copy that
7687 overlay's machine code from the large memory into the space set aside
7688 for it in the instruction memory, and then jump to its entry point
7691 @c NB: In the below the mapped area's size is greater or equal to the
7692 @c size of all overlays. This is intentional to remind the developer
7693 @c that overlays don't necessarily need to be the same size.
7697 Data Instruction Larger
7698 Address Space Address Space Address Space
7699 +-----------+ +-----------+ +-----------+
7701 +-----------+ +-----------+ +-----------+<-- overlay 1
7702 | program | | main | .----| overlay 1 | load address
7703 | variables | | program | | +-----------+
7704 | and heap | | | | | |
7705 +-----------+ | | | +-----------+<-- overlay 2
7706 | | +-----------+ | | | load address
7707 +-----------+ | | | .-| overlay 2 |
7709 mapped --->+-----------+ | | +-----------+
7711 | overlay | <-' | | |
7712 | area | <---' +-----------+<-- overlay 3
7713 | | <---. | | load address
7714 +-----------+ `--| overlay 3 |
7721 @anchor{A code overlay}A code overlay
7725 The diagram (@pxref{A code overlay}) shows a system with separate data
7726 and instruction address spaces. To map an overlay, the program copies
7727 its code from the larger address space to the instruction address space.
7728 Since the overlays shown here all use the same mapped address, only one
7729 may be mapped at a time. For a system with a single address space for
7730 data and instructions, the diagram would be similar, except that the
7731 program variables and heap would share an address space with the main
7732 program and the overlay area.
7734 An overlay loaded into instruction memory and ready for use is called a
7735 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7736 instruction memory. An overlay not present (or only partially present)
7737 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7738 is its address in the larger memory. The mapped address is also called
7739 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7740 called the @dfn{load memory address}, or @dfn{LMA}.
7742 Unfortunately, overlays are not a completely transparent way to adapt a
7743 program to limited instruction memory. They introduce a new set of
7744 global constraints you must keep in mind as you design your program:
7749 Before calling or returning to a function in an overlay, your program
7750 must make sure that overlay is actually mapped. Otherwise, the call or
7751 return will transfer control to the right address, but in the wrong
7752 overlay, and your program will probably crash.
7755 If the process of mapping an overlay is expensive on your system, you
7756 will need to choose your overlays carefully to minimize their effect on
7757 your program's performance.
7760 The executable file you load onto your system must contain each
7761 overlay's instructions, appearing at the overlay's load address, not its
7762 mapped address. However, each overlay's instructions must be relocated
7763 and its symbols defined as if the overlay were at its mapped address.
7764 You can use GNU linker scripts to specify different load and relocation
7765 addresses for pieces of your program; see @ref{Overlay Description,,,
7766 ld.info, Using ld: the GNU linker}.
7769 The procedure for loading executable files onto your system must be able
7770 to load their contents into the larger address space as well as the
7771 instruction and data spaces.
7775 The overlay system described above is rather simple, and could be
7776 improved in many ways:
7781 If your system has suitable bank switch registers or memory management
7782 hardware, you could use those facilities to make an overlay's load area
7783 contents simply appear at their mapped address in instruction space.
7784 This would probably be faster than copying the overlay to its mapped
7785 area in the usual way.
7788 If your overlays are small enough, you could set aside more than one
7789 overlay area, and have more than one overlay mapped at a time.
7792 You can use overlays to manage data, as well as instructions. In
7793 general, data overlays are even less transparent to your design than
7794 code overlays: whereas code overlays only require care when you call or
7795 return to functions, data overlays require care every time you access
7796 the data. Also, if you change the contents of a data overlay, you
7797 must copy its contents back out to its load address before you can copy a
7798 different data overlay into the same mapped area.
7803 @node Overlay Commands
7804 @section Overlay Commands
7806 To use @value{GDBN}'s overlay support, each overlay in your program must
7807 correspond to a separate section of the executable file. The section's
7808 virtual memory address and load memory address must be the overlay's
7809 mapped and load addresses. Identifying overlays with sections allows
7810 @value{GDBN} to determine the appropriate address of a function or
7811 variable, depending on whether the overlay is mapped or not.
7813 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7814 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7819 Disable @value{GDBN}'s overlay support. When overlay support is
7820 disabled, @value{GDBN} assumes that all functions and variables are
7821 always present at their mapped addresses. By default, @value{GDBN}'s
7822 overlay support is disabled.
7824 @item overlay manual
7825 @cindex manual overlay debugging
7826 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7827 relies on you to tell it which overlays are mapped, and which are not,
7828 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7829 commands described below.
7831 @item overlay map-overlay @var{overlay}
7832 @itemx overlay map @var{overlay}
7833 @cindex map an overlay
7834 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7835 be the name of the object file section containing the overlay. When an
7836 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7837 functions and variables at their mapped addresses. @value{GDBN} assumes
7838 that any other overlays whose mapped ranges overlap that of
7839 @var{overlay} are now unmapped.
7841 @item overlay unmap-overlay @var{overlay}
7842 @itemx overlay unmap @var{overlay}
7843 @cindex unmap an overlay
7844 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7845 must be the name of the object file section containing the overlay.
7846 When an overlay is unmapped, @value{GDBN} assumes it can find the
7847 overlay's functions and variables at their load addresses.
7850 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7851 consults a data structure the overlay manager maintains in the inferior
7852 to see which overlays are mapped. For details, see @ref{Automatic
7855 @item overlay load-target
7857 @cindex reloading the overlay table
7858 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7859 re-reads the table @value{GDBN} automatically each time the inferior
7860 stops, so this command should only be necessary if you have changed the
7861 overlay mapping yourself using @value{GDBN}. This command is only
7862 useful when using automatic overlay debugging.
7864 @item overlay list-overlays
7866 @cindex listing mapped overlays
7867 Display a list of the overlays currently mapped, along with their mapped
7868 addresses, load addresses, and sizes.
7872 Normally, when @value{GDBN} prints a code address, it includes the name
7873 of the function the address falls in:
7876 (@value{GDBP}) print main
7877 $3 = @{int ()@} 0x11a0 <main>
7880 When overlay debugging is enabled, @value{GDBN} recognizes code in
7881 unmapped overlays, and prints the names of unmapped functions with
7882 asterisks around them. For example, if @code{foo} is a function in an
7883 unmapped overlay, @value{GDBN} prints it this way:
7886 (@value{GDBP}) overlay list
7887 No sections are mapped.
7888 (@value{GDBP}) print foo
7889 $5 = @{int (int)@} 0x100000 <*foo*>
7892 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7896 (@value{GDBP}) overlay list
7897 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7898 mapped at 0x1016 - 0x104a
7899 (@value{GDBP}) print foo
7900 $6 = @{int (int)@} 0x1016 <foo>
7903 When overlay debugging is enabled, @value{GDBN} can find the correct
7904 address for functions and variables in an overlay, whether or not the
7905 overlay is mapped. This allows most @value{GDBN} commands, like
7906 @code{break} and @code{disassemble}, to work normally, even on unmapped
7907 code. However, @value{GDBN}'s breakpoint support has some limitations:
7911 @cindex breakpoints in overlays
7912 @cindex overlays, setting breakpoints in
7913 You can set breakpoints in functions in unmapped overlays, as long as
7914 @value{GDBN} can write to the overlay at its load address.
7916 @value{GDBN} can not set hardware or simulator-based breakpoints in
7917 unmapped overlays. However, if you set a breakpoint at the end of your
7918 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7919 you are using manual overlay management), @value{GDBN} will re-set its
7920 breakpoints properly.
7924 @node Automatic Overlay Debugging
7925 @section Automatic Overlay Debugging
7926 @cindex automatic overlay debugging
7928 @value{GDBN} can automatically track which overlays are mapped and which
7929 are not, given some simple co-operation from the overlay manager in the
7930 inferior. If you enable automatic overlay debugging with the
7931 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7932 looks in the inferior's memory for certain variables describing the
7933 current state of the overlays.
7935 Here are the variables your overlay manager must define to support
7936 @value{GDBN}'s automatic overlay debugging:
7940 @item @code{_ovly_table}:
7941 This variable must be an array of the following structures:
7946 /* The overlay's mapped address. */
7949 /* The size of the overlay, in bytes. */
7952 /* The overlay's load address. */
7955 /* Non-zero if the overlay is currently mapped;
7957 unsigned long mapped;
7961 @item @code{_novlys}:
7962 This variable must be a four-byte signed integer, holding the total
7963 number of elements in @code{_ovly_table}.
7967 To decide whether a particular overlay is mapped or not, @value{GDBN}
7968 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7969 @code{lma} members equal the VMA and LMA of the overlay's section in the
7970 executable file. When @value{GDBN} finds a matching entry, it consults
7971 the entry's @code{mapped} member to determine whether the overlay is
7974 In addition, your overlay manager may define a function called
7975 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7976 will silently set a breakpoint there. If the overlay manager then
7977 calls this function whenever it has changed the overlay table, this
7978 will enable @value{GDBN} to accurately keep track of which overlays
7979 are in program memory, and update any breakpoints that may be set
7980 in overlays. This will allow breakpoints to work even if the
7981 overlays are kept in ROM or other non-writable memory while they
7982 are not being executed.
7984 @node Overlay Sample Program
7985 @section Overlay Sample Program
7986 @cindex overlay example program
7988 When linking a program which uses overlays, you must place the overlays
7989 at their load addresses, while relocating them to run at their mapped
7990 addresses. To do this, you must write a linker script (@pxref{Overlay
7991 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7992 since linker scripts are specific to a particular host system, target
7993 architecture, and target memory layout, this manual cannot provide
7994 portable sample code demonstrating @value{GDBN}'s overlay support.
7996 However, the @value{GDBN} source distribution does contain an overlaid
7997 program, with linker scripts for a few systems, as part of its test
7998 suite. The program consists of the following files from
7999 @file{gdb/testsuite/gdb.base}:
8003 The main program file.
8005 A simple overlay manager, used by @file{overlays.c}.
8010 Overlay modules, loaded and used by @file{overlays.c}.
8013 Linker scripts for linking the test program on the @code{d10v-elf}
8014 and @code{m32r-elf} targets.
8017 You can build the test program using the @code{d10v-elf} GCC
8018 cross-compiler like this:
8021 $ d10v-elf-gcc -g -c overlays.c
8022 $ d10v-elf-gcc -g -c ovlymgr.c
8023 $ d10v-elf-gcc -g -c foo.c
8024 $ d10v-elf-gcc -g -c bar.c
8025 $ d10v-elf-gcc -g -c baz.c
8026 $ d10v-elf-gcc -g -c grbx.c
8027 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
8028 baz.o grbx.o -Wl,-Td10v.ld -o overlays
8031 The build process is identical for any other architecture, except that
8032 you must substitute the appropriate compiler and linker script for the
8033 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
8037 @chapter Using @value{GDBN} with Different Languages
8040 Although programming languages generally have common aspects, they are
8041 rarely expressed in the same manner. For instance, in ANSI C,
8042 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
8043 Modula-2, it is accomplished by @code{p^}. Values can also be
8044 represented (and displayed) differently. Hex numbers in C appear as
8045 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
8047 @cindex working language
8048 Language-specific information is built into @value{GDBN} for some languages,
8049 allowing you to express operations like the above in your program's
8050 native language, and allowing @value{GDBN} to output values in a manner
8051 consistent with the syntax of your program's native language. The
8052 language you use to build expressions is called the @dfn{working
8056 * Setting:: Switching between source languages
8057 * Show:: Displaying the language
8058 * Checks:: Type and range checks
8059 * Supported languages:: Supported languages
8060 * Unsupported languages:: Unsupported languages
8064 @section Switching between source languages
8066 There are two ways to control the working language---either have @value{GDBN}
8067 set it automatically, or select it manually yourself. You can use the
8068 @code{set language} command for either purpose. On startup, @value{GDBN}
8069 defaults to setting the language automatically. The working language is
8070 used to determine how expressions you type are interpreted, how values
8073 In addition to the working language, every source file that
8074 @value{GDBN} knows about has its own working language. For some object
8075 file formats, the compiler might indicate which language a particular
8076 source file is in. However, most of the time @value{GDBN} infers the
8077 language from the name of the file. The language of a source file
8078 controls whether C@t{++} names are demangled---this way @code{backtrace} can
8079 show each frame appropriately for its own language. There is no way to
8080 set the language of a source file from within @value{GDBN}, but you can
8081 set the language associated with a filename extension. @xref{Show, ,
8082 Displaying the language}.
8084 This is most commonly a problem when you use a program, such
8085 as @code{cfront} or @code{f2c}, that generates C but is written in
8086 another language. In that case, make the
8087 program use @code{#line} directives in its C output; that way
8088 @value{GDBN} will know the correct language of the source code of the original
8089 program, and will display that source code, not the generated C code.
8092 * Filenames:: Filename extensions and languages.
8093 * Manually:: Setting the working language manually
8094 * Automatically:: Having @value{GDBN} infer the source language
8098 @subsection List of filename extensions and languages
8100 If a source file name ends in one of the following extensions, then
8101 @value{GDBN} infers that its language is the one indicated.
8122 Objective-C source file
8129 Modula-2 source file
8133 Assembler source file. This actually behaves almost like C, but
8134 @value{GDBN} does not skip over function prologues when stepping.
8137 In addition, you may set the language associated with a filename
8138 extension. @xref{Show, , Displaying the language}.
8141 @subsection Setting the working language
8143 If you allow @value{GDBN} to set the language automatically,
8144 expressions are interpreted the same way in your debugging session and
8147 @kindex set language
8148 If you wish, you may set the language manually. To do this, issue the
8149 command @samp{set language @var{lang}}, where @var{lang} is the name of
8151 @code{c} or @code{modula-2}.
8152 For a list of the supported languages, type @samp{set language}.
8154 Setting the language manually prevents @value{GDBN} from updating the working
8155 language automatically. This can lead to confusion if you try
8156 to debug a program when the working language is not the same as the
8157 source language, when an expression is acceptable to both
8158 languages---but means different things. For instance, if the current
8159 source file were written in C, and @value{GDBN} was parsing Modula-2, a
8167 might not have the effect you intended. In C, this means to add
8168 @code{b} and @code{c} and place the result in @code{a}. The result
8169 printed would be the value of @code{a}. In Modula-2, this means to compare
8170 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
8173 @subsection Having @value{GDBN} infer the source language
8175 To have @value{GDBN} set the working language automatically, use
8176 @samp{set language local} or @samp{set language auto}. @value{GDBN}
8177 then infers the working language. That is, when your program stops in a
8178 frame (usually by encountering a breakpoint), @value{GDBN} sets the
8179 working language to the language recorded for the function in that
8180 frame. If the language for a frame is unknown (that is, if the function
8181 or block corresponding to the frame was defined in a source file that
8182 does not have a recognized extension), the current working language is
8183 not changed, and @value{GDBN} issues a warning.
8185 This may not seem necessary for most programs, which are written
8186 entirely in one source language. However, program modules and libraries
8187 written in one source language can be used by a main program written in
8188 a different source language. Using @samp{set language auto} in this
8189 case frees you from having to set the working language manually.
8192 @section Displaying the language
8194 The following commands help you find out which language is the
8195 working language, and also what language source files were written in.
8199 @kindex show language
8200 Display the current working language. This is the
8201 language you can use with commands such as @code{print} to
8202 build and compute expressions that may involve variables in your program.
8205 @kindex info frame@r{, show the source language}
8206 Display the source language for this frame. This language becomes the
8207 working language if you use an identifier from this frame.
8208 @xref{Frame Info, ,Information about a frame}, to identify the other
8209 information listed here.
8212 @kindex info source@r{, show the source language}
8213 Display the source language of this source file.
8214 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
8215 information listed here.
8218 In unusual circumstances, you may have source files with extensions
8219 not in the standard list. You can then set the extension associated
8220 with a language explicitly:
8223 @item set extension-language @var{ext} @var{language}
8224 @kindex set extension-language
8225 Tell @value{GDBN} that source files with extension @var{ext} are to be
8226 assumed as written in the source language @var{language}.
8228 @item info extensions
8229 @kindex info extensions
8230 List all the filename extensions and the associated languages.
8234 @section Type and range checking
8237 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
8238 checking are included, but they do not yet have any effect. This
8239 section documents the intended facilities.
8241 @c FIXME remove warning when type/range code added
8243 Some languages are designed to guard you against making seemingly common
8244 errors through a series of compile- and run-time checks. These include
8245 checking the type of arguments to functions and operators, and making
8246 sure mathematical overflows are caught at run time. Checks such as
8247 these help to ensure a program's correctness once it has been compiled
8248 by eliminating type mismatches, and providing active checks for range
8249 errors when your program is running.
8251 @value{GDBN} can check for conditions like the above if you wish.
8252 Although @value{GDBN} does not check the statements in your program,
8253 it can check expressions entered directly into @value{GDBN} for
8254 evaluation via the @code{print} command, for example. As with the
8255 working language, @value{GDBN} can also decide whether or not to check
8256 automatically based on your program's source language.
8257 @xref{Supported languages, ,Supported languages}, for the default
8258 settings of supported languages.
8261 * Type Checking:: An overview of type checking
8262 * Range Checking:: An overview of range checking
8265 @cindex type checking
8266 @cindex checks, type
8268 @subsection An overview of type checking
8270 Some languages, such as Modula-2, are strongly typed, meaning that the
8271 arguments to operators and functions have to be of the correct type,
8272 otherwise an error occurs. These checks prevent type mismatch
8273 errors from ever causing any run-time problems. For example,
8281 The second example fails because the @code{CARDINAL} 1 is not
8282 type-compatible with the @code{REAL} 2.3.
8284 For the expressions you use in @value{GDBN} commands, you can tell the
8285 @value{GDBN} type checker to skip checking;
8286 to treat any mismatches as errors and abandon the expression;
8287 or to only issue warnings when type mismatches occur,
8288 but evaluate the expression anyway. When you choose the last of
8289 these, @value{GDBN} evaluates expressions like the second example above, but
8290 also issues a warning.
8292 Even if you turn type checking off, there may be other reasons
8293 related to type that prevent @value{GDBN} from evaluating an expression.
8294 For instance, @value{GDBN} does not know how to add an @code{int} and
8295 a @code{struct foo}. These particular type errors have nothing to do
8296 with the language in use, and usually arise from expressions, such as
8297 the one described above, which make little sense to evaluate anyway.
8299 Each language defines to what degree it is strict about type. For
8300 instance, both Modula-2 and C require the arguments to arithmetical
8301 operators to be numbers. In C, enumerated types and pointers can be
8302 represented as numbers, so that they are valid arguments to mathematical
8303 operators. @xref{Supported languages, ,Supported languages}, for further
8304 details on specific languages.
8306 @value{GDBN} provides some additional commands for controlling the type checker:
8308 @kindex set check type
8309 @kindex show check type
8311 @item set check type auto
8312 Set type checking on or off based on the current working language.
8313 @xref{Supported languages, ,Supported languages}, for the default settings for
8316 @item set check type on
8317 @itemx set check type off
8318 Set type checking on or off, overriding the default setting for the
8319 current working language. Issue a warning if the setting does not
8320 match the language default. If any type mismatches occur in
8321 evaluating an expression while type checking is on, @value{GDBN} prints a
8322 message and aborts evaluation of the expression.
8324 @item set check type warn
8325 Cause the type checker to issue warnings, but to always attempt to
8326 evaluate the expression. Evaluating the expression may still
8327 be impossible for other reasons. For example, @value{GDBN} cannot add
8328 numbers and structures.
8331 Show the current setting of the type checker, and whether or not @value{GDBN}
8332 is setting it automatically.
8335 @cindex range checking
8336 @cindex checks, range
8337 @node Range Checking
8338 @subsection An overview of range checking
8340 In some languages (such as Modula-2), it is an error to exceed the
8341 bounds of a type; this is enforced with run-time checks. Such range
8342 checking is meant to ensure program correctness by making sure
8343 computations do not overflow, or indices on an array element access do
8344 not exceed the bounds of the array.
8346 For expressions you use in @value{GDBN} commands, you can tell
8347 @value{GDBN} to treat range errors in one of three ways: ignore them,
8348 always treat them as errors and abandon the expression, or issue
8349 warnings but evaluate the expression anyway.
8351 A range error can result from numerical overflow, from exceeding an
8352 array index bound, or when you type a constant that is not a member
8353 of any type. Some languages, however, do not treat overflows as an
8354 error. In many implementations of C, mathematical overflow causes the
8355 result to ``wrap around'' to lower values---for example, if @var{m} is
8356 the largest integer value, and @var{s} is the smallest, then
8359 @var{m} + 1 @result{} @var{s}
8362 This, too, is specific to individual languages, and in some cases
8363 specific to individual compilers or machines. @xref{Supported languages, ,
8364 Supported languages}, for further details on specific languages.
8366 @value{GDBN} provides some additional commands for controlling the range checker:
8368 @kindex set check range
8369 @kindex show check range
8371 @item set check range auto
8372 Set range checking on or off based on the current working language.
8373 @xref{Supported languages, ,Supported languages}, for the default settings for
8376 @item set check range on
8377 @itemx set check range off
8378 Set range checking on or off, overriding the default setting for the
8379 current working language. A warning is issued if the setting does not
8380 match the language default. If a range error occurs and range checking is on,
8381 then a message is printed and evaluation of the expression is aborted.
8383 @item set check range warn
8384 Output messages when the @value{GDBN} range checker detects a range error,
8385 but attempt to evaluate the expression anyway. Evaluating the
8386 expression may still be impossible for other reasons, such as accessing
8387 memory that the process does not own (a typical example from many Unix
8391 Show the current setting of the range checker, and whether or not it is
8392 being set automatically by @value{GDBN}.
8395 @node Supported languages
8396 @section Supported languages
8398 @value{GDBN} supports C, C@t{++}, Objective-C, Fortran, Java, Pascal,
8399 assembly, Modula-2, and Ada.
8400 @c This is false ...
8401 Some @value{GDBN} features may be used in expressions regardless of the
8402 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
8403 and the @samp{@{type@}addr} construct (@pxref{Expressions,
8404 ,Expressions}) can be used with the constructs of any supported
8407 The following sections detail to what degree each source language is
8408 supported by @value{GDBN}. These sections are not meant to be language
8409 tutorials or references, but serve only as a reference guide to what the
8410 @value{GDBN} expression parser accepts, and what input and output
8411 formats should look like for different languages. There are many good
8412 books written on each of these languages; please look to these for a
8413 language reference or tutorial.
8417 * Objective-C:: Objective-C
8420 * Modula-2:: Modula-2
8425 @subsection C and C@t{++}
8427 @cindex C and C@t{++}
8428 @cindex expressions in C or C@t{++}
8430 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
8431 to both languages. Whenever this is the case, we discuss those languages
8435 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
8436 @cindex @sc{gnu} C@t{++}
8437 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
8438 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
8439 effectively, you must compile your C@t{++} programs with a supported
8440 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
8441 compiler (@code{aCC}).
8443 For best results when using @sc{gnu} C@t{++}, use the DWARF 2 debugging
8444 format; if it doesn't work on your system, try the stabs+ debugging
8445 format. You can select those formats explicitly with the @code{g++}
8446 command-line options @option{-gdwarf-2} and @option{-gstabs+}.
8447 @xref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
8448 CC, gcc.info, Using @sc{gnu} CC}.
8451 * C Operators:: C and C@t{++} operators
8452 * C Constants:: C and C@t{++} constants
8453 * C plus plus expressions:: C@t{++} expressions
8454 * C Defaults:: Default settings for C and C@t{++}
8455 * C Checks:: C and C@t{++} type and range checks
8456 * Debugging C:: @value{GDBN} and C
8457 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
8461 @subsubsection C and C@t{++} operators
8463 @cindex C and C@t{++} operators
8465 Operators must be defined on values of specific types. For instance,
8466 @code{+} is defined on numbers, but not on structures. Operators are
8467 often defined on groups of types.
8469 For the purposes of C and C@t{++}, the following definitions hold:
8474 @emph{Integral types} include @code{int} with any of its storage-class
8475 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
8478 @emph{Floating-point types} include @code{float}, @code{double}, and
8479 @code{long double} (if supported by the target platform).
8482 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
8485 @emph{Scalar types} include all of the above.
8490 The following operators are supported. They are listed here
8491 in order of increasing precedence:
8495 The comma or sequencing operator. Expressions in a comma-separated list
8496 are evaluated from left to right, with the result of the entire
8497 expression being the last expression evaluated.
8500 Assignment. The value of an assignment expression is the value
8501 assigned. Defined on scalar types.
8504 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
8505 and translated to @w{@code{@var{a} = @var{a op b}}}.
8506 @w{@code{@var{op}=}} and @code{=} have the same precedence.
8507 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
8508 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
8511 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
8512 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
8516 Logical @sc{or}. Defined on integral types.
8519 Logical @sc{and}. Defined on integral types.
8522 Bitwise @sc{or}. Defined on integral types.
8525 Bitwise exclusive-@sc{or}. Defined on integral types.
8528 Bitwise @sc{and}. Defined on integral types.
8531 Equality and inequality. Defined on scalar types. The value of these
8532 expressions is 0 for false and non-zero for true.
8534 @item <@r{, }>@r{, }<=@r{, }>=
8535 Less than, greater than, less than or equal, greater than or equal.
8536 Defined on scalar types. The value of these expressions is 0 for false
8537 and non-zero for true.
8540 left shift, and right shift. Defined on integral types.
8543 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8546 Addition and subtraction. Defined on integral types, floating-point types and
8549 @item *@r{, }/@r{, }%
8550 Multiplication, division, and modulus. Multiplication and division are
8551 defined on integral and floating-point types. Modulus is defined on
8555 Increment and decrement. When appearing before a variable, the
8556 operation is performed before the variable is used in an expression;
8557 when appearing after it, the variable's value is used before the
8558 operation takes place.
8561 Pointer dereferencing. Defined on pointer types. Same precedence as
8565 Address operator. Defined on variables. Same precedence as @code{++}.
8567 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
8568 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
8569 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
8570 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
8574 Negative. Defined on integral and floating-point types. Same
8575 precedence as @code{++}.
8578 Logical negation. Defined on integral types. Same precedence as
8582 Bitwise complement operator. Defined on integral types. Same precedence as
8587 Structure member, and pointer-to-structure member. For convenience,
8588 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
8589 pointer based on the stored type information.
8590 Defined on @code{struct} and @code{union} data.
8593 Dereferences of pointers to members.
8596 Array indexing. @code{@var{a}[@var{i}]} is defined as
8597 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
8600 Function parameter list. Same precedence as @code{->}.
8603 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
8604 and @code{class} types.
8607 Doubled colons also represent the @value{GDBN} scope operator
8608 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
8612 If an operator is redefined in the user code, @value{GDBN} usually
8613 attempts to invoke the redefined version instead of using the operator's
8621 @subsubsection C and C@t{++} constants
8623 @cindex C and C@t{++} constants
8625 @value{GDBN} allows you to express the constants of C and C@t{++} in the
8630 Integer constants are a sequence of digits. Octal constants are
8631 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
8632 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
8633 @samp{l}, specifying that the constant should be treated as a
8637 Floating point constants are a sequence of digits, followed by a decimal
8638 point, followed by a sequence of digits, and optionally followed by an
8639 exponent. An exponent is of the form:
8640 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
8641 sequence of digits. The @samp{+} is optional for positive exponents.
8642 A floating-point constant may also end with a letter @samp{f} or
8643 @samp{F}, specifying that the constant should be treated as being of
8644 the @code{float} (as opposed to the default @code{double}) type; or with
8645 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
8649 Enumerated constants consist of enumerated identifiers, or their
8650 integral equivalents.
8653 Character constants are a single character surrounded by single quotes
8654 (@code{'}), or a number---the ordinal value of the corresponding character
8655 (usually its @sc{ascii} value). Within quotes, the single character may
8656 be represented by a letter or by @dfn{escape sequences}, which are of
8657 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
8658 of the character's ordinal value; or of the form @samp{\@var{x}}, where
8659 @samp{@var{x}} is a predefined special character---for example,
8660 @samp{\n} for newline.
8663 String constants are a sequence of character constants surrounded by
8664 double quotes (@code{"}). Any valid character constant (as described
8665 above) may appear. Double quotes within the string must be preceded by
8666 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8670 Pointer constants are an integral value. You can also write pointers
8671 to constants using the C operator @samp{&}.
8674 Array constants are comma-separated lists surrounded by braces @samp{@{}
8675 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8676 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8677 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8681 * C plus plus expressions::
8688 @node C plus plus expressions
8689 @subsubsection C@t{++} expressions
8691 @cindex expressions in C@t{++}
8692 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8694 @cindex debugging C@t{++} programs
8695 @cindex C@t{++} compilers
8696 @cindex debug formats and C@t{++}
8697 @cindex @value{NGCC} and C@t{++}
8699 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8700 proper compiler and the proper debug format. Currently, @value{GDBN}
8701 works best when debugging C@t{++} code that is compiled with
8702 @value{NGCC} 2.95.3 or with @value{NGCC} 3.1 or newer, using the options
8703 @option{-gdwarf-2} or @option{-gstabs+}. DWARF 2 is preferred over
8704 stabs+. Most configurations of @value{NGCC} emit either DWARF 2 or
8705 stabs+ as their default debug format, so you usually don't need to
8706 specify a debug format explicitly. Other compilers and/or debug formats
8707 are likely to work badly or not at all when using @value{GDBN} to debug
8713 @cindex member functions
8715 Member function calls are allowed; you can use expressions like
8718 count = aml->GetOriginal(x, y)
8721 @vindex this@r{, inside C@t{++} member functions}
8722 @cindex namespace in C@t{++}
8724 While a member function is active (in the selected stack frame), your
8725 expressions have the same namespace available as the member function;
8726 that is, @value{GDBN} allows implicit references to the class instance
8727 pointer @code{this} following the same rules as C@t{++}.
8729 @cindex call overloaded functions
8730 @cindex overloaded functions, calling
8731 @cindex type conversions in C@t{++}
8733 You can call overloaded functions; @value{GDBN} resolves the function
8734 call to the right definition, with some restrictions. @value{GDBN} does not
8735 perform overload resolution involving user-defined type conversions,
8736 calls to constructors, or instantiations of templates that do not exist
8737 in the program. It also cannot handle ellipsis argument lists or
8740 It does perform integral conversions and promotions, floating-point
8741 promotions, arithmetic conversions, pointer conversions, conversions of
8742 class objects to base classes, and standard conversions such as those of
8743 functions or arrays to pointers; it requires an exact match on the
8744 number of function arguments.
8746 Overload resolution is always performed, unless you have specified
8747 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8748 ,@value{GDBN} features for C@t{++}}.
8750 You must specify @code{set overload-resolution off} in order to use an
8751 explicit function signature to call an overloaded function, as in
8753 p 'foo(char,int)'('x', 13)
8756 The @value{GDBN} command-completion facility can simplify this;
8757 see @ref{Completion, ,Command completion}.
8759 @cindex reference declarations
8761 @value{GDBN} understands variables declared as C@t{++} references; you can use
8762 them in expressions just as you do in C@t{++} source---they are automatically
8765 In the parameter list shown when @value{GDBN} displays a frame, the values of
8766 reference variables are not displayed (unlike other variables); this
8767 avoids clutter, since references are often used for large structures.
8768 The @emph{address} of a reference variable is always shown, unless
8769 you have specified @samp{set print address off}.
8772 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8773 expressions can use it just as expressions in your program do. Since
8774 one scope may be defined in another, you can use @code{::} repeatedly if
8775 necessary, for example in an expression like
8776 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8777 resolving name scope by reference to source files, in both C and C@t{++}
8778 debugging (@pxref{Variables, ,Program variables}).
8781 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8782 calling virtual functions correctly, printing out virtual bases of
8783 objects, calling functions in a base subobject, casting objects, and
8784 invoking user-defined operators.
8787 @subsubsection C and C@t{++} defaults
8789 @cindex C and C@t{++} defaults
8791 If you allow @value{GDBN} to set type and range checking automatically, they
8792 both default to @code{off} whenever the working language changes to
8793 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8794 selects the working language.
8796 If you allow @value{GDBN} to set the language automatically, it
8797 recognizes source files whose names end with @file{.c}, @file{.C}, or
8798 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8799 these files, it sets the working language to C or C@t{++}.
8800 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8801 for further details.
8803 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8804 @c unimplemented. If (b) changes, it might make sense to let this node
8805 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8808 @subsubsection C and C@t{++} type and range checks
8810 @cindex C and C@t{++} checks
8812 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8813 is not used. However, if you turn type checking on, @value{GDBN}
8814 considers two variables type equivalent if:
8818 The two variables are structured and have the same structure, union, or
8822 The two variables have the same type name, or types that have been
8823 declared equivalent through @code{typedef}.
8826 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8829 The two @code{struct}, @code{union}, or @code{enum} variables are
8830 declared in the same declaration. (Note: this may not be true for all C
8835 Range checking, if turned on, is done on mathematical operations. Array
8836 indices are not checked, since they are often used to index a pointer
8837 that is not itself an array.
8840 @subsubsection @value{GDBN} and C
8842 The @code{set print union} and @code{show print union} commands apply to
8843 the @code{union} type. When set to @samp{on}, any @code{union} that is
8844 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8845 appears as @samp{@{...@}}.
8847 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8848 with pointers and a memory allocation function. @xref{Expressions,
8852 * Debugging C plus plus::
8855 @node Debugging C plus plus
8856 @subsubsection @value{GDBN} features for C@t{++}
8858 @cindex commands for C@t{++}
8860 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8861 designed specifically for use with C@t{++}. Here is a summary:
8864 @cindex break in overloaded functions
8865 @item @r{breakpoint menus}
8866 When you want a breakpoint in a function whose name is overloaded,
8867 @value{GDBN} breakpoint menus help you specify which function definition
8868 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8870 @cindex overloading in C@t{++}
8871 @item rbreak @var{regex}
8872 Setting breakpoints using regular expressions is helpful for setting
8873 breakpoints on overloaded functions that are not members of any special
8875 @xref{Set Breaks, ,Setting breakpoints}.
8877 @cindex C@t{++} exception handling
8880 Debug C@t{++} exception handling using these commands. @xref{Set
8881 Catchpoints, , Setting catchpoints}.
8884 @item ptype @var{typename}
8885 Print inheritance relationships as well as other information for type
8887 @xref{Symbols, ,Examining the Symbol Table}.
8889 @cindex C@t{++} symbol display
8890 @item set print demangle
8891 @itemx show print demangle
8892 @itemx set print asm-demangle
8893 @itemx show print asm-demangle
8894 Control whether C@t{++} symbols display in their source form, both when
8895 displaying code as C@t{++} source and when displaying disassemblies.
8896 @xref{Print Settings, ,Print settings}.
8898 @item set print object
8899 @itemx show print object
8900 Choose whether to print derived (actual) or declared types of objects.
8901 @xref{Print Settings, ,Print settings}.
8903 @item set print vtbl
8904 @itemx show print vtbl
8905 Control the format for printing virtual function tables.
8906 @xref{Print Settings, ,Print settings}.
8907 (The @code{vtbl} commands do not work on programs compiled with the HP
8908 ANSI C@t{++} compiler (@code{aCC}).)
8910 @kindex set overload-resolution
8911 @cindex overloaded functions, overload resolution
8912 @item set overload-resolution on
8913 Enable overload resolution for C@t{++} expression evaluation. The default
8914 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8915 and searches for a function whose signature matches the argument types,
8916 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8917 expressions}, for details). If it cannot find a match, it emits a
8920 @item set overload-resolution off
8921 Disable overload resolution for C@t{++} expression evaluation. For
8922 overloaded functions that are not class member functions, @value{GDBN}
8923 chooses the first function of the specified name that it finds in the
8924 symbol table, whether or not its arguments are of the correct type. For
8925 overloaded functions that are class member functions, @value{GDBN}
8926 searches for a function whose signature @emph{exactly} matches the
8929 @kindex show overload-resolution
8930 @item show overload-resolution
8931 Show the current setting of overload resolution.
8933 @item @r{Overloaded symbol names}
8934 You can specify a particular definition of an overloaded symbol, using
8935 the same notation that is used to declare such symbols in C@t{++}: type
8936 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8937 also use the @value{GDBN} command-line word completion facilities to list the
8938 available choices, or to finish the type list for you.
8939 @xref{Completion,, Command completion}, for details on how to do this.
8943 @subsection Objective-C
8946 This section provides information about some commands and command
8947 options that are useful for debugging Objective-C code. See also
8948 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
8949 few more commands specific to Objective-C support.
8952 * Method Names in Commands::
8953 * The Print Command with Objective-C::
8956 @node Method Names in Commands, The Print Command with Objective-C, Objective-C, Objective-C
8957 @subsubsection Method Names in Commands
8959 The following commands have been extended to accept Objective-C method
8960 names as line specifications:
8962 @kindex clear@r{, and Objective-C}
8963 @kindex break@r{, and Objective-C}
8964 @kindex info line@r{, and Objective-C}
8965 @kindex jump@r{, and Objective-C}
8966 @kindex list@r{, and Objective-C}
8970 @item @code{info line}
8975 A fully qualified Objective-C method name is specified as
8978 -[@var{Class} @var{methodName}]
8981 where the minus sign is used to indicate an instance method and a
8982 plus sign (not shown) is used to indicate a class method. The class
8983 name @var{Class} and method name @var{methodName} are enclosed in
8984 brackets, similar to the way messages are specified in Objective-C
8985 source code. For example, to set a breakpoint at the @code{create}
8986 instance method of class @code{Fruit} in the program currently being
8990 break -[Fruit create]
8993 To list ten program lines around the @code{initialize} class method,
8997 list +[NSText initialize]
9000 In the current version of @value{GDBN}, the plus or minus sign is
9001 required. In future versions of @value{GDBN}, the plus or minus
9002 sign will be optional, but you can use it to narrow the search. It
9003 is also possible to specify just a method name:
9009 You must specify the complete method name, including any colons. If
9010 your program's source files contain more than one @code{create} method,
9011 you'll be presented with a numbered list of classes that implement that
9012 method. Indicate your choice by number, or type @samp{0} to exit if
9015 As another example, to clear a breakpoint established at the
9016 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
9019 clear -[NSWindow makeKeyAndOrderFront:]
9022 @node The Print Command with Objective-C
9023 @subsubsection The Print Command With Objective-C
9024 @cindex Objective-C, print objects
9025 @kindex print-object
9026 @kindex po @r{(@code{print-object})}
9028 The print command has also been extended to accept methods. For example:
9031 print -[@var{object} hash]
9034 @cindex print an Objective-C object description
9035 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
9037 will tell @value{GDBN} to send the @code{hash} message to @var{object}
9038 and print the result. Also, an additional command has been added,
9039 @code{print-object} or @code{po} for short, which is meant to print
9040 the description of an object. However, this command may only work
9041 with certain Objective-C libraries that have a particular hook
9042 function, @code{_NSPrintForDebugger}, defined.
9046 @cindex Fortran-specific support in @value{GDBN}
9049 @cindex @code{COMMON} blocks, Fortran
9051 @item info common @r{[}@var{common-name}@r{]}
9052 This command prints the values contained in the Fortran @code{COMMON}
9053 block whose name is @var{common-name}. With no argument, the names of
9054 all @code{COMMON} blocks visible at current program location are
9058 Fortran symbols are usually case-insensitive, so @value{GDBN} by
9059 default uses case-insensitive matches for Fortran symbols. You can
9060 change that with the @samp{set case-insensitive} command, see
9061 @ref{Symbols}, for the details.
9066 @cindex Pascal support in @value{GDBN}, limitations
9067 Debugging Pascal programs which use sets, subranges, file variables, or
9068 nested functions does not currently work. @value{GDBN} does not support
9069 entering expressions, printing values, or similar features using Pascal
9072 The Pascal-specific command @code{set print pascal_static-members}
9073 controls whether static members of Pascal objects are displayed.
9074 @xref{Print Settings, pascal_static-members}.
9077 @subsection Modula-2
9079 @cindex Modula-2, @value{GDBN} support
9081 The extensions made to @value{GDBN} to support Modula-2 only support
9082 output from the @sc{gnu} Modula-2 compiler (which is currently being
9083 developed). Other Modula-2 compilers are not currently supported, and
9084 attempting to debug executables produced by them is most likely
9085 to give an error as @value{GDBN} reads in the executable's symbol
9088 @cindex expressions in Modula-2
9090 * M2 Operators:: Built-in operators
9091 * Built-In Func/Proc:: Built-in functions and procedures
9092 * M2 Constants:: Modula-2 constants
9093 * M2 Defaults:: Default settings for Modula-2
9094 * Deviations:: Deviations from standard Modula-2
9095 * M2 Checks:: Modula-2 type and range checks
9096 * M2 Scope:: The scope operators @code{::} and @code{.}
9097 * GDB/M2:: @value{GDBN} and Modula-2
9101 @subsubsection Operators
9102 @cindex Modula-2 operators
9104 Operators must be defined on values of specific types. For instance,
9105 @code{+} is defined on numbers, but not on structures. Operators are
9106 often defined on groups of types. For the purposes of Modula-2, the
9107 following definitions hold:
9112 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
9116 @emph{Character types} consist of @code{CHAR} and its subranges.
9119 @emph{Floating-point types} consist of @code{REAL}.
9122 @emph{Pointer types} consist of anything declared as @code{POINTER TO
9126 @emph{Scalar types} consist of all of the above.
9129 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
9132 @emph{Boolean types} consist of @code{BOOLEAN}.
9136 The following operators are supported, and appear in order of
9137 increasing precedence:
9141 Function argument or array index separator.
9144 Assignment. The value of @var{var} @code{:=} @var{value} is
9148 Less than, greater than on integral, floating-point, or enumerated
9152 Less than or equal to, greater than or equal to
9153 on integral, floating-point and enumerated types, or set inclusion on
9154 set types. Same precedence as @code{<}.
9156 @item =@r{, }<>@r{, }#
9157 Equality and two ways of expressing inequality, valid on scalar types.
9158 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
9159 available for inequality, since @code{#} conflicts with the script
9163 Set membership. Defined on set types and the types of their members.
9164 Same precedence as @code{<}.
9167 Boolean disjunction. Defined on boolean types.
9170 Boolean conjunction. Defined on boolean types.
9173 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
9176 Addition and subtraction on integral and floating-point types, or union
9177 and difference on set types.
9180 Multiplication on integral and floating-point types, or set intersection
9184 Division on floating-point types, or symmetric set difference on set
9185 types. Same precedence as @code{*}.
9188 Integer division and remainder. Defined on integral types. Same
9189 precedence as @code{*}.
9192 Negative. Defined on @code{INTEGER} and @code{REAL} data.
9195 Pointer dereferencing. Defined on pointer types.
9198 Boolean negation. Defined on boolean types. Same precedence as
9202 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
9203 precedence as @code{^}.
9206 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
9209 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
9213 @value{GDBN} and Modula-2 scope operators.
9217 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
9218 treats the use of the operator @code{IN}, or the use of operators
9219 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
9220 @code{<=}, and @code{>=} on sets as an error.
9224 @node Built-In Func/Proc
9225 @subsubsection Built-in functions and procedures
9226 @cindex Modula-2 built-ins
9228 Modula-2 also makes available several built-in procedures and functions.
9229 In describing these, the following metavariables are used:
9234 represents an @code{ARRAY} variable.
9237 represents a @code{CHAR} constant or variable.
9240 represents a variable or constant of integral type.
9243 represents an identifier that belongs to a set. Generally used in the
9244 same function with the metavariable @var{s}. The type of @var{s} should
9245 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
9248 represents a variable or constant of integral or floating-point type.
9251 represents a variable or constant of floating-point type.
9257 represents a variable.
9260 represents a variable or constant of one of many types. See the
9261 explanation of the function for details.
9264 All Modula-2 built-in procedures also return a result, described below.
9268 Returns the absolute value of @var{n}.
9271 If @var{c} is a lower case letter, it returns its upper case
9272 equivalent, otherwise it returns its argument.
9275 Returns the character whose ordinal value is @var{i}.
9278 Decrements the value in the variable @var{v} by one. Returns the new value.
9280 @item DEC(@var{v},@var{i})
9281 Decrements the value in the variable @var{v} by @var{i}. Returns the
9284 @item EXCL(@var{m},@var{s})
9285 Removes the element @var{m} from the set @var{s}. Returns the new
9288 @item FLOAT(@var{i})
9289 Returns the floating point equivalent of the integer @var{i}.
9292 Returns the index of the last member of @var{a}.
9295 Increments the value in the variable @var{v} by one. Returns the new value.
9297 @item INC(@var{v},@var{i})
9298 Increments the value in the variable @var{v} by @var{i}. Returns the
9301 @item INCL(@var{m},@var{s})
9302 Adds the element @var{m} to the set @var{s} if it is not already
9303 there. Returns the new set.
9306 Returns the maximum value of the type @var{t}.
9309 Returns the minimum value of the type @var{t}.
9312 Returns boolean TRUE if @var{i} is an odd number.
9315 Returns the ordinal value of its argument. For example, the ordinal
9316 value of a character is its @sc{ascii} value (on machines supporting the
9317 @sc{ascii} character set). @var{x} must be of an ordered type, which include
9318 integral, character and enumerated types.
9321 Returns the size of its argument. @var{x} can be a variable or a type.
9323 @item TRUNC(@var{r})
9324 Returns the integral part of @var{r}.
9326 @item VAL(@var{t},@var{i})
9327 Returns the member of the type @var{t} whose ordinal value is @var{i}.
9331 @emph{Warning:} Sets and their operations are not yet supported, so
9332 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
9336 @cindex Modula-2 constants
9338 @subsubsection Constants
9340 @value{GDBN} allows you to express the constants of Modula-2 in the following
9346 Integer constants are simply a sequence of digits. When used in an
9347 expression, a constant is interpreted to be type-compatible with the
9348 rest of the expression. Hexadecimal integers are specified by a
9349 trailing @samp{H}, and octal integers by a trailing @samp{B}.
9352 Floating point constants appear as a sequence of digits, followed by a
9353 decimal point and another sequence of digits. An optional exponent can
9354 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
9355 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
9356 digits of the floating point constant must be valid decimal (base 10)
9360 Character constants consist of a single character enclosed by a pair of
9361 like quotes, either single (@code{'}) or double (@code{"}). They may
9362 also be expressed by their ordinal value (their @sc{ascii} value, usually)
9363 followed by a @samp{C}.
9366 String constants consist of a sequence of characters enclosed by a
9367 pair of like quotes, either single (@code{'}) or double (@code{"}).
9368 Escape sequences in the style of C are also allowed. @xref{C
9369 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
9373 Enumerated constants consist of an enumerated identifier.
9376 Boolean constants consist of the identifiers @code{TRUE} and
9380 Pointer constants consist of integral values only.
9383 Set constants are not yet supported.
9387 @subsubsection Modula-2 defaults
9388 @cindex Modula-2 defaults
9390 If type and range checking are set automatically by @value{GDBN}, they
9391 both default to @code{on} whenever the working language changes to
9392 Modula-2. This happens regardless of whether you or @value{GDBN}
9393 selected the working language.
9395 If you allow @value{GDBN} to set the language automatically, then entering
9396 code compiled from a file whose name ends with @file{.mod} sets the
9397 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
9398 the language automatically}, for further details.
9401 @subsubsection Deviations from standard Modula-2
9402 @cindex Modula-2, deviations from
9404 A few changes have been made to make Modula-2 programs easier to debug.
9405 This is done primarily via loosening its type strictness:
9409 Unlike in standard Modula-2, pointer constants can be formed by
9410 integers. This allows you to modify pointer variables during
9411 debugging. (In standard Modula-2, the actual address contained in a
9412 pointer variable is hidden from you; it can only be modified
9413 through direct assignment to another pointer variable or expression that
9414 returned a pointer.)
9417 C escape sequences can be used in strings and characters to represent
9418 non-printable characters. @value{GDBN} prints out strings with these
9419 escape sequences embedded. Single non-printable characters are
9420 printed using the @samp{CHR(@var{nnn})} format.
9423 The assignment operator (@code{:=}) returns the value of its right-hand
9427 All built-in procedures both modify @emph{and} return their argument.
9431 @subsubsection Modula-2 type and range checks
9432 @cindex Modula-2 checks
9435 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
9438 @c FIXME remove warning when type/range checks added
9440 @value{GDBN} considers two Modula-2 variables type equivalent if:
9444 They are of types that have been declared equivalent via a @code{TYPE
9445 @var{t1} = @var{t2}} statement
9448 They have been declared on the same line. (Note: This is true of the
9449 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
9452 As long as type checking is enabled, any attempt to combine variables
9453 whose types are not equivalent is an error.
9455 Range checking is done on all mathematical operations, assignment, array
9456 index bounds, and all built-in functions and procedures.
9459 @subsubsection The scope operators @code{::} and @code{.}
9461 @cindex @code{.}, Modula-2 scope operator
9462 @cindex colon, doubled as scope operator
9464 @vindex colon-colon@r{, in Modula-2}
9465 @c Info cannot handle :: but TeX can.
9468 @vindex ::@r{, in Modula-2}
9471 There are a few subtle differences between the Modula-2 scope operator
9472 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
9477 @var{module} . @var{id}
9478 @var{scope} :: @var{id}
9482 where @var{scope} is the name of a module or a procedure,
9483 @var{module} the name of a module, and @var{id} is any declared
9484 identifier within your program, except another module.
9486 Using the @code{::} operator makes @value{GDBN} search the scope
9487 specified by @var{scope} for the identifier @var{id}. If it is not
9488 found in the specified scope, then @value{GDBN} searches all scopes
9489 enclosing the one specified by @var{scope}.
9491 Using the @code{.} operator makes @value{GDBN} search the current scope for
9492 the identifier specified by @var{id} that was imported from the
9493 definition module specified by @var{module}. With this operator, it is
9494 an error if the identifier @var{id} was not imported from definition
9495 module @var{module}, or if @var{id} is not an identifier in
9499 @subsubsection @value{GDBN} and Modula-2
9501 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
9502 Five subcommands of @code{set print} and @code{show print} apply
9503 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
9504 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
9505 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
9506 analogue in Modula-2.
9508 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
9509 with any language, is not useful with Modula-2. Its
9510 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
9511 created in Modula-2 as they can in C or C@t{++}. However, because an
9512 address can be specified by an integral constant, the construct
9513 @samp{@{@var{type}@}@var{adrexp}} is still useful.
9515 @cindex @code{#} in Modula-2
9516 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
9517 interpreted as the beginning of a comment. Use @code{<>} instead.
9523 The extensions made to @value{GDBN} for Ada only support
9524 output from the @sc{gnu} Ada (GNAT) compiler.
9525 Other Ada compilers are not currently supported, and
9526 attempting to debug executables produced by them is most likely
9530 @cindex expressions in Ada
9532 * Ada Mode Intro:: General remarks on the Ada syntax
9533 and semantics supported by Ada mode
9535 * Omissions from Ada:: Restrictions on the Ada expression syntax.
9536 * Additions to Ada:: Extensions of the Ada expression syntax.
9537 * Stopping Before Main Program:: Debugging the program during elaboration.
9538 * Ada Glitches:: Known peculiarities of Ada mode.
9541 @node Ada Mode Intro
9542 @subsubsection Introduction
9543 @cindex Ada mode, general
9545 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
9546 syntax, with some extensions.
9547 The philosophy behind the design of this subset is
9551 That @value{GDBN} should provide basic literals and access to operations for
9552 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
9553 leaving more sophisticated computations to subprograms written into the
9554 program (which therefore may be called from @value{GDBN}).
9557 That type safety and strict adherence to Ada language restrictions
9558 are not particularly important to the @value{GDBN} user.
9561 That brevity is important to the @value{GDBN} user.
9564 Thus, for brevity, the debugger acts as if there were
9565 implicit @code{with} and @code{use} clauses in effect for all user-written
9566 packages, making it unnecessary to fully qualify most names with
9567 their packages, regardless of context. Where this causes ambiguity,
9568 @value{GDBN} asks the user's intent.
9570 The debugger will start in Ada mode if it detects an Ada main program.
9571 As for other languages, it will enter Ada mode when stopped in a program that
9572 was translated from an Ada source file.
9574 While in Ada mode, you may use `@t{--}' for comments. This is useful
9575 mostly for documenting command files. The standard @value{GDBN} comment
9576 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
9577 middle (to allow based literals).
9579 The debugger supports limited overloading. Given a subprogram call in which
9580 the function symbol has multiple definitions, it will use the number of
9581 actual parameters and some information about their types to attempt to narrow
9582 the set of definitions. It also makes very limited use of context, preferring
9583 procedures to functions in the context of the @code{call} command, and
9584 functions to procedures elsewhere.
9586 @node Omissions from Ada
9587 @subsubsection Omissions from Ada
9588 @cindex Ada, omissions from
9590 Here are the notable omissions from the subset:
9594 Only a subset of the attributes are supported:
9598 @t{'First}, @t{'Last}, and @t{'Length}
9599 on array objects (not on types and subtypes).
9602 @t{'Min} and @t{'Max}.
9605 @t{'Pos} and @t{'Val}.
9611 @t{'Range} on array objects (not subtypes), but only as the right
9612 operand of the membership (@code{in}) operator.
9615 @t{'Access}, @t{'Unchecked_Access}, and
9616 @t{'Unrestricted_Access} (a GNAT extension).
9624 @code{Characters.Latin_1} are not available and
9625 concatenation is not implemented. Thus, escape characters in strings are
9626 not currently available.
9629 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
9630 equality of representations. They will generally work correctly
9631 for strings and arrays whose elements have integer or enumeration types.
9632 They may not work correctly for arrays whose element
9633 types have user-defined equality, for arrays of real values
9634 (in particular, IEEE-conformant floating point, because of negative
9635 zeroes and NaNs), and for arrays whose elements contain unused bits with
9636 indeterminate values.
9639 The other component-by-component array operations (@code{and}, @code{or},
9640 @code{xor}, @code{not}, and relational tests other than equality)
9641 are not implemented.
9644 There are no record or array aggregates.
9647 Calls to dispatching subprograms are not implemented.
9650 The overloading algorithm is much more limited (i.e., less selective)
9651 than that of real Ada. It makes only limited use of the context in which a subexpression
9652 appears to resolve its meaning, and it is much looser in its rules for allowing
9653 type matches. As a result, some function calls will be ambiguous, and the user
9654 will be asked to choose the proper resolution.
9657 The @code{new} operator is not implemented.
9660 Entry calls are not implemented.
9663 Aside from printing, arithmetic operations on the native VAX floating-point
9664 formats are not supported.
9667 It is not possible to slice a packed array.
9670 @node Additions to Ada
9671 @subsubsection Additions to Ada
9672 @cindex Ada, deviations from
9674 As it does for other languages, @value{GDBN} makes certain generic
9675 extensions to Ada (@pxref{Expressions}):
9679 If the expression @var{E} is a variable residing in memory
9680 (typically a local variable or array element) and @var{N} is
9681 a positive integer, then @code{@var{E}@@@var{N}} displays the values of
9682 @var{E} and the @var{N}-1 adjacent variables following it in memory as an array.
9683 In Ada, this operator is generally not necessary, since its prime use
9684 is in displaying parts of an array, and slicing will usually do this in Ada.
9685 However, there are occasional uses when debugging programs
9686 in which certain debugging information has been optimized away.
9689 @code{@var{B}::@var{var}} means ``the variable named @var{var} that appears
9690 in function or file @var{B}.'' When @var{B} is a file name, you must typically
9691 surround it in single quotes.
9694 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
9695 @var{type} that appears at address @var{addr}.''
9698 A name starting with @samp{$} is a convenience variable
9699 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
9702 In addition, @value{GDBN} provides a few other shortcuts and outright additions specific
9707 The assignment statement is allowed as an expression, returning
9708 its right-hand operand as its value. Thus, you may enter
9712 print A(tmp := y + 1)
9716 The semicolon is allowed as an ``operator,'' returning as its value
9717 the value of its right-hand operand.
9718 This allows, for example,
9719 complex conditional breaks:
9723 condition 1 (report(i); k += 1; A(k) > 100)
9727 Rather than use catenation and symbolic character names to introduce special
9728 characters into strings, one may instead use a special bracket notation,
9729 which is also used to print strings. A sequence of characters of the form
9730 @samp{["@var{XX}"]} within a string or character literal denotes the
9731 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
9732 sequence of characters @samp{["""]} also denotes a single quotation mark
9733 in strings. For example,
9735 "One line.["0a"]Next line.["0a"]"
9738 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF}) after each
9742 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
9743 @t{'Max} is optional (and is ignored in any case). For example, it is valid
9751 When printing arrays, @value{GDBN} uses positional notation when the
9752 array has a lower bound of 1, and uses a modified named notation otherwise.
9753 For example, a one-dimensional array of three integers with a lower bound of 3 might print as
9760 That is, in contrast to valid Ada, only the first component has a @code{=>}
9764 You may abbreviate attributes in expressions with any unique,
9765 multi-character subsequence of
9766 their names (an exact match gets preference).
9767 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
9768 in place of @t{a'length}.
9771 @cindex quoting Ada internal identifiers
9772 Since Ada is case-insensitive, the debugger normally maps identifiers you type
9773 to lower case. The GNAT compiler uses upper-case characters for
9774 some of its internal identifiers, which are normally of no interest to users.
9775 For the rare occasions when you actually have to look at them,
9776 enclose them in angle brackets to avoid the lower-case mapping.
9779 @value{GDBP} print <JMPBUF_SAVE>[0]
9783 Printing an object of class-wide type or dereferencing an
9784 access-to-class-wide value will display all the components of the object's
9785 specific type (as indicated by its run-time tag). Likewise, component
9786 selection on such a value will operate on the specific type of the
9791 @node Stopping Before Main Program
9792 @subsubsection Stopping at the Very Beginning
9794 @cindex breakpointing Ada elaboration code
9795 It is sometimes necessary to debug the program during elaboration, and
9796 before reaching the main procedure.
9797 As defined in the Ada Reference
9798 Manual, the elaboration code is invoked from a procedure called
9799 @code{adainit}. To run your program up to the beginning of
9800 elaboration, simply use the following two commands:
9801 @code{tbreak adainit} and @code{run}.
9804 @subsubsection Known Peculiarities of Ada Mode
9805 @cindex Ada, problems
9807 Besides the omissions listed previously (@pxref{Omissions from Ada}),
9808 we know of several problems with and limitations of Ada mode in
9810 some of which will be fixed with planned future releases of the debugger
9811 and the GNU Ada compiler.
9815 Currently, the debugger
9816 has insufficient information to determine whether certain pointers represent
9817 pointers to objects or the objects themselves.
9818 Thus, the user may have to tack an extra @code{.all} after an expression
9819 to get it printed properly.
9822 Static constants that the compiler chooses not to materialize as objects in
9823 storage are invisible to the debugger.
9826 Named parameter associations in function argument lists are ignored (the
9827 argument lists are treated as positional).
9830 Many useful library packages are currently invisible to the debugger.
9833 Fixed-point arithmetic, conversions, input, and output is carried out using
9834 floating-point arithmetic, and may give results that only approximate those on
9838 The type of the @t{'Address} attribute may not be @code{System.Address}.
9841 The GNAT compiler never generates the prefix @code{Standard} for any of
9842 the standard symbols defined by the Ada language. @value{GDBN} knows about
9843 this: it will strip the prefix from names when you use it, and will never
9844 look for a name you have so qualified among local symbols, nor match against
9845 symbols in other packages or subprograms. If you have
9846 defined entities anywhere in your program other than parameters and
9847 local variables whose simple names match names in @code{Standard},
9848 GNAT's lack of qualification here can cause confusion. When this happens,
9849 you can usually resolve the confusion
9850 by qualifying the problematic names with package
9851 @code{Standard} explicitly.
9854 @node Unsupported languages
9855 @section Unsupported languages
9857 @cindex unsupported languages
9858 @cindex minimal language
9859 In addition to the other fully-supported programming languages,
9860 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
9861 It does not represent a real programming language, but provides a set
9862 of capabilities close to what the C or assembly languages provide.
9863 This should allow most simple operations to be performed while debugging
9864 an application that uses a language currently not supported by @value{GDBN}.
9866 If the language is set to @code{auto}, @value{GDBN} will automatically
9867 select this language if the current frame corresponds to an unsupported
9871 @chapter Examining the Symbol Table
9873 The commands described in this chapter allow you to inquire about the
9874 symbols (names of variables, functions and types) defined in your
9875 program. This information is inherent in the text of your program and
9876 does not change as your program executes. @value{GDBN} finds it in your
9877 program's symbol table, in the file indicated when you started @value{GDBN}
9878 (@pxref{File Options, ,Choosing files}), or by one of the
9879 file-management commands (@pxref{Files, ,Commands to specify files}).
9881 @cindex symbol names
9882 @cindex names of symbols
9883 @cindex quoting names
9884 Occasionally, you may need to refer to symbols that contain unusual
9885 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9886 most frequent case is in referring to static variables in other
9887 source files (@pxref{Variables,,Program variables}). File names
9888 are recorded in object files as debugging symbols, but @value{GDBN} would
9889 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9890 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9891 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9898 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9901 @cindex case-insensitive symbol names
9902 @cindex case sensitivity in symbol names
9903 @kindex set case-sensitive
9904 @item set case-sensitive on
9905 @itemx set case-sensitive off
9906 @itemx set case-sensitive auto
9907 Normally, when @value{GDBN} looks up symbols, it matches their names
9908 with case sensitivity determined by the current source language.
9909 Occasionally, you may wish to control that. The command @code{set
9910 case-sensitive} lets you do that by specifying @code{on} for
9911 case-sensitive matches or @code{off} for case-insensitive ones. If
9912 you specify @code{auto}, case sensitivity is reset to the default
9913 suitable for the source language. The default is case-sensitive
9914 matches for all languages except for Fortran, for which the default is
9915 case-insensitive matches.
9917 @kindex show case-sensitive
9918 @item show case-sensitive
9919 This command shows the current setting of case sensitivity for symbols
9922 @kindex info address
9923 @cindex address of a symbol
9924 @item info address @var{symbol}
9925 Describe where the data for @var{symbol} is stored. For a register
9926 variable, this says which register it is kept in. For a non-register
9927 local variable, this prints the stack-frame offset at which the variable
9930 Note the contrast with @samp{print &@var{symbol}}, which does not work
9931 at all for a register variable, and for a stack local variable prints
9932 the exact address of the current instantiation of the variable.
9935 @cindex symbol from address
9936 @cindex closest symbol and offset for an address
9937 @item info symbol @var{addr}
9938 Print the name of a symbol which is stored at the address @var{addr}.
9939 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9940 nearest symbol and an offset from it:
9943 (@value{GDBP}) info symbol 0x54320
9944 _initialize_vx + 396 in section .text
9948 This is the opposite of the @code{info address} command. You can use
9949 it to find out the name of a variable or a function given its address.
9952 @item whatis @var{expr}
9953 Print the data type of expression @var{expr}. @var{expr} is not
9954 actually evaluated, and any side-effecting operations (such as
9955 assignments or function calls) inside it do not take place.
9956 @xref{Expressions, ,Expressions}.
9959 Print the data type of @code{$}, the last value in the value history.
9962 @item ptype @var{typename}
9963 Print a description of data type @var{typename}. @var{typename} may be
9964 the name of a type, or for C code it may have the form @samp{class
9965 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9966 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9968 @item ptype @var{expr}
9970 Print a description of the type of expression @var{expr}. @code{ptype}
9971 differs from @code{whatis} by printing a detailed description, instead
9972 of just the name of the type.
9974 For example, for this variable declaration:
9977 struct complex @{double real; double imag;@} v;
9981 the two commands give this output:
9985 (@value{GDBP}) whatis v
9986 type = struct complex
9987 (@value{GDBP}) ptype v
9988 type = struct complex @{
9996 As with @code{whatis}, using @code{ptype} without an argument refers to
9997 the type of @code{$}, the last value in the value history.
10000 @item info types @var{regexp}
10002 Print a brief description of all types whose names match the regular
10003 expression @var{regexp} (or all types in your program, if you supply
10004 no argument). Each complete typename is matched as though it were a
10005 complete line; thus, @samp{i type value} gives information on all
10006 types in your program whose names include the string @code{value}, but
10007 @samp{i type ^value$} gives information only on types whose complete
10008 name is @code{value}.
10010 This command differs from @code{ptype} in two ways: first, like
10011 @code{whatis}, it does not print a detailed description; second, it
10012 lists all source files where a type is defined.
10015 @cindex local variables
10016 @item info scope @var{location}
10017 List all the variables local to a particular scope. This command
10018 accepts a @var{location} argument---a function name, a source line, or
10019 an address preceded by a @samp{*}, and prints all the variables local
10020 to the scope defined by that location. For example:
10023 (@value{GDBP}) @b{info scope command_line_handler}
10024 Scope for command_line_handler:
10025 Symbol rl is an argument at stack/frame offset 8, length 4.
10026 Symbol linebuffer is in static storage at address 0x150a18, length 4.
10027 Symbol linelength is in static storage at address 0x150a1c, length 4.
10028 Symbol p is a local variable in register $esi, length 4.
10029 Symbol p1 is a local variable in register $ebx, length 4.
10030 Symbol nline is a local variable in register $edx, length 4.
10031 Symbol repeat is a local variable at frame offset -8, length 4.
10035 This command is especially useful for determining what data to collect
10036 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
10039 @kindex info source
10041 Show information about the current source file---that is, the source file for
10042 the function containing the current point of execution:
10045 the name of the source file, and the directory containing it,
10047 the directory it was compiled in,
10049 its length, in lines,
10051 which programming language it is written in,
10053 whether the executable includes debugging information for that file, and
10054 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
10056 whether the debugging information includes information about
10057 preprocessor macros.
10061 @kindex info sources
10063 Print the names of all source files in your program for which there is
10064 debugging information, organized into two lists: files whose symbols
10065 have already been read, and files whose symbols will be read when needed.
10067 @kindex info functions
10068 @item info functions
10069 Print the names and data types of all defined functions.
10071 @item info functions @var{regexp}
10072 Print the names and data types of all defined functions
10073 whose names contain a match for regular expression @var{regexp}.
10074 Thus, @samp{info fun step} finds all functions whose names
10075 include @code{step}; @samp{info fun ^step} finds those whose names
10076 start with @code{step}. If a function name contains characters
10077 that conflict with the regular expression language (eg.
10078 @samp{operator*()}), they may be quoted with a backslash.
10080 @kindex info variables
10081 @item info variables
10082 Print the names and data types of all variables that are declared
10083 outside of functions (i.e.@: excluding local variables).
10085 @item info variables @var{regexp}
10086 Print the names and data types of all variables (except for local
10087 variables) whose names contain a match for regular expression
10090 @kindex info classes
10091 @cindex Objective-C, classes and selectors
10093 @itemx info classes @var{regexp}
10094 Display all Objective-C classes in your program, or
10095 (with the @var{regexp} argument) all those matching a particular regular
10098 @kindex info selectors
10099 @item info selectors
10100 @itemx info selectors @var{regexp}
10101 Display all Objective-C selectors in your program, or
10102 (with the @var{regexp} argument) all those matching a particular regular
10106 This was never implemented.
10107 @kindex info methods
10109 @itemx info methods @var{regexp}
10110 The @code{info methods} command permits the user to examine all defined
10111 methods within C@t{++} program, or (with the @var{regexp} argument) a
10112 specific set of methods found in the various C@t{++} classes. Many
10113 C@t{++} classes provide a large number of methods. Thus, the output
10114 from the @code{ptype} command can be overwhelming and hard to use. The
10115 @code{info-methods} command filters the methods, printing only those
10116 which match the regular-expression @var{regexp}.
10119 @cindex reloading symbols
10120 Some systems allow individual object files that make up your program to
10121 be replaced without stopping and restarting your program. For example,
10122 in VxWorks you can simply recompile a defective object file and keep on
10123 running. If you are running on one of these systems, you can allow
10124 @value{GDBN} to reload the symbols for automatically relinked modules:
10127 @kindex set symbol-reloading
10128 @item set symbol-reloading on
10129 Replace symbol definitions for the corresponding source file when an
10130 object file with a particular name is seen again.
10132 @item set symbol-reloading off
10133 Do not replace symbol definitions when encountering object files of the
10134 same name more than once. This is the default state; if you are not
10135 running on a system that permits automatic relinking of modules, you
10136 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
10137 may discard symbols when linking large programs, that may contain
10138 several modules (from different directories or libraries) with the same
10141 @kindex show symbol-reloading
10142 @item show symbol-reloading
10143 Show the current @code{on} or @code{off} setting.
10146 @cindex opaque data types
10147 @kindex set opaque-type-resolution
10148 @item set opaque-type-resolution on
10149 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
10150 declared as a pointer to a @code{struct}, @code{class}, or
10151 @code{union}---for example, @code{struct MyType *}---that is used in one
10152 source file although the full declaration of @code{struct MyType} is in
10153 another source file. The default is on.
10155 A change in the setting of this subcommand will not take effect until
10156 the next time symbols for a file are loaded.
10158 @item set opaque-type-resolution off
10159 Tell @value{GDBN} not to resolve opaque types. In this case, the type
10160 is printed as follows:
10162 @{<no data fields>@}
10165 @kindex show opaque-type-resolution
10166 @item show opaque-type-resolution
10167 Show whether opaque types are resolved or not.
10169 @kindex maint print symbols
10170 @cindex symbol dump
10171 @kindex maint print psymbols
10172 @cindex partial symbol dump
10173 @item maint print symbols @var{filename}
10174 @itemx maint print psymbols @var{filename}
10175 @itemx maint print msymbols @var{filename}
10176 Write a dump of debugging symbol data into the file @var{filename}.
10177 These commands are used to debug the @value{GDBN} symbol-reading code. Only
10178 symbols with debugging data are included. If you use @samp{maint print
10179 symbols}, @value{GDBN} includes all the symbols for which it has already
10180 collected full details: that is, @var{filename} reflects symbols for
10181 only those files whose symbols @value{GDBN} has read. You can use the
10182 command @code{info sources} to find out which files these are. If you
10183 use @samp{maint print psymbols} instead, the dump shows information about
10184 symbols that @value{GDBN} only knows partially---that is, symbols defined in
10185 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
10186 @samp{maint print msymbols} dumps just the minimal symbol information
10187 required for each object file from which @value{GDBN} has read some symbols.
10188 @xref{Files, ,Commands to specify files}, for a discussion of how
10189 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
10191 @kindex maint info symtabs
10192 @kindex maint info psymtabs
10193 @cindex listing @value{GDBN}'s internal symbol tables
10194 @cindex symbol tables, listing @value{GDBN}'s internal
10195 @cindex full symbol tables, listing @value{GDBN}'s internal
10196 @cindex partial symbol tables, listing @value{GDBN}'s internal
10197 @item maint info symtabs @r{[} @var{regexp} @r{]}
10198 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
10200 List the @code{struct symtab} or @code{struct partial_symtab}
10201 structures whose names match @var{regexp}. If @var{regexp} is not
10202 given, list them all. The output includes expressions which you can
10203 copy into a @value{GDBN} debugging this one to examine a particular
10204 structure in more detail. For example:
10207 (@value{GDBP}) maint info psymtabs dwarf2read
10208 @{ objfile /home/gnu/build/gdb/gdb
10209 ((struct objfile *) 0x82e69d0)
10210 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
10211 ((struct partial_symtab *) 0x8474b10)
10214 text addresses 0x814d3c8 -- 0x8158074
10215 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
10216 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
10217 dependencies (none)
10220 (@value{GDBP}) maint info symtabs
10224 We see that there is one partial symbol table whose filename contains
10225 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
10226 and we see that @value{GDBN} has not read in any symtabs yet at all.
10227 If we set a breakpoint on a function, that will cause @value{GDBN} to
10228 read the symtab for the compilation unit containing that function:
10231 (@value{GDBP}) break dwarf2_psymtab_to_symtab
10232 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
10234 (@value{GDBP}) maint info symtabs
10235 @{ objfile /home/gnu/build/gdb/gdb
10236 ((struct objfile *) 0x82e69d0)
10237 @{ symtab /home/gnu/src/gdb/dwarf2read.c
10238 ((struct symtab *) 0x86c1f38)
10241 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
10242 debugformat DWARF 2
10251 @chapter Altering Execution
10253 Once you think you have found an error in your program, you might want to
10254 find out for certain whether correcting the apparent error would lead to
10255 correct results in the rest of the run. You can find the answer by
10256 experiment, using the @value{GDBN} features for altering execution of the
10259 For example, you can store new values into variables or memory
10260 locations, give your program a signal, restart it at a different
10261 address, or even return prematurely from a function.
10264 * Assignment:: Assignment to variables
10265 * Jumping:: Continuing at a different address
10266 * Signaling:: Giving your program a signal
10267 * Returning:: Returning from a function
10268 * Calling:: Calling your program's functions
10269 * Patching:: Patching your program
10273 @section Assignment to variables
10276 @cindex setting variables
10277 To alter the value of a variable, evaluate an assignment expression.
10278 @xref{Expressions, ,Expressions}. For example,
10285 stores the value 4 into the variable @code{x}, and then prints the
10286 value of the assignment expression (which is 4).
10287 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
10288 information on operators in supported languages.
10290 @kindex set variable
10291 @cindex variables, setting
10292 If you are not interested in seeing the value of the assignment, use the
10293 @code{set} command instead of the @code{print} command. @code{set} is
10294 really the same as @code{print} except that the expression's value is
10295 not printed and is not put in the value history (@pxref{Value History,
10296 ,Value history}). The expression is evaluated only for its effects.
10298 If the beginning of the argument string of the @code{set} command
10299 appears identical to a @code{set} subcommand, use the @code{set
10300 variable} command instead of just @code{set}. This command is identical
10301 to @code{set} except for its lack of subcommands. For example, if your
10302 program has a variable @code{width}, you get an error if you try to set
10303 a new value with just @samp{set width=13}, because @value{GDBN} has the
10304 command @code{set width}:
10307 (@value{GDBP}) whatis width
10309 (@value{GDBP}) p width
10311 (@value{GDBP}) set width=47
10312 Invalid syntax in expression.
10316 The invalid expression, of course, is @samp{=47}. In
10317 order to actually set the program's variable @code{width}, use
10320 (@value{GDBP}) set var width=47
10323 Because the @code{set} command has many subcommands that can conflict
10324 with the names of program variables, it is a good idea to use the
10325 @code{set variable} command instead of just @code{set}. For example, if
10326 your program has a variable @code{g}, you run into problems if you try
10327 to set a new value with just @samp{set g=4}, because @value{GDBN} has
10328 the command @code{set gnutarget}, abbreviated @code{set g}:
10332 (@value{GDBP}) whatis g
10336 (@value{GDBP}) set g=4
10340 The program being debugged has been started already.
10341 Start it from the beginning? (y or n) y
10342 Starting program: /home/smith/cc_progs/a.out
10343 "/home/smith/cc_progs/a.out": can't open to read symbols:
10344 Invalid bfd target.
10345 (@value{GDBP}) show g
10346 The current BFD target is "=4".
10351 The program variable @code{g} did not change, and you silently set the
10352 @code{gnutarget} to an invalid value. In order to set the variable
10356 (@value{GDBP}) set var g=4
10359 @value{GDBN} allows more implicit conversions in assignments than C; you can
10360 freely store an integer value into a pointer variable or vice versa,
10361 and you can convert any structure to any other structure that is the
10362 same length or shorter.
10363 @comment FIXME: how do structs align/pad in these conversions?
10364 @comment /doc@cygnus.com 18dec1990
10366 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
10367 construct to generate a value of specified type at a specified address
10368 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
10369 to memory location @code{0x83040} as an integer (which implies a certain size
10370 and representation in memory), and
10373 set @{int@}0x83040 = 4
10377 stores the value 4 into that memory location.
10380 @section Continuing at a different address
10382 Ordinarily, when you continue your program, you do so at the place where
10383 it stopped, with the @code{continue} command. You can instead continue at
10384 an address of your own choosing, with the following commands:
10388 @item jump @var{linespec}
10389 Resume execution at line @var{linespec}. Execution stops again
10390 immediately if there is a breakpoint there. @xref{List, ,Printing
10391 source lines}, for a description of the different forms of
10392 @var{linespec}. It is common practice to use the @code{tbreak} command
10393 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
10396 The @code{jump} command does not change the current stack frame, or
10397 the stack pointer, or the contents of any memory location or any
10398 register other than the program counter. If line @var{linespec} is in
10399 a different function from the one currently executing, the results may
10400 be bizarre if the two functions expect different patterns of arguments or
10401 of local variables. For this reason, the @code{jump} command requests
10402 confirmation if the specified line is not in the function currently
10403 executing. However, even bizarre results are predictable if you are
10404 well acquainted with the machine-language code of your program.
10406 @item jump *@var{address}
10407 Resume execution at the instruction at address @var{address}.
10410 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
10411 On many systems, you can get much the same effect as the @code{jump}
10412 command by storing a new value into the register @code{$pc}. The
10413 difference is that this does not start your program running; it only
10414 changes the address of where it @emph{will} run when you continue. For
10422 makes the next @code{continue} command or stepping command execute at
10423 address @code{0x485}, rather than at the address where your program stopped.
10424 @xref{Continuing and Stepping, ,Continuing and stepping}.
10426 The most common occasion to use the @code{jump} command is to back
10427 up---perhaps with more breakpoints set---over a portion of a program
10428 that has already executed, in order to examine its execution in more
10433 @section Giving your program a signal
10434 @cindex deliver a signal to a program
10438 @item signal @var{signal}
10439 Resume execution where your program stopped, but immediately give it the
10440 signal @var{signal}. @var{signal} can be the name or the number of a
10441 signal. For example, on many systems @code{signal 2} and @code{signal
10442 SIGINT} are both ways of sending an interrupt signal.
10444 Alternatively, if @var{signal} is zero, continue execution without
10445 giving a signal. This is useful when your program stopped on account of
10446 a signal and would ordinary see the signal when resumed with the
10447 @code{continue} command; @samp{signal 0} causes it to resume without a
10450 @code{signal} does not repeat when you press @key{RET} a second time
10451 after executing the command.
10455 Invoking the @code{signal} command is not the same as invoking the
10456 @code{kill} utility from the shell. Sending a signal with @code{kill}
10457 causes @value{GDBN} to decide what to do with the signal depending on
10458 the signal handling tables (@pxref{Signals}). The @code{signal} command
10459 passes the signal directly to your program.
10463 @section Returning from a function
10466 @cindex returning from a function
10469 @itemx return @var{expression}
10470 You can cancel execution of a function call with the @code{return}
10471 command. If you give an
10472 @var{expression} argument, its value is used as the function's return
10476 When you use @code{return}, @value{GDBN} discards the selected stack frame
10477 (and all frames within it). You can think of this as making the
10478 discarded frame return prematurely. If you wish to specify a value to
10479 be returned, give that value as the argument to @code{return}.
10481 This pops the selected stack frame (@pxref{Selection, ,Selecting a
10482 frame}), and any other frames inside of it, leaving its caller as the
10483 innermost remaining frame. That frame becomes selected. The
10484 specified value is stored in the registers used for returning values
10487 The @code{return} command does not resume execution; it leaves the
10488 program stopped in the state that would exist if the function had just
10489 returned. In contrast, the @code{finish} command (@pxref{Continuing
10490 and Stepping, ,Continuing and stepping}) resumes execution until the
10491 selected stack frame returns naturally.
10494 @section Calling program functions
10497 @cindex calling functions
10498 @cindex inferior functions, calling
10499 @item print @var{expr}
10500 Evaluate the expression @var{expr} and display the resuling value.
10501 @var{expr} may include calls to functions in the program being
10505 @item call @var{expr}
10506 Evaluate the expression @var{expr} without displaying @code{void}
10509 You can use this variant of the @code{print} command if you want to
10510 execute a function from your program that does not return anything
10511 (a.k.a.@: @dfn{a void function}), but without cluttering the output
10512 with @code{void} returned values that @value{GDBN} will otherwise
10513 print. If the result is not void, it is printed and saved in the
10517 It is possible for the function you call via the @code{print} or
10518 @code{call} command to generate a signal (e.g., if there's a bug in
10519 the function, or if you passed it incorrect arguments). What happens
10520 in that case is controlled by the @code{set unwindonsignal} command.
10523 @item set unwindonsignal
10524 @kindex set unwindonsignal
10525 @cindex unwind stack in called functions
10526 @cindex call dummy stack unwinding
10527 Set unwinding of the stack if a signal is received while in a function
10528 that @value{GDBN} called in the program being debugged. If set to on,
10529 @value{GDBN} unwinds the stack it created for the call and restores
10530 the context to what it was before the call. If set to off (the
10531 default), @value{GDBN} stops in the frame where the signal was
10534 @item show unwindonsignal
10535 @kindex show unwindonsignal
10536 Show the current setting of stack unwinding in the functions called by
10540 @cindex weak alias functions
10541 Sometimes, a function you wish to call is actually a @dfn{weak alias}
10542 for another function. In such case, @value{GDBN} might not pick up
10543 the type information, including the types of the function arguments,
10544 which causes @value{GDBN} to call the inferior function incorrectly.
10545 As a result, the called function will function erroneously and may
10546 even crash. A solution to that is to use the name of the aliased
10550 @section Patching programs
10552 @cindex patching binaries
10553 @cindex writing into executables
10554 @cindex writing into corefiles
10556 By default, @value{GDBN} opens the file containing your program's
10557 executable code (or the corefile) read-only. This prevents accidental
10558 alterations to machine code; but it also prevents you from intentionally
10559 patching your program's binary.
10561 If you'd like to be able to patch the binary, you can specify that
10562 explicitly with the @code{set write} command. For example, you might
10563 want to turn on internal debugging flags, or even to make emergency
10569 @itemx set write off
10570 If you specify @samp{set write on}, @value{GDBN} opens executable and
10571 core files for both reading and writing; if you specify @samp{set write
10572 off} (the default), @value{GDBN} opens them read-only.
10574 If you have already loaded a file, you must load it again (using the
10575 @code{exec-file} or @code{core-file} command) after changing @code{set
10576 write}, for your new setting to take effect.
10580 Display whether executable files and core files are opened for writing
10581 as well as reading.
10585 @chapter @value{GDBN} Files
10587 @value{GDBN} needs to know the file name of the program to be debugged,
10588 both in order to read its symbol table and in order to start your
10589 program. To debug a core dump of a previous run, you must also tell
10590 @value{GDBN} the name of the core dump file.
10593 * Files:: Commands to specify files
10594 * Separate Debug Files:: Debugging information in separate files
10595 * Symbol Errors:: Errors reading symbol files
10599 @section Commands to specify files
10601 @cindex symbol table
10602 @cindex core dump file
10604 You may want to specify executable and core dump file names. The usual
10605 way to do this is at start-up time, using the arguments to
10606 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
10607 Out of @value{GDBN}}).
10609 Occasionally it is necessary to change to a different file during a
10610 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
10611 a file you want to use. In these situations the @value{GDBN} commands
10612 to specify new files are useful.
10615 @cindex executable file
10617 @item file @var{filename}
10618 Use @var{filename} as the program to be debugged. It is read for its
10619 symbols and for the contents of pure memory. It is also the program
10620 executed when you use the @code{run} command. If you do not specify a
10621 directory and the file is not found in the @value{GDBN} working directory,
10622 @value{GDBN} uses the environment variable @code{PATH} as a list of
10623 directories to search, just as the shell does when looking for a program
10624 to run. You can change the value of this variable, for both @value{GDBN}
10625 and your program, using the @code{path} command.
10627 On systems with memory-mapped files, an auxiliary file named
10628 @file{@var{filename}.syms} may hold symbol table information for
10629 @var{filename}. If so, @value{GDBN} maps in the symbol table from
10630 @file{@var{filename}.syms}, starting up more quickly. See the
10631 descriptions of the file options @samp{-mapped} and @samp{-readnow}
10632 (available on the command line, see @ref{File Options, , -readnow},
10633 and with the commands @code{file}, @code{symbol-file}, or
10634 @code{add-symbol-file}, described below), for more information.
10637 @code{file} with no argument makes @value{GDBN} discard any information it
10638 has on both executable file and the symbol table.
10641 @item exec-file @r{[} @var{filename} @r{]}
10642 Specify that the program to be run (but not the symbol table) is found
10643 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
10644 if necessary to locate your program. Omitting @var{filename} means to
10645 discard information on the executable file.
10647 @kindex symbol-file
10648 @item symbol-file @r{[} @var{filename} @r{]}
10649 Read symbol table information from file @var{filename}. @code{PATH} is
10650 searched when necessary. Use the @code{file} command to get both symbol
10651 table and program to run from the same file.
10653 @code{symbol-file} with no argument clears out @value{GDBN} information on your
10654 program's symbol table.
10656 The @code{symbol-file} command causes @value{GDBN} to forget the contents
10657 of its convenience variables, the value history, and all breakpoints and
10658 auto-display expressions. This is because they may contain pointers to
10659 the internal data recording symbols and data types, which are part of
10660 the old symbol table data being discarded inside @value{GDBN}.
10662 @code{symbol-file} does not repeat if you press @key{RET} again after
10665 When @value{GDBN} is configured for a particular environment, it
10666 understands debugging information in whatever format is the standard
10667 generated for that environment; you may use either a @sc{gnu} compiler, or
10668 other compilers that adhere to the local conventions.
10669 Best results are usually obtained from @sc{gnu} compilers; for example,
10670 using @code{@value{GCC}} you can generate debugging information for
10673 For most kinds of object files, with the exception of old SVR3 systems
10674 using COFF, the @code{symbol-file} command does not normally read the
10675 symbol table in full right away. Instead, it scans the symbol table
10676 quickly to find which source files and which symbols are present. The
10677 details are read later, one source file at a time, as they are needed.
10679 The purpose of this two-stage reading strategy is to make @value{GDBN}
10680 start up faster. For the most part, it is invisible except for
10681 occasional pauses while the symbol table details for a particular source
10682 file are being read. (The @code{set verbose} command can turn these
10683 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
10684 warnings and messages}.)
10686 We have not implemented the two-stage strategy for COFF yet. When the
10687 symbol table is stored in COFF format, @code{symbol-file} reads the
10688 symbol table data in full right away. Note that ``stabs-in-COFF''
10689 still does the two-stage strategy, since the debug info is actually
10693 @cindex reading symbols immediately
10694 @cindex symbols, reading immediately
10696 @cindex memory-mapped symbol file
10697 @cindex saving symbol table
10698 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10699 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10700 You can override the @value{GDBN} two-stage strategy for reading symbol
10701 tables by using the @samp{-readnow} option with any of the commands that
10702 load symbol table information, if you want to be sure @value{GDBN} has the
10703 entire symbol table available.
10705 If memory-mapped files are available on your system through the
10706 @code{mmap} system call, you can use another option, @samp{-mapped}, to
10707 cause @value{GDBN} to write the symbols for your program into a reusable
10708 file. Future @value{GDBN} debugging sessions map in symbol information
10709 from this auxiliary symbol file (if the program has not changed), rather
10710 than spending time reading the symbol table from the executable
10711 program. Using the @samp{-mapped} option has the same effect as
10712 starting @value{GDBN} with the @samp{-mapped} command-line option.
10714 You can use both options together, to make sure the auxiliary symbol
10715 file has all the symbol information for your program.
10717 The auxiliary symbol file for a program called @var{myprog} is called
10718 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
10719 than the corresponding executable), @value{GDBN} always attempts to use
10720 it when you debug @var{myprog}; no special options or commands are
10723 The @file{.syms} file is specific to the host machine where you run
10724 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
10725 symbol table. It cannot be shared across multiple host platforms.
10727 @c FIXME: for now no mention of directories, since this seems to be in
10728 @c flux. 13mar1992 status is that in theory GDB would look either in
10729 @c current dir or in same dir as myprog; but issues like competing
10730 @c GDB's, or clutter in system dirs, mean that in practice right now
10731 @c only current dir is used. FFish says maybe a special GDB hierarchy
10732 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
10736 @item core-file @r{[}@var{filename}@r{]}
10738 Specify the whereabouts of a core dump file to be used as the ``contents
10739 of memory''. Traditionally, core files contain only some parts of the
10740 address space of the process that generated them; @value{GDBN} can access the
10741 executable file itself for other parts.
10743 @code{core-file} with no argument specifies that no core file is
10746 Note that the core file is ignored when your program is actually running
10747 under @value{GDBN}. So, if you have been running your program and you
10748 wish to debug a core file instead, you must kill the subprocess in which
10749 the program is running. To do this, use the @code{kill} command
10750 (@pxref{Kill Process, ,Killing the child process}).
10752 @kindex add-symbol-file
10753 @cindex dynamic linking
10754 @item add-symbol-file @var{filename} @var{address}
10755 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
10756 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
10757 The @code{add-symbol-file} command reads additional symbol table
10758 information from the file @var{filename}. You would use this command
10759 when @var{filename} has been dynamically loaded (by some other means)
10760 into the program that is running. @var{address} should be the memory
10761 address at which the file has been loaded; @value{GDBN} cannot figure
10762 this out for itself. You can additionally specify an arbitrary number
10763 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
10764 section name and base address for that section. You can specify any
10765 @var{address} as an expression.
10767 The symbol table of the file @var{filename} is added to the symbol table
10768 originally read with the @code{symbol-file} command. You can use the
10769 @code{add-symbol-file} command any number of times; the new symbol data
10770 thus read keeps adding to the old. To discard all old symbol data
10771 instead, use the @code{symbol-file} command without any arguments.
10773 @cindex relocatable object files, reading symbols from
10774 @cindex object files, relocatable, reading symbols from
10775 @cindex reading symbols from relocatable object files
10776 @cindex symbols, reading from relocatable object files
10777 @cindex @file{.o} files, reading symbols from
10778 Although @var{filename} is typically a shared library file, an
10779 executable file, or some other object file which has been fully
10780 relocated for loading into a process, you can also load symbolic
10781 information from relocatable @file{.o} files, as long as:
10785 the file's symbolic information refers only to linker symbols defined in
10786 that file, not to symbols defined by other object files,
10788 every section the file's symbolic information refers to has actually
10789 been loaded into the inferior, as it appears in the file, and
10791 you can determine the address at which every section was loaded, and
10792 provide these to the @code{add-symbol-file} command.
10796 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10797 relocatable files into an already running program; such systems
10798 typically make the requirements above easy to meet. However, it's
10799 important to recognize that many native systems use complex link
10800 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
10801 assembly, for example) that make the requirements difficult to meet. In
10802 general, one cannot assume that using @code{add-symbol-file} to read a
10803 relocatable object file's symbolic information will have the same effect
10804 as linking the relocatable object file into the program in the normal
10807 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10809 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10810 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10811 table information for @var{filename}.
10813 @kindex add-symbol-file-from-memory
10814 @cindex @code{syscall DSO}
10815 @cindex load symbols from memory
10816 @item add-symbol-file-from-memory @var{address}
10817 Load symbols from the given @var{address} in a dynamically loaded
10818 object file whose image is mapped directly into the inferior's memory.
10819 For example, the Linux kernel maps a @code{syscall DSO} into each
10820 process's address space; this DSO provides kernel-specific code for
10821 some system calls. The argument can be any expression whose
10822 evaluation yields the address of the file's shared object file header.
10823 For this command to work, you must have used @code{symbol-file} or
10824 @code{exec-file} commands in advance.
10826 @kindex add-shared-symbol-files
10828 @item add-shared-symbol-files @var{library-file}
10829 @itemx assf @var{library-file}
10830 The @code{add-shared-symbol-files} command can currently be used only
10831 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
10832 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
10833 @value{GDBN} automatically looks for shared libraries, however if
10834 @value{GDBN} does not find yours, you can invoke
10835 @code{add-shared-symbol-files}. It takes one argument: the shared
10836 library's file name. @code{assf} is a shorthand alias for
10837 @code{add-shared-symbol-files}.
10840 @item section @var{section} @var{addr}
10841 The @code{section} command changes the base address of the named
10842 @var{section} of the exec file to @var{addr}. This can be used if the
10843 exec file does not contain section addresses, (such as in the
10844 @code{a.out} format), or when the addresses specified in the file
10845 itself are wrong. Each section must be changed separately. The
10846 @code{info files} command, described below, lists all the sections and
10850 @kindex info target
10853 @code{info files} and @code{info target} are synonymous; both print the
10854 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10855 including the names of the executable and core dump files currently in
10856 use by @value{GDBN}, and the files from which symbols were loaded. The
10857 command @code{help target} lists all possible targets rather than
10860 @kindex maint info sections
10861 @item maint info sections
10862 Another command that can give you extra information about program sections
10863 is @code{maint info sections}. In addition to the section information
10864 displayed by @code{info files}, this command displays the flags and file
10865 offset of each section in the executable and core dump files. In addition,
10866 @code{maint info sections} provides the following command options (which
10867 may be arbitrarily combined):
10871 Display sections for all loaded object files, including shared libraries.
10872 @item @var{sections}
10873 Display info only for named @var{sections}.
10874 @item @var{section-flags}
10875 Display info only for sections for which @var{section-flags} are true.
10876 The section flags that @value{GDBN} currently knows about are:
10879 Section will have space allocated in the process when loaded.
10880 Set for all sections except those containing debug information.
10882 Section will be loaded from the file into the child process memory.
10883 Set for pre-initialized code and data, clear for @code{.bss} sections.
10885 Section needs to be relocated before loading.
10887 Section cannot be modified by the child process.
10889 Section contains executable code only.
10891 Section contains data only (no executable code).
10893 Section will reside in ROM.
10895 Section contains data for constructor/destructor lists.
10897 Section is not empty.
10899 An instruction to the linker to not output the section.
10900 @item COFF_SHARED_LIBRARY
10901 A notification to the linker that the section contains
10902 COFF shared library information.
10904 Section contains common symbols.
10907 @kindex set trust-readonly-sections
10908 @cindex read-only sections
10909 @item set trust-readonly-sections on
10910 Tell @value{GDBN} that readonly sections in your object file
10911 really are read-only (i.e.@: that their contents will not change).
10912 In that case, @value{GDBN} can fetch values from these sections
10913 out of the object file, rather than from the target program.
10914 For some targets (notably embedded ones), this can be a significant
10915 enhancement to debugging performance.
10917 The default is off.
10919 @item set trust-readonly-sections off
10920 Tell @value{GDBN} not to trust readonly sections. This means that
10921 the contents of the section might change while the program is running,
10922 and must therefore be fetched from the target when needed.
10924 @item show trust-readonly-sections
10925 Show the current setting of trusting readonly sections.
10928 All file-specifying commands allow both absolute and relative file names
10929 as arguments. @value{GDBN} always converts the file name to an absolute file
10930 name and remembers it that way.
10932 @cindex shared libraries
10933 @value{GDBN} supports GNU/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
10934 and IBM RS/6000 AIX shared libraries.
10936 @value{GDBN} automatically loads symbol definitions from shared libraries
10937 when you use the @code{run} command, or when you examine a core file.
10938 (Before you issue the @code{run} command, @value{GDBN} does not understand
10939 references to a function in a shared library, however---unless you are
10940 debugging a core file).
10942 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10943 automatically loads the symbols at the time of the @code{shl_load} call.
10945 @c FIXME: some @value{GDBN} release may permit some refs to undef
10946 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10947 @c FIXME...lib; check this from time to time when updating manual
10949 There are times, however, when you may wish to not automatically load
10950 symbol definitions from shared libraries, such as when they are
10951 particularly large or there are many of them.
10953 To control the automatic loading of shared library symbols, use the
10957 @kindex set auto-solib-add
10958 @item set auto-solib-add @var{mode}
10959 If @var{mode} is @code{on}, symbols from all shared object libraries
10960 will be loaded automatically when the inferior begins execution, you
10961 attach to an independently started inferior, or when the dynamic linker
10962 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10963 is @code{off}, symbols must be loaded manually, using the
10964 @code{sharedlibrary} command. The default value is @code{on}.
10966 @cindex memory used for symbol tables
10967 If your program uses lots of shared libraries with debug info that
10968 takes large amounts of memory, you can decrease the @value{GDBN}
10969 memory footprint by preventing it from automatically loading the
10970 symbols from shared libraries. To that end, type @kbd{set
10971 auto-solib-add off} before running the inferior, then load each
10972 library whose debug symbols you do need with @kbd{sharedlibrary
10973 @var{regexp}}, where @var{regexp} is a regular expresion that matches
10974 the libraries whose symbols you want to be loaded.
10976 @kindex show auto-solib-add
10977 @item show auto-solib-add
10978 Display the current autoloading mode.
10981 @cindex load shared library
10982 To explicitly load shared library symbols, use the @code{sharedlibrary}
10986 @kindex info sharedlibrary
10989 @itemx info sharedlibrary
10990 Print the names of the shared libraries which are currently loaded.
10992 @kindex sharedlibrary
10994 @item sharedlibrary @var{regex}
10995 @itemx share @var{regex}
10996 Load shared object library symbols for files matching a
10997 Unix regular expression.
10998 As with files loaded automatically, it only loads shared libraries
10999 required by your program for a core file or after typing @code{run}. If
11000 @var{regex} is omitted all shared libraries required by your program are
11003 @item nosharedlibrary
11004 @kindex nosharedlibrary
11005 @cindex unload symbols from shared libraries
11006 Unload all shared object library symbols. This discards all symbols
11007 that have been loaded from all shared libraries. Symbols from shared
11008 libraries that were loaded by explicit user requests are not
11012 Sometimes you may wish that @value{GDBN} stops and gives you control
11013 when any of shared library events happen. Use the @code{set
11014 stop-on-solib-events} command for this:
11017 @item set stop-on-solib-events
11018 @kindex set stop-on-solib-events
11019 This command controls whether @value{GDBN} should give you control
11020 when the dynamic linker notifies it about some shared library event.
11021 The most common event of interest is loading or unloading of a new
11024 @item show stop-on-solib-events
11025 @kindex show stop-on-solib-events
11026 Show whether @value{GDBN} stops and gives you control when shared
11027 library events happen.
11030 Shared libraries are also supported in many cross or remote debugging
11031 configurations. A copy of the target's libraries need to be present on the
11032 host system; they need to be the same as the target libraries, although the
11033 copies on the target can be stripped as long as the copies on the host are
11036 You need to tell @value{GDBN} where the target libraries are, so that it can
11037 load the correct copies---otherwise, it may try to load the host's libraries.
11038 @value{GDBN} has two variables to specify the search directories for target
11042 @kindex set solib-absolute-prefix
11043 @item set solib-absolute-prefix @var{path}
11044 If this variable is set, @var{path} will be used as a prefix for any
11045 absolute shared library paths; many runtime loaders store the absolute
11046 paths to the shared library in the target program's memory. If you use
11047 @samp{solib-absolute-prefix} to find shared libraries, they need to be laid
11048 out in the same way that they are on the target, with e.g.@: a
11049 @file{/usr/lib} hierarchy under @var{path}.
11051 You can set the default value of @samp{solib-absolute-prefix} by using the
11052 configure-time @samp{--with-sysroot} option.
11054 @kindex show solib-absolute-prefix
11055 @item show solib-absolute-prefix
11056 Display the current shared library prefix.
11058 @kindex set solib-search-path
11059 @item set solib-search-path @var{path}
11060 If this variable is set, @var{path} is a colon-separated list of directories
11061 to search for shared libraries. @samp{solib-search-path} is used after
11062 @samp{solib-absolute-prefix} fails to locate the library, or if the path to
11063 the library is relative instead of absolute. If you want to use
11064 @samp{solib-search-path} instead of @samp{solib-absolute-prefix}, be sure to
11065 set @samp{solib-absolute-prefix} to a nonexistant directory to prevent
11066 @value{GDBN} from finding your host's libraries.
11068 @kindex show solib-search-path
11069 @item show solib-search-path
11070 Display the current shared library search path.
11074 @node Separate Debug Files
11075 @section Debugging Information in Separate Files
11076 @cindex separate debugging information files
11077 @cindex debugging information in separate files
11078 @cindex @file{.debug} subdirectories
11079 @cindex debugging information directory, global
11080 @cindex global debugging information directory
11082 @value{GDBN} allows you to put a program's debugging information in a
11083 file separate from the executable itself, in a way that allows
11084 @value{GDBN} to find and load the debugging information automatically.
11085 Since debugging information can be very large --- sometimes larger
11086 than the executable code itself --- some systems distribute debugging
11087 information for their executables in separate files, which users can
11088 install only when they need to debug a problem.
11090 If an executable's debugging information has been extracted to a
11091 separate file, the executable should contain a @dfn{debug link} giving
11092 the name of the debugging information file (with no directory
11093 components), and a checksum of its contents. (The exact form of a
11094 debug link is described below.) If the full name of the directory
11095 containing the executable is @var{execdir}, and the executable has a
11096 debug link that specifies the name @var{debugfile}, then @value{GDBN}
11097 will automatically search for the debugging information file in three
11102 the directory containing the executable file (that is, it will look
11103 for a file named @file{@var{execdir}/@var{debugfile}},
11105 a subdirectory of that directory named @file{.debug} (that is, the
11106 file @file{@var{execdir}/.debug/@var{debugfile}}, and
11108 a subdirectory of the global debug file directory that includes the
11109 executable's full path, and the name from the link (that is, the file
11110 @file{@var{globaldebugdir}/@var{execdir}/@var{debugfile}}, where
11111 @var{globaldebugdir} is the global debug file directory, and
11112 @var{execdir} has been turned into a relative path).
11115 @value{GDBN} checks under each of these names for a debugging
11116 information file whose checksum matches that given in the link, and
11117 reads the debugging information from the first one it finds.
11119 So, for example, if you ask @value{GDBN} to debug @file{/usr/bin/ls},
11120 which has a link containing the name @file{ls.debug}, and the global
11121 debug directory is @file{/usr/lib/debug}, then @value{GDBN} will look
11122 for debug information in @file{/usr/bin/ls.debug},
11123 @file{/usr/bin/.debug/ls.debug}, and
11124 @file{/usr/lib/debug/usr/bin/ls.debug}.
11126 You can set the global debugging info directory's name, and view the
11127 name @value{GDBN} is currently using.
11131 @kindex set debug-file-directory
11132 @item set debug-file-directory @var{directory}
11133 Set the directory which @value{GDBN} searches for separate debugging
11134 information files to @var{directory}.
11136 @kindex show debug-file-directory
11137 @item show debug-file-directory
11138 Show the directory @value{GDBN} searches for separate debugging
11143 @cindex @code{.gnu_debuglink} sections
11144 @cindex debug links
11145 A debug link is a special section of the executable file named
11146 @code{.gnu_debuglink}. The section must contain:
11150 A filename, with any leading directory components removed, followed by
11153 zero to three bytes of padding, as needed to reach the next four-byte
11154 boundary within the section, and
11156 a four-byte CRC checksum, stored in the same endianness used for the
11157 executable file itself. The checksum is computed on the debugging
11158 information file's full contents by the function given below, passing
11159 zero as the @var{crc} argument.
11162 Any executable file format can carry a debug link, as long as it can
11163 contain a section named @code{.gnu_debuglink} with the contents
11166 The debugging information file itself should be an ordinary
11167 executable, containing a full set of linker symbols, sections, and
11168 debugging information. The sections of the debugging information file
11169 should have the same names, addresses and sizes as the original file,
11170 but they need not contain any data --- much like a @code{.bss} section
11171 in an ordinary executable.
11173 As of December 2002, there is no standard GNU utility to produce
11174 separated executable / debugging information file pairs. Ulrich
11175 Drepper's @file{elfutils} package, starting with version 0.53,
11176 contains a version of the @code{strip} command such that the command
11177 @kbd{strip foo -f foo.debug} removes the debugging information from
11178 the executable file @file{foo}, places it in the file
11179 @file{foo.debug}, and leaves behind a debug link in @file{foo}.
11181 Since there are many different ways to compute CRC's (different
11182 polynomials, reversals, byte ordering, etc.), the simplest way to
11183 describe the CRC used in @code{.gnu_debuglink} sections is to give the
11184 complete code for a function that computes it:
11186 @kindex gnu_debuglink_crc32
11189 gnu_debuglink_crc32 (unsigned long crc,
11190 unsigned char *buf, size_t len)
11192 static const unsigned long crc32_table[256] =
11194 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
11195 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
11196 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
11197 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
11198 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
11199 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
11200 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
11201 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
11202 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
11203 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
11204 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
11205 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
11206 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
11207 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
11208 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
11209 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
11210 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
11211 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
11212 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
11213 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
11214 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
11215 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
11216 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
11217 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
11218 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
11219 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
11220 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
11221 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
11222 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
11223 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
11224 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
11225 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
11226 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
11227 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
11228 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
11229 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
11230 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
11231 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
11232 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
11233 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
11234 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
11235 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
11236 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
11237 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
11238 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
11239 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
11240 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
11241 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
11242 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
11243 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
11244 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
11247 unsigned char *end;
11249 crc = ~crc & 0xffffffff;
11250 for (end = buf + len; buf < end; ++buf)
11251 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
11252 return ~crc & 0xffffffff;
11257 @node Symbol Errors
11258 @section Errors reading symbol files
11260 While reading a symbol file, @value{GDBN} occasionally encounters problems,
11261 such as symbol types it does not recognize, or known bugs in compiler
11262 output. By default, @value{GDBN} does not notify you of such problems, since
11263 they are relatively common and primarily of interest to people
11264 debugging compilers. If you are interested in seeing information
11265 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
11266 only one message about each such type of problem, no matter how many
11267 times the problem occurs; or you can ask @value{GDBN} to print more messages,
11268 to see how many times the problems occur, with the @code{set
11269 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
11272 The messages currently printed, and their meanings, include:
11275 @item inner block not inside outer block in @var{symbol}
11277 The symbol information shows where symbol scopes begin and end
11278 (such as at the start of a function or a block of statements). This
11279 error indicates that an inner scope block is not fully contained
11280 in its outer scope blocks.
11282 @value{GDBN} circumvents the problem by treating the inner block as if it had
11283 the same scope as the outer block. In the error message, @var{symbol}
11284 may be shown as ``@code{(don't know)}'' if the outer block is not a
11287 @item block at @var{address} out of order
11289 The symbol information for symbol scope blocks should occur in
11290 order of increasing addresses. This error indicates that it does not
11293 @value{GDBN} does not circumvent this problem, and has trouble
11294 locating symbols in the source file whose symbols it is reading. (You
11295 can often determine what source file is affected by specifying
11296 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
11299 @item bad block start address patched
11301 The symbol information for a symbol scope block has a start address
11302 smaller than the address of the preceding source line. This is known
11303 to occur in the SunOS 4.1.1 (and earlier) C compiler.
11305 @value{GDBN} circumvents the problem by treating the symbol scope block as
11306 starting on the previous source line.
11308 @item bad string table offset in symbol @var{n}
11311 Symbol number @var{n} contains a pointer into the string table which is
11312 larger than the size of the string table.
11314 @value{GDBN} circumvents the problem by considering the symbol to have the
11315 name @code{foo}, which may cause other problems if many symbols end up
11318 @item unknown symbol type @code{0x@var{nn}}
11320 The symbol information contains new data types that @value{GDBN} does
11321 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
11322 uncomprehended information, in hexadecimal.
11324 @value{GDBN} circumvents the error by ignoring this symbol information.
11325 This usually allows you to debug your program, though certain symbols
11326 are not accessible. If you encounter such a problem and feel like
11327 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
11328 on @code{complain}, then go up to the function @code{read_dbx_symtab}
11329 and examine @code{*bufp} to see the symbol.
11331 @item stub type has NULL name
11333 @value{GDBN} could not find the full definition for a struct or class.
11335 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
11336 The symbol information for a C@t{++} member function is missing some
11337 information that recent versions of the compiler should have output for
11340 @item info mismatch between compiler and debugger
11342 @value{GDBN} could not parse a type specification output by the compiler.
11347 @chapter Specifying a Debugging Target
11349 @cindex debugging target
11350 A @dfn{target} is the execution environment occupied by your program.
11352 Often, @value{GDBN} runs in the same host environment as your program;
11353 in that case, the debugging target is specified as a side effect when
11354 you use the @code{file} or @code{core} commands. When you need more
11355 flexibility---for example, running @value{GDBN} on a physically separate
11356 host, or controlling a standalone system over a serial port or a
11357 realtime system over a TCP/IP connection---you can use the @code{target}
11358 command to specify one of the target types configured for @value{GDBN}
11359 (@pxref{Target Commands, ,Commands for managing targets}).
11361 @cindex target architecture
11362 It is possible to build @value{GDBN} for several different @dfn{target
11363 architectures}. When @value{GDBN} is built like that, you can choose
11364 one of the available architectures with the @kbd{set architecture}
11368 @kindex set architecture
11369 @kindex show architecture
11370 @item set architecture @var{arch}
11371 This command sets the current target architecture to @var{arch}. The
11372 value of @var{arch} can be @code{"auto"}, in addition to one of the
11373 supported architectures.
11375 @item show architecture
11376 Show the current target architecture.
11378 @item set processor
11380 @kindex set processor
11381 @kindex show processor
11382 These are alias commands for, respectively, @code{set architecture}
11383 and @code{show architecture}.
11387 * Active Targets:: Active targets
11388 * Target Commands:: Commands for managing targets
11389 * Byte Order:: Choosing target byte order
11390 * Remote:: Remote debugging
11391 * KOD:: Kernel Object Display
11395 @node Active Targets
11396 @section Active targets
11398 @cindex stacking targets
11399 @cindex active targets
11400 @cindex multiple targets
11402 There are three classes of targets: processes, core files, and
11403 executable files. @value{GDBN} can work concurrently on up to three
11404 active targets, one in each class. This allows you to (for example)
11405 start a process and inspect its activity without abandoning your work on
11408 For example, if you execute @samp{gdb a.out}, then the executable file
11409 @code{a.out} is the only active target. If you designate a core file as
11410 well---presumably from a prior run that crashed and coredumped---then
11411 @value{GDBN} has two active targets and uses them in tandem, looking
11412 first in the corefile target, then in the executable file, to satisfy
11413 requests for memory addresses. (Typically, these two classes of target
11414 are complementary, since core files contain only a program's
11415 read-write memory---variables and so on---plus machine status, while
11416 executable files contain only the program text and initialized data.)
11418 When you type @code{run}, your executable file becomes an active process
11419 target as well. When a process target is active, all @value{GDBN}
11420 commands requesting memory addresses refer to that target; addresses in
11421 an active core file or executable file target are obscured while the
11422 process target is active.
11424 Use the @code{core-file} and @code{exec-file} commands to select a new
11425 core file or executable target (@pxref{Files, ,Commands to specify
11426 files}). To specify as a target a process that is already running, use
11427 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
11430 @node Target Commands
11431 @section Commands for managing targets
11434 @item target @var{type} @var{parameters}
11435 Connects the @value{GDBN} host environment to a target machine or
11436 process. A target is typically a protocol for talking to debugging
11437 facilities. You use the argument @var{type} to specify the type or
11438 protocol of the target machine.
11440 Further @var{parameters} are interpreted by the target protocol, but
11441 typically include things like device names or host names to connect
11442 with, process numbers, and baud rates.
11444 The @code{target} command does not repeat if you press @key{RET} again
11445 after executing the command.
11447 @kindex help target
11449 Displays the names of all targets available. To display targets
11450 currently selected, use either @code{info target} or @code{info files}
11451 (@pxref{Files, ,Commands to specify files}).
11453 @item help target @var{name}
11454 Describe a particular target, including any parameters necessary to
11457 @kindex set gnutarget
11458 @item set gnutarget @var{args}
11459 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
11460 knows whether it is reading an @dfn{executable},
11461 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
11462 with the @code{set gnutarget} command. Unlike most @code{target} commands,
11463 with @code{gnutarget} the @code{target} refers to a program, not a machine.
11466 @emph{Warning:} To specify a file format with @code{set gnutarget},
11467 you must know the actual BFD name.
11471 @xref{Files, , Commands to specify files}.
11473 @kindex show gnutarget
11474 @item show gnutarget
11475 Use the @code{show gnutarget} command to display what file format
11476 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
11477 @value{GDBN} will determine the file format for each file automatically,
11478 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
11481 @cindex common targets
11482 Here are some common targets (available, or not, depending on the GDB
11487 @item target exec @var{program}
11488 @cindex executable file target
11489 An executable file. @samp{target exec @var{program}} is the same as
11490 @samp{exec-file @var{program}}.
11492 @item target core @var{filename}
11493 @cindex core dump file target
11494 A core dump file. @samp{target core @var{filename}} is the same as
11495 @samp{core-file @var{filename}}.
11497 @item target remote @var{dev}
11498 @cindex remote target
11499 Remote serial target in GDB-specific protocol. The argument @var{dev}
11500 specifies what serial device to use for the connection (e.g.
11501 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
11502 supports the @code{load} command. This is only useful if you have
11503 some other way of getting the stub to the target system, and you can put
11504 it somewhere in memory where it won't get clobbered by the download.
11507 @cindex built-in simulator target
11508 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
11516 works; however, you cannot assume that a specific memory map, device
11517 drivers, or even basic I/O is available, although some simulators do
11518 provide these. For info about any processor-specific simulator details,
11519 see the appropriate section in @ref{Embedded Processors, ,Embedded
11524 Some configurations may include these targets as well:
11528 @item target nrom @var{dev}
11529 @cindex NetROM ROM emulator target
11530 NetROM ROM emulator. This target only supports downloading.
11534 Different targets are available on different configurations of @value{GDBN};
11535 your configuration may have more or fewer targets.
11537 Many remote targets require you to download the executable's code once
11538 you've successfully established a connection. You may wish to control
11539 various aspects of this process, such as the size of the data chunks
11540 used by @value{GDBN} to download program parts to the remote target.
11543 @kindex set download-write-size
11544 @item set download-write-size @var{size}
11545 Set the write size used when downloading a program. Only used when
11546 downloading a program onto a remote target. Specify zero or a
11547 negative value to disable blocked writes. The actual size of each
11548 transfer is also limited by the size of the target packet and the
11551 @kindex show download-write-size
11552 @item show download-write-size
11553 @kindex show download-write-size
11554 Show the current value of the write size.
11557 @kindex set hash@r{, for remote monitors}
11558 @cindex hash mark while downloading
11559 This command controls whether a hash mark @samp{#} is displayed while
11560 downloading a file to the remote monitor. If on, a hash mark is
11561 displayed after each S-record is successfully downloaded to the
11565 @kindex show hash@r{, for remote monitors}
11566 Show the current status of displaying the hash mark.
11568 @item set debug monitor
11569 @kindex set debug monitor
11570 @cindex display remote monitor communications
11571 Enable or disable display of communications messages between
11572 @value{GDBN} and the remote monitor.
11574 @item show debug monitor
11575 @kindex show debug monitor
11576 Show the current status of displaying communications between
11577 @value{GDBN} and the remote monitor.
11582 @kindex load @var{filename}
11583 @item load @var{filename}
11584 Depending on what remote debugging facilities are configured into
11585 @value{GDBN}, the @code{load} command may be available. Where it exists, it
11586 is meant to make @var{filename} (an executable) available for debugging
11587 on the remote system---by downloading, or dynamic linking, for example.
11588 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
11589 the @code{add-symbol-file} command.
11591 If your @value{GDBN} does not have a @code{load} command, attempting to
11592 execute it gets the error message ``@code{You can't do that when your
11593 target is @dots{}}''
11595 The file is loaded at whatever address is specified in the executable.
11596 For some object file formats, you can specify the load address when you
11597 link the program; for other formats, like a.out, the object file format
11598 specifies a fixed address.
11599 @c FIXME! This would be a good place for an xref to the GNU linker doc.
11601 @code{load} does not repeat if you press @key{RET} again after using it.
11605 @section Choosing target byte order
11607 @cindex choosing target byte order
11608 @cindex target byte order
11610 Some types of processors, such as the MIPS, PowerPC, and Renesas SH,
11611 offer the ability to run either big-endian or little-endian byte
11612 orders. Usually the executable or symbol will include a bit to
11613 designate the endian-ness, and you will not need to worry about
11614 which to use. However, you may still find it useful to adjust
11615 @value{GDBN}'s idea of processor endian-ness manually.
11619 @item set endian big
11620 Instruct @value{GDBN} to assume the target is big-endian.
11622 @item set endian little
11623 Instruct @value{GDBN} to assume the target is little-endian.
11625 @item set endian auto
11626 Instruct @value{GDBN} to use the byte order associated with the
11630 Display @value{GDBN}'s current idea of the target byte order.
11634 Note that these commands merely adjust interpretation of symbolic
11635 data on the host, and that they have absolutely no effect on the
11639 @section Remote debugging
11640 @cindex remote debugging
11642 If you are trying to debug a program running on a machine that cannot run
11643 @value{GDBN} in the usual way, it is often useful to use remote debugging.
11644 For example, you might use remote debugging on an operating system kernel,
11645 or on a small system which does not have a general purpose operating system
11646 powerful enough to run a full-featured debugger.
11648 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
11649 to make this work with particular debugging targets. In addition,
11650 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
11651 but not specific to any particular target system) which you can use if you
11652 write the remote stubs---the code that runs on the remote system to
11653 communicate with @value{GDBN}.
11655 Other remote targets may be available in your
11656 configuration of @value{GDBN}; use @code{help target} to list them.
11658 Once you've connected to the remote target, @value{GDBN} allows you to
11659 send arbitrary commands to the remote monitor:
11662 @item remote @var{command}
11663 @kindex remote@r{, a command}
11664 @cindex send command to remote monitor
11665 Send an arbitrary @var{command} string to the remote monitor.
11670 @section Kernel Object Display
11671 @cindex kernel object display
11674 Some targets support kernel object display. Using this facility,
11675 @value{GDBN} communicates specially with the underlying operating system
11676 and can display information about operating system-level objects such as
11677 mutexes and other synchronization objects. Exactly which objects can be
11678 displayed is determined on a per-OS basis.
11681 Use the @code{set os} command to set the operating system. This tells
11682 @value{GDBN} which kernel object display module to initialize:
11685 (@value{GDBP}) set os cisco
11689 The associated command @code{show os} displays the operating system
11690 set with the @code{set os} command; if no operating system has been
11691 set, @code{show os} will display an empty string @samp{""}.
11693 If @code{set os} succeeds, @value{GDBN} will display some information
11694 about the operating system, and will create a new @code{info} command
11695 which can be used to query the target. The @code{info} command is named
11696 after the operating system:
11700 (@value{GDBP}) info cisco
11701 List of Cisco Kernel Objects
11703 any Any and all objects
11706 Further subcommands can be used to query about particular objects known
11709 There is currently no way to determine whether a given operating
11710 system is supported other than to try setting it with @kbd{set os
11711 @var{name}}, where @var{name} is the name of the operating system you
11715 @node Remote Debugging
11716 @chapter Debugging remote programs
11719 * Connecting:: Connecting to a remote target
11720 * Server:: Using the gdbserver program
11721 * NetWare:: Using the gdbserve.nlm program
11722 * Remote configuration:: Remote configuration
11723 * remote stub:: Implementing a remote stub
11727 @section Connecting to a remote target
11729 On the @value{GDBN} host machine, you will need an unstripped copy of
11730 your program, since @value{GDBN} needs symobl and debugging information.
11731 Start up @value{GDBN} as usual, using the name of the local copy of your
11732 program as the first argument.
11734 @cindex serial line, @code{target remote}
11735 If you're using a serial line, you may want to give @value{GDBN} the
11736 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
11737 (@pxref{Remote configuration, set remotebaud}) before the
11738 @code{target} command.
11740 After that, use @code{target remote} to establish communications with
11741 the target machine. Its argument specifies how to communicate---either
11742 via a devicename attached to a direct serial line, or a TCP or UDP port
11743 (possibly to a terminal server which in turn has a serial line to the
11744 target). For example, to use a serial line connected to the device
11745 named @file{/dev/ttyb}:
11748 target remote /dev/ttyb
11751 @cindex TCP port, @code{target remote}
11752 To use a TCP connection, use an argument of the form
11753 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11754 For example, to connect to port 2828 on a
11755 terminal server named @code{manyfarms}:
11758 target remote manyfarms:2828
11761 If your remote target is actually running on the same machine as
11762 your debugger session (e.g.@: a simulator of your target running on
11763 the same host), you can omit the hostname. For example, to connect
11764 to port 1234 on your local machine:
11767 target remote :1234
11771 Note that the colon is still required here.
11773 @cindex UDP port, @code{target remote}
11774 To use a UDP connection, use an argument of the form
11775 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11776 on a terminal server named @code{manyfarms}:
11779 target remote udp:manyfarms:2828
11782 When using a UDP connection for remote debugging, you should keep in mind
11783 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11784 busy or unreliable networks, which will cause havoc with your debugging
11787 Now you can use all the usual commands to examine and change data and to
11788 step and continue the remote program.
11790 @cindex interrupting remote programs
11791 @cindex remote programs, interrupting
11792 Whenever @value{GDBN} is waiting for the remote program, if you type the
11793 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11794 program. This may or may not succeed, depending in part on the hardware
11795 and the serial drivers the remote system uses. If you type the
11796 interrupt character once again, @value{GDBN} displays this prompt:
11799 Interrupted while waiting for the program.
11800 Give up (and stop debugging it)? (y or n)
11803 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11804 (If you decide you want to try again later, you can use @samp{target
11805 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11806 goes back to waiting.
11809 @kindex detach (remote)
11811 When you have finished debugging the remote program, you can use the
11812 @code{detach} command to release it from @value{GDBN} control.
11813 Detaching from the target normally resumes its execution, but the results
11814 will depend on your particular remote stub. After the @code{detach}
11815 command, @value{GDBN} is free to connect to another target.
11819 The @code{disconnect} command behaves like @code{detach}, except that
11820 the target is generally not resumed. It will wait for @value{GDBN}
11821 (this instance or another one) to connect and continue debugging. After
11822 the @code{disconnect} command, @value{GDBN} is again free to connect to
11825 @cindex send command to remote monitor
11827 @item monitor @var{cmd}
11828 This command allows you to send commands directly to the remote
11833 @section Using the @code{gdbserver} program
11836 @cindex remote connection without stubs
11837 @code{gdbserver} is a control program for Unix-like systems, which
11838 allows you to connect your program with a remote @value{GDBN} via
11839 @code{target remote}---but without linking in the usual debugging stub.
11841 @code{gdbserver} is not a complete replacement for the debugging stubs,
11842 because it requires essentially the same operating-system facilities
11843 that @value{GDBN} itself does. In fact, a system that can run
11844 @code{gdbserver} to connect to a remote @value{GDBN} could also run
11845 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
11846 because it is a much smaller program than @value{GDBN} itself. It is
11847 also easier to port than all of @value{GDBN}, so you may be able to get
11848 started more quickly on a new system by using @code{gdbserver}.
11849 Finally, if you develop code for real-time systems, you may find that
11850 the tradeoffs involved in real-time operation make it more convenient to
11851 do as much development work as possible on another system, for example
11852 by cross-compiling. You can use @code{gdbserver} to make a similar
11853 choice for debugging.
11855 @value{GDBN} and @code{gdbserver} communicate via either a serial line
11856 or a TCP connection, using the standard @value{GDBN} remote serial
11860 @item On the target machine,
11861 you need to have a copy of the program you want to debug.
11862 @code{gdbserver} does not need your program's symbol table, so you can
11863 strip the program if necessary to save space. @value{GDBN} on the host
11864 system does all the symbol handling.
11866 To use the server, you must tell it how to communicate with @value{GDBN};
11867 the name of your program; and the arguments for your program. The usual
11871 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
11874 @var{comm} is either a device name (to use a serial line) or a TCP
11875 hostname and portnumber. For example, to debug Emacs with the argument
11876 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
11880 target> gdbserver /dev/com1 emacs foo.txt
11883 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
11886 To use a TCP connection instead of a serial line:
11889 target> gdbserver host:2345 emacs foo.txt
11892 The only difference from the previous example is the first argument,
11893 specifying that you are communicating with the host @value{GDBN} via
11894 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
11895 expect a TCP connection from machine @samp{host} to local TCP port 2345.
11896 (Currently, the @samp{host} part is ignored.) You can choose any number
11897 you want for the port number as long as it does not conflict with any
11898 TCP ports already in use on the target system (for example, @code{23} is
11899 reserved for @code{telnet}).@footnote{If you choose a port number that
11900 conflicts with another service, @code{gdbserver} prints an error message
11901 and exits.} You must use the same port number with the host @value{GDBN}
11902 @code{target remote} command.
11904 On some targets, @code{gdbserver} can also attach to running programs.
11905 This is accomplished via the @code{--attach} argument. The syntax is:
11908 target> gdbserver @var{comm} --attach @var{pid}
11911 @var{pid} is the process ID of a currently running process. It isn't necessary
11912 to point @code{gdbserver} at a binary for the running process.
11915 @cindex attach to a program by name
11916 You can debug processes by name instead of process ID if your target has the
11917 @code{pidof} utility:
11920 target> gdbserver @var{comm} --attach `pidof @var{PROGRAM}`
11923 In case more than one copy of @var{PROGRAM} is running, or @var{PROGRAM}
11924 has multiple threads, most versions of @code{pidof} support the
11925 @code{-s} option to only return the first process ID.
11927 @item On the host machine,
11928 connect to your target (@pxref{Connecting,,Connecting to a remote target}).
11929 For TCP connections, you must start up @code{gdbserver} prior to using
11930 the @code{target remote} command. Otherwise you may get an error whose
11931 text depends on the host system, but which usually looks something like
11932 @samp{Connection refused}. You don't need to use the @code{load}
11933 command in @value{GDBN} when using gdbserver, since the program is
11934 already on the target.
11939 @section Using the @code{gdbserve.nlm} program
11941 @kindex gdbserve.nlm
11942 @code{gdbserve.nlm} is a control program for NetWare systems, which
11943 allows you to connect your program with a remote @value{GDBN} via
11944 @code{target remote}.
11946 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
11947 using the standard @value{GDBN} remote serial protocol.
11950 @item On the target machine,
11951 you need to have a copy of the program you want to debug.
11952 @code{gdbserve.nlm} does not need your program's symbol table, so you
11953 can strip the program if necessary to save space. @value{GDBN} on the
11954 host system does all the symbol handling.
11956 To use the server, you must tell it how to communicate with
11957 @value{GDBN}; the name of your program; and the arguments for your
11958 program. The syntax is:
11961 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
11962 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
11965 @var{board} and @var{port} specify the serial line; @var{baud} specifies
11966 the baud rate used by the connection. @var{port} and @var{node} default
11967 to 0, @var{baud} defaults to 9600@dmn{bps}.
11969 For example, to debug Emacs with the argument @samp{foo.txt}and
11970 communicate with @value{GDBN} over serial port number 2 or board 1
11971 using a 19200@dmn{bps} connection:
11974 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
11978 On the @value{GDBN} host machine, connect to your target (@pxref{Connecting,,
11979 Connecting to a remote target}).
11983 @node Remote configuration
11984 @section Remote configuration
11987 @kindex show remote
11988 This section documents the configuration options available when
11989 debugging remote programs. For the options related to the File I/O
11990 extensions of the remote protocol, see @ref{The system call,
11991 system-call-allowed}.
11994 @item set remoteaddresssize @var{bits}
11995 @cindex adress size for remote targets
11996 @cindex bits in remote address
11997 Set the maximum size of address in a memory packet to the specified
11998 number of bits. @value{GDBN} will mask off the address bits above
11999 that number, when it passes addresses to the remote target. The
12000 default value is the number of bits in the target's address.
12002 @item show remoteaddresssize
12003 Show the current value of remote address size in bits.
12005 @item set remotebaud @var{n}
12006 @cindex baud rate for remote targets
12007 Set the baud rate for the remote serial I/O to @var{n} baud. The
12008 value is used to set the speed of the serial port used for debugging
12011 @item show remotebaud
12012 Show the current speed of the remote connection.
12014 @item set remotebreak
12015 @cindex interrupt remote programs
12016 @cindex BREAK signal instead of Ctrl-C
12017 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
12018 when you press the @key{Ctrl-C} key to interrupt the program running
12019 on the remote. If set to off, @value{GDBN} sends the @samp{Strl-C}
12020 character instead. The default is off, since most remote systems
12021 expect to see @samp{Ctrl-C} as the interrupt signal.
12023 @item show remotebreak
12024 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
12025 interrupt the remote program.
12027 @item set remotedebug
12028 @cindex debug remote protocol
12029 @cindex remote protocol debugging
12030 @cindex display remote packets
12031 Control the debugging of the remote protocol. When enabled, each
12032 packet sent to or received from the remote target is displayed. The
12035 @item show remotedebug
12036 Show the current setting of the remote protocol debugging.
12038 @item set remotedevice @var{device}
12039 @cindex serial port name
12040 Set the name of the serial port through which to communicate to the
12041 remote target to @var{device}. This is the device used by
12042 @value{GDBN} to open the serial communications line to the remote
12043 target. There's no default, so you must set a valid port name for the
12044 remote serial communications to work. (Some varieties of the
12045 @code{target} command accept the port name as part of their
12048 @item show remotedevice
12049 Show the current name of the serial port.
12051 @item set remotelogbase @var{base}
12052 Set the base (a.k.a.@: radix) of logging serial protocol
12053 communications to @var{base}. Supported values of @var{base} are:
12054 @code{ascii}, @code{octal}, and @code{hex}. The default is
12057 @item show remotelogbase
12058 Show the current setting of the radix for logging remote serial
12061 @item set remotelogfile @var{file}
12062 @cindex record serial communications on file
12063 Record remote serial communications on the named @var{file}. The
12064 default is not to record at all.
12066 @item show remotelogfile.
12067 Show the current setting of the file name on which to record the
12068 serial communications.
12070 @item set remotetimeout @var{num}
12071 @cindex timeout for serial communications
12072 @cindex remote timeout
12073 Set the timeout limit to wait for the remote target to respond to
12074 @var{num} seconds. The default is 2 seconds.
12076 @item show remotetimeout
12077 Show the current number of seconds to wait for the remote target
12080 @cindex limit hardware breakpoints and watchpoints
12081 @cindex remote target, limit break- and watchpoints
12082 @anchor{set remote hardware-watchpoint-limit}
12083 @anchor{set remote hardware-breakpoint-limit}
12084 @item set remote hardware-watchpoint-limit @var{limit}
12085 @itemx set remote hardware-breakpoint-limit @var{limit}
12086 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
12087 watchpoints. A limit of -1, the default, is treated as unlimited.
12089 @item set remote fetch-register-packet
12090 @itemx set remote set-register-packet
12091 @itemx set remote P-packet
12092 @itemx set remote p-packet
12094 @cindex fetch registers from remote targets
12095 @cindex set registers in remote targets
12096 Determine whether @value{GDBN} can set and fetch registers from the
12097 remote target using the @samp{P} packets. The default depends on the
12098 remote stub's support of the @samp{P} packets (@value{GDBN} queries
12099 the stub when this packet is first required).
12101 @item show remote fetch-register-packet
12102 @itemx show remote set-register-packet
12103 @itemx show remote P-packet
12104 @itemx show remote p-packet
12105 Show the current setting of using the @samp{P} packets for setting and
12106 fetching registers from the remote target.
12108 @cindex binary downloads
12110 @item set remote binary-download-packet
12111 @itemx set remote X-packet
12112 Determine whether @value{GDBN} sends downloads in binary mode using
12113 the @samp{X} packets. The default is on.
12115 @item show remote binary-download-packet
12116 @itemx show remote X-packet
12117 Show the current setting of using the @samp{X} packets for binary
12120 @item set remote read-aux-vector-packet
12121 @cindex auxiliary vector of remote target
12122 @cindex @code{auxv}, and remote targets
12123 Set the use of the remote protocol's @samp{qPart:auxv:read} (target
12124 auxiliary vector read) request. This request is used to fetch the
12125 remote target's @dfn{auxiliary vector}, see @ref{OS Information,
12126 Auxiliary Vector}. The default setting depends on the remote stub's
12127 support of this request (@value{GDBN} queries the stub when this
12128 request is first required). @xref{General Query Packets, qPart}, for
12129 more information about this request.
12131 @item show remote read-aux-vector-packet
12132 Show the current setting of use of the @samp{qPart:auxv:read} request.
12134 @item set remote symbol-lookup-packet
12135 @cindex remote symbol lookup request
12136 Set the use of the remote protocol's @samp{qSymbol} (target symbol
12137 lookup) request. This request is used to communicate symbol
12138 information to the remote target, e.g., whenever a new shared library
12139 is loaded by the remote (@pxref{Files, shared libraries}). The
12140 default setting depends on the remote stub's support of this request
12141 (@value{GDBN} queries the stub when this request is first required).
12142 @xref{General Query Packets, qSymbol}, for more information about this
12145 @item show remote symbol-lookup-packet
12146 Show the current setting of use of the @samp{qSymbol} request.
12148 @item set remote verbose-resume-packet
12149 @cindex resume remote target
12150 @cindex signal thread, and remote targets
12151 @cindex single-step thread, and remote targets
12152 @cindex thread-specific operations on remote targets
12153 Set the use of the remote protocol's @samp{vCont} (descriptive resume)
12154 request. This request is used to resume specific threads in the
12155 remote target, and to single-step or signal them. The default setting
12156 depends on the remote stub's support of this request (@value{GDBN}
12157 queries the stub when this request is first required). This setting
12158 affects debugging of multithreaded programs: if @samp{vCont} cannot be
12159 used, @value{GDBN} might be unable to single-step a specific thread,
12160 especially under @code{set scheduler-locking off}; it is also
12161 impossible to pause a specific thread. @xref{Packets, vCont}, for
12164 @item show remote verbose-resume-packet
12165 Show the current setting of use of the @samp{vCont} request
12167 @item set remote software-breakpoint-packet
12168 @itemx set remote hardware-breakpoint-packet
12169 @itemx set remote write-watchpoint-packet
12170 @itemx set remote read-watchpoint-packet
12171 @itemx set remote access-watchpoint-packet
12172 @itemx set remote Z-packet
12174 @cindex remote hardware breakpoints and watchpoints
12175 These commands enable or disable the use of @samp{Z} packets for
12176 setting breakpoints and watchpoints in the remote target. The default
12177 depends on the remote stub's support of the @samp{Z} packets
12178 (@value{GDBN} queries the stub when each packet is first required).
12179 The command @code{set remote Z-packet}, kept for back-compatibility,
12180 turns on or off all the features that require the use of @samp{Z}
12183 @item show remote software-breakpoint-packet
12184 @itemx show remote hardware-breakpoint-packet
12185 @itemx show remote write-watchpoint-packet
12186 @itemx show remote read-watchpoint-packet
12187 @itemx show remote access-watchpoint-packet
12188 @itemx show remote Z-packet
12189 Show the current setting of @samp{Z} packets usage.
12191 @item set remote get-thread-local-storage-address
12192 @kindex set remote get-thread-local-storage-address
12193 @cindex thread local storage of remote targets
12194 This command enables or disables the use of the @samp{qGetTLSAddr}
12195 (Get Thread Local Storage Address) request packet. The default
12196 depends on whether the remote stub supports this request.
12197 @xref{General Query Packets, qGetTLSAddr}, for more details about this
12200 @item show remote get-thread-local-storage-address
12201 @kindex show remote get-thread-local-storage-address
12202 Show the current setting of @samp{qGetTLSAddr} packet usage.
12206 @section Implementing a remote stub
12208 @cindex debugging stub, example
12209 @cindex remote stub, example
12210 @cindex stub example, remote debugging
12211 The stub files provided with @value{GDBN} implement the target side of the
12212 communication protocol, and the @value{GDBN} side is implemented in the
12213 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
12214 these subroutines to communicate, and ignore the details. (If you're
12215 implementing your own stub file, you can still ignore the details: start
12216 with one of the existing stub files. @file{sparc-stub.c} is the best
12217 organized, and therefore the easiest to read.)
12219 @cindex remote serial debugging, overview
12220 To debug a program running on another machine (the debugging
12221 @dfn{target} machine), you must first arrange for all the usual
12222 prerequisites for the program to run by itself. For example, for a C
12227 A startup routine to set up the C runtime environment; these usually
12228 have a name like @file{crt0}. The startup routine may be supplied by
12229 your hardware supplier, or you may have to write your own.
12232 A C subroutine library to support your program's
12233 subroutine calls, notably managing input and output.
12236 A way of getting your program to the other machine---for example, a
12237 download program. These are often supplied by the hardware
12238 manufacturer, but you may have to write your own from hardware
12242 The next step is to arrange for your program to use a serial port to
12243 communicate with the machine where @value{GDBN} is running (the @dfn{host}
12244 machine). In general terms, the scheme looks like this:
12248 @value{GDBN} already understands how to use this protocol; when everything
12249 else is set up, you can simply use the @samp{target remote} command
12250 (@pxref{Targets,,Specifying a Debugging Target}).
12252 @item On the target,
12253 you must link with your program a few special-purpose subroutines that
12254 implement the @value{GDBN} remote serial protocol. The file containing these
12255 subroutines is called a @dfn{debugging stub}.
12257 On certain remote targets, you can use an auxiliary program
12258 @code{gdbserver} instead of linking a stub into your program.
12259 @xref{Server,,Using the @code{gdbserver} program}, for details.
12262 The debugging stub is specific to the architecture of the remote
12263 machine; for example, use @file{sparc-stub.c} to debug programs on
12266 @cindex remote serial stub list
12267 These working remote stubs are distributed with @value{GDBN}:
12272 @cindex @file{i386-stub.c}
12275 For Intel 386 and compatible architectures.
12278 @cindex @file{m68k-stub.c}
12279 @cindex Motorola 680x0
12281 For Motorola 680x0 architectures.
12284 @cindex @file{sh-stub.c}
12287 For Renesas SH architectures.
12290 @cindex @file{sparc-stub.c}
12292 For @sc{sparc} architectures.
12294 @item sparcl-stub.c
12295 @cindex @file{sparcl-stub.c}
12298 For Fujitsu @sc{sparclite} architectures.
12302 The @file{README} file in the @value{GDBN} distribution may list other
12303 recently added stubs.
12306 * Stub Contents:: What the stub can do for you
12307 * Bootstrapping:: What you must do for the stub
12308 * Debug Session:: Putting it all together
12311 @node Stub Contents
12312 @subsection What the stub can do for you
12314 @cindex remote serial stub
12315 The debugging stub for your architecture supplies these three
12319 @item set_debug_traps
12320 @findex set_debug_traps
12321 @cindex remote serial stub, initialization
12322 This routine arranges for @code{handle_exception} to run when your
12323 program stops. You must call this subroutine explicitly near the
12324 beginning of your program.
12326 @item handle_exception
12327 @findex handle_exception
12328 @cindex remote serial stub, main routine
12329 This is the central workhorse, but your program never calls it
12330 explicitly---the setup code arranges for @code{handle_exception} to
12331 run when a trap is triggered.
12333 @code{handle_exception} takes control when your program stops during
12334 execution (for example, on a breakpoint), and mediates communications
12335 with @value{GDBN} on the host machine. This is where the communications
12336 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
12337 representative on the target machine. It begins by sending summary
12338 information on the state of your program, then continues to execute,
12339 retrieving and transmitting any information @value{GDBN} needs, until you
12340 execute a @value{GDBN} command that makes your program resume; at that point,
12341 @code{handle_exception} returns control to your own code on the target
12345 @cindex @code{breakpoint} subroutine, remote
12346 Use this auxiliary subroutine to make your program contain a
12347 breakpoint. Depending on the particular situation, this may be the only
12348 way for @value{GDBN} to get control. For instance, if your target
12349 machine has some sort of interrupt button, you won't need to call this;
12350 pressing the interrupt button transfers control to
12351 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
12352 simply receiving characters on the serial port may also trigger a trap;
12353 again, in that situation, you don't need to call @code{breakpoint} from
12354 your own program---simply running @samp{target remote} from the host
12355 @value{GDBN} session gets control.
12357 Call @code{breakpoint} if none of these is true, or if you simply want
12358 to make certain your program stops at a predetermined point for the
12359 start of your debugging session.
12362 @node Bootstrapping
12363 @subsection What you must do for the stub
12365 @cindex remote stub, support routines
12366 The debugging stubs that come with @value{GDBN} are set up for a particular
12367 chip architecture, but they have no information about the rest of your
12368 debugging target machine.
12370 First of all you need to tell the stub how to communicate with the
12374 @item int getDebugChar()
12375 @findex getDebugChar
12376 Write this subroutine to read a single character from the serial port.
12377 It may be identical to @code{getchar} for your target system; a
12378 different name is used to allow you to distinguish the two if you wish.
12380 @item void putDebugChar(int)
12381 @findex putDebugChar
12382 Write this subroutine to write a single character to the serial port.
12383 It may be identical to @code{putchar} for your target system; a
12384 different name is used to allow you to distinguish the two if you wish.
12387 @cindex control C, and remote debugging
12388 @cindex interrupting remote targets
12389 If you want @value{GDBN} to be able to stop your program while it is
12390 running, you need to use an interrupt-driven serial driver, and arrange
12391 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
12392 character). That is the character which @value{GDBN} uses to tell the
12393 remote system to stop.
12395 Getting the debugging target to return the proper status to @value{GDBN}
12396 probably requires changes to the standard stub; one quick and dirty way
12397 is to just execute a breakpoint instruction (the ``dirty'' part is that
12398 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
12400 Other routines you need to supply are:
12403 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
12404 @findex exceptionHandler
12405 Write this function to install @var{exception_address} in the exception
12406 handling tables. You need to do this because the stub does not have any
12407 way of knowing what the exception handling tables on your target system
12408 are like (for example, the processor's table might be in @sc{rom},
12409 containing entries which point to a table in @sc{ram}).
12410 @var{exception_number} is the exception number which should be changed;
12411 its meaning is architecture-dependent (for example, different numbers
12412 might represent divide by zero, misaligned access, etc). When this
12413 exception occurs, control should be transferred directly to
12414 @var{exception_address}, and the processor state (stack, registers,
12415 and so on) should be just as it is when a processor exception occurs. So if
12416 you want to use a jump instruction to reach @var{exception_address}, it
12417 should be a simple jump, not a jump to subroutine.
12419 For the 386, @var{exception_address} should be installed as an interrupt
12420 gate so that interrupts are masked while the handler runs. The gate
12421 should be at privilege level 0 (the most privileged level). The
12422 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
12423 help from @code{exceptionHandler}.
12425 @item void flush_i_cache()
12426 @findex flush_i_cache
12427 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
12428 instruction cache, if any, on your target machine. If there is no
12429 instruction cache, this subroutine may be a no-op.
12431 On target machines that have instruction caches, @value{GDBN} requires this
12432 function to make certain that the state of your program is stable.
12436 You must also make sure this library routine is available:
12439 @item void *memset(void *, int, int)
12441 This is the standard library function @code{memset} that sets an area of
12442 memory to a known value. If you have one of the free versions of
12443 @code{libc.a}, @code{memset} can be found there; otherwise, you must
12444 either obtain it from your hardware manufacturer, or write your own.
12447 If you do not use the GNU C compiler, you may need other standard
12448 library subroutines as well; this varies from one stub to another,
12449 but in general the stubs are likely to use any of the common library
12450 subroutines which @code{@value{GCC}} generates as inline code.
12453 @node Debug Session
12454 @subsection Putting it all together
12456 @cindex remote serial debugging summary
12457 In summary, when your program is ready to debug, you must follow these
12462 Make sure you have defined the supporting low-level routines
12463 (@pxref{Bootstrapping,,What you must do for the stub}):
12465 @code{getDebugChar}, @code{putDebugChar},
12466 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
12470 Insert these lines near the top of your program:
12478 For the 680x0 stub only, you need to provide a variable called
12479 @code{exceptionHook}. Normally you just use:
12482 void (*exceptionHook)() = 0;
12486 but if before calling @code{set_debug_traps}, you set it to point to a
12487 function in your program, that function is called when
12488 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
12489 error). The function indicated by @code{exceptionHook} is called with
12490 one parameter: an @code{int} which is the exception number.
12493 Compile and link together: your program, the @value{GDBN} debugging stub for
12494 your target architecture, and the supporting subroutines.
12497 Make sure you have a serial connection between your target machine and
12498 the @value{GDBN} host, and identify the serial port on the host.
12501 @c The "remote" target now provides a `load' command, so we should
12502 @c document that. FIXME.
12503 Download your program to your target machine (or get it there by
12504 whatever means the manufacturer provides), and start it.
12507 Start @value{GDBN} on the host, and connect to the target
12508 (@pxref{Connecting,,Connecting to a remote target}).
12512 @node Configurations
12513 @chapter Configuration-Specific Information
12515 While nearly all @value{GDBN} commands are available for all native and
12516 cross versions of the debugger, there are some exceptions. This chapter
12517 describes things that are only available in certain configurations.
12519 There are three major categories of configurations: native
12520 configurations, where the host and target are the same, embedded
12521 operating system configurations, which are usually the same for several
12522 different processor architectures, and bare embedded processors, which
12523 are quite different from each other.
12528 * Embedded Processors::
12535 This section describes details specific to particular native
12540 * BSD libkvm Interface:: Debugging BSD kernel memory images
12541 * SVR4 Process Information:: SVR4 process information
12542 * DJGPP Native:: Features specific to the DJGPP port
12543 * Cygwin Native:: Features specific to the Cygwin port
12544 * Hurd Native:: Features specific to @sc{gnu} Hurd
12545 * Neutrino:: Features specific to QNX Neutrino
12551 On HP-UX systems, if you refer to a function or variable name that
12552 begins with a dollar sign, @value{GDBN} searches for a user or system
12553 name first, before it searches for a convenience variable.
12556 @node BSD libkvm Interface
12557 @subsection BSD libkvm Interface
12560 @cindex kernel memory image
12561 @cindex kernel crash dump
12563 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
12564 interface that provides a uniform interface for accessing kernel virtual
12565 memory images, including live systems and crash dumps. @value{GDBN}
12566 uses this interface to allow you to debug live kernels and kernel crash
12567 dumps on many native BSD configurations. This is implemented as a
12568 special @code{kvm} debugging target. For debugging a live system, load
12569 the currently running kernel into @value{GDBN} and connect to the
12573 (@value{GDBP}) @b{target kvm}
12576 For debugging crash dumps, provide the file name of the crash dump as an
12580 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
12583 Once connected to the @code{kvm} target, the following commands are
12589 Set current context from the @dfn{Process Control Block} (PCB) address.
12592 Set current context from proc address. This command isn't available on
12593 modern FreeBSD systems.
12596 @node SVR4 Process Information
12597 @subsection SVR4 process information
12599 @cindex examine process image
12600 @cindex process info via @file{/proc}
12602 Many versions of SVR4 and compatible systems provide a facility called
12603 @samp{/proc} that can be used to examine the image of a running
12604 process using file-system subroutines. If @value{GDBN} is configured
12605 for an operating system with this facility, the command @code{info
12606 proc} is available to report information about the process running
12607 your program, or about any process running on your system. @code{info
12608 proc} works only on SVR4 systems that include the @code{procfs} code.
12609 This includes, as of this writing, @sc{gnu}/Linux, OSF/1 (Digital
12610 Unix), Solaris, Irix, and Unixware, but not HP-UX, for example.
12616 @itemx info proc @var{process-id}
12617 Summarize available information about any running process. If a
12618 process ID is specified by @var{process-id}, display information about
12619 that process; otherwise display information about the program being
12620 debugged. The summary includes the debugged process ID, the command
12621 line used to invoke it, its current working directory, and its
12622 executable file's absolute file name.
12624 On some systems, @var{process-id} can be of the form
12625 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
12626 within a process. If the optional @var{pid} part is missing, it means
12627 a thread from the process being debugged (the leading @samp{/} still
12628 needs to be present, or else @value{GDBN} will interpret the number as
12629 a process ID rather than a thread ID).
12631 @item info proc mappings
12632 @cindex memory address space mappings
12633 Report the memory address space ranges accessible in the program, with
12634 information on whether the process has read, write, or execute access
12635 rights to each range. On @sc{gnu}/Linux systems, each memory range
12636 includes the object file which is mapped to that range, instead of the
12637 memory access rights to that range.
12639 @item info proc stat
12640 @itemx info proc status
12641 @cindex process detailed status information
12642 These subcommands are specific to @sc{gnu}/Linux systems. They show
12643 the process-related information, including the user ID and group ID;
12644 how many threads are there in the process; its virtual memory usage;
12645 the signals that are pending, blocked, and ignored; its TTY; its
12646 consumption of system and user time; its stack size; its @samp{nice}
12647 value; etc. For more information, see the @samp{proc} man page
12648 (type @kbd{man 5 proc} from your shell prompt).
12650 @item info proc all
12651 Show all the information about the process described under all of the
12652 above @code{info proc} subcommands.
12655 @comment These sub-options of 'info proc' were not included when
12656 @comment procfs.c was re-written. Keep their descriptions around
12657 @comment against the day when someone finds the time to put them back in.
12658 @kindex info proc times
12659 @item info proc times
12660 Starting time, user CPU time, and system CPU time for your program and
12663 @kindex info proc id
12665 Report on the process IDs related to your program: its own process ID,
12666 the ID of its parent, the process group ID, and the session ID.
12669 @item set procfs-trace
12670 @kindex set procfs-trace
12671 @cindex @code{procfs} API calls
12672 This command enables and disables tracing of @code{procfs} API calls.
12674 @item show procfs-trace
12675 @kindex show procfs-trace
12676 Show the current state of @code{procfs} API call tracing.
12678 @item set procfs-file @var{file}
12679 @kindex set procfs-file
12680 Tell @value{GDBN} to write @code{procfs} API trace to the named
12681 @var{file}. @value{GDBN} appends the trace info to the previous
12682 contents of the file. The default is to display the trace on the
12685 @item show procfs-file
12686 @kindex show procfs-file
12687 Show the file to which @code{procfs} API trace is written.
12689 @item proc-trace-entry
12690 @itemx proc-trace-exit
12691 @itemx proc-untrace-entry
12692 @itemx proc-untrace-exit
12693 @kindex proc-trace-entry
12694 @kindex proc-trace-exit
12695 @kindex proc-untrace-entry
12696 @kindex proc-untrace-exit
12697 These commands enable and disable tracing of entries into and exits
12698 from the @code{syscall} interface.
12701 @kindex info pidlist
12702 @cindex process list, QNX Neutrino
12703 For QNX Neutrino only, this command displays the list of all the
12704 processes and all the threads within each process.
12707 @kindex info meminfo
12708 @cindex mapinfo list, QNX Neutrino
12709 For QNX Neutrino only, this command displays the list of all mapinfos.
12713 @subsection Features for Debugging @sc{djgpp} Programs
12714 @cindex @sc{djgpp} debugging
12715 @cindex native @sc{djgpp} debugging
12716 @cindex MS-DOS-specific commands
12719 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
12720 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
12721 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
12722 top of real-mode DOS systems and their emulations.
12724 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
12725 defines a few commands specific to the @sc{djgpp} port. This
12726 subsection describes those commands.
12731 This is a prefix of @sc{djgpp}-specific commands which print
12732 information about the target system and important OS structures.
12735 @cindex MS-DOS system info
12736 @cindex free memory information (MS-DOS)
12737 @item info dos sysinfo
12738 This command displays assorted information about the underlying
12739 platform: the CPU type and features, the OS version and flavor, the
12740 DPMI version, and the available conventional and DPMI memory.
12745 @cindex segment descriptor tables
12746 @cindex descriptor tables display
12748 @itemx info dos ldt
12749 @itemx info dos idt
12750 These 3 commands display entries from, respectively, Global, Local,
12751 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
12752 tables are data structures which store a descriptor for each segment
12753 that is currently in use. The segment's selector is an index into a
12754 descriptor table; the table entry for that index holds the
12755 descriptor's base address and limit, and its attributes and access
12758 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
12759 segment (used for both data and the stack), and a DOS segment (which
12760 allows access to DOS/BIOS data structures and absolute addresses in
12761 conventional memory). However, the DPMI host will usually define
12762 additional segments in order to support the DPMI environment.
12764 @cindex garbled pointers
12765 These commands allow to display entries from the descriptor tables.
12766 Without an argument, all entries from the specified table are
12767 displayed. An argument, which should be an integer expression, means
12768 display a single entry whose index is given by the argument. For
12769 example, here's a convenient way to display information about the
12770 debugged program's data segment:
12773 @exdent @code{(@value{GDBP}) info dos ldt $ds}
12774 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
12778 This comes in handy when you want to see whether a pointer is outside
12779 the data segment's limit (i.e.@: @dfn{garbled}).
12781 @cindex page tables display (MS-DOS)
12783 @itemx info dos pte
12784 These two commands display entries from, respectively, the Page
12785 Directory and the Page Tables. Page Directories and Page Tables are
12786 data structures which control how virtual memory addresses are mapped
12787 into physical addresses. A Page Table includes an entry for every
12788 page of memory that is mapped into the program's address space; there
12789 may be several Page Tables, each one holding up to 4096 entries. A
12790 Page Directory has up to 4096 entries, one each for every Page Table
12791 that is currently in use.
12793 Without an argument, @kbd{info dos pde} displays the entire Page
12794 Directory, and @kbd{info dos pte} displays all the entries in all of
12795 the Page Tables. An argument, an integer expression, given to the
12796 @kbd{info dos pde} command means display only that entry from the Page
12797 Directory table. An argument given to the @kbd{info dos pte} command
12798 means display entries from a single Page Table, the one pointed to by
12799 the specified entry in the Page Directory.
12801 @cindex direct memory access (DMA) on MS-DOS
12802 These commands are useful when your program uses @dfn{DMA} (Direct
12803 Memory Access), which needs physical addresses to program the DMA
12806 These commands are supported only with some DPMI servers.
12808 @cindex physical address from linear address
12809 @item info dos address-pte @var{addr}
12810 This command displays the Page Table entry for a specified linear
12811 address. The argument @var{addr} is a linear address which should
12812 already have the appropriate segment's base address added to it,
12813 because this command accepts addresses which may belong to @emph{any}
12814 segment. For example, here's how to display the Page Table entry for
12815 the page where a variable @code{i} is stored:
12818 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
12819 @exdent @code{Page Table entry for address 0x11a00d30:}
12820 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
12824 This says that @code{i} is stored at offset @code{0xd30} from the page
12825 whose physical base address is @code{0x02698000}, and shows all the
12826 attributes of that page.
12828 Note that you must cast the addresses of variables to a @code{char *},
12829 since otherwise the value of @code{__djgpp_base_address}, the base
12830 address of all variables and functions in a @sc{djgpp} program, will
12831 be added using the rules of C pointer arithmetics: if @code{i} is
12832 declared an @code{int}, @value{GDBN} will add 4 times the value of
12833 @code{__djgpp_base_address} to the address of @code{i}.
12835 Here's another example, it displays the Page Table entry for the
12839 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
12840 @exdent @code{Page Table entry for address 0x29110:}
12841 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
12845 (The @code{+ 3} offset is because the transfer buffer's address is the
12846 3rd member of the @code{_go32_info_block} structure.) The output
12847 clearly shows that this DPMI server maps the addresses in conventional
12848 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
12849 linear (@code{0x29110}) addresses are identical.
12851 This command is supported only with some DPMI servers.
12854 @cindex DOS serial data link, remote debugging
12855 In addition to native debugging, the DJGPP port supports remote
12856 debugging via a serial data link. The following commands are specific
12857 to remote serial debugging in the DJGPP port of @value{GDBN}.
12860 @kindex set com1base
12861 @kindex set com1irq
12862 @kindex set com2base
12863 @kindex set com2irq
12864 @kindex set com3base
12865 @kindex set com3irq
12866 @kindex set com4base
12867 @kindex set com4irq
12868 @item set com1base @var{addr}
12869 This command sets the base I/O port address of the @file{COM1} serial
12872 @item set com1irq @var{irq}
12873 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
12874 for the @file{COM1} serial port.
12876 There are similar commands @samp{set com2base}, @samp{set com3irq},
12877 etc.@: for setting the port address and the @code{IRQ} lines for the
12880 @kindex show com1base
12881 @kindex show com1irq
12882 @kindex show com2base
12883 @kindex show com2irq
12884 @kindex show com3base
12885 @kindex show com3irq
12886 @kindex show com4base
12887 @kindex show com4irq
12888 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
12889 display the current settings of the base address and the @code{IRQ}
12890 lines used by the COM ports.
12893 @kindex info serial
12894 @cindex DOS serial port status
12895 This command prints the status of the 4 DOS serial ports. For each
12896 port, it prints whether it's active or not, its I/O base address and
12897 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
12898 counts of various errors encountered so far.
12902 @node Cygwin Native
12903 @subsection Features for Debugging MS Windows PE executables
12904 @cindex MS Windows debugging
12905 @cindex native Cygwin debugging
12906 @cindex Cygwin-specific commands
12908 @value{GDBN} supports native debugging of MS Windows programs, including
12909 DLLs with and without symbolic debugging information. There are various
12910 additional Cygwin-specific commands, described in this subsection. The
12911 subsubsection @pxref{Non-debug DLL symbols} describes working with DLLs
12912 that have no debugging symbols.
12918 This is a prefix of MS Windows specific commands which print
12919 information about the target system and important OS structures.
12921 @item info w32 selector
12922 This command displays information returned by
12923 the Win32 API @code{GetThreadSelectorEntry} function.
12924 It takes an optional argument that is evaluated to
12925 a long value to give the information about this given selector.
12926 Without argument, this command displays information
12927 about the the six segment registers.
12931 This is a Cygwin specific alias of info shared.
12933 @kindex dll-symbols
12935 This command loads symbols from a dll similarly to
12936 add-sym command but without the need to specify a base address.
12938 @kindex set new-console
12939 @item set new-console @var{mode}
12940 If @var{mode} is @code{on} the debuggee will
12941 be started in a new console on next start.
12942 If @var{mode} is @code{off}i, the debuggee will
12943 be started in the same console as the debugger.
12945 @kindex show new-console
12946 @item show new-console
12947 Displays whether a new console is used
12948 when the debuggee is started.
12950 @kindex set new-group
12951 @item set new-group @var{mode}
12952 This boolean value controls whether the debuggee should
12953 start a new group or stay in the same group as the debugger.
12954 This affects the way the Windows OS handles
12957 @kindex show new-group
12958 @item show new-group
12959 Displays current value of new-group boolean.
12961 @kindex set debugevents
12962 @item set debugevents
12963 This boolean value adds debug output concerning events seen by the debugger.
12965 @kindex set debugexec
12966 @item set debugexec
12967 This boolean value adds debug output concerning execute events
12968 seen by the debugger.
12970 @kindex set debugexceptions
12971 @item set debugexceptions
12972 This boolean value adds debug ouptut concerning exception events
12973 seen by the debugger.
12975 @kindex set debugmemory
12976 @item set debugmemory
12977 This boolean value adds debug ouptut concerning memory events
12978 seen by the debugger.
12982 This boolean values specifies whether the debuggee is called
12983 via a shell or directly (default value is on).
12987 Displays if the debuggee will be started with a shell.
12992 * Non-debug DLL symbols:: Support for DLLs without debugging symbols
12995 @node Non-debug DLL symbols
12996 @subsubsection Support for DLLs without debugging symbols
12997 @cindex DLLs with no debugging symbols
12998 @cindex Minimal symbols and DLLs
13000 Very often on windows, some of the DLLs that your program relies on do
13001 not include symbolic debugging information (for example,
13002 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
13003 symbols in a DLL, it relies on the minimal amount of symbolic
13004 information contained in the DLL's export table. This subsubsection
13005 describes working with such symbols, known internally to @value{GDBN} as
13006 ``minimal symbols''.
13008 Note that before the debugged program has started execution, no DLLs
13009 will have been loaded. The easiest way around this problem is simply to
13010 start the program --- either by setting a breakpoint or letting the
13011 program run once to completion. It is also possible to force
13012 @value{GDBN} to load a particular DLL before starting the executable ---
13013 see the shared library information in @pxref{Files} or the
13014 @code{dll-symbols} command in @pxref{Cygwin Native}. Currently,
13015 explicitly loading symbols from a DLL with no debugging information will
13016 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
13017 which may adversely affect symbol lookup performance.
13019 @subsubsection DLL name prefixes
13021 In keeping with the naming conventions used by the Microsoft debugging
13022 tools, DLL export symbols are made available with a prefix based on the
13023 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
13024 also entered into the symbol table, so @code{CreateFileA} is often
13025 sufficient. In some cases there will be name clashes within a program
13026 (particularly if the executable itself includes full debugging symbols)
13027 necessitating the use of the fully qualified name when referring to the
13028 contents of the DLL. Use single-quotes around the name to avoid the
13029 exclamation mark (``!'') being interpreted as a language operator.
13031 Note that the internal name of the DLL may be all upper-case, even
13032 though the file name of the DLL is lower-case, or vice-versa. Since
13033 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
13034 some confusion. If in doubt, try the @code{info functions} and
13035 @code{info variables} commands or even @code{maint print msymbols} (see
13036 @pxref{Symbols}). Here's an example:
13039 (@value{GDBP}) info function CreateFileA
13040 All functions matching regular expression "CreateFileA":
13042 Non-debugging symbols:
13043 0x77e885f4 CreateFileA
13044 0x77e885f4 KERNEL32!CreateFileA
13048 (@value{GDBP}) info function !
13049 All functions matching regular expression "!":
13051 Non-debugging symbols:
13052 0x6100114c cygwin1!__assert
13053 0x61004034 cygwin1!_dll_crt0@@0
13054 0x61004240 cygwin1!dll_crt0(per_process *)
13058 @subsubsection Working with minimal symbols
13060 Symbols extracted from a DLL's export table do not contain very much
13061 type information. All that @value{GDBN} can do is guess whether a symbol
13062 refers to a function or variable depending on the linker section that
13063 contains the symbol. Also note that the actual contents of the memory
13064 contained in a DLL are not available unless the program is running. This
13065 means that you cannot examine the contents of a variable or disassemble
13066 a function within a DLL without a running program.
13068 Variables are generally treated as pointers and dereferenced
13069 automatically. For this reason, it is often necessary to prefix a
13070 variable name with the address-of operator (``&'') and provide explicit
13071 type information in the command. Here's an example of the type of
13075 (@value{GDBP}) print 'cygwin1!__argv'
13080 (@value{GDBP}) x 'cygwin1!__argv'
13081 0x10021610: "\230y\""
13084 And two possible solutions:
13087 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
13088 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
13092 (@value{GDBP}) x/2x &'cygwin1!__argv'
13093 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
13094 (@value{GDBP}) x/x 0x10021608
13095 0x10021608: 0x0022fd98
13096 (@value{GDBP}) x/s 0x0022fd98
13097 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
13100 Setting a break point within a DLL is possible even before the program
13101 starts execution. However, under these circumstances, @value{GDBN} can't
13102 examine the initial instructions of the function in order to skip the
13103 function's frame set-up code. You can work around this by using ``*&''
13104 to set the breakpoint at a raw memory address:
13107 (@value{GDBP}) break *&'python22!PyOS_Readline'
13108 Breakpoint 1 at 0x1e04eff0
13111 The author of these extensions is not entirely convinced that setting a
13112 break point within a shared DLL like @file{kernel32.dll} is completely
13116 @subsection Commands specific to @sc{gnu} Hurd systems
13117 @cindex @sc{gnu} Hurd debugging
13119 This subsection describes @value{GDBN} commands specific to the
13120 @sc{gnu} Hurd native debugging.
13125 @kindex set signals@r{, Hurd command}
13126 @kindex set sigs@r{, Hurd command}
13127 This command toggles the state of inferior signal interception by
13128 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
13129 affected by this command. @code{sigs} is a shorthand alias for
13134 @kindex show signals@r{, Hurd command}
13135 @kindex show sigs@r{, Hurd command}
13136 Show the current state of intercepting inferior's signals.
13138 @item set signal-thread
13139 @itemx set sigthread
13140 @kindex set signal-thread
13141 @kindex set sigthread
13142 This command tells @value{GDBN} which thread is the @code{libc} signal
13143 thread. That thread is run when a signal is delivered to a running
13144 process. @code{set sigthread} is the shorthand alias of @code{set
13147 @item show signal-thread
13148 @itemx show sigthread
13149 @kindex show signal-thread
13150 @kindex show sigthread
13151 These two commands show which thread will run when the inferior is
13152 delivered a signal.
13155 @kindex set stopped@r{, Hurd command}
13156 This commands tells @value{GDBN} that the inferior process is stopped,
13157 as with the @code{SIGSTOP} signal. The stopped process can be
13158 continued by delivering a signal to it.
13161 @kindex show stopped@r{, Hurd command}
13162 This command shows whether @value{GDBN} thinks the debuggee is
13165 @item set exceptions
13166 @kindex set exceptions@r{, Hurd command}
13167 Use this command to turn off trapping of exceptions in the inferior.
13168 When exception trapping is off, neither breakpoints nor
13169 single-stepping will work. To restore the default, set exception
13172 @item show exceptions
13173 @kindex show exceptions@r{, Hurd command}
13174 Show the current state of trapping exceptions in the inferior.
13176 @item set task pause
13177 @kindex set task@r{, Hurd commands}
13178 @cindex task attributes (@sc{gnu} Hurd)
13179 @cindex pause current task (@sc{gnu} Hurd)
13180 This command toggles task suspension when @value{GDBN} has control.
13181 Setting it to on takes effect immediately, and the task is suspended
13182 whenever @value{GDBN} gets control. Setting it to off will take
13183 effect the next time the inferior is continued. If this option is set
13184 to off, you can use @code{set thread default pause on} or @code{set
13185 thread pause on} (see below) to pause individual threads.
13187 @item show task pause
13188 @kindex show task@r{, Hurd commands}
13189 Show the current state of task suspension.
13191 @item set task detach-suspend-count
13192 @cindex task suspend count
13193 @cindex detach from task, @sc{gnu} Hurd
13194 This command sets the suspend count the task will be left with when
13195 @value{GDBN} detaches from it.
13197 @item show task detach-suspend-count
13198 Show the suspend count the task will be left with when detaching.
13200 @item set task exception-port
13201 @itemx set task excp
13202 @cindex task exception port, @sc{gnu} Hurd
13203 This command sets the task exception port to which @value{GDBN} will
13204 forward exceptions. The argument should be the value of the @dfn{send
13205 rights} of the task. @code{set task excp} is a shorthand alias.
13207 @item set noninvasive
13208 @cindex noninvasive task options
13209 This command switches @value{GDBN} to a mode that is the least
13210 invasive as far as interfering with the inferior is concerned. This
13211 is the same as using @code{set task pause}, @code{set exceptions}, and
13212 @code{set signals} to values opposite to the defaults.
13214 @item info send-rights
13215 @itemx info receive-rights
13216 @itemx info port-rights
13217 @itemx info port-sets
13218 @itemx info dead-names
13221 @cindex send rights, @sc{gnu} Hurd
13222 @cindex receive rights, @sc{gnu} Hurd
13223 @cindex port rights, @sc{gnu} Hurd
13224 @cindex port sets, @sc{gnu} Hurd
13225 @cindex dead names, @sc{gnu} Hurd
13226 These commands display information about, respectively, send rights,
13227 receive rights, port rights, port sets, and dead names of a task.
13228 There are also shorthand aliases: @code{info ports} for @code{info
13229 port-rights} and @code{info psets} for @code{info port-sets}.
13231 @item set thread pause
13232 @kindex set thread@r{, Hurd command}
13233 @cindex thread properties, @sc{gnu} Hurd
13234 @cindex pause current thread (@sc{gnu} Hurd)
13235 This command toggles current thread suspension when @value{GDBN} has
13236 control. Setting it to on takes effect immediately, and the current
13237 thread is suspended whenever @value{GDBN} gets control. Setting it to
13238 off will take effect the next time the inferior is continued.
13239 Normally, this command has no effect, since when @value{GDBN} has
13240 control, the whole task is suspended. However, if you used @code{set
13241 task pause off} (see above), this command comes in handy to suspend
13242 only the current thread.
13244 @item show thread pause
13245 @kindex show thread@r{, Hurd command}
13246 This command shows the state of current thread suspension.
13248 @item set thread run
13249 This comamnd sets whether the current thread is allowed to run.
13251 @item show thread run
13252 Show whether the current thread is allowed to run.
13254 @item set thread detach-suspend-count
13255 @cindex thread suspend count, @sc{gnu} Hurd
13256 @cindex detach from thread, @sc{gnu} Hurd
13257 This command sets the suspend count @value{GDBN} will leave on a
13258 thread when detaching. This number is relative to the suspend count
13259 found by @value{GDBN} when it notices the thread; use @code{set thread
13260 takeover-suspend-count} to force it to an absolute value.
13262 @item show thread detach-suspend-count
13263 Show the suspend count @value{GDBN} will leave on the thread when
13266 @item set thread exception-port
13267 @itemx set thread excp
13268 Set the thread exception port to which to forward exceptions. This
13269 overrides the port set by @code{set task exception-port} (see above).
13270 @code{set thread excp} is the shorthand alias.
13272 @item set thread takeover-suspend-count
13273 Normally, @value{GDBN}'s thread suspend counts are relative to the
13274 value @value{GDBN} finds when it notices each thread. This command
13275 changes the suspend counts to be absolute instead.
13277 @item set thread default
13278 @itemx show thread default
13279 @cindex thread default settings, @sc{gnu} Hurd
13280 Each of the above @code{set thread} commands has a @code{set thread
13281 default} counterpart (e.g., @code{set thread default pause}, @code{set
13282 thread default exception-port}, etc.). The @code{thread default}
13283 variety of commands sets the default thread properties for all
13284 threads; you can then change the properties of individual threads with
13285 the non-default commands.
13290 @subsection QNX Neutrino
13291 @cindex QNX Neutrino
13293 @value{GDBN} provides the following commands specific to the QNX
13297 @item set debug nto-debug
13298 @kindex set debug nto-debug
13299 When set to on, enables debugging messages specific to the QNX
13302 @item show debug nto-debug
13303 @kindex show debug nto-debug
13304 Show the current state of QNX Neutrino messages.
13309 @section Embedded Operating Systems
13311 This section describes configurations involving the debugging of
13312 embedded operating systems that are available for several different
13316 * VxWorks:: Using @value{GDBN} with VxWorks
13319 @value{GDBN} includes the ability to debug programs running on
13320 various real-time operating systems.
13323 @subsection Using @value{GDBN} with VxWorks
13329 @kindex target vxworks
13330 @item target vxworks @var{machinename}
13331 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
13332 is the target system's machine name or IP address.
13336 On VxWorks, @code{load} links @var{filename} dynamically on the
13337 current target system as well as adding its symbols in @value{GDBN}.
13339 @value{GDBN} enables developers to spawn and debug tasks running on networked
13340 VxWorks targets from a Unix host. Already-running tasks spawned from
13341 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
13342 both the Unix host and on the VxWorks target. The program
13343 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
13344 installed with the name @code{vxgdb}, to distinguish it from a
13345 @value{GDBN} for debugging programs on the host itself.)
13348 @item VxWorks-timeout @var{args}
13349 @kindex vxworks-timeout
13350 All VxWorks-based targets now support the option @code{vxworks-timeout}.
13351 This option is set by the user, and @var{args} represents the number of
13352 seconds @value{GDBN} waits for responses to rpc's. You might use this if
13353 your VxWorks target is a slow software simulator or is on the far side
13354 of a thin network line.
13357 The following information on connecting to VxWorks was current when
13358 this manual was produced; newer releases of VxWorks may use revised
13361 @findex INCLUDE_RDB
13362 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
13363 to include the remote debugging interface routines in the VxWorks
13364 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
13365 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
13366 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
13367 source debugging task @code{tRdbTask} when VxWorks is booted. For more
13368 information on configuring and remaking VxWorks, see the manufacturer's
13370 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
13372 Once you have included @file{rdb.a} in your VxWorks system image and set
13373 your Unix execution search path to find @value{GDBN}, you are ready to
13374 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
13375 @code{vxgdb}, depending on your installation).
13377 @value{GDBN} comes up showing the prompt:
13384 * VxWorks Connection:: Connecting to VxWorks
13385 * VxWorks Download:: VxWorks download
13386 * VxWorks Attach:: Running tasks
13389 @node VxWorks Connection
13390 @subsubsection Connecting to VxWorks
13392 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
13393 network. To connect to a target whose host name is ``@code{tt}'', type:
13396 (vxgdb) target vxworks tt
13400 @value{GDBN} displays messages like these:
13403 Attaching remote machine across net...
13408 @value{GDBN} then attempts to read the symbol tables of any object modules
13409 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
13410 these files by searching the directories listed in the command search
13411 path (@pxref{Environment, ,Your program's environment}); if it fails
13412 to find an object file, it displays a message such as:
13415 prog.o: No such file or directory.
13418 When this happens, add the appropriate directory to the search path with
13419 the @value{GDBN} command @code{path}, and execute the @code{target}
13422 @node VxWorks Download
13423 @subsubsection VxWorks download
13425 @cindex download to VxWorks
13426 If you have connected to the VxWorks target and you want to debug an
13427 object that has not yet been loaded, you can use the @value{GDBN}
13428 @code{load} command to download a file from Unix to VxWorks
13429 incrementally. The object file given as an argument to the @code{load}
13430 command is actually opened twice: first by the VxWorks target in order
13431 to download the code, then by @value{GDBN} in order to read the symbol
13432 table. This can lead to problems if the current working directories on
13433 the two systems differ. If both systems have NFS mounted the same
13434 filesystems, you can avoid these problems by using absolute paths.
13435 Otherwise, it is simplest to set the working directory on both systems
13436 to the directory in which the object file resides, and then to reference
13437 the file by its name, without any path. For instance, a program
13438 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
13439 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
13440 program, type this on VxWorks:
13443 -> cd "@var{vxpath}/vw/demo/rdb"
13447 Then, in @value{GDBN}, type:
13450 (vxgdb) cd @var{hostpath}/vw/demo/rdb
13451 (vxgdb) load prog.o
13454 @value{GDBN} displays a response similar to this:
13457 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
13460 You can also use the @code{load} command to reload an object module
13461 after editing and recompiling the corresponding source file. Note that
13462 this makes @value{GDBN} delete all currently-defined breakpoints,
13463 auto-displays, and convenience variables, and to clear the value
13464 history. (This is necessary in order to preserve the integrity of
13465 debugger's data structures that reference the target system's symbol
13468 @node VxWorks Attach
13469 @subsubsection Running tasks
13471 @cindex running VxWorks tasks
13472 You can also attach to an existing task using the @code{attach} command as
13476 (vxgdb) attach @var{task}
13480 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
13481 or suspended when you attach to it. Running tasks are suspended at
13482 the time of attachment.
13484 @node Embedded Processors
13485 @section Embedded Processors
13487 This section goes into details specific to particular embedded
13490 @cindex send command to simulator
13491 Whenever a specific embedded processor has a simulator, @value{GDBN}
13492 allows to send an arbitrary command to the simulator.
13495 @item sim @var{command}
13496 @kindex sim@r{, a command}
13497 Send an arbitrary @var{command} string to the simulator. Consult the
13498 documentation for the specific simulator in use for information about
13499 acceptable commands.
13505 * H8/300:: Renesas H8/300
13506 * H8/500:: Renesas H8/500
13507 * M32R/D:: Renesas M32R/D
13508 * M68K:: Motorola M68K
13509 * MIPS Embedded:: MIPS Embedded
13510 * OpenRISC 1000:: OpenRisc 1000
13511 * PA:: HP PA Embedded
13514 * Sparclet:: Tsqware Sparclet
13515 * Sparclite:: Fujitsu Sparclite
13516 * ST2000:: Tandem ST2000
13517 * Z8000:: Zilog Z8000
13520 * Super-H:: Renesas Super-H
13521 * WinCE:: Windows CE child processes
13530 @item target rdi @var{dev}
13531 ARM Angel monitor, via RDI library interface to ADP protocol. You may
13532 use this target to communicate with both boards running the Angel
13533 monitor, or with the EmbeddedICE JTAG debug device.
13536 @item target rdp @var{dev}
13541 @value{GDBN} provides the following ARM-specific commands:
13544 @item set arm disassembler
13546 This commands selects from a list of disassembly styles. The
13547 @code{"std"} style is the standard style.
13549 @item show arm disassembler
13551 Show the current disassembly style.
13553 @item set arm apcs32
13554 @cindex ARM 32-bit mode
13555 This command toggles ARM operation mode between 32-bit and 26-bit.
13557 @item show arm apcs32
13558 Display the current usage of the ARM 32-bit mode.
13560 @item set arm fpu @var{fputype}
13561 This command sets the ARM floating-point unit (FPU) type. The
13562 argument @var{fputype} can be one of these:
13566 Determine the FPU type by querying the OS ABI.
13568 Software FPU, with mixed-endian doubles on little-endian ARM
13571 GCC-compiled FPA co-processor.
13573 Software FPU with pure-endian doubles.
13579 Show the current type of the FPU.
13582 This command forces @value{GDBN} to use the specified ABI.
13585 Show the currently used ABI.
13587 @item set debug arm
13588 Toggle whether to display ARM-specific debugging messages from the ARM
13589 target support subsystem.
13591 @item show debug arm
13592 Show whether ARM-specific debugging messages are enabled.
13595 The following commands are available when an ARM target is debugged
13596 using the RDI interface:
13599 @item rdilogfile @r{[}@var{file}@r{]}
13601 @cindex ADP (Angel Debugger Protocol) logging
13602 Set the filename for the ADP (Angel Debugger Protocol) packet log.
13603 With an argument, sets the log file to the specified @var{file}. With
13604 no argument, show the current log file name. The default log file is
13607 @item rdilogenable @r{[}@var{arg}@r{]}
13608 @kindex rdilogenable
13609 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
13610 enables logging, with an argument 0 or @code{"no"} disables it. With
13611 no arguments displays the current setting. When logging is enabled,
13612 ADP packets exchanged between @value{GDBN} and the RDI target device
13613 are logged to a file.
13615 @item set rdiromatzero
13616 @kindex set rdiromatzero
13617 @cindex ROM at zero address, RDI
13618 Tell @value{GDBN} whether the target has ROM at address 0. If on,
13619 vector catching is disabled, so that zero address can be used. If off
13620 (the default), vector catching is enabled. For this command to take
13621 effect, it needs to be invoked prior to the @code{target rdi} command.
13623 @item show rdiromatzero
13624 @kindex show rdiromatzero
13625 Show the current setting of ROM at zero address.
13627 @item set rdiheartbeat
13628 @kindex set rdiheartbeat
13629 @cindex RDI heartbeat
13630 Enable or disable RDI heartbeat packets. It is not recommended to
13631 turn on this option, since it confuses ARM and EPI JTAG interface, as
13632 well as the Angel monitor.
13634 @item show rdiheartbeat
13635 @kindex show rdiheartbeat
13636 Show the setting of RDI heartbeat packets.
13641 @subsection Renesas H8/300
13645 @kindex target hms@r{, with H8/300}
13646 @item target hms @var{dev}
13647 A Renesas SH, H8/300, or H8/500 board, attached via serial line to your host.
13648 Use special commands @code{device} and @code{speed} to control the serial
13649 line and the communications speed used.
13651 @kindex target e7000@r{, with H8/300}
13652 @item target e7000 @var{dev}
13653 E7000 emulator for Renesas H8 and SH.
13655 @kindex target sh3@r{, with H8/300}
13656 @kindex target sh3e@r{, with H8/300}
13657 @item target sh3 @var{dev}
13658 @itemx target sh3e @var{dev}
13659 Renesas SH-3 and SH-3E target systems.
13663 @cindex download to H8/300 or H8/500
13664 @cindex H8/300 or H8/500 download
13665 @cindex download to Renesas SH
13666 @cindex Renesas SH download
13667 When you select remote debugging to a Renesas SH, H8/300, or H8/500
13668 board, the @code{load} command downloads your program to the Renesas
13669 board and also opens it as the current executable target for
13670 @value{GDBN} on your host (like the @code{file} command).
13672 @value{GDBN} needs to know these things to talk to your
13673 Renesas SH, H8/300, or H8/500:
13677 that you want to use @samp{target hms}, the remote debugging interface
13678 for Renesas microprocessors, or @samp{target e7000}, the in-circuit
13679 emulator for the Renesas SH and the Renesas 300H. (@samp{target hms} is
13680 the default when @value{GDBN} is configured specifically for the Renesas SH,
13681 H8/300, or H8/500.)
13684 what serial device connects your host to your Renesas board (the first
13685 serial device available on your host is the default).
13688 what speed to use over the serial device.
13692 * Renesas Boards:: Connecting to Renesas boards.
13693 * Renesas ICE:: Using the E7000 In-Circuit Emulator.
13694 * Renesas Special:: Special @value{GDBN} commands for Renesas micros.
13697 @node Renesas Boards
13698 @subsubsection Connecting to Renesas boards
13700 @c only for Unix hosts
13702 @cindex serial device, Renesas micros
13703 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
13704 need to explicitly set the serial device. The default @var{port} is the
13705 first available port on your host. This is only necessary on Unix
13706 hosts, where it is typically something like @file{/dev/ttya}.
13709 @cindex serial line speed, Renesas micros
13710 @code{@value{GDBN}} has another special command to set the communications
13711 speed: @samp{speed @var{bps}}. This command also is only used from Unix
13712 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
13713 the DOS @code{mode} command (for instance,
13714 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
13716 The @samp{device} and @samp{speed} commands are available only when you
13717 use a Unix host to debug your Renesas microprocessor programs. If you
13719 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
13720 called @code{asynctsr} to communicate with the development board
13721 through a PC serial port. You must also use the DOS @code{mode} command
13722 to set up the serial port on the DOS side.
13724 The following sample session illustrates the steps needed to start a
13725 program under @value{GDBN} control on an H8/300. The example uses a
13726 sample H8/300 program called @file{t.x}. The procedure is the same for
13727 the Renesas SH and the H8/500.
13729 First hook up your development board. In this example, we use a
13730 board attached to serial port @code{COM2}; if you use a different serial
13731 port, substitute its name in the argument of the @code{mode} command.
13732 When you call @code{asynctsr}, the auxiliary comms program used by the
13733 debugger, you give it just the numeric part of the serial port's name;
13734 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
13738 C:\H8300\TEST> asynctsr 2
13739 C:\H8300\TEST> mode com2:9600,n,8,1,p
13741 Resident portion of MODE loaded
13743 COM2: 9600, n, 8, 1, p
13748 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
13749 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
13750 disable it, or even boot without it, to use @code{asynctsr} to control
13751 your development board.
13754 @kindex target hms@r{, and serial protocol}
13755 Now that serial communications are set up, and the development board is
13756 connected, you can start up @value{GDBN}. Call @code{@value{GDBN}} with
13757 the name of your program as the argument. @code{@value{GDBN}} prompts
13758 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
13759 commands to begin your debugging session: @samp{target hms} to specify
13760 cross-debugging to the Renesas board, and the @code{load} command to
13761 download your program to the board. @code{load} displays the names of
13762 the program's sections, and a @samp{*} for each 2K of data downloaded.
13763 (If you want to refresh @value{GDBN} data on symbols or on the
13764 executable file without downloading, use the @value{GDBN} commands
13765 @code{file} or @code{symbol-file}. These commands, and @code{load}
13766 itself, are described in @ref{Files,,Commands to specify files}.)
13769 (eg-C:\H8300\TEST) @value{GDBP} t.x
13770 @value{GDBN} is free software and you are welcome to distribute copies
13771 of it under certain conditions; type "show copying" to see
13773 There is absolutely no warranty for @value{GDBN}; type "show warranty"
13775 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
13776 (@value{GDBP}) target hms
13777 Connected to remote H8/300 HMS system.
13778 (@value{GDBP}) load t.x
13779 .text : 0x8000 .. 0xabde ***********
13780 .data : 0xabde .. 0xad30 *
13781 .stack : 0xf000 .. 0xf014 *
13784 At this point, you're ready to run or debug your program. From here on,
13785 you can use all the usual @value{GDBN} commands. The @code{break} command
13786 sets breakpoints; the @code{run} command starts your program;
13787 @code{print} or @code{x} display data; the @code{continue} command
13788 resumes execution after stopping at a breakpoint. You can use the
13789 @code{help} command at any time to find out more about @value{GDBN} commands.
13791 Remember, however, that @emph{operating system} facilities aren't
13792 available on your development board; for example, if your program hangs,
13793 you can't send an interrupt---but you can press the @sc{reset} switch!
13795 Use the @sc{reset} button on the development board
13798 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
13799 no way to pass an interrupt signal to the development board); and
13802 to return to the @value{GDBN} command prompt after your program finishes
13803 normally. The communications protocol provides no other way for @value{GDBN}
13804 to detect program completion.
13807 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
13808 development board as a ``normal exit'' of your program.
13811 @subsubsection Using the E7000 in-circuit emulator
13813 @kindex target e7000@r{, with Renesas ICE}
13814 You can use the E7000 in-circuit emulator to develop code for either the
13815 Renesas SH or the H8/300H. Use one of these forms of the @samp{target
13816 e7000} command to connect @value{GDBN} to your E7000:
13819 @item target e7000 @var{port} @var{speed}
13820 Use this form if your E7000 is connected to a serial port. The
13821 @var{port} argument identifies what serial port to use (for example,
13822 @samp{com2}). The third argument is the line speed in bits per second
13823 (for example, @samp{9600}).
13825 @item target e7000 @var{hostname}
13826 If your E7000 is installed as a host on a TCP/IP network, you can just
13827 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
13830 The following special commands are available when debugging with the
13834 @item e7000 @var{command}
13836 @cindex send command to E7000 monitor
13837 This sends the specified @var{command} to the E7000 monitor.
13839 @item ftplogin @var{machine} @var{username} @var{password} @var{dir}
13840 @kindex ftplogin@r{, E7000}
13841 This command records information for subsequent interface with the
13842 E7000 monitor via the FTP protocol: @value{GDBN} will log into the
13843 named @var{machine} using specified @var{username} and @var{password},
13844 and then chdir to the named directory @var{dir}.
13846 @item ftpload @var{file}
13847 @kindex ftpload@r{, E7000}
13848 This command uses credentials recorded by @code{ftplogin} to fetch and
13849 load the named @var{file} from the E7000 monitor.
13852 @kindex drain@r{, E7000}
13853 This command drains any pending text buffers stored on the E7000.
13855 @item set usehardbreakpoints
13856 @itemx show usehardbreakpoints
13857 @kindex set usehardbreakpoints@r{, E7000}
13858 @kindex show usehardbreakpoints@r{, E7000}
13859 @cindex hardware breakpoints, and E7000
13860 These commands set and show the use of hardware breakpoints for all
13861 breakpoints. @xref{Set Breaks, hardware-assisted breakpoint}, for
13862 more information about using hardware breakpoints selectively.
13865 @node Renesas Special
13866 @subsubsection Special @value{GDBN} commands for Renesas micros
13868 Some @value{GDBN} commands are available only for the H8/300:
13872 @kindex set machine
13873 @kindex show machine
13874 @item set machine h8300
13875 @itemx set machine h8300h
13876 Condition @value{GDBN} for one of the two variants of the H8/300
13877 architecture with @samp{set machine}. You can use @samp{show machine}
13878 to check which variant is currently in effect.
13887 @kindex set memory @var{mod}
13888 @cindex memory models, H8/500
13889 @item set memory @var{mod}
13891 Specify which H8/500 memory model (@var{mod}) you are using with
13892 @samp{set memory}; check which memory model is in effect with @samp{show
13893 memory}. The accepted values for @var{mod} are @code{small},
13894 @code{big}, @code{medium}, and @code{compact}.
13899 @subsection Renesas M32R/D and M32R/SDI
13902 @kindex target m32r
13903 @item target m32r @var{dev}
13904 Renesas M32R/D ROM monitor.
13906 @kindex target m32rsdi
13907 @item target m32rsdi @var{dev}
13908 Renesas M32R SDI server, connected via parallel port to the board.
13911 The following @value{GDBN} commands are specific to the M32R monitor:
13914 @item set download-path @var{path}
13915 @kindex set download-path
13916 @cindex find downloadable @sc{srec} files (M32R)
13917 Set the default path for finding donwloadable @sc{srec} files.
13919 @item show download-path
13920 @kindex show download-path
13921 Show the default path for downloadable @sc{srec} files.
13923 @item set board-address @var{addr}
13924 @kindex set board-address
13925 @cindex M32-EVA target board address
13926 Set the IP address for the M32R-EVA target board.
13928 @item show board-address
13929 @kindex show board-address
13930 Show the current IP address of the target board.
13932 @item set server-address @var{addr}
13933 @kindex set server-address
13934 @cindex download server address (M32R)
13935 Set the IP address for the download server, which is the @value{GDBN}'s
13938 @item show server-address
13939 @kindex show server-address
13940 Display the IP address of the download server.
13942 @item upload @r{[}@var{file}@r{]}
13943 @kindex upload@r{, M32R}
13944 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
13945 upload capability. If no @var{file} argument is given, the current
13946 executable file is uploaded.
13948 @item tload @r{[}@var{file}@r{]}
13949 @kindex tload@r{, M32R}
13950 Test the @code{upload} command.
13953 The following commands are available for M32R/SDI:
13958 @cindex reset SDI connection, M32R
13959 This command resets the SDI connection.
13963 This command shows the SDI connection status.
13966 @kindex debug_chaos
13967 @cindex M32R/Chaos debugging
13968 Instructs the remote that M32R/Chaos debugging is to be used.
13970 @item use_debug_dma
13971 @kindex use_debug_dma
13972 Instructs the remote to use the DEBUG_DMA method of accessing memory.
13975 @kindex use_mon_code
13976 Instructs the remote to use the MON_CODE method of accessing memory.
13979 @kindex use_ib_break
13980 Instructs the remote to set breakpoints by IB break.
13982 @item use_dbt_break
13983 @kindex use_dbt_break
13984 Instructs the remote to set breakpoints by DBT.
13990 The Motorola m68k configuration includes ColdFire support, and
13991 target command for the following ROM monitors.
13995 @kindex target abug
13996 @item target abug @var{dev}
13997 ABug ROM monitor for M68K.
13999 @kindex target cpu32bug
14000 @item target cpu32bug @var{dev}
14001 CPU32BUG monitor, running on a CPU32 (M68K) board.
14003 @kindex target dbug
14004 @item target dbug @var{dev}
14005 dBUG ROM monitor for Motorola ColdFire.
14008 @item target est @var{dev}
14009 EST-300 ICE monitor, running on a CPU32 (M68K) board.
14011 @kindex target rom68k
14012 @item target rom68k @var{dev}
14013 ROM 68K monitor, running on an M68K IDP board.
14019 @kindex target rombug
14020 @item target rombug @var{dev}
14021 ROMBUG ROM monitor for OS/9000.
14025 @node MIPS Embedded
14026 @subsection MIPS Embedded
14028 @cindex MIPS boards
14029 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
14030 MIPS board attached to a serial line. This is available when
14031 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
14034 Use these @value{GDBN} commands to specify the connection to your target board:
14037 @item target mips @var{port}
14038 @kindex target mips @var{port}
14039 To run a program on the board, start up @code{@value{GDBP}} with the
14040 name of your program as the argument. To connect to the board, use the
14041 command @samp{target mips @var{port}}, where @var{port} is the name of
14042 the serial port connected to the board. If the program has not already
14043 been downloaded to the board, you may use the @code{load} command to
14044 download it. You can then use all the usual @value{GDBN} commands.
14046 For example, this sequence connects to the target board through a serial
14047 port, and loads and runs a program called @var{prog} through the
14051 host$ @value{GDBP} @var{prog}
14052 @value{GDBN} is free software and @dots{}
14053 (@value{GDBP}) target mips /dev/ttyb
14054 (@value{GDBP}) load @var{prog}
14058 @item target mips @var{hostname}:@var{portnumber}
14059 On some @value{GDBN} host configurations, you can specify a TCP
14060 connection (for instance, to a serial line managed by a terminal
14061 concentrator) instead of a serial port, using the syntax
14062 @samp{@var{hostname}:@var{portnumber}}.
14064 @item target pmon @var{port}
14065 @kindex target pmon @var{port}
14068 @item target ddb @var{port}
14069 @kindex target ddb @var{port}
14070 NEC's DDB variant of PMON for Vr4300.
14072 @item target lsi @var{port}
14073 @kindex target lsi @var{port}
14074 LSI variant of PMON.
14076 @kindex target r3900
14077 @item target r3900 @var{dev}
14078 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
14080 @kindex target array
14081 @item target array @var{dev}
14082 Array Tech LSI33K RAID controller board.
14088 @value{GDBN} also supports these special commands for MIPS targets:
14091 @item set mipsfpu double
14092 @itemx set mipsfpu single
14093 @itemx set mipsfpu none
14094 @itemx set mipsfpu auto
14095 @itemx show mipsfpu
14096 @kindex set mipsfpu
14097 @kindex show mipsfpu
14098 @cindex MIPS remote floating point
14099 @cindex floating point, MIPS remote
14100 If your target board does not support the MIPS floating point
14101 coprocessor, you should use the command @samp{set mipsfpu none} (if you
14102 need this, you may wish to put the command in your @value{GDBN} init
14103 file). This tells @value{GDBN} how to find the return value of
14104 functions which return floating point values. It also allows
14105 @value{GDBN} to avoid saving the floating point registers when calling
14106 functions on the board. If you are using a floating point coprocessor
14107 with only single precision floating point support, as on the @sc{r4650}
14108 processor, use the command @samp{set mipsfpu single}. The default
14109 double precision floating point coprocessor may be selected using
14110 @samp{set mipsfpu double}.
14112 In previous versions the only choices were double precision or no
14113 floating point, so @samp{set mipsfpu on} will select double precision
14114 and @samp{set mipsfpu off} will select no floating point.
14116 As usual, you can inquire about the @code{mipsfpu} variable with
14117 @samp{show mipsfpu}.
14119 @item set timeout @var{seconds}
14120 @itemx set retransmit-timeout @var{seconds}
14121 @itemx show timeout
14122 @itemx show retransmit-timeout
14123 @cindex @code{timeout}, MIPS protocol
14124 @cindex @code{retransmit-timeout}, MIPS protocol
14125 @kindex set timeout
14126 @kindex show timeout
14127 @kindex set retransmit-timeout
14128 @kindex show retransmit-timeout
14129 You can control the timeout used while waiting for a packet, in the MIPS
14130 remote protocol, with the @code{set timeout @var{seconds}} command. The
14131 default is 5 seconds. Similarly, you can control the timeout used while
14132 waiting for an acknowledgement of a packet with the @code{set
14133 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
14134 You can inspect both values with @code{show timeout} and @code{show
14135 retransmit-timeout}. (These commands are @emph{only} available when
14136 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
14138 The timeout set by @code{set timeout} does not apply when @value{GDBN}
14139 is waiting for your program to stop. In that case, @value{GDBN} waits
14140 forever because it has no way of knowing how long the program is going
14141 to run before stopping.
14143 @item set syn-garbage-limit @var{num}
14144 @kindex set syn-garbage-limit@r{, MIPS remote}
14145 @cindex synchronize with remote MIPS target
14146 Limit the maximum number of characters @value{GDBN} should ignore when
14147 it tries to synchronize with the remote target. The default is 10
14148 characters. Setting the limit to -1 means there's no limit.
14150 @item show syn-garbage-limit
14151 @kindex show syn-garbage-limit@r{, MIPS remote}
14152 Show the current limit on the number of characters to ignore when
14153 trying to synchronize with the remote system.
14155 @item set monitor-prompt @var{prompt}
14156 @kindex set monitor-prompt@r{, MIPS remote}
14157 @cindex remote monitor prompt
14158 Tell @value{GDBN} to expect the specified @var{prompt} string from the
14159 remote monitor. The default depends on the target:
14169 @item show monitor-prompt
14170 @kindex show monitor-prompt@r{, MIPS remote}
14171 Show the current strings @value{GDBN} expects as the prompt from the
14174 @item set monitor-warnings
14175 @kindex set monitor-warnings@r{, MIPS remote}
14176 Enable or disable monitor warnings about hardware breakpoints. This
14177 has effect only for the @code{lsi} target. When on, @value{GDBN} will
14178 display warning messages whose codes are returned by the @code{lsi}
14179 PMON monitor for breakpoint commands.
14181 @item show monitor-warnings
14182 @kindex show monitor-warnings@r{, MIPS remote}
14183 Show the current setting of printing monitor warnings.
14185 @item pmon @var{command}
14186 @kindex pmon@r{, MIPS remote}
14187 @cindex send PMON command
14188 This command allows sending an arbitrary @var{command} string to the
14189 monitor. The monitor must be in debug mode for this to work.
14192 @node OpenRISC 1000
14193 @subsection OpenRISC 1000
14194 @cindex OpenRISC 1000
14196 @cindex or1k boards
14197 See OR1k Architecture document (@uref{www.opencores.org}) for more information
14198 about platform and commands.
14202 @kindex target jtag
14203 @item target jtag jtag://@var{host}:@var{port}
14205 Connects to remote JTAG server.
14206 JTAG remote server can be either an or1ksim or JTAG server,
14207 connected via parallel port to the board.
14209 Example: @code{target jtag jtag://localhost:9999}
14212 @item or1ksim @var{command}
14213 If connected to @code{or1ksim} OpenRISC 1000 Architectural
14214 Simulator, proprietary commands can be executed.
14216 @kindex info or1k spr
14217 @item info or1k spr
14218 Displays spr groups.
14220 @item info or1k spr @var{group}
14221 @itemx info or1k spr @var{groupno}
14222 Displays register names in selected group.
14224 @item info or1k spr @var{group} @var{register}
14225 @itemx info or1k spr @var{register}
14226 @itemx info or1k spr @var{groupno} @var{registerno}
14227 @itemx info or1k spr @var{registerno}
14228 Shows information about specified spr register.
14231 @item spr @var{group} @var{register} @var{value}
14232 @itemx spr @var{register @var{value}}
14233 @itemx spr @var{groupno} @var{registerno @var{value}}
14234 @itemx spr @var{registerno @var{value}}
14235 Writes @var{value} to specified spr register.
14238 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
14239 It is very similar to @value{GDBN} trace, except it does not interfere with normal
14240 program execution and is thus much faster. Hardware breakpoints/watchpoint
14241 triggers can be set using:
14244 Load effective address/data
14246 Store effective address/data
14248 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
14253 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
14254 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
14256 @code{htrace} commands:
14257 @cindex OpenRISC 1000 htrace
14260 @item hwatch @var{conditional}
14261 Set hardware watchpoint on combination of Load/Store Effecive Address(es)
14262 or Data. For example:
14264 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14266 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
14270 Display information about current HW trace configuration.
14272 @item htrace trigger @var{conditional}
14273 Set starting criteria for HW trace.
14275 @item htrace qualifier @var{conditional}
14276 Set acquisition qualifier for HW trace.
14278 @item htrace stop @var{conditional}
14279 Set HW trace stopping criteria.
14281 @item htrace record [@var{data}]*
14282 Selects the data to be recorded, when qualifier is met and HW trace was
14285 @item htrace enable
14286 @itemx htrace disable
14287 Enables/disables the HW trace.
14289 @item htrace rewind [@var{filename}]
14290 Clears currently recorded trace data.
14292 If filename is specified, new trace file is made and any newly collected data
14293 will be written there.
14295 @item htrace print [@var{start} [@var{len}]]
14296 Prints trace buffer, using current record configuration.
14298 @item htrace mode continuous
14299 Set continuous trace mode.
14301 @item htrace mode suspend
14302 Set suspend trace mode.
14307 @subsection PowerPC
14310 @kindex target dink32
14311 @item target dink32 @var{dev}
14312 DINK32 ROM monitor.
14314 @kindex target ppcbug
14315 @item target ppcbug @var{dev}
14316 @kindex target ppcbug1
14317 @item target ppcbug1 @var{dev}
14318 PPCBUG ROM monitor for PowerPC.
14321 @item target sds @var{dev}
14322 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
14325 @cindex SDS protocol
14326 The following commands specifi to the SDS protocol are supported
14330 @item set sdstimeout @var{nsec}
14331 @kindex set sdstimeout
14332 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
14333 default is 2 seconds.
14335 @item show sdstimeout
14336 @kindex show sdstimeout
14337 Show the current value of the SDS timeout.
14339 @item sds @var{command}
14340 @kindex sds@r{, a command}
14341 Send the specified @var{command} string to the SDS monitor.
14346 @subsection HP PA Embedded
14350 @kindex target op50n
14351 @item target op50n @var{dev}
14352 OP50N monitor, running on an OKI HPPA board.
14354 @kindex target w89k
14355 @item target w89k @var{dev}
14356 W89K monitor, running on a Winbond HPPA board.
14361 @subsection Renesas SH
14365 @kindex target hms@r{, with Renesas SH}
14366 @item target hms @var{dev}
14367 A Renesas SH board attached via serial line to your host. Use special
14368 commands @code{device} and @code{speed} to control the serial line and
14369 the communications speed used.
14371 @kindex target e7000@r{, with Renesas SH}
14372 @item target e7000 @var{dev}
14373 E7000 emulator for Renesas SH.
14375 @kindex target sh3@r{, with SH}
14376 @kindex target sh3e@r{, with SH}
14377 @item target sh3 @var{dev}
14378 @item target sh3e @var{dev}
14379 Renesas SH-3 and SH-3E target systems.
14384 @subsection Tsqware Sparclet
14388 @value{GDBN} enables developers to debug tasks running on
14389 Sparclet targets from a Unix host.
14390 @value{GDBN} uses code that runs on
14391 both the Unix host and on the Sparclet target. The program
14392 @code{@value{GDBP}} is installed and executed on the Unix host.
14395 @item remotetimeout @var{args}
14396 @kindex remotetimeout
14397 @value{GDBN} supports the option @code{remotetimeout}.
14398 This option is set by the user, and @var{args} represents the number of
14399 seconds @value{GDBN} waits for responses.
14402 @cindex compiling, on Sparclet
14403 When compiling for debugging, include the options @samp{-g} to get debug
14404 information and @samp{-Ttext} to relocate the program to where you wish to
14405 load it on the target. You may also want to add the options @samp{-n} or
14406 @samp{-N} in order to reduce the size of the sections. Example:
14409 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
14412 You can use @code{objdump} to verify that the addresses are what you intended:
14415 sparclet-aout-objdump --headers --syms prog
14418 @cindex running, on Sparclet
14420 your Unix execution search path to find @value{GDBN}, you are ready to
14421 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
14422 (or @code{sparclet-aout-gdb}, depending on your installation).
14424 @value{GDBN} comes up showing the prompt:
14431 * Sparclet File:: Setting the file to debug
14432 * Sparclet Connection:: Connecting to Sparclet
14433 * Sparclet Download:: Sparclet download
14434 * Sparclet Execution:: Running and debugging
14437 @node Sparclet File
14438 @subsubsection Setting file to debug
14440 The @value{GDBN} command @code{file} lets you choose with program to debug.
14443 (gdbslet) file prog
14447 @value{GDBN} then attempts to read the symbol table of @file{prog}.
14448 @value{GDBN} locates
14449 the file by searching the directories listed in the command search
14451 If the file was compiled with debug information (option "-g"), source
14452 files will be searched as well.
14453 @value{GDBN} locates
14454 the source files by searching the directories listed in the directory search
14455 path (@pxref{Environment, ,Your program's environment}).
14457 to find a file, it displays a message such as:
14460 prog: No such file or directory.
14463 When this happens, add the appropriate directories to the search paths with
14464 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
14465 @code{target} command again.
14467 @node Sparclet Connection
14468 @subsubsection Connecting to Sparclet
14470 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
14471 To connect to a target on serial port ``@code{ttya}'', type:
14474 (gdbslet) target sparclet /dev/ttya
14475 Remote target sparclet connected to /dev/ttya
14476 main () at ../prog.c:3
14480 @value{GDBN} displays messages like these:
14486 @node Sparclet Download
14487 @subsubsection Sparclet download
14489 @cindex download to Sparclet
14490 Once connected to the Sparclet target,
14491 you can use the @value{GDBN}
14492 @code{load} command to download the file from the host to the target.
14493 The file name and load offset should be given as arguments to the @code{load}
14495 Since the file format is aout, the program must be loaded to the starting
14496 address. You can use @code{objdump} to find out what this value is. The load
14497 offset is an offset which is added to the VMA (virtual memory address)
14498 of each of the file's sections.
14499 For instance, if the program
14500 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
14501 and bss at 0x12010170, in @value{GDBN}, type:
14504 (gdbslet) load prog 0x12010000
14505 Loading section .text, size 0xdb0 vma 0x12010000
14508 If the code is loaded at a different address then what the program was linked
14509 to, you may need to use the @code{section} and @code{add-symbol-file} commands
14510 to tell @value{GDBN} where to map the symbol table.
14512 @node Sparclet Execution
14513 @subsubsection Running and debugging
14515 @cindex running and debugging Sparclet programs
14516 You can now begin debugging the task using @value{GDBN}'s execution control
14517 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
14518 manual for the list of commands.
14522 Breakpoint 1 at 0x12010000: file prog.c, line 3.
14524 Starting program: prog
14525 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
14526 3 char *symarg = 0;
14528 4 char *execarg = "hello!";
14533 @subsection Fujitsu Sparclite
14537 @kindex target sparclite
14538 @item target sparclite @var{dev}
14539 Fujitsu sparclite boards, used only for the purpose of loading.
14540 You must use an additional command to debug the program.
14541 For example: target remote @var{dev} using @value{GDBN} standard
14547 @subsection Tandem ST2000
14549 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
14552 To connect your ST2000 to the host system, see the manufacturer's
14553 manual. Once the ST2000 is physically attached, you can run:
14556 target st2000 @var{dev} @var{speed}
14560 to establish it as your debugging environment. @var{dev} is normally
14561 the name of a serial device, such as @file{/dev/ttya}, connected to the
14562 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
14563 connection (for example, to a serial line attached via a terminal
14564 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
14566 The @code{load} and @code{attach} commands are @emph{not} defined for
14567 this target; you must load your program into the ST2000 as you normally
14568 would for standalone operation. @value{GDBN} reads debugging information
14569 (such as symbols) from a separate, debugging version of the program
14570 available on your host computer.
14571 @c FIXME!! This is terribly vague; what little content is here is
14572 @c basically hearsay.
14574 @cindex ST2000 auxiliary commands
14575 These auxiliary @value{GDBN} commands are available to help you with the ST2000
14579 @item st2000 @var{command}
14580 @kindex st2000 @var{cmd}
14581 @cindex STDBUG commands (ST2000)
14582 @cindex commands to STDBUG (ST2000)
14583 Send a @var{command} to the STDBUG monitor. See the manufacturer's
14584 manual for available commands.
14587 @cindex connect (to STDBUG)
14588 Connect the controlling terminal to the STDBUG command monitor. When
14589 you are done interacting with STDBUG, typing either of two character
14590 sequences gets you back to the @value{GDBN} command prompt:
14591 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
14592 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
14596 @subsection Zilog Z8000
14599 @cindex simulator, Z8000
14600 @cindex Zilog Z8000 simulator
14602 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
14605 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
14606 unsegmented variant of the Z8000 architecture) or the Z8001 (the
14607 segmented variant). The simulator recognizes which architecture is
14608 appropriate by inspecting the object code.
14611 @item target sim @var{args}
14613 @kindex target sim@r{, with Z8000}
14614 Debug programs on a simulated CPU. If the simulator supports setup
14615 options, specify them via @var{args}.
14619 After specifying this target, you can debug programs for the simulated
14620 CPU in the same style as programs for your host computer; use the
14621 @code{file} command to load a new program image, the @code{run} command
14622 to run your program, and so on.
14624 As well as making available all the usual machine registers
14625 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
14626 additional items of information as specially named registers:
14631 Counts clock-ticks in the simulator.
14634 Counts instructions run in the simulator.
14637 Execution time in 60ths of a second.
14641 You can refer to these values in @value{GDBN} expressions with the usual
14642 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
14643 conditional breakpoint that suspends only after at least 5000
14644 simulated clock ticks.
14647 @subsection Atmel AVR
14650 When configured for debugging the Atmel AVR, @value{GDBN} supports the
14651 following AVR-specific commands:
14654 @item info io_registers
14655 @kindex info io_registers@r{, AVR}
14656 @cindex I/O registers (Atmel AVR)
14657 This command displays information about the AVR I/O registers. For
14658 each register, @value{GDBN} prints its number and value.
14665 When configured for debugging CRIS, @value{GDBN} provides the
14666 following CRIS-specific commands:
14669 @item set cris-version @var{ver}
14670 @cindex CRIS version
14671 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
14672 The CRIS version affects register names and sizes. This command is useful in
14673 case autodetection of the CRIS version fails.
14675 @item show cris-version
14676 Show the current CRIS version.
14678 @item set cris-dwarf2-cfi
14679 @cindex DWARF-2 CFI and CRIS
14680 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
14681 Change to @samp{off} when using @code{gcc-cris} whose version is below
14684 @item show cris-dwarf2-cfi
14685 Show the current state of using DWARF-2 CFI.
14687 @item set cris-mode @var{mode}
14689 Set the current CRIS mode to @var{mode}. It should only be changed when
14690 debugging in guru mode, in which case it should be set to
14691 @samp{guru} (the default is @samp{normal}).
14693 @item show cris-mode
14694 Show the current CRIS mode.
14698 @subsection Renesas Super-H
14701 For the Renesas Super-H processor, @value{GDBN} provides these
14706 @kindex regs@r{, Super-H}
14707 Show the values of all Super-H registers.
14711 @subsection Windows CE
14714 The following commands are available for Windows CE:
14717 @item set remotedirectory @var{dir}
14718 @kindex set remotedirectory
14719 Tell @value{GDBN} to upload files from the named directory @var{dir}.
14720 The default is @file{/gdb}, i.e.@: the root directory on the current
14723 @item show remotedirectory
14724 @kindex show remotedirectory
14725 Show the current value of the upload directory.
14727 @item set remoteupload @var{method}
14728 @kindex set remoteupload
14729 Set the method used to upload files to remote device. Valid values
14730 for @var{method} are @samp{always}, @samp{newer}, and @samp{never}.
14731 The default is @samp{newer}.
14733 @item show remoteupload
14734 @kindex show remoteupload
14735 Show the current setting of the upload method.
14737 @item set remoteaddhost
14738 @kindex set remoteaddhost
14739 Tell @value{GDBN} whether to add this host to the remote stub's
14740 arguments when you debug over a network.
14742 @item show remoteaddhost
14743 @kindex show remoteaddhost
14744 Show whether to add this host to remote stub's arguments when
14745 debugging over a network.
14749 @node Architectures
14750 @section Architectures
14752 This section describes characteristics of architectures that affect
14753 all uses of @value{GDBN} with the architecture, both native and cross.
14760 * HPPA:: HP PA architecture
14764 @subsection x86 Architecture-specific issues.
14767 @item set struct-convention @var{mode}
14768 @kindex set struct-convention
14769 @cindex struct return convention
14770 @cindex struct/union returned in registers
14771 Set the convention used by the inferior to return @code{struct}s and
14772 @code{union}s from functions to @var{mode}. Possible values of
14773 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
14774 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
14775 are returned on the stack, while @code{"reg"} means that a
14776 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
14777 be returned in a register.
14779 @item show struct-convention
14780 @kindex show struct-convention
14781 Show the current setting of the convention to return @code{struct}s
14790 @kindex set rstack_high_address
14791 @cindex AMD 29K register stack
14792 @cindex register stack, AMD29K
14793 @item set rstack_high_address @var{address}
14794 On AMD 29000 family processors, registers are saved in a separate
14795 @dfn{register stack}. There is no way for @value{GDBN} to determine the
14796 extent of this stack. Normally, @value{GDBN} just assumes that the
14797 stack is ``large enough''. This may result in @value{GDBN} referencing
14798 memory locations that do not exist. If necessary, you can get around
14799 this problem by specifying the ending address of the register stack with
14800 the @code{set rstack_high_address} command. The argument should be an
14801 address, which you probably want to precede with @samp{0x} to specify in
14804 @kindex show rstack_high_address
14805 @item show rstack_high_address
14806 Display the current limit of the register stack, on AMD 29000 family
14814 See the following section.
14819 @cindex stack on Alpha
14820 @cindex stack on MIPS
14821 @cindex Alpha stack
14823 Alpha- and MIPS-based computers use an unusual stack frame, which
14824 sometimes requires @value{GDBN} to search backward in the object code to
14825 find the beginning of a function.
14827 @cindex response time, MIPS debugging
14828 To improve response time (especially for embedded applications, where
14829 @value{GDBN} may be restricted to a slow serial line for this search)
14830 you may want to limit the size of this search, using one of these
14834 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
14835 @item set heuristic-fence-post @var{limit}
14836 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
14837 search for the beginning of a function. A value of @var{0} (the
14838 default) means there is no limit. However, except for @var{0}, the
14839 larger the limit the more bytes @code{heuristic-fence-post} must search
14840 and therefore the longer it takes to run. You should only need to use
14841 this command when debugging a stripped executable.
14843 @item show heuristic-fence-post
14844 Display the current limit.
14848 These commands are available @emph{only} when @value{GDBN} is configured
14849 for debugging programs on Alpha or MIPS processors.
14851 Several MIPS-specific commands are available when debugging MIPS
14855 @item set mips saved-gpreg-size @var{size}
14856 @kindex set mips saved-gpreg-size
14857 @cindex MIPS GP register size on stack
14858 Set the size of MIPS general-purpose registers saved on the stack.
14859 The argument @var{size} can be one of the following:
14863 32-bit GP registers
14865 64-bit GP registers
14867 Use the target's default setting or autodetect the saved size from the
14868 information contained in the executable. This is the default
14871 @item show mips saved-gpreg-size
14872 @kindex show mips saved-gpreg-size
14873 Show the current size of MIPS GP registers on the stack.
14875 @item set mips stack-arg-size @var{size}
14876 @kindex set mips stack-arg-size
14877 @cindex MIPS stack space for arguments
14878 Set the amount of stack space reserved for arguments to functions.
14879 The argument can be one of @code{"32"}, @code{"64"} or @code{"auto"}
14882 @item set mips abi @var{arg}
14883 @kindex set mips abi
14884 @cindex set ABI for MIPS
14885 Tell @value{GDBN} which MIPS ABI is used by the inferior. Possible
14886 values of @var{arg} are:
14890 The default ABI associated with the current binary (this is the
14901 @item show mips abi
14902 @kindex show mips abi
14903 Show the MIPS ABI used by @value{GDBN} to debug the inferior.
14906 @itemx show mipsfpu
14907 @xref{MIPS Embedded, set mipsfpu}.
14909 @item set mips mask-address @var{arg}
14910 @kindex set mips mask-address
14911 @cindex MIPS addresses, masking
14912 This command determines whether the most-significant 32 bits of 64-bit
14913 MIPS addresses are masked off. The argument @var{arg} can be
14914 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
14915 setting, which lets @value{GDBN} determine the correct value.
14917 @item show mips mask-address
14918 @kindex show mips mask-address
14919 Show whether the upper 32 bits of MIPS addresses are masked off or
14922 @item set remote-mips64-transfers-32bit-regs
14923 @kindex set remote-mips64-transfers-32bit-regs
14924 This command controls compatibility with 64-bit MIPS targets that
14925 transfer data in 32-bit quantities. If you have an old MIPS 64 target
14926 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
14927 and 64 bits for other registers, set this option to @samp{on}.
14929 @item show remote-mips64-transfers-32bit-regs
14930 @kindex show remote-mips64-transfers-32bit-regs
14931 Show the current setting of compatibility with older MIPS 64 targets.
14933 @item set debug mips
14934 @kindex set debug mips
14935 This command turns on and off debugging messages for the MIPS-specific
14936 target code in @value{GDBN}.
14938 @item show debug mips
14939 @kindex show debug mips
14940 Show the current setting of MIPS debugging messages.
14946 @cindex HPPA support
14948 When @value{GDBN} is debugging te HP PA architecture, it provides the
14949 following special commands:
14952 @item set debug hppa
14953 @kindex set debug hppa
14954 THis command determines whether HPPA architecture specific debugging
14955 messages are to be displayed.
14957 @item show debug hppa
14958 Show whether HPPA debugging messages are displayed.
14960 @item maint print unwind @var{address}
14961 @kindex maint print unwind@r{, HPPA}
14962 This command displays the contents of the unwind table entry at the
14963 given @var{address}.
14968 @node Controlling GDB
14969 @chapter Controlling @value{GDBN}
14971 You can alter the way @value{GDBN} interacts with you by using the
14972 @code{set} command. For commands controlling how @value{GDBN} displays
14973 data, see @ref{Print Settings, ,Print settings}. Other settings are
14978 * Editing:: Command editing
14979 * History:: Command history
14980 * Screen Size:: Screen size
14981 * Numbers:: Numbers
14982 * ABI:: Configuring the current ABI
14983 * Messages/Warnings:: Optional warnings and messages
14984 * Debugging Output:: Optional messages about internal happenings
14992 @value{GDBN} indicates its readiness to read a command by printing a string
14993 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
14994 can change the prompt string with the @code{set prompt} command. For
14995 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
14996 the prompt in one of the @value{GDBN} sessions so that you can always tell
14997 which one you are talking to.
14999 @emph{Note:} @code{set prompt} does not add a space for you after the
15000 prompt you set. This allows you to set a prompt which ends in a space
15001 or a prompt that does not.
15005 @item set prompt @var{newprompt}
15006 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
15008 @kindex show prompt
15010 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
15014 @section Command editing
15016 @cindex command line editing
15018 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
15019 @sc{gnu} library provides consistent behavior for programs which provide a
15020 command line interface to the user. Advantages are @sc{gnu} Emacs-style
15021 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
15022 substitution, and a storage and recall of command history across
15023 debugging sessions.
15025 You may control the behavior of command line editing in @value{GDBN} with the
15026 command @code{set}.
15029 @kindex set editing
15032 @itemx set editing on
15033 Enable command line editing (enabled by default).
15035 @item set editing off
15036 Disable command line editing.
15038 @kindex show editing
15040 Show whether command line editing is enabled.
15043 @xref{Command Line Editing}, for more details about the Readline
15044 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
15045 encouraged to read that chapter.
15048 @section Command history
15049 @cindex command history
15051 @value{GDBN} can keep track of the commands you type during your
15052 debugging sessions, so that you can be certain of precisely what
15053 happened. Use these commands to manage the @value{GDBN} command
15056 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
15057 package, to provide the history facility. @xref{Using History
15058 Interactively}, for the detailed description of the History library.
15060 Here is the description of @value{GDBN} commands related to command
15064 @cindex history substitution
15065 @cindex history file
15066 @kindex set history filename
15067 @cindex @env{GDBHISTFILE}, environment variable
15068 @item set history filename @var{fname}
15069 Set the name of the @value{GDBN} command history file to @var{fname}.
15070 This is the file where @value{GDBN} reads an initial command history
15071 list, and where it writes the command history from this session when it
15072 exits. You can access this list through history expansion or through
15073 the history command editing characters listed below. This file defaults
15074 to the value of the environment variable @code{GDBHISTFILE}, or to
15075 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
15078 @cindex save command history
15079 @kindex set history save
15080 @item set history save
15081 @itemx set history save on
15082 Record command history in a file, whose name may be specified with the
15083 @code{set history filename} command. By default, this option is disabled.
15085 @item set history save off
15086 Stop recording command history in a file.
15088 @cindex history size
15089 @kindex set history size
15090 @cindex @env{HISTSIZE}, environment variable
15091 @item set history size @var{size}
15092 Set the number of commands which @value{GDBN} keeps in its history list.
15093 This defaults to the value of the environment variable
15094 @code{HISTSIZE}, or to 256 if this variable is not set.
15097 History expansion assigns special meaning to the character @kbd{!}.
15098 @xref{Event Designators}, for more details.
15100 @cindex history expansion, turn on/off
15101 Since @kbd{!} is also the logical not operator in C, history expansion
15102 is off by default. If you decide to enable history expansion with the
15103 @code{set history expansion on} command, you may sometimes need to
15104 follow @kbd{!} (when it is used as logical not, in an expression) with
15105 a space or a tab to prevent it from being expanded. The readline
15106 history facilities do not attempt substitution on the strings
15107 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
15109 The commands to control history expansion are:
15112 @item set history expansion on
15113 @itemx set history expansion
15114 @kindex set history expansion
15115 Enable history expansion. History expansion is off by default.
15117 @item set history expansion off
15118 Disable history expansion.
15121 @kindex show history
15123 @itemx show history filename
15124 @itemx show history save
15125 @itemx show history size
15126 @itemx show history expansion
15127 These commands display the state of the @value{GDBN} history parameters.
15128 @code{show history} by itself displays all four states.
15133 @kindex show commands
15134 @cindex show last commands
15135 @cindex display command history
15136 @item show commands
15137 Display the last ten commands in the command history.
15139 @item show commands @var{n}
15140 Print ten commands centered on command number @var{n}.
15142 @item show commands +
15143 Print ten commands just after the commands last printed.
15147 @section Screen size
15148 @cindex size of screen
15149 @cindex pauses in output
15151 Certain commands to @value{GDBN} may produce large amounts of
15152 information output to the screen. To help you read all of it,
15153 @value{GDBN} pauses and asks you for input at the end of each page of
15154 output. Type @key{RET} when you want to continue the output, or @kbd{q}
15155 to discard the remaining output. Also, the screen width setting
15156 determines when to wrap lines of output. Depending on what is being
15157 printed, @value{GDBN} tries to break the line at a readable place,
15158 rather than simply letting it overflow onto the following line.
15160 Normally @value{GDBN} knows the size of the screen from the terminal
15161 driver software. For example, on Unix @value{GDBN} uses the termcap data base
15162 together with the value of the @code{TERM} environment variable and the
15163 @code{stty rows} and @code{stty cols} settings. If this is not correct,
15164 you can override it with the @code{set height} and @code{set
15171 @kindex show height
15172 @item set height @var{lpp}
15174 @itemx set width @var{cpl}
15176 These @code{set} commands specify a screen height of @var{lpp} lines and
15177 a screen width of @var{cpl} characters. The associated @code{show}
15178 commands display the current settings.
15180 If you specify a height of zero lines, @value{GDBN} does not pause during
15181 output no matter how long the output is. This is useful if output is to a
15182 file or to an editor buffer.
15184 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
15185 from wrapping its output.
15187 @item set pagination on
15188 @itemx set pagination off
15189 @kindex set pagination
15190 Turn the output pagination on or off; the default is on. Turning
15191 pagination off is the alternative to @code{set height 0}.
15193 @item show pagination
15194 @kindex show pagination
15195 Show the current pagination mode.
15200 @cindex number representation
15201 @cindex entering numbers
15203 You can always enter numbers in octal, decimal, or hexadecimal in
15204 @value{GDBN} by the usual conventions: octal numbers begin with
15205 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
15206 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
15207 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
15208 10; likewise, the default display for numbers---when no particular
15209 format is specified---is base 10. You can change the default base for
15210 both input and output with the commands described below.
15213 @kindex set input-radix
15214 @item set input-radix @var{base}
15215 Set the default base for numeric input. Supported choices
15216 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15217 specified either unambiguously or using the current input radix; for
15221 set input-radix 012
15222 set input-radix 10.
15223 set input-radix 0xa
15227 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
15228 leaves the input radix unchanged, no matter what it was, since
15229 @samp{10}, being without any leading or trailing signs of its base, is
15230 interpreted in the current radix. Thus, if the current radix is 16,
15231 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
15234 @kindex set output-radix
15235 @item set output-radix @var{base}
15236 Set the default base for numeric display. Supported choices
15237 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
15238 specified either unambiguously or using the current input radix.
15240 @kindex show input-radix
15241 @item show input-radix
15242 Display the current default base for numeric input.
15244 @kindex show output-radix
15245 @item show output-radix
15246 Display the current default base for numeric display.
15248 @item set radix @r{[}@var{base}@r{]}
15252 These commands set and show the default base for both input and output
15253 of numbers. @code{set radix} sets the radix of input and output to
15254 the same base; without an argument, it resets the radix back to its
15255 default value of 10.
15260 @section Configuring the current ABI
15262 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
15263 application automatically. However, sometimes you need to override its
15264 conclusions. Use these commands to manage @value{GDBN}'s view of the
15271 One @value{GDBN} configuration can debug binaries for multiple operating
15272 system targets, either via remote debugging or native emulation.
15273 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
15274 but you can override its conclusion using the @code{set osabi} command.
15275 One example where this is useful is in debugging of binaries which use
15276 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
15277 not have the same identifying marks that the standard C library for your
15282 Show the OS ABI currently in use.
15285 With no argument, show the list of registered available OS ABI's.
15287 @item set osabi @var{abi}
15288 Set the current OS ABI to @var{abi}.
15291 @cindex float promotion
15293 Generally, the way that an argument of type @code{float} is passed to a
15294 function depends on whether the function is prototyped. For a prototyped
15295 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
15296 according to the architecture's convention for @code{float}. For unprototyped
15297 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
15298 @code{double} and then passed.
15300 Unfortunately, some forms of debug information do not reliably indicate whether
15301 a function is prototyped. If @value{GDBN} calls a function that is not marked
15302 as prototyped, it consults @kbd{set coerce-float-to-double}.
15305 @kindex set coerce-float-to-double
15306 @item set coerce-float-to-double
15307 @itemx set coerce-float-to-double on
15308 Arguments of type @code{float} will be promoted to @code{double} when passed
15309 to an unprototyped function. This is the default setting.
15311 @item set coerce-float-to-double off
15312 Arguments of type @code{float} will be passed directly to unprototyped
15315 @kindex show coerce-float-to-double
15316 @item show coerce-float-to-double
15317 Show the current setting of promoting @code{float} to @code{double}.
15321 @kindex show cp-abi
15322 @value{GDBN} needs to know the ABI used for your program's C@t{++}
15323 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
15324 used to build your application. @value{GDBN} only fully supports
15325 programs with a single C@t{++} ABI; if your program contains code using
15326 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
15327 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
15328 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
15329 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
15330 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
15331 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
15336 Show the C@t{++} ABI currently in use.
15339 With no argument, show the list of supported C@t{++} ABI's.
15341 @item set cp-abi @var{abi}
15342 @itemx set cp-abi auto
15343 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
15346 @node Messages/Warnings
15347 @section Optional warnings and messages
15349 @cindex verbose operation
15350 @cindex optional warnings
15351 By default, @value{GDBN} is silent about its inner workings. If you are
15352 running on a slow machine, you may want to use the @code{set verbose}
15353 command. This makes @value{GDBN} tell you when it does a lengthy
15354 internal operation, so you will not think it has crashed.
15356 Currently, the messages controlled by @code{set verbose} are those
15357 which announce that the symbol table for a source file is being read;
15358 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
15361 @kindex set verbose
15362 @item set verbose on
15363 Enables @value{GDBN} output of certain informational messages.
15365 @item set verbose off
15366 Disables @value{GDBN} output of certain informational messages.
15368 @kindex show verbose
15370 Displays whether @code{set verbose} is on or off.
15373 By default, if @value{GDBN} encounters bugs in the symbol table of an
15374 object file, it is silent; but if you are debugging a compiler, you may
15375 find this information useful (@pxref{Symbol Errors, ,Errors reading
15380 @kindex set complaints
15381 @item set complaints @var{limit}
15382 Permits @value{GDBN} to output @var{limit} complaints about each type of
15383 unusual symbols before becoming silent about the problem. Set
15384 @var{limit} to zero to suppress all complaints; set it to a large number
15385 to prevent complaints from being suppressed.
15387 @kindex show complaints
15388 @item show complaints
15389 Displays how many symbol complaints @value{GDBN} is permitted to produce.
15393 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
15394 lot of stupid questions to confirm certain commands. For example, if
15395 you try to run a program which is already running:
15399 The program being debugged has been started already.
15400 Start it from the beginning? (y or n)
15403 If you are willing to unflinchingly face the consequences of your own
15404 commands, you can disable this ``feature'':
15408 @kindex set confirm
15410 @cindex confirmation
15411 @cindex stupid questions
15412 @item set confirm off
15413 Disables confirmation requests.
15415 @item set confirm on
15416 Enables confirmation requests (the default).
15418 @kindex show confirm
15420 Displays state of confirmation requests.
15424 @node Debugging Output
15425 @section Optional messages about internal happenings
15426 @cindex optional debugging messages
15428 @value{GDBN} has commands that enable optional debugging messages from
15429 various @value{GDBN} subsystems; normally these commands are of
15430 interest to @value{GDBN} maintainers, or when reporting a bug. This
15431 section documents those commands.
15434 @kindex set exec-done-display
15435 @item set exec-done-display
15436 Turns on or off the notification of asynchronous commands'
15437 completion. When on, @value{GDBN} will print a message when an
15438 asynchronous command finishes its execution. The default is off.
15439 @kindex show exec-done-display
15440 @item show exec-done-display
15441 Displays the current setting of asynchronous command completion
15444 @cindex gdbarch debugging info
15445 @cindex architecture debugging info
15446 @item set debug arch
15447 Turns on or off display of gdbarch debugging info. The default is off
15449 @item show debug arch
15450 Displays the current state of displaying gdbarch debugging info.
15451 @item set debug aix-thread
15452 @cindex AIX threads
15453 Display debugging messages about inner workings of the AIX thread
15455 @item show debug aix-thread
15456 Show the current state of AIX thread debugging info display.
15457 @item set debug event
15458 @cindex event debugging info
15459 Turns on or off display of @value{GDBN} event debugging info. The
15461 @item show debug event
15462 Displays the current state of displaying @value{GDBN} event debugging
15464 @item set debug expression
15465 @cindex expression debugging info
15466 Turns on or off display of debugging info about @value{GDBN}
15467 expression parsing. The default is off.
15468 @item show debug expression
15469 Displays the current state of displaying debugging info about
15470 @value{GDBN} expression parsing.
15471 @item set debug frame
15472 @cindex frame debugging info
15473 Turns on or off display of @value{GDBN} frame debugging info. The
15475 @item show debug frame
15476 Displays the current state of displaying @value{GDBN} frame debugging
15478 @item set debug infrun
15479 @cindex inferior debugging info
15480 Turns on or off display of @value{GDBN} debugging info for running the inferior.
15481 The default is off. @file{infrun.c} contains GDB's runtime state machine used
15482 for implementing operations such as single-stepping the inferior.
15483 @item show debug infrun
15484 Displays the current state of @value{GDBN} inferior debugging.
15485 @item set debug lin-lwp
15486 @cindex @sc{gnu}/Linux LWP debug messages
15487 @cindex Linux lightweight processes
15488 Turns on or off debugging messages from the Linux LWP debug support.
15489 @item show debug lin-lwp
15490 Show the current state of Linux LWP debugging messages.
15491 @item set debug observer
15492 @cindex observer debugging info
15493 Turns on or off display of @value{GDBN} observer debugging. This
15494 includes info such as the notification of observable events.
15495 @item show debug observer
15496 Displays the current state of observer debugging.
15497 @item set debug overload
15498 @cindex C@t{++} overload debugging info
15499 Turns on or off display of @value{GDBN} C@t{++} overload debugging
15500 info. This includes info such as ranking of functions, etc. The default
15502 @item show debug overload
15503 Displays the current state of displaying @value{GDBN} C@t{++} overload
15505 @cindex packets, reporting on stdout
15506 @cindex serial connections, debugging
15507 @item set debug remote
15508 Turns on or off display of reports on all packets sent back and forth across
15509 the serial line to the remote machine. The info is printed on the
15510 @value{GDBN} standard output stream. The default is off.
15511 @item show debug remote
15512 Displays the state of display of remote packets.
15513 @item set debug serial
15514 Turns on or off display of @value{GDBN} serial debugging info. The
15516 @item show debug serial
15517 Displays the current state of displaying @value{GDBN} serial debugging
15519 @item set debug solib-frv
15520 @cindex FR-V shared-library debugging
15521 Turns on or off debugging messages for FR-V shared-library code.
15522 @item show debug solib-frv
15523 Display the current state of FR-V shared-library code debugging
15525 @item set debug target
15526 @cindex target debugging info
15527 Turns on or off display of @value{GDBN} target debugging info. This info
15528 includes what is going on at the target level of GDB, as it happens. The
15529 default is 0. Set it to 1 to track events, and to 2 to also track the
15530 value of large memory transfers. Changes to this flag do not take effect
15531 until the next time you connect to a target or use the @code{run} command.
15532 @item show debug target
15533 Displays the current state of displaying @value{GDBN} target debugging
15535 @item set debugvarobj
15536 @cindex variable object debugging info
15537 Turns on or off display of @value{GDBN} variable object debugging
15538 info. The default is off.
15539 @item show debugvarobj
15540 Displays the current state of displaying @value{GDBN} variable object
15545 @chapter Canned Sequences of Commands
15547 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
15548 command lists}), @value{GDBN} provides two ways to store sequences of
15549 commands for execution as a unit: user-defined commands and command
15553 * Define:: User-defined commands
15554 * Hooks:: User-defined command hooks
15555 * Command Files:: Command files
15556 * Output:: Commands for controlled output
15560 @section User-defined commands
15562 @cindex user-defined command
15563 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
15564 which you assign a new name as a command. This is done with the
15565 @code{define} command. User commands may accept up to 10 arguments
15566 separated by whitespace. Arguments are accessed within the user command
15567 via @var{$arg0@dots{}$arg9}. A trivial example:
15571 print $arg0 + $arg1 + $arg2
15575 To execute the command use:
15582 This defines the command @code{adder}, which prints the sum of
15583 its three arguments. Note the arguments are text substitutions, so they may
15584 reference variables, use complex expressions, or even perform inferior
15590 @item define @var{commandname}
15591 Define a command named @var{commandname}. If there is already a command
15592 by that name, you are asked to confirm that you want to redefine it.
15594 The definition of the command is made up of other @value{GDBN} command lines,
15595 which are given following the @code{define} command. The end of these
15596 commands is marked by a line containing @code{end}.
15602 Takes a single argument, which is an expression to evaluate.
15603 It is followed by a series of commands that are executed
15604 only if the expression is true (nonzero).
15605 There can then optionally be a line @code{else}, followed
15606 by a series of commands that are only executed if the expression
15607 was false. The end of the list is marked by a line containing @code{end}.
15611 The syntax is similar to @code{if}: the command takes a single argument,
15612 which is an expression to evaluate, and must be followed by the commands to
15613 execute, one per line, terminated by an @code{end}.
15614 The commands are executed repeatedly as long as the expression
15618 @item document @var{commandname}
15619 Document the user-defined command @var{commandname}, so that it can be
15620 accessed by @code{help}. The command @var{commandname} must already be
15621 defined. This command reads lines of documentation just as @code{define}
15622 reads the lines of the command definition, ending with @code{end}.
15623 After the @code{document} command is finished, @code{help} on command
15624 @var{commandname} displays the documentation you have written.
15626 You may use the @code{document} command again to change the
15627 documentation of a command. Redefining the command with @code{define}
15628 does not change the documentation.
15630 @kindex dont-repeat
15631 @cindex don't repeat command
15633 Used inside a user-defined command, this tells @value{GDBN} that this
15634 command should not be repeated when the user hits @key{RET}
15635 (@pxref{Command Syntax, repeat last command}).
15637 @kindex help user-defined
15638 @item help user-defined
15639 List all user-defined commands, with the first line of the documentation
15644 @itemx show user @var{commandname}
15645 Display the @value{GDBN} commands used to define @var{commandname} (but
15646 not its documentation). If no @var{commandname} is given, display the
15647 definitions for all user-defined commands.
15649 @cindex infinite recusrion in user-defined commands
15650 @kindex show max-user-call-depth
15651 @kindex set max-user-call-depth
15652 @item show max-user-call-depth
15653 @itemx set max-user-call-depth
15654 The value of @code{max-user-call-depth} controls how many recursion
15655 levels are allowed in user-defined commands before GDB suspects an
15656 infinite recursion and aborts the command.
15660 When user-defined commands are executed, the
15661 commands of the definition are not printed. An error in any command
15662 stops execution of the user-defined command.
15664 If used interactively, commands that would ask for confirmation proceed
15665 without asking when used inside a user-defined command. Many @value{GDBN}
15666 commands that normally print messages to say what they are doing omit the
15667 messages when used in a user-defined command.
15670 @section User-defined command hooks
15671 @cindex command hooks
15672 @cindex hooks, for commands
15673 @cindex hooks, pre-command
15676 You may define @dfn{hooks}, which are a special kind of user-defined
15677 command. Whenever you run the command @samp{foo}, if the user-defined
15678 command @samp{hook-foo} exists, it is executed (with no arguments)
15679 before that command.
15681 @cindex hooks, post-command
15683 A hook may also be defined which is run after the command you executed.
15684 Whenever you run the command @samp{foo}, if the user-defined command
15685 @samp{hookpost-foo} exists, it is executed (with no arguments) after
15686 that command. Post-execution hooks may exist simultaneously with
15687 pre-execution hooks, for the same command.
15689 It is valid for a hook to call the command which it hooks. If this
15690 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
15692 @c It would be nice if hookpost could be passed a parameter indicating
15693 @c if the command it hooks executed properly or not. FIXME!
15695 @kindex stop@r{, a pseudo-command}
15696 In addition, a pseudo-command, @samp{stop} exists. Defining
15697 (@samp{hook-stop}) makes the associated commands execute every time
15698 execution stops in your program: before breakpoint commands are run,
15699 displays are printed, or the stack frame is printed.
15701 For example, to ignore @code{SIGALRM} signals while
15702 single-stepping, but treat them normally during normal execution,
15707 handle SIGALRM nopass
15711 handle SIGALRM pass
15714 define hook-continue
15715 handle SIGLARM pass
15719 As a further example, to hook at the begining and end of the @code{echo}
15720 command, and to add extra text to the beginning and end of the message,
15728 define hookpost-echo
15732 (@value{GDBP}) echo Hello World
15733 <<<---Hello World--->>>
15738 You can define a hook for any single-word command in @value{GDBN}, but
15739 not for command aliases; you should define a hook for the basic command
15740 name, e.g. @code{backtrace} rather than @code{bt}.
15741 @c FIXME! So how does Joe User discover whether a command is an alias
15743 If an error occurs during the execution of your hook, execution of
15744 @value{GDBN} commands stops and @value{GDBN} issues a prompt
15745 (before the command that you actually typed had a chance to run).
15747 If you try to define a hook which does not match any known command, you
15748 get a warning from the @code{define} command.
15750 @node Command Files
15751 @section Command files
15753 @cindex command files
15754 A command file for @value{GDBN} is a text file made of lines that are
15755 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
15756 also be included. An empty line in a command file does nothing; it
15757 does not mean to repeat the last command, as it would from the
15760 You can request the execution of a command file with the @code{source}
15765 @item source @var{filename}
15766 Execute the command file @var{filename}.
15769 The lines in a command file are executed sequentially. They are not
15770 printed as they are executed. An error in any command terminates
15771 execution of the command file and control is returned to the console.
15773 Commands that would ask for confirmation if used interactively proceed
15774 without asking when used in a command file. Many @value{GDBN} commands that
15775 normally print messages to say what they are doing omit the messages
15776 when called from command files.
15778 @value{GDBN} also accepts command input from standard input. In this
15779 mode, normal output goes to standard output and error output goes to
15780 standard error. Errors in a command file supplied on standard input do
15781 not terminate execution of the command file---execution continues with
15785 gdb < cmds > log 2>&1
15788 (The syntax above will vary depending on the shell used.) This example
15789 will execute commands from the file @file{cmds}. All output and errors
15790 would be directed to @file{log}.
15793 @section Commands for controlled output
15795 During the execution of a command file or a user-defined command, normal
15796 @value{GDBN} output is suppressed; the only output that appears is what is
15797 explicitly printed by the commands in the definition. This section
15798 describes three commands useful for generating exactly the output you
15803 @item echo @var{text}
15804 @c I do not consider backslash-space a standard C escape sequence
15805 @c because it is not in ANSI.
15806 Print @var{text}. Nonprinting characters can be included in
15807 @var{text} using C escape sequences, such as @samp{\n} to print a
15808 newline. @strong{No newline is printed unless you specify one.}
15809 In addition to the standard C escape sequences, a backslash followed
15810 by a space stands for a space. This is useful for displaying a
15811 string with spaces at the beginning or the end, since leading and
15812 trailing spaces are otherwise trimmed from all arguments.
15813 To print @samp{@w{ }and foo =@w{ }}, use the command
15814 @samp{echo \@w{ }and foo = \@w{ }}.
15816 A backslash at the end of @var{text} can be used, as in C, to continue
15817 the command onto subsequent lines. For example,
15820 echo This is some text\n\
15821 which is continued\n\
15822 onto several lines.\n
15825 produces the same output as
15828 echo This is some text\n
15829 echo which is continued\n
15830 echo onto several lines.\n
15834 @item output @var{expression}
15835 Print the value of @var{expression} and nothing but that value: no
15836 newlines, no @samp{$@var{nn} = }. The value is not entered in the
15837 value history either. @xref{Expressions, ,Expressions}, for more information
15840 @item output/@var{fmt} @var{expression}
15841 Print the value of @var{expression} in format @var{fmt}. You can use
15842 the same formats as for @code{print}. @xref{Output Formats,,Output
15843 formats}, for more information.
15846 @item printf @var{string}, @var{expressions}@dots{}
15847 Print the values of the @var{expressions} under the control of
15848 @var{string}. The @var{expressions} are separated by commas and may be
15849 either numbers or pointers. Their values are printed as specified by
15850 @var{string}, exactly as if your program were to execute the C
15852 @c FIXME: the above implies that at least all ANSI C formats are
15853 @c supported, but it isn't true: %E and %G don't work (or so it seems).
15854 @c Either this is a bug, or the manual should document what formats are
15858 printf (@var{string}, @var{expressions}@dots{});
15861 For example, you can print two values in hex like this:
15864 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
15867 The only backslash-escape sequences that you can use in the format
15868 string are the simple ones that consist of backslash followed by a
15873 @chapter Command Interpreters
15874 @cindex command interpreters
15876 @value{GDBN} supports multiple command interpreters, and some command
15877 infrastructure to allow users or user interface writers to switch
15878 between interpreters or run commands in other interpreters.
15880 @value{GDBN} currently supports two command interpreters, the console
15881 interpreter (sometimes called the command-line interpreter or @sc{cli})
15882 and the machine interface interpreter (or @sc{gdb/mi}). This manual
15883 describes both of these interfaces in great detail.
15885 By default, @value{GDBN} will start with the console interpreter.
15886 However, the user may choose to start @value{GDBN} with another
15887 interpreter by specifying the @option{-i} or @option{--interpreter}
15888 startup options. Defined interpreters include:
15892 @cindex console interpreter
15893 The traditional console or command-line interpreter. This is the most often
15894 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
15895 @value{GDBN} will use this interpreter.
15898 @cindex mi interpreter
15899 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
15900 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
15901 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
15905 @cindex mi2 interpreter
15906 The current @sc{gdb/mi} interface.
15909 @cindex mi1 interpreter
15910 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
15914 @cindex invoke another interpreter
15915 The interpreter being used by @value{GDBN} may not be dynamically
15916 switched at runtime. Although possible, this could lead to a very
15917 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
15918 enters the command "interpreter-set console" in a console view,
15919 @value{GDBN} would switch to using the console interpreter, rendering
15920 the IDE inoperable!
15922 @kindex interpreter-exec
15923 Although you may only choose a single interpreter at startup, you may execute
15924 commands in any interpreter from the current interpreter using the appropriate
15925 command. If you are running the console interpreter, simply use the
15926 @code{interpreter-exec} command:
15929 interpreter-exec mi "-data-list-register-names"
15932 @sc{gdb/mi} has a similar command, although it is only available in versions of
15933 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
15936 @chapter @value{GDBN} Text User Interface
15938 @cindex Text User Interface
15941 * TUI Overview:: TUI overview
15942 * TUI Keys:: TUI key bindings
15943 * TUI Single Key Mode:: TUI single key mode
15944 * TUI Commands:: TUI specific commands
15945 * TUI Configuration:: TUI configuration variables
15948 The @value{GDBN} Text User Interface, TUI in short, is a terminal
15949 interface which uses the @code{curses} library to show the source
15950 file, the assembly output, the program registers and @value{GDBN}
15951 commands in separate text windows.
15953 The TUI is enabled by invoking @value{GDBN} using either
15955 @samp{gdbtui} or @samp{gdb -tui}.
15958 @section TUI overview
15960 The TUI has two display modes that can be switched while
15965 A curses (or TUI) mode in which it displays several text
15966 windows on the terminal.
15969 A standard mode which corresponds to the @value{GDBN} configured without
15973 In the TUI mode, @value{GDBN} can display several text window
15978 This window is the @value{GDBN} command window with the @value{GDBN}
15979 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
15980 managed using readline but through the TUI. The @emph{command}
15981 window is always visible.
15984 The source window shows the source file of the program. The current
15985 line as well as active breakpoints are displayed in this window.
15988 The assembly window shows the disassembly output of the program.
15991 This window shows the processor registers. It detects when
15992 a register is changed and when this is the case, registers that have
15993 changed are highlighted.
15997 The source and assembly windows show the current program position
15998 by highlighting the current line and marking them with the @samp{>} marker.
15999 Breakpoints are also indicated with two markers. A first one
16000 indicates the breakpoint type:
16004 Breakpoint which was hit at least once.
16007 Breakpoint which was never hit.
16010 Hardware breakpoint which was hit at least once.
16013 Hardware breakpoint which was never hit.
16017 The second marker indicates whether the breakpoint is enabled or not:
16021 Breakpoint is enabled.
16024 Breakpoint is disabled.
16028 The source, assembly and register windows are attached to the thread
16029 and the frame position. They are updated when the current thread
16030 changes, when the frame changes or when the program counter changes.
16031 These three windows are arranged by the TUI according to several
16032 layouts. The layout defines which of these three windows are visible.
16033 The following layouts are available:
16043 source and assembly
16046 source and registers
16049 assembly and registers
16053 On top of the command window a status line gives various information
16054 concerning the current process begin debugged. The status line is
16055 updated when the information it shows changes. The following fields
16060 Indicates the current gdb target
16061 (@pxref{Targets, ,Specifying a Debugging Target}).
16064 Gives information about the current process or thread number.
16065 When no process is being debugged, this field is set to @code{No process}.
16068 Gives the current function name for the selected frame.
16069 The name is demangled if demangling is turned on (@pxref{Print Settings}).
16070 When there is no symbol corresponding to the current program counter
16071 the string @code{??} is displayed.
16074 Indicates the current line number for the selected frame.
16075 When the current line number is not known the string @code{??} is displayed.
16078 Indicates the current program counter address.
16083 @section TUI Key Bindings
16084 @cindex TUI key bindings
16086 The TUI installs several key bindings in the readline keymaps
16087 (@pxref{Command Line Editing}).
16088 They allow to leave or enter in the TUI mode or they operate
16089 directly on the TUI layout and windows. The TUI also provides
16090 a @emph{SingleKey} keymap which binds several keys directly to
16091 @value{GDBN} commands. The following key bindings
16092 are installed for both TUI mode and the @value{GDBN} standard mode.
16101 Enter or leave the TUI mode. When the TUI mode is left,
16102 the curses window management is left and @value{GDBN} operates using
16103 its standard mode writing on the terminal directly. When the TUI
16104 mode is entered, the control is given back to the curses windows.
16105 The screen is then refreshed.
16109 Use a TUI layout with only one window. The layout will
16110 either be @samp{source} or @samp{assembly}. When the TUI mode
16111 is not active, it will switch to the TUI mode.
16113 Think of this key binding as the Emacs @kbd{C-x 1} binding.
16117 Use a TUI layout with at least two windows. When the current
16118 layout shows already two windows, a next layout with two windows is used.
16119 When a new layout is chosen, one window will always be common to the
16120 previous layout and the new one.
16122 Think of it as the Emacs @kbd{C-x 2} binding.
16126 Change the active window. The TUI associates several key bindings
16127 (like scrolling and arrow keys) to the active window. This command
16128 gives the focus to the next TUI window.
16130 Think of it as the Emacs @kbd{C-x o} binding.
16134 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
16135 (@pxref{TUI Single Key Mode}).
16139 The following key bindings are handled only by the TUI mode:
16144 Scroll the active window one page up.
16148 Scroll the active window one page down.
16152 Scroll the active window one line up.
16156 Scroll the active window one line down.
16160 Scroll the active window one column left.
16164 Scroll the active window one column right.
16168 Refresh the screen.
16172 In the TUI mode, the arrow keys are used by the active window
16173 for scrolling. This means they are available for readline when the
16174 active window is the command window. When the command window
16175 does not have the focus, it is necessary to use other readline
16176 key bindings such as @key{C-p}, @key{C-n}, @key{C-b} and @key{C-f}.
16178 @node TUI Single Key Mode
16179 @section TUI Single Key Mode
16180 @cindex TUI single key mode
16182 The TUI provides a @emph{SingleKey} mode in which it installs a particular
16183 key binding in the readline keymaps to connect single keys to
16187 @kindex c @r{(SingleKey TUI key)}
16191 @kindex d @r{(SingleKey TUI key)}
16195 @kindex f @r{(SingleKey TUI key)}
16199 @kindex n @r{(SingleKey TUI key)}
16203 @kindex q @r{(SingleKey TUI key)}
16205 exit the @emph{SingleKey} mode.
16207 @kindex r @r{(SingleKey TUI key)}
16211 @kindex s @r{(SingleKey TUI key)}
16215 @kindex u @r{(SingleKey TUI key)}
16219 @kindex v @r{(SingleKey TUI key)}
16223 @kindex w @r{(SingleKey TUI key)}
16229 Other keys temporarily switch to the @value{GDBN} command prompt.
16230 The key that was pressed is inserted in the editing buffer so that
16231 it is possible to type most @value{GDBN} commands without interaction
16232 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
16233 @emph{SingleKey} mode is restored. The only way to permanently leave
16234 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
16238 @section TUI specific commands
16239 @cindex TUI commands
16241 The TUI has specific commands to control the text windows.
16242 These commands are always available, that is they do not depend on
16243 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
16244 is in the standard mode, using these commands will automatically switch
16250 List and give the size of all displayed windows.
16254 Display the next layout.
16257 Display the previous layout.
16260 Display the source window only.
16263 Display the assembly window only.
16266 Display the source and assembly window.
16269 Display the register window together with the source or assembly window.
16271 @item focus next | prev | src | asm | regs | split
16273 Set the focus to the named window.
16274 This command allows to change the active window so that scrolling keys
16275 can be affected to another window.
16279 Refresh the screen. This is similar to using @key{C-L} key.
16281 @item tui reg float
16283 Show the floating point registers in the register window.
16285 @item tui reg general
16286 Show the general registers in the register window.
16289 Show the next register group. The list of register groups as well as
16290 their order is target specific. The predefined register groups are the
16291 following: @code{general}, @code{float}, @code{system}, @code{vector},
16292 @code{all}, @code{save}, @code{restore}.
16294 @item tui reg system
16295 Show the system registers in the register window.
16299 Update the source window and the current execution point.
16301 @item winheight @var{name} +@var{count}
16302 @itemx winheight @var{name} -@var{count}
16304 Change the height of the window @var{name} by @var{count}
16305 lines. Positive counts increase the height, while negative counts
16309 @kindex tabset @var{nchars}
16310 Set the width of tab stops to be @var{nchars} characters.
16314 @node TUI Configuration
16315 @section TUI configuration variables
16316 @cindex TUI configuration variables
16318 The TUI has several configuration variables that control the
16319 appearance of windows on the terminal.
16322 @item set tui border-kind @var{kind}
16323 @kindex set tui border-kind
16324 Select the border appearance for the source, assembly and register windows.
16325 The possible values are the following:
16328 Use a space character to draw the border.
16331 Use ascii characters + - and | to draw the border.
16334 Use the Alternate Character Set to draw the border. The border is
16335 drawn using character line graphics if the terminal supports them.
16339 @item set tui active-border-mode @var{mode}
16340 @kindex set tui active-border-mode
16341 Select the attributes to display the border of the active window.
16342 The possible values are @code{normal}, @code{standout}, @code{reverse},
16343 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
16345 @item set tui border-mode @var{mode}
16346 @kindex set tui border-mode
16347 Select the attributes to display the border of other windows.
16348 The @var{mode} can be one of the following:
16351 Use normal attributes to display the border.
16357 Use reverse video mode.
16360 Use half bright mode.
16362 @item half-standout
16363 Use half bright and standout mode.
16366 Use extra bright or bold mode.
16368 @item bold-standout
16369 Use extra bright or bold and standout mode.
16376 @chapter Using @value{GDBN} under @sc{gnu} Emacs
16379 @cindex @sc{gnu} Emacs
16380 A special interface allows you to use @sc{gnu} Emacs to view (and
16381 edit) the source files for the program you are debugging with
16384 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
16385 executable file you want to debug as an argument. This command starts
16386 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
16387 created Emacs buffer.
16388 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
16390 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
16395 All ``terminal'' input and output goes through the Emacs buffer.
16398 This applies both to @value{GDBN} commands and their output, and to the input
16399 and output done by the program you are debugging.
16401 This is useful because it means that you can copy the text of previous
16402 commands and input them again; you can even use parts of the output
16405 All the facilities of Emacs' Shell mode are available for interacting
16406 with your program. In particular, you can send signals the usual
16407 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
16412 @value{GDBN} displays source code through Emacs.
16415 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
16416 source file for that frame and puts an arrow (@samp{=>}) at the
16417 left margin of the current line. Emacs uses a separate buffer for
16418 source display, and splits the screen to show both your @value{GDBN} session
16421 Explicit @value{GDBN} @code{list} or search commands still produce output as
16422 usual, but you probably have no reason to use them from Emacs.
16424 If you specify an absolute file name when prompted for the @kbd{M-x
16425 gdb} argument, then Emacs sets your current working directory to where
16426 your program resides. If you only specify the file name, then Emacs
16427 sets your current working directory to to the directory associated
16428 with the previous buffer. In this case, @value{GDBN} may find your
16429 program by searching your environment's @code{PATH} variable, but on
16430 some operating systems it might not find the source. So, although the
16431 @value{GDBN} input and output session proceeds normally, the auxiliary
16432 buffer does not display the current source and line of execution.
16434 The initial working directory of @value{GDBN} is printed on the top
16435 line of the @value{GDBN} I/O buffer and this serves as a default for
16436 the commands that specify files for @value{GDBN} to operate
16437 on. @xref{Files, ,Commands to specify files}.
16439 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
16440 need to call @value{GDBN} by a different name (for example, if you
16441 keep several configurations around, with different names) you can
16442 customize the Emacs variable @code{gud-gdb-command-name} to run the
16445 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
16446 addition to the standard Shell mode commands:
16450 Describe the features of Emacs' @value{GDBN} Mode.
16453 Execute to another source line, like the @value{GDBN} @code{step} command; also
16454 update the display window to show the current file and location.
16457 Execute to next source line in this function, skipping all function
16458 calls, like the @value{GDBN} @code{next} command. Then update the display window
16459 to show the current file and location.
16462 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
16463 display window accordingly.
16466 Execute until exit from the selected stack frame, like the @value{GDBN}
16467 @code{finish} command.
16470 Continue execution of your program, like the @value{GDBN} @code{continue}
16474 Go up the number of frames indicated by the numeric argument
16475 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
16476 like the @value{GDBN} @code{up} command.
16479 Go down the number of frames indicated by the numeric argument, like the
16480 @value{GDBN} @code{down} command.
16483 In any source file, the Emacs command @kbd{C-x SPC} (@code{gud-break})
16484 tells @value{GDBN} to set a breakpoint on the source line point is on.
16486 If you type @kbd{M-x speedbar}, then Emacs displays a separate frame which
16487 shows a backtrace when the @value{GDBN} I/O buffer is current. Move
16488 point to any frame in the stack and type @key{RET} to make it become the
16489 current frame and display the associated source in the source buffer.
16490 Alternatively, click @kbd{Mouse-2} to make the selected frame become the
16493 If you accidentally delete the source-display buffer, an easy way to get
16494 it back is to type the command @code{f} in the @value{GDBN} buffer, to
16495 request a frame display; when you run under Emacs, this recreates
16496 the source buffer if necessary to show you the context of the current
16499 The source files displayed in Emacs are in ordinary Emacs buffers
16500 which are visiting the source files in the usual way. You can edit
16501 the files with these buffers if you wish; but keep in mind that @value{GDBN}
16502 communicates with Emacs in terms of line numbers. If you add or
16503 delete lines from the text, the line numbers that @value{GDBN} knows cease
16504 to correspond properly with the code.
16506 The description given here is for GNU Emacs version 21.3 and a more
16507 detailed description of its interaction with @value{GDBN} is given in
16508 the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu} Emacs Manual}).
16510 @c The following dropped because Epoch is nonstandard. Reactivate
16511 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
16513 @kindex Emacs Epoch environment
16517 Version 18 of @sc{gnu} Emacs has a built-in window system
16518 called the @code{epoch}
16519 environment. Users of this environment can use a new command,
16520 @code{inspect} which performs identically to @code{print} except that
16521 each value is printed in its own window.
16526 @chapter The @sc{gdb/mi} Interface
16528 @unnumberedsec Function and Purpose
16530 @cindex @sc{gdb/mi}, its purpose
16531 @sc{gdb/mi} is a line based machine oriented text interface to
16532 @value{GDBN} and is activated by specifying using the
16533 @option{--interpreter} command line option (@pxref{Mode Options}). It
16534 is specifically intended to support the development of systems which
16535 use the debugger as just one small component of a larger system.
16537 This chapter is a specification of the @sc{gdb/mi} interface. It is written
16538 in the form of a reference manual.
16540 Note that @sc{gdb/mi} is still under construction, so some of the
16541 features described below are incomplete and subject to change.
16543 @unnumberedsec Notation and Terminology
16545 @cindex notational conventions, for @sc{gdb/mi}
16546 This chapter uses the following notation:
16550 @code{|} separates two alternatives.
16553 @code{[ @var{something} ]} indicates that @var{something} is optional:
16554 it may or may not be given.
16557 @code{( @var{group} )*} means that @var{group} inside the parentheses
16558 may repeat zero or more times.
16561 @code{( @var{group} )+} means that @var{group} inside the parentheses
16562 may repeat one or more times.
16565 @code{"@var{string}"} means a literal @var{string}.
16569 @heading Dependencies
16572 @heading Acknowledgments
16574 In alphabetic order: Andrew Cagney, Fernando Nasser, Stan Shebs and
16578 * GDB/MI Command Syntax::
16579 * GDB/MI Compatibility with CLI::
16580 * GDB/MI Output Records::
16581 * GDB/MI Command Description Format::
16582 * GDB/MI Breakpoint Table Commands::
16583 * GDB/MI Data Manipulation::
16584 * GDB/MI Program Control::
16585 * GDB/MI Miscellaneous Commands::
16587 * GDB/MI Kod Commands::
16588 * GDB/MI Memory Overlay Commands::
16589 * GDB/MI Signal Handling Commands::
16591 * GDB/MI Stack Manipulation::
16592 * GDB/MI Symbol Query::
16593 * GDB/MI Target Manipulation::
16594 * GDB/MI Thread Commands::
16595 * GDB/MI Tracepoint Commands::
16596 * GDB/MI Variable Objects::
16599 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16600 @node GDB/MI Command Syntax
16601 @section @sc{gdb/mi} Command Syntax
16604 * GDB/MI Input Syntax::
16605 * GDB/MI Output Syntax::
16606 * GDB/MI Simple Examples::
16609 @node GDB/MI Input Syntax
16610 @subsection @sc{gdb/mi} Input Syntax
16612 @cindex input syntax for @sc{gdb/mi}
16613 @cindex @sc{gdb/mi}, input syntax
16615 @item @var{command} @expansion{}
16616 @code{@var{cli-command} | @var{mi-command}}
16618 @item @var{cli-command} @expansion{}
16619 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
16620 @var{cli-command} is any existing @value{GDBN} CLI command.
16622 @item @var{mi-command} @expansion{}
16623 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
16624 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
16626 @item @var{token} @expansion{}
16627 "any sequence of digits"
16629 @item @var{option} @expansion{}
16630 @code{"-" @var{parameter} [ " " @var{parameter} ]}
16632 @item @var{parameter} @expansion{}
16633 @code{@var{non-blank-sequence} | @var{c-string}}
16635 @item @var{operation} @expansion{}
16636 @emph{any of the operations described in this chapter}
16638 @item @var{non-blank-sequence} @expansion{}
16639 @emph{anything, provided it doesn't contain special characters such as
16640 "-", @var{nl}, """ and of course " "}
16642 @item @var{c-string} @expansion{}
16643 @code{""" @var{seven-bit-iso-c-string-content} """}
16645 @item @var{nl} @expansion{}
16654 The CLI commands are still handled by the @sc{mi} interpreter; their
16655 output is described below.
16658 The @code{@var{token}}, when present, is passed back when the command
16662 Some @sc{mi} commands accept optional arguments as part of the parameter
16663 list. Each option is identified by a leading @samp{-} (dash) and may be
16664 followed by an optional argument parameter. Options occur first in the
16665 parameter list and can be delimited from normal parameters using
16666 @samp{--} (this is useful when some parameters begin with a dash).
16673 We want easy access to the existing CLI syntax (for debugging).
16676 We want it to be easy to spot a @sc{mi} operation.
16679 @node GDB/MI Output Syntax
16680 @subsection @sc{gdb/mi} Output Syntax
16682 @cindex output syntax of @sc{gdb/mi}
16683 @cindex @sc{gdb/mi}, output syntax
16684 The output from @sc{gdb/mi} consists of zero or more out-of-band records
16685 followed, optionally, by a single result record. This result record
16686 is for the most recent command. The sequence of output records is
16687 terminated by @samp{(@value{GDBP})}.
16689 If an input command was prefixed with a @code{@var{token}} then the
16690 corresponding output for that command will also be prefixed by that same
16694 @item @var{output} @expansion{}
16695 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(@value{GDBP})" @var{nl}}
16697 @item @var{result-record} @expansion{}
16698 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
16700 @item @var{out-of-band-record} @expansion{}
16701 @code{@var{async-record} | @var{stream-record}}
16703 @item @var{async-record} @expansion{}
16704 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
16706 @item @var{exec-async-output} @expansion{}
16707 @code{[ @var{token} ] "*" @var{async-output}}
16709 @item @var{status-async-output} @expansion{}
16710 @code{[ @var{token} ] "+" @var{async-output}}
16712 @item @var{notify-async-output} @expansion{}
16713 @code{[ @var{token} ] "=" @var{async-output}}
16715 @item @var{async-output} @expansion{}
16716 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
16718 @item @var{result-class} @expansion{}
16719 @code{"done" | "running" | "connected" | "error" | "exit"}
16721 @item @var{async-class} @expansion{}
16722 @code{"stopped" | @var{others}} (where @var{others} will be added
16723 depending on the needs---this is still in development).
16725 @item @var{result} @expansion{}
16726 @code{ @var{variable} "=" @var{value}}
16728 @item @var{variable} @expansion{}
16729 @code{ @var{string} }
16731 @item @var{value} @expansion{}
16732 @code{ @var{const} | @var{tuple} | @var{list} }
16734 @item @var{const} @expansion{}
16735 @code{@var{c-string}}
16737 @item @var{tuple} @expansion{}
16738 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
16740 @item @var{list} @expansion{}
16741 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
16742 @var{result} ( "," @var{result} )* "]" }
16744 @item @var{stream-record} @expansion{}
16745 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
16747 @item @var{console-stream-output} @expansion{}
16748 @code{"~" @var{c-string}}
16750 @item @var{target-stream-output} @expansion{}
16751 @code{"@@" @var{c-string}}
16753 @item @var{log-stream-output} @expansion{}
16754 @code{"&" @var{c-string}}
16756 @item @var{nl} @expansion{}
16759 @item @var{token} @expansion{}
16760 @emph{any sequence of digits}.
16768 All output sequences end in a single line containing a period.
16771 The @code{@var{token}} is from the corresponding request. If an execution
16772 command is interrupted by the @samp{-exec-interrupt} command, the
16773 @var{token} associated with the @samp{*stopped} message is the one of the
16774 original execution command, not the one of the interrupt command.
16777 @cindex status output in @sc{gdb/mi}
16778 @var{status-async-output} contains on-going status information about the
16779 progress of a slow operation. It can be discarded. All status output is
16780 prefixed by @samp{+}.
16783 @cindex async output in @sc{gdb/mi}
16784 @var{exec-async-output} contains asynchronous state change on the target
16785 (stopped, started, disappeared). All async output is prefixed by
16789 @cindex notify output in @sc{gdb/mi}
16790 @var{notify-async-output} contains supplementary information that the
16791 client should handle (e.g., a new breakpoint information). All notify
16792 output is prefixed by @samp{=}.
16795 @cindex console output in @sc{gdb/mi}
16796 @var{console-stream-output} is output that should be displayed as is in the
16797 console. It is the textual response to a CLI command. All the console
16798 output is prefixed by @samp{~}.
16801 @cindex target output in @sc{gdb/mi}
16802 @var{target-stream-output} is the output produced by the target program.
16803 All the target output is prefixed by @samp{@@}.
16806 @cindex log output in @sc{gdb/mi}
16807 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
16808 instance messages that should be displayed as part of an error log. All
16809 the log output is prefixed by @samp{&}.
16812 @cindex list output in @sc{gdb/mi}
16813 New @sc{gdb/mi} commands should only output @var{lists} containing
16819 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
16820 details about the various output records.
16822 @node GDB/MI Simple Examples
16823 @subsection Simple Examples of @sc{gdb/mi} Interaction
16824 @cindex @sc{gdb/mi}, simple examples
16826 This subsection presents several simple examples of interaction using
16827 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
16828 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
16829 the output received from @sc{gdb/mi}.
16831 @subsubheading Target Stop
16832 @c Ummm... There is no "-stop" command. This assumes async, no?
16833 Here's an example of stopping the inferior process:
16844 <- *stop,reason="stop",address="0x123",source="a.c:123"
16848 @subsubheading Simple CLI Command
16850 Here's an example of a simple CLI command being passed through
16851 @sc{gdb/mi} and on to the CLI.
16861 @subsubheading Command With Side Effects
16864 -> -symbol-file xyz.exe
16865 <- *breakpoint,nr="3",address="0x123",source="a.c:123"
16869 @subsubheading A Bad Command
16871 Here's what happens if you pass a non-existent command:
16875 <- ^error,msg="Undefined MI command: rubbish"
16879 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16880 @node GDB/MI Compatibility with CLI
16881 @section @sc{gdb/mi} Compatibility with CLI
16883 @cindex compatibility, @sc{gdb/mi} and CLI
16884 @cindex @sc{gdb/mi}, compatibility with CLI
16885 To help users familiar with @value{GDBN}'s existing CLI interface, @sc{gdb/mi}
16886 accepts existing CLI commands. As specified by the syntax, such
16887 commands can be directly entered into the @sc{gdb/mi} interface and @value{GDBN} will
16890 This mechanism is provided as an aid to developers of @sc{gdb/mi}
16891 clients and not as a reliable interface into the CLI. Since the command
16892 is being interpreteted in an environment that assumes @sc{gdb/mi}
16893 behaviour, the exact output of such commands is likely to end up being
16894 an un-supported hybrid of @sc{gdb/mi} and CLI output.
16896 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
16897 @node GDB/MI Output Records
16898 @section @sc{gdb/mi} Output Records
16901 * GDB/MI Result Records::
16902 * GDB/MI Stream Records::
16903 * GDB/MI Out-of-band Records::
16906 @node GDB/MI Result Records
16907 @subsection @sc{gdb/mi} Result Records
16909 @cindex result records in @sc{gdb/mi}
16910 @cindex @sc{gdb/mi}, result records
16911 In addition to a number of out-of-band notifications, the response to a
16912 @sc{gdb/mi} command includes one of the following result indications:
16916 @item "^done" [ "," @var{results} ]
16917 The synchronous operation was successful, @code{@var{results}} are the return
16922 @c Is this one correct? Should it be an out-of-band notification?
16923 The asynchronous operation was successfully started. The target is
16926 @item "^error" "," @var{c-string}
16928 The operation failed. The @code{@var{c-string}} contains the corresponding
16932 @node GDB/MI Stream Records
16933 @subsection @sc{gdb/mi} Stream Records
16935 @cindex @sc{gdb/mi}, stream records
16936 @cindex stream records in @sc{gdb/mi}
16937 @value{GDBN} internally maintains a number of output streams: the console, the
16938 target, and the log. The output intended for each of these streams is
16939 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
16941 Each stream record begins with a unique @dfn{prefix character} which
16942 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
16943 Syntax}). In addition to the prefix, each stream record contains a
16944 @code{@var{string-output}}. This is either raw text (with an implicit new
16945 line) or a quoted C string (which does not contain an implicit newline).
16948 @item "~" @var{string-output}
16949 The console output stream contains text that should be displayed in the
16950 CLI console window. It contains the textual responses to CLI commands.
16952 @item "@@" @var{string-output}
16953 The target output stream contains any textual output from the running
16956 @item "&" @var{string-output}
16957 The log stream contains debugging messages being produced by @value{GDBN}'s
16961 @node GDB/MI Out-of-band Records
16962 @subsection @sc{gdb/mi} Out-of-band Records
16964 @cindex out-of-band records in @sc{gdb/mi}
16965 @cindex @sc{gdb/mi}, out-of-band records
16966 @dfn{Out-of-band} records are used to notify the @sc{gdb/mi} client of
16967 additional changes that have occurred. Those changes can either be a
16968 consequence of @sc{gdb/mi} (e.g., a breakpoint modified) or a result of
16969 target activity (e.g., target stopped).
16971 The following is a preliminary list of possible out-of-band records.
16972 In particular, the @var{exec-async-output} records.
16975 @item *stopped,reason="@var{reason}"
16978 @var{reason} can be one of the following:
16981 @item breakpoint-hit
16982 A breakpoint was reached.
16983 @item watchpoint-trigger
16984 A watchpoint was triggered.
16985 @item read-watchpoint-trigger
16986 A read watchpoint was triggered.
16987 @item access-watchpoint-trigger
16988 An access watchpoint was triggered.
16989 @item function-finished
16990 An -exec-finish or similar CLI command was accomplished.
16991 @item location-reached
16992 An -exec-until or similar CLI command was accomplished.
16993 @item watchpoint-scope
16994 A watchpoint has gone out of scope.
16995 @item end-stepping-range
16996 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
16997 similar CLI command was accomplished.
16998 @item exited-signalled
16999 The inferior exited because of a signal.
17001 The inferior exited.
17002 @item exited-normally
17003 The inferior exited normally.
17004 @item signal-received
17005 A signal was received by the inferior.
17009 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17010 @node GDB/MI Command Description Format
17011 @section @sc{gdb/mi} Command Description Format
17013 The remaining sections describe blocks of commands. Each block of
17014 commands is laid out in a fashion similar to this section.
17016 Note the the line breaks shown in the examples are here only for
17017 readability. They don't appear in the real output.
17018 Also note that the commands with a non-available example (N.A.@:) are
17019 not yet implemented.
17021 @subheading Motivation
17023 The motivation for this collection of commands.
17025 @subheading Introduction
17027 A brief introduction to this collection of commands as a whole.
17029 @subheading Commands
17031 For each command in the block, the following is described:
17033 @subsubheading Synopsis
17036 -command @var{args}@dots{}
17039 @subsubheading @value{GDBN} Command
17041 The corresponding @value{GDBN} CLI command.
17043 @subsubheading Result
17045 @subsubheading Out-of-band
17047 @subsubheading Notes
17049 @subsubheading Example
17052 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17053 @node GDB/MI Breakpoint Table Commands
17054 @section @sc{gdb/mi} Breakpoint table commands
17056 @cindex breakpoint commands for @sc{gdb/mi}
17057 @cindex @sc{gdb/mi}, breakpoint commands
17058 This section documents @sc{gdb/mi} commands for manipulating
17061 @subheading The @code{-break-after} Command
17062 @findex -break-after
17064 @subsubheading Synopsis
17067 -break-after @var{number} @var{count}
17070 The breakpoint number @var{number} is not in effect until it has been
17071 hit @var{count} times. To see how this is reflected in the output of
17072 the @samp{-break-list} command, see the description of the
17073 @samp{-break-list} command below.
17075 @subsubheading @value{GDBN} Command
17077 The corresponding @value{GDBN} command is @samp{ignore}.
17079 @subsubheading Example
17084 ^done,bkpt=@{number="1",addr="0x000100d0",file="hello.c",line="5"@}
17091 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17092 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17093 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17094 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17095 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17096 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17097 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17098 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17099 addr="0x000100d0",func="main",file="hello.c",line="5",times="0",
17105 @subheading The @code{-break-catch} Command
17106 @findex -break-catch
17108 @subheading The @code{-break-commands} Command
17109 @findex -break-commands
17113 @subheading The @code{-break-condition} Command
17114 @findex -break-condition
17116 @subsubheading Synopsis
17119 -break-condition @var{number} @var{expr}
17122 Breakpoint @var{number} will stop the program only if the condition in
17123 @var{expr} is true. The condition becomes part of the
17124 @samp{-break-list} output (see the description of the @samp{-break-list}
17127 @subsubheading @value{GDBN} Command
17129 The corresponding @value{GDBN} command is @samp{condition}.
17131 @subsubheading Example
17135 -break-condition 1 1
17139 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17140 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17141 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17142 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17143 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17144 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17145 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17146 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17147 addr="0x000100d0",func="main",file="hello.c",line="5",cond="1",
17148 times="0",ignore="3"@}]@}
17152 @subheading The @code{-break-delete} Command
17153 @findex -break-delete
17155 @subsubheading Synopsis
17158 -break-delete ( @var{breakpoint} )+
17161 Delete the breakpoint(s) whose number(s) are specified in the argument
17162 list. This is obviously reflected in the breakpoint list.
17164 @subsubheading @value{GDBN} command
17166 The corresponding @value{GDBN} command is @samp{delete}.
17168 @subsubheading Example
17176 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17177 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17178 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17179 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17180 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17181 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17182 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17187 @subheading The @code{-break-disable} Command
17188 @findex -break-disable
17190 @subsubheading Synopsis
17193 -break-disable ( @var{breakpoint} )+
17196 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
17197 break list is now set to @samp{n} for the named @var{breakpoint}(s).
17199 @subsubheading @value{GDBN} Command
17201 The corresponding @value{GDBN} command is @samp{disable}.
17203 @subsubheading Example
17211 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17212 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17213 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17214 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17215 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17216 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17217 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17218 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
17219 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17223 @subheading The @code{-break-enable} Command
17224 @findex -break-enable
17226 @subsubheading Synopsis
17229 -break-enable ( @var{breakpoint} )+
17232 Enable (previously disabled) @var{breakpoint}(s).
17234 @subsubheading @value{GDBN} Command
17236 The corresponding @value{GDBN} command is @samp{enable}.
17238 @subsubheading Example
17246 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17247 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17248 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17249 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17250 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17251 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17252 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17253 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17254 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@}]@}
17258 @subheading The @code{-break-info} Command
17259 @findex -break-info
17261 @subsubheading Synopsis
17264 -break-info @var{breakpoint}
17268 Get information about a single breakpoint.
17270 @subsubheading @value{GDBN} command
17272 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
17274 @subsubheading Example
17277 @subheading The @code{-break-insert} Command
17278 @findex -break-insert
17280 @subsubheading Synopsis
17283 -break-insert [ -t ] [ -h ] [ -r ]
17284 [ -c @var{condition} ] [ -i @var{ignore-count} ]
17285 [ -p @var{thread} ] [ @var{line} | @var{addr} ]
17289 If specified, @var{line}, can be one of:
17296 @item filename:linenum
17297 @item filename:function
17301 The possible optional parameters of this command are:
17305 Insert a tempoary breakpoint.
17307 Insert a hardware breakpoint.
17308 @item -c @var{condition}
17309 Make the breakpoint conditional on @var{condition}.
17310 @item -i @var{ignore-count}
17311 Initialize the @var{ignore-count}.
17313 Insert a regular breakpoint in all the functions whose names match the
17314 given regular expression. Other flags are not applicable to regular
17318 @subsubheading Result
17320 The result is in the form:
17323 ^done,bkptno="@var{number}",func="@var{funcname}",
17324 file="@var{filename}",line="@var{lineno}"
17328 where @var{number} is the @value{GDBN} number for this breakpoint, @var{funcname}
17329 is the name of the function where the breakpoint was inserted,
17330 @var{filename} is the name of the source file which contains this
17331 function, and @var{lineno} is the source line number within that file.
17333 Note: this format is open to change.
17334 @c An out-of-band breakpoint instead of part of the result?
17336 @subsubheading @value{GDBN} Command
17338 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
17339 @samp{hbreak}, @samp{thbreak}, and @samp{rbreak}.
17341 @subsubheading Example
17346 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
17348 -break-insert -t foo
17349 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",line="11"@}
17352 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17353 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17354 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17355 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17356 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17357 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17358 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17359 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17360 addr="0x0001072c", func="main",file="recursive2.c",line="4",times="0"@},
17361 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
17362 addr="0x00010774",func="foo",file="recursive2.c",line="11",times="0"@}]@}
17364 -break-insert -r foo.*
17365 ~int foo(int, int);
17366 ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c",line="11"@}
17370 @subheading The @code{-break-list} Command
17371 @findex -break-list
17373 @subsubheading Synopsis
17379 Displays the list of inserted breakpoints, showing the following fields:
17383 number of the breakpoint
17385 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
17387 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
17390 is the breakpoint enabled or no: @samp{y} or @samp{n}
17392 memory location at which the breakpoint is set
17394 logical location of the breakpoint, expressed by function name, file
17397 number of times the breakpoint has been hit
17400 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
17401 @code{body} field is an empty list.
17403 @subsubheading @value{GDBN} Command
17405 The corresponding @value{GDBN} command is @samp{info break}.
17407 @subsubheading Example
17412 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17413 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17414 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17415 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17416 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17417 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17418 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17419 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17420 addr="0x000100d0",func="main",file="hello.c",line="5",times="0"@},
17421 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
17422 addr="0x00010114",func="foo",file="hello.c",line="13",times="0"@}]@}
17426 Here's an example of the result when there are no breakpoints:
17431 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
17432 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17433 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17434 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17435 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17436 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17437 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17442 @subheading The @code{-break-watch} Command
17443 @findex -break-watch
17445 @subsubheading Synopsis
17448 -break-watch [ -a | -r ]
17451 Create a watchpoint. With the @samp{-a} option it will create an
17452 @dfn{access} watchpoint, i.e. a watchpoint that triggers either on a
17453 read from or on a write to the memory location. With the @samp{-r}
17454 option, the watchpoint created is a @dfn{read} watchpoint, i.e. it will
17455 trigger only when the memory location is accessed for reading. Without
17456 either of the options, the watchpoint created is a regular watchpoint,
17457 i.e. it will trigger when the memory location is accessed for writing.
17458 @xref{Set Watchpoints, , Setting watchpoints}.
17460 Note that @samp{-break-list} will report a single list of watchpoints and
17461 breakpoints inserted.
17463 @subsubheading @value{GDBN} Command
17465 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
17468 @subsubheading Example
17470 Setting a watchpoint on a variable in the @code{main} function:
17475 ^done,wpt=@{number="2",exp="x"@}
17479 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
17480 value=@{old="-268439212",new="55"@},
17481 frame=@{func="main",args=[],file="recursive2.c",
17482 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="5"@}
17486 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
17487 the program execution twice: first for the variable changing value, then
17488 for the watchpoint going out of scope.
17493 ^done,wpt=@{number="5",exp="C"@}
17497 ^done,reason="watchpoint-trigger",
17498 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
17499 frame=@{func="callee4",args=[],
17500 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17501 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17505 ^done,reason="watchpoint-scope",wpnum="5",
17506 frame=@{func="callee3",args=[@{name="strarg",
17507 value="0x11940 \"A string argument.\""@}],
17508 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17509 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17513 Listing breakpoints and watchpoints, at different points in the program
17514 execution. Note that once the watchpoint goes out of scope, it is
17520 ^done,wpt=@{number="2",exp="C"@}
17523 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17524 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17525 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17526 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17527 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17528 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17529 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17530 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17531 addr="0x00010734",func="callee4",
17532 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17533 bkpt=@{number="2",type="watchpoint",disp="keep",
17534 enabled="y",addr="",what="C",times="0"@}]@}
17538 ^done,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
17539 value=@{old="-276895068",new="3"@},
17540 frame=@{func="callee4",args=[],
17541 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17542 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
17545 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
17546 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17547 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17548 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17549 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17550 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17551 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17552 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17553 addr="0x00010734",func="callee4",
17554 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@},
17555 bkpt=@{number="2",type="watchpoint",disp="keep",
17556 enabled="y",addr="",what="C",times="-5"@}]@}
17560 ^done,reason="watchpoint-scope",wpnum="2",
17561 frame=@{func="callee3",args=[@{name="strarg",
17562 value="0x11940 \"A string argument.\""@}],
17563 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
17564 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
17567 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
17568 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
17569 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
17570 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
17571 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
17572 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
17573 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
17574 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
17575 addr="0x00010734",func="callee4",
17576 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"@}]@}
17580 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
17581 @node GDB/MI Data Manipulation
17582 @section @sc{gdb/mi} Data Manipulation
17584 @cindex data manipulation, in @sc{gdb/mi}
17585 @cindex @sc{gdb/mi}, data manipulation
17586 This section describes the @sc{gdb/mi} commands that manipulate data:
17587 examine memory and registers, evaluate expressions, etc.
17589 @c REMOVED FROM THE INTERFACE.
17590 @c @subheading -data-assign
17591 @c Change the value of a program variable. Plenty of side effects.
17592 @c @subsubheading GDB command
17594 @c @subsubheading Example
17597 @subheading The @code{-data-disassemble} Command
17598 @findex -data-disassemble
17600 @subsubheading Synopsis
17604 [ -s @var{start-addr} -e @var{end-addr} ]
17605 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
17613 @item @var{start-addr}
17614 is the beginning address (or @code{$pc})
17615 @item @var{end-addr}
17617 @item @var{filename}
17618 is the name of the file to disassemble
17619 @item @var{linenum}
17620 is the line number to disassemble around
17622 is the the number of disassembly lines to be produced. If it is -1,
17623 the whole function will be disassembled, in case no @var{end-addr} is
17624 specified. If @var{end-addr} is specified as a non-zero value, and
17625 @var{lines} is lower than the number of disassembly lines between
17626 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
17627 displayed; if @var{lines} is higher than the number of lines between
17628 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
17631 is either 0 (meaning only disassembly) or 1 (meaning mixed source and
17635 @subsubheading Result
17637 The output for each instruction is composed of four fields:
17646 Note that whatever included in the instruction field, is not manipulated
17647 directely by @sc{gdb/mi}, i.e. it is not possible to adjust its format.
17649 @subsubheading @value{GDBN} Command
17651 There's no direct mapping from this command to the CLI.
17653 @subsubheading Example
17655 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
17659 -data-disassemble -s $pc -e "$pc + 20" -- 0
17662 @{address="0x000107c0",func-name="main",offset="4",
17663 inst="mov 2, %o0"@},
17664 @{address="0x000107c4",func-name="main",offset="8",
17665 inst="sethi %hi(0x11800), %o2"@},
17666 @{address="0x000107c8",func-name="main",offset="12",
17667 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
17668 @{address="0x000107cc",func-name="main",offset="16",
17669 inst="sethi %hi(0x11800), %o2"@},
17670 @{address="0x000107d0",func-name="main",offset="20",
17671 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
17675 Disassemble the whole @code{main} function. Line 32 is part of
17679 -data-disassemble -f basics.c -l 32 -- 0
17681 @{address="0x000107bc",func-name="main",offset="0",
17682 inst="save %sp, -112, %sp"@},
17683 @{address="0x000107c0",func-name="main",offset="4",
17684 inst="mov 2, %o0"@},
17685 @{address="0x000107c4",func-name="main",offset="8",
17686 inst="sethi %hi(0x11800), %o2"@},
17688 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
17689 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
17693 Disassemble 3 instructions from the start of @code{main}:
17697 -data-disassemble -f basics.c -l 32 -n 3 -- 0
17699 @{address="0x000107bc",func-name="main",offset="0",
17700 inst="save %sp, -112, %sp"@},
17701 @{address="0x000107c0",func-name="main",offset="4",
17702 inst="mov 2, %o0"@},
17703 @{address="0x000107c4",func-name="main",offset="8",
17704 inst="sethi %hi(0x11800), %o2"@}]
17708 Disassemble 3 instructions from the start of @code{main} in mixed mode:
17712 -data-disassemble -f basics.c -l 32 -n 3 -- 1
17714 src_and_asm_line=@{line="31",
17715 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17716 testsuite/gdb.mi/basics.c",line_asm_insn=[
17717 @{address="0x000107bc",func-name="main",offset="0",
17718 inst="save %sp, -112, %sp"@}]@},
17719 src_and_asm_line=@{line="32",
17720 file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
17721 testsuite/gdb.mi/basics.c",line_asm_insn=[
17722 @{address="0x000107c0",func-name="main",offset="4",
17723 inst="mov 2, %o0"@},
17724 @{address="0x000107c4",func-name="main",offset="8",
17725 inst="sethi %hi(0x11800), %o2"@}]@}]
17730 @subheading The @code{-data-evaluate-expression} Command
17731 @findex -data-evaluate-expression
17733 @subsubheading Synopsis
17736 -data-evaluate-expression @var{expr}
17739 Evaluate @var{expr} as an expression. The expression could contain an
17740 inferior function call. The function call will execute synchronously.
17741 If the expression contains spaces, it must be enclosed in double quotes.
17743 @subsubheading @value{GDBN} Command
17745 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
17746 @samp{call}. In @code{gdbtk} only, there's a corresponding
17747 @samp{gdb_eval} command.
17749 @subsubheading Example
17751 In the following example, the numbers that precede the commands are the
17752 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
17753 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
17757 211-data-evaluate-expression A
17760 311-data-evaluate-expression &A
17761 311^done,value="0xefffeb7c"
17763 411-data-evaluate-expression A+3
17766 511-data-evaluate-expression "A + 3"
17772 @subheading The @code{-data-list-changed-registers} Command
17773 @findex -data-list-changed-registers
17775 @subsubheading Synopsis
17778 -data-list-changed-registers
17781 Display a list of the registers that have changed.
17783 @subsubheading @value{GDBN} Command
17785 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
17786 has the corresponding command @samp{gdb_changed_register_list}.
17788 @subsubheading Example
17790 On a PPC MBX board:
17798 *stopped,reason="breakpoint-hit",bkptno="1",frame=@{func="main",
17799 args=[],file="try.c",fullname="/home/foo/bar/devo/myproject/try.c",line="5"@}
17801 -data-list-changed-registers
17802 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
17803 "10","11","13","14","15","16","17","18","19","20","21","22","23",
17804 "24","25","26","27","28","30","31","64","65","66","67","69"]
17809 @subheading The @code{-data-list-register-names} Command
17810 @findex -data-list-register-names
17812 @subsubheading Synopsis
17815 -data-list-register-names [ ( @var{regno} )+ ]
17818 Show a list of register names for the current target. If no arguments
17819 are given, it shows a list of the names of all the registers. If
17820 integer numbers are given as arguments, it will print a list of the
17821 names of the registers corresponding to the arguments. To ensure
17822 consistency between a register name and its number, the output list may
17823 include empty register names.
17825 @subsubheading @value{GDBN} Command
17827 @value{GDBN} does not have a command which corresponds to
17828 @samp{-data-list-register-names}. In @code{gdbtk} there is a
17829 corresponding command @samp{gdb_regnames}.
17831 @subsubheading Example
17833 For the PPC MBX board:
17836 -data-list-register-names
17837 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
17838 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
17839 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
17840 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
17841 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
17842 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
17843 "", "pc","ps","cr","lr","ctr","xer"]
17845 -data-list-register-names 1 2 3
17846 ^done,register-names=["r1","r2","r3"]
17850 @subheading The @code{-data-list-register-values} Command
17851 @findex -data-list-register-values
17853 @subsubheading Synopsis
17856 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
17859 Display the registers' contents. @var{fmt} is the format according to
17860 which the registers' contents are to be returned, followed by an optional
17861 list of numbers specifying the registers to display. A missing list of
17862 numbers indicates that the contents of all the registers must be returned.
17864 Allowed formats for @var{fmt} are:
17881 @subsubheading @value{GDBN} Command
17883 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
17884 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
17886 @subsubheading Example
17888 For a PPC MBX board (note: line breaks are for readability only, they
17889 don't appear in the actual output):
17893 -data-list-register-values r 64 65
17894 ^done,register-values=[@{number="64",value="0xfe00a300"@},
17895 @{number="65",value="0x00029002"@}]
17897 -data-list-register-values x
17898 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
17899 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
17900 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
17901 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
17902 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
17903 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
17904 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
17905 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
17906 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
17907 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
17908 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
17909 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
17910 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
17911 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
17912 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
17913 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
17914 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
17915 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
17916 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
17917 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
17918 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
17919 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
17920 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
17921 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
17922 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
17923 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
17924 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
17925 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
17926 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
17927 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
17928 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
17929 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
17930 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
17931 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
17932 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
17933 @{number="69",value="0x20002b03"@}]
17938 @subheading The @code{-data-read-memory} Command
17939 @findex -data-read-memory
17941 @subsubheading Synopsis
17944 -data-read-memory [ -o @var{byte-offset} ]
17945 @var{address} @var{word-format} @var{word-size}
17946 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
17953 @item @var{address}
17954 An expression specifying the address of the first memory word to be
17955 read. Complex expressions containing embedded white space should be
17956 quoted using the C convention.
17958 @item @var{word-format}
17959 The format to be used to print the memory words. The notation is the
17960 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
17963 @item @var{word-size}
17964 The size of each memory word in bytes.
17966 @item @var{nr-rows}
17967 The number of rows in the output table.
17969 @item @var{nr-cols}
17970 The number of columns in the output table.
17973 If present, indicates that each row should include an @sc{ascii} dump. The
17974 value of @var{aschar} is used as a padding character when a byte is not a
17975 member of the printable @sc{ascii} character set (printable @sc{ascii}
17976 characters are those whose code is between 32 and 126, inclusively).
17978 @item @var{byte-offset}
17979 An offset to add to the @var{address} before fetching memory.
17982 This command displays memory contents as a table of @var{nr-rows} by
17983 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
17984 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
17985 (returned as @samp{total-bytes}). Should less than the requested number
17986 of bytes be returned by the target, the missing words are identified
17987 using @samp{N/A}. The number of bytes read from the target is returned
17988 in @samp{nr-bytes} and the starting address used to read memory in
17991 The address of the next/previous row or page is available in
17992 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
17995 @subsubheading @value{GDBN} Command
17997 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
17998 @samp{gdb_get_mem} memory read command.
18000 @subsubheading Example
18002 Read six bytes of memory starting at @code{bytes+6} but then offset by
18003 @code{-6} bytes. Format as three rows of two columns. One byte per
18004 word. Display each word in hex.
18008 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
18009 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
18010 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
18011 prev-page="0x0000138a",memory=[
18012 @{addr="0x00001390",data=["0x00","0x01"]@},
18013 @{addr="0x00001392",data=["0x02","0x03"]@},
18014 @{addr="0x00001394",data=["0x04","0x05"]@}]
18018 Read two bytes of memory starting at address @code{shorts + 64} and
18019 display as a single word formatted in decimal.
18023 5-data-read-memory shorts+64 d 2 1 1
18024 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
18025 next-row="0x00001512",prev-row="0x0000150e",
18026 next-page="0x00001512",prev-page="0x0000150e",memory=[
18027 @{addr="0x00001510",data=["128"]@}]
18031 Read thirty two bytes of memory starting at @code{bytes+16} and format
18032 as eight rows of four columns. Include a string encoding with @samp{x}
18033 used as the non-printable character.
18037 4-data-read-memory bytes+16 x 1 8 4 x
18038 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
18039 next-row="0x000013c0",prev-row="0x0000139c",
18040 next-page="0x000013c0",prev-page="0x00001380",memory=[
18041 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
18042 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
18043 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
18044 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
18045 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
18046 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
18047 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
18048 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
18052 @subheading The @code{-display-delete} Command
18053 @findex -display-delete
18055 @subsubheading Synopsis
18058 -display-delete @var{number}
18061 Delete the display @var{number}.
18063 @subsubheading @value{GDBN} Command
18065 The corresponding @value{GDBN} command is @samp{delete display}.
18067 @subsubheading Example
18071 @subheading The @code{-display-disable} Command
18072 @findex -display-disable
18074 @subsubheading Synopsis
18077 -display-disable @var{number}
18080 Disable display @var{number}.
18082 @subsubheading @value{GDBN} Command
18084 The corresponding @value{GDBN} command is @samp{disable display}.
18086 @subsubheading Example
18090 @subheading The @code{-display-enable} Command
18091 @findex -display-enable
18093 @subsubheading Synopsis
18096 -display-enable @var{number}
18099 Enable display @var{number}.
18101 @subsubheading @value{GDBN} Command
18103 The corresponding @value{GDBN} command is @samp{enable display}.
18105 @subsubheading Example
18109 @subheading The @code{-display-insert} Command
18110 @findex -display-insert
18112 @subsubheading Synopsis
18115 -display-insert @var{expression}
18118 Display @var{expression} every time the program stops.
18120 @subsubheading @value{GDBN} Command
18122 The corresponding @value{GDBN} command is @samp{display}.
18124 @subsubheading Example
18128 @subheading The @code{-display-list} Command
18129 @findex -display-list
18131 @subsubheading Synopsis
18137 List the displays. Do not show the current values.
18139 @subsubheading @value{GDBN} Command
18141 The corresponding @value{GDBN} command is @samp{info display}.
18143 @subsubheading Example
18147 @subheading The @code{-environment-cd} Command
18148 @findex -environment-cd
18150 @subsubheading Synopsis
18153 -environment-cd @var{pathdir}
18156 Set @value{GDBN}'s working directory.
18158 @subsubheading @value{GDBN} Command
18160 The corresponding @value{GDBN} command is @samp{cd}.
18162 @subsubheading Example
18166 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18172 @subheading The @code{-environment-directory} Command
18173 @findex -environment-directory
18175 @subsubheading Synopsis
18178 -environment-directory [ -r ] [ @var{pathdir} ]+
18181 Add directories @var{pathdir} to beginning of search path for source files.
18182 If the @samp{-r} option is used, the search path is reset to the default
18183 search path. If directories @var{pathdir} are supplied in addition to the
18184 @samp{-r} option, the search path is first reset and then addition
18186 Multiple directories may be specified, separated by blanks. Specifying
18187 multiple directories in a single command
18188 results in the directories added to the beginning of the
18189 search path in the same order they were presented in the command.
18190 If blanks are needed as
18191 part of a directory name, double-quotes should be used around
18192 the name. In the command output, the path will show up separated
18193 by the system directory-separator character. The directory-seperator
18194 character must not be used
18195 in any directory name.
18196 If no directories are specified, the current search path is displayed.
18198 @subsubheading @value{GDBN} Command
18200 The corresponding @value{GDBN} command is @samp{dir}.
18202 @subsubheading Example
18206 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
18207 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18209 -environment-directory ""
18210 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
18212 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
18213 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
18215 -environment-directory -r
18216 ^done,source-path="$cdir:$cwd"
18221 @subheading The @code{-environment-path} Command
18222 @findex -environment-path
18224 @subsubheading Synopsis
18227 -environment-path [ -r ] [ @var{pathdir} ]+
18230 Add directories @var{pathdir} to beginning of search path for object files.
18231 If the @samp{-r} option is used, the search path is reset to the original
18232 search path that existed at gdb start-up. If directories @var{pathdir} are
18233 supplied in addition to the
18234 @samp{-r} option, the search path is first reset and then addition
18236 Multiple directories may be specified, separated by blanks. Specifying
18237 multiple directories in a single command
18238 results in the directories added to the beginning of the
18239 search path in the same order they were presented in the command.
18240 If blanks are needed as
18241 part of a directory name, double-quotes should be used around
18242 the name. In the command output, the path will show up separated
18243 by the system directory-separator character. The directory-seperator
18244 character must not be used
18245 in any directory name.
18246 If no directories are specified, the current path is displayed.
18249 @subsubheading @value{GDBN} Command
18251 The corresponding @value{GDBN} command is @samp{path}.
18253 @subsubheading Example
18258 ^done,path="/usr/bin"
18260 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
18261 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
18263 -environment-path -r /usr/local/bin
18264 ^done,path="/usr/local/bin:/usr/bin"
18269 @subheading The @code{-environment-pwd} Command
18270 @findex -environment-pwd
18272 @subsubheading Synopsis
18278 Show the current working directory.
18280 @subsubheading @value{GDBN} command
18282 The corresponding @value{GDBN} command is @samp{pwd}.
18284 @subsubheading Example
18289 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
18293 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18294 @node GDB/MI Program Control
18295 @section @sc{gdb/mi} Program control
18297 @subsubheading Program termination
18299 As a result of execution, the inferior program can run to completion, if
18300 it doesn't encounter any breakpoints. In this case the output will
18301 include an exit code, if the program has exited exceptionally.
18303 @subsubheading Examples
18306 Program exited normally:
18314 *stopped,reason="exited-normally"
18319 Program exited exceptionally:
18327 *stopped,reason="exited",exit-code="01"
18331 Another way the program can terminate is if it receives a signal such as
18332 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
18336 *stopped,reason="exited-signalled",signal-name="SIGINT",
18337 signal-meaning="Interrupt"
18341 @subheading The @code{-exec-abort} Command
18342 @findex -exec-abort
18344 @subsubheading Synopsis
18350 Kill the inferior running program.
18352 @subsubheading @value{GDBN} Command
18354 The corresponding @value{GDBN} command is @samp{kill}.
18356 @subsubheading Example
18360 @subheading The @code{-exec-arguments} Command
18361 @findex -exec-arguments
18363 @subsubheading Synopsis
18366 -exec-arguments @var{args}
18369 Set the inferior program arguments, to be used in the next
18372 @subsubheading @value{GDBN} Command
18374 The corresponding @value{GDBN} command is @samp{set args}.
18376 @subsubheading Example
18379 Don't have one around.
18382 @subheading The @code{-exec-continue} Command
18383 @findex -exec-continue
18385 @subsubheading Synopsis
18391 Asynchronous command. Resumes the execution of the inferior program
18392 until a breakpoint is encountered, or until the inferior exits.
18394 @subsubheading @value{GDBN} Command
18396 The corresponding @value{GDBN} corresponding is @samp{continue}.
18398 @subsubheading Example
18405 *stopped,reason="breakpoint-hit",bkptno="2",frame=@{func="foo",args=[],
18406 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="13"@}
18411 @subheading The @code{-exec-finish} Command
18412 @findex -exec-finish
18414 @subsubheading Synopsis
18420 Asynchronous command. Resumes the execution of the inferior program
18421 until the current function is exited. Displays the results returned by
18424 @subsubheading @value{GDBN} Command
18426 The corresponding @value{GDBN} command is @samp{finish}.
18428 @subsubheading Example
18430 Function returning @code{void}.
18437 *stopped,reason="function-finished",frame=@{func="main",args=[],
18438 file="hello.c",fullname="/home/foo/bar/devo/myproject/hello.c",line="7"@}
18442 Function returning other than @code{void}. The name of the internal
18443 @value{GDBN} variable storing the result is printed, together with the
18450 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
18451 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
18452 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
18453 gdb-result-var="$1",return-value="0"
18458 @subheading The @code{-exec-interrupt} Command
18459 @findex -exec-interrupt
18461 @subsubheading Synopsis
18467 Asynchronous command. Interrupts the background execution of the target.
18468 Note how the token associated with the stop message is the one for the
18469 execution command that has been interrupted. The token for the interrupt
18470 itself only appears in the @samp{^done} output. If the user is trying to
18471 interrupt a non-running program, an error message will be printed.
18473 @subsubheading @value{GDBN} Command
18475 The corresponding @value{GDBN} command is @samp{interrupt}.
18477 @subsubheading Example
18488 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
18489 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
18490 fullname="/home/foo/bar/devo/myproject/try.c",line="13"@}
18495 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
18500 @subheading The @code{-exec-next} Command
18503 @subsubheading Synopsis
18509 Asynchronous command. Resumes execution of the inferior program, stopping
18510 when the beginning of the next source line is reached.
18512 @subsubheading @value{GDBN} Command
18514 The corresponding @value{GDBN} command is @samp{next}.
18516 @subsubheading Example
18522 *stopped,reason="end-stepping-range",line="8",file="hello.c"
18527 @subheading The @code{-exec-next-instruction} Command
18528 @findex -exec-next-instruction
18530 @subsubheading Synopsis
18533 -exec-next-instruction
18536 Asynchronous command. Executes one machine instruction. If the
18537 instruction is a function call continues until the function returns. If
18538 the program stops at an instruction in the middle of a source line, the
18539 address will be printed as well.
18541 @subsubheading @value{GDBN} Command
18543 The corresponding @value{GDBN} command is @samp{nexti}.
18545 @subsubheading Example
18549 -exec-next-instruction
18553 *stopped,reason="end-stepping-range",
18554 addr="0x000100d4",line="5",file="hello.c"
18559 @subheading The @code{-exec-return} Command
18560 @findex -exec-return
18562 @subsubheading Synopsis
18568 Makes current function return immediately. Doesn't execute the inferior.
18569 Displays the new current frame.
18571 @subsubheading @value{GDBN} Command
18573 The corresponding @value{GDBN} command is @samp{return}.
18575 @subsubheading Example
18579 200-break-insert callee4
18580 200^done,bkpt=@{number="1",addr="0x00010734",
18581 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18586 000*stopped,reason="breakpoint-hit",bkptno="1",
18587 frame=@{func="callee4",args=[],
18588 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18589 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
18595 111^done,frame=@{level="0",func="callee3",
18596 args=[@{name="strarg",
18597 value="0x11940 \"A string argument.\""@}],
18598 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
18599 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
18604 @subheading The @code{-exec-run} Command
18607 @subsubheading Synopsis
18613 Asynchronous command. Starts execution of the inferior from the
18614 beginning. The inferior executes until either a breakpoint is
18615 encountered or the program exits.
18617 @subsubheading @value{GDBN} Command
18619 The corresponding @value{GDBN} command is @samp{run}.
18621 @subsubheading Example
18626 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
18631 *stopped,reason="breakpoint-hit",bkptno="1",
18632 frame=@{func="main",args=[],file="recursive2.c",
18633 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}
18638 @subheading The @code{-exec-show-arguments} Command
18639 @findex -exec-show-arguments
18641 @subsubheading Synopsis
18644 -exec-show-arguments
18647 Print the arguments of the program.
18649 @subsubheading @value{GDBN} Command
18651 The corresponding @value{GDBN} command is @samp{show args}.
18653 @subsubheading Example
18656 @c @subheading -exec-signal
18658 @subheading The @code{-exec-step} Command
18661 @subsubheading Synopsis
18667 Asynchronous command. Resumes execution of the inferior program, stopping
18668 when the beginning of the next source line is reached, if the next
18669 source line is not a function call. If it is, stop at the first
18670 instruction of the called function.
18672 @subsubheading @value{GDBN} Command
18674 The corresponding @value{GDBN} command is @samp{step}.
18676 @subsubheading Example
18678 Stepping into a function:
18684 *stopped,reason="end-stepping-range",
18685 frame=@{func="foo",args=[@{name="a",value="10"@},
18686 @{name="b",value="0"@}],file="recursive2.c",
18687 fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@}
18697 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
18702 @subheading The @code{-exec-step-instruction} Command
18703 @findex -exec-step-instruction
18705 @subsubheading Synopsis
18708 -exec-step-instruction
18711 Asynchronous command. Resumes the inferior which executes one machine
18712 instruction. The output, once @value{GDBN} has stopped, will vary depending on
18713 whether we have stopped in the middle of a source line or not. In the
18714 former case, the address at which the program stopped will be printed as
18717 @subsubheading @value{GDBN} Command
18719 The corresponding @value{GDBN} command is @samp{stepi}.
18721 @subsubheading Example
18725 -exec-step-instruction
18729 *stopped,reason="end-stepping-range",
18730 frame=@{func="foo",args=[],file="try.c",
18731 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18733 -exec-step-instruction
18737 *stopped,reason="end-stepping-range",
18738 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
18739 fullname="/home/foo/bar/devo/myproject/try.c",line="10"@}
18744 @subheading The @code{-exec-until} Command
18745 @findex -exec-until
18747 @subsubheading Synopsis
18750 -exec-until [ @var{location} ]
18753 Asynchronous command. Executes the inferior until the @var{location}
18754 specified in the argument is reached. If there is no argument, the inferior
18755 executes until a source line greater than the current one is reached.
18756 The reason for stopping in this case will be @samp{location-reached}.
18758 @subsubheading @value{GDBN} Command
18760 The corresponding @value{GDBN} command is @samp{until}.
18762 @subsubheading Example
18766 -exec-until recursive2.c:6
18770 *stopped,reason="location-reached",frame=@{func="main",args=[],
18771 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="6"@}
18776 @subheading -file-clear
18777 Is this going away????
18781 @subheading The @code{-file-exec-and-symbols} Command
18782 @findex -file-exec-and-symbols
18784 @subsubheading Synopsis
18787 -file-exec-and-symbols @var{file}
18790 Specify the executable file to be debugged. This file is the one from
18791 which the symbol table is also read. If no file is specified, the
18792 command clears the executable and symbol information. If breakpoints
18793 are set when using this command with no arguments, @value{GDBN} will produce
18794 error messages. Otherwise, no output is produced, except a completion
18797 @subsubheading @value{GDBN} Command
18799 The corresponding @value{GDBN} command is @samp{file}.
18801 @subsubheading Example
18805 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18811 @subheading The @code{-file-exec-file} Command
18812 @findex -file-exec-file
18814 @subsubheading Synopsis
18817 -file-exec-file @var{file}
18820 Specify the executable file to be debugged. Unlike
18821 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
18822 from this file. If used without argument, @value{GDBN} clears the information
18823 about the executable file. No output is produced, except a completion
18826 @subsubheading @value{GDBN} Command
18828 The corresponding @value{GDBN} command is @samp{exec-file}.
18830 @subsubheading Example
18834 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18840 @subheading The @code{-file-list-exec-sections} Command
18841 @findex -file-list-exec-sections
18843 @subsubheading Synopsis
18846 -file-list-exec-sections
18849 List the sections of the current executable file.
18851 @subsubheading @value{GDBN} Command
18853 The @value{GDBN} command @samp{info file} shows, among the rest, the same
18854 information as this command. @code{gdbtk} has a corresponding command
18855 @samp{gdb_load_info}.
18857 @subsubheading Example
18861 @subheading The @code{-file-list-exec-source-file} Command
18862 @findex -file-list-exec-source-file
18864 @subsubheading Synopsis
18867 -file-list-exec-source-file
18870 List the line number, the current source file, and the absolute path
18871 to the current source file for the current executable.
18873 @subsubheading @value{GDBN} Command
18875 There's no @value{GDBN} command which directly corresponds to this one.
18877 @subsubheading Example
18881 123-file-list-exec-source-file
18882 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
18887 @subheading The @code{-file-list-exec-source-files} Command
18888 @findex -file-list-exec-source-files
18890 @subsubheading Synopsis
18893 -file-list-exec-source-files
18896 List the source files for the current executable.
18898 It will always output the filename, but only when GDB can find the absolute
18899 file name of a source file, will it output the fullname.
18901 @subsubheading @value{GDBN} Command
18903 There's no @value{GDBN} command which directly corresponds to this one.
18904 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
18906 @subsubheading Example
18909 -file-list-exec-source-files
18911 @{file=foo.c,fullname=/home/foo.c@},
18912 @{file=/home/bar.c,fullname=/home/bar.c@},
18913 @{file=gdb_could_not_find_fullpath.c@}]
18917 @subheading The @code{-file-list-shared-libraries} Command
18918 @findex -file-list-shared-libraries
18920 @subsubheading Synopsis
18923 -file-list-shared-libraries
18926 List the shared libraries in the program.
18928 @subsubheading @value{GDBN} Command
18930 The corresponding @value{GDBN} command is @samp{info shared}.
18932 @subsubheading Example
18936 @subheading The @code{-file-list-symbol-files} Command
18937 @findex -file-list-symbol-files
18939 @subsubheading Synopsis
18942 -file-list-symbol-files
18947 @subsubheading @value{GDBN} Command
18949 The corresponding @value{GDBN} command is @samp{info file} (part of it).
18951 @subsubheading Example
18955 @subheading The @code{-file-symbol-file} Command
18956 @findex -file-symbol-file
18958 @subsubheading Synopsis
18961 -file-symbol-file @var{file}
18964 Read symbol table info from the specified @var{file} argument. When
18965 used without arguments, clears @value{GDBN}'s symbol table info. No output is
18966 produced, except for a completion notification.
18968 @subsubheading @value{GDBN} Command
18970 The corresponding @value{GDBN} command is @samp{symbol-file}.
18972 @subsubheading Example
18976 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
18981 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
18982 @node GDB/MI Miscellaneous Commands
18983 @section Miscellaneous @value{GDBN} commands in @sc{gdb/mi}
18985 @c @subheading -gdb-complete
18987 @subheading The @code{-gdb-exit} Command
18990 @subsubheading Synopsis
18996 Exit @value{GDBN} immediately.
18998 @subsubheading @value{GDBN} Command
19000 Approximately corresponds to @samp{quit}.
19002 @subsubheading Example
19009 @subheading The @code{-gdb-set} Command
19012 @subsubheading Synopsis
19018 Set an internal @value{GDBN} variable.
19019 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
19021 @subsubheading @value{GDBN} Command
19023 The corresponding @value{GDBN} command is @samp{set}.
19025 @subsubheading Example
19035 @subheading The @code{-gdb-show} Command
19038 @subsubheading Synopsis
19044 Show the current value of a @value{GDBN} variable.
19046 @subsubheading @value{GDBN} command
19048 The corresponding @value{GDBN} command is @samp{show}.
19050 @subsubheading Example
19059 @c @subheading -gdb-source
19062 @subheading The @code{-gdb-version} Command
19063 @findex -gdb-version
19065 @subsubheading Synopsis
19071 Show version information for @value{GDBN}. Used mostly in testing.
19073 @subsubheading @value{GDBN} Command
19075 There's no equivalent @value{GDBN} command. @value{GDBN} by default shows this
19076 information when you start an interactive session.
19078 @subsubheading Example
19080 @c This example modifies the actual output from GDB to avoid overfull
19086 ~Copyright 2000 Free Software Foundation, Inc.
19087 ~GDB is free software, covered by the GNU General Public License, and
19088 ~you are welcome to change it and/or distribute copies of it under
19089 ~ certain conditions.
19090 ~Type "show copying" to see the conditions.
19091 ~There is absolutely no warranty for GDB. Type "show warranty" for
19093 ~This GDB was configured as
19094 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
19099 @subheading The @code{-interpreter-exec} Command
19100 @findex -interpreter-exec
19102 @subheading Synopsis
19105 -interpreter-exec @var{interpreter} @var{command}
19108 Execute the specified @var{command} in the given @var{interpreter}.
19110 @subheading @value{GDBN} Command
19112 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
19114 @subheading Example
19118 -interpreter-exec console "break main"
19119 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
19120 &"During symbol reading, bad structure-type format.\n"
19121 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
19127 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19128 @node GDB/MI Kod Commands
19129 @section @sc{gdb/mi} Kod Commands
19131 The Kod commands are not implemented.
19133 @c @subheading -kod-info
19135 @c @subheading -kod-list
19137 @c @subheading -kod-list-object-types
19139 @c @subheading -kod-show
19141 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19142 @node GDB/MI Memory Overlay Commands
19143 @section @sc{gdb/mi} Memory Overlay Commands
19145 The memory overlay commands are not implemented.
19147 @c @subheading -overlay-auto
19149 @c @subheading -overlay-list-mapping-state
19151 @c @subheading -overlay-list-overlays
19153 @c @subheading -overlay-map
19155 @c @subheading -overlay-off
19157 @c @subheading -overlay-on
19159 @c @subheading -overlay-unmap
19161 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19162 @node GDB/MI Signal Handling Commands
19163 @section @sc{gdb/mi} Signal Handling Commands
19165 Signal handling commands are not implemented.
19167 @c @subheading -signal-handle
19169 @c @subheading -signal-list-handle-actions
19171 @c @subheading -signal-list-signal-types
19175 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19176 @node GDB/MI Stack Manipulation
19177 @section @sc{gdb/mi} Stack Manipulation Commands
19180 @subheading The @code{-stack-info-frame} Command
19181 @findex -stack-info-frame
19183 @subsubheading Synopsis
19189 Get info on the current frame.
19191 @subsubheading @value{GDBN} Command
19193 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
19194 (without arguments).
19196 @subsubheading Example
19199 @subheading The @code{-stack-info-depth} Command
19200 @findex -stack-info-depth
19202 @subsubheading Synopsis
19205 -stack-info-depth [ @var{max-depth} ]
19208 Return the depth of the stack. If the integer argument @var{max-depth}
19209 is specified, do not count beyond @var{max-depth} frames.
19211 @subsubheading @value{GDBN} Command
19213 There's no equivalent @value{GDBN} command.
19215 @subsubheading Example
19217 For a stack with frame levels 0 through 11:
19224 -stack-info-depth 4
19227 -stack-info-depth 12
19230 -stack-info-depth 11
19233 -stack-info-depth 13
19238 @subheading The @code{-stack-list-arguments} Command
19239 @findex -stack-list-arguments
19241 @subsubheading Synopsis
19244 -stack-list-arguments @var{show-values}
19245 [ @var{low-frame} @var{high-frame} ]
19248 Display a list of the arguments for the frames between @var{low-frame}
19249 and @var{high-frame} (inclusive). If @var{low-frame} and
19250 @var{high-frame} are not provided, list the arguments for the whole call
19253 The @var{show-values} argument must have a value of 0 or 1. A value of
19254 0 means that only the names of the arguments are listed, a value of 1
19255 means that both names and values of the arguments are printed.
19257 @subsubheading @value{GDBN} Command
19259 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
19260 @samp{gdb_get_args} command which partially overlaps with the
19261 functionality of @samp{-stack-list-arguments}.
19263 @subsubheading Example
19270 frame=@{level="0",addr="0x00010734",func="callee4",
19271 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19272 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
19273 frame=@{level="1",addr="0x0001076c",func="callee3",
19274 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19275 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
19276 frame=@{level="2",addr="0x0001078c",func="callee2",
19277 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19278 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
19279 frame=@{level="3",addr="0x000107b4",func="callee1",
19280 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19281 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
19282 frame=@{level="4",addr="0x000107e0",func="main",
19283 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
19284 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
19286 -stack-list-arguments 0
19289 frame=@{level="0",args=[]@},
19290 frame=@{level="1",args=[name="strarg"]@},
19291 frame=@{level="2",args=[name="intarg",name="strarg"]@},
19292 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
19293 frame=@{level="4",args=[]@}]
19295 -stack-list-arguments 1
19298 frame=@{level="0",args=[]@},
19300 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19301 frame=@{level="2",args=[
19302 @{name="intarg",value="2"@},
19303 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
19304 @{frame=@{level="3",args=[
19305 @{name="intarg",value="2"@},
19306 @{name="strarg",value="0x11940 \"A string argument.\""@},
19307 @{name="fltarg",value="3.5"@}]@},
19308 frame=@{level="4",args=[]@}]
19310 -stack-list-arguments 0 2 2
19311 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
19313 -stack-list-arguments 1 2 2
19314 ^done,stack-args=[frame=@{level="2",
19315 args=[@{name="intarg",value="2"@},
19316 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
19320 @c @subheading -stack-list-exception-handlers
19323 @subheading The @code{-stack-list-frames} Command
19324 @findex -stack-list-frames
19326 @subsubheading Synopsis
19329 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
19332 List the frames currently on the stack. For each frame it displays the
19337 The frame number, 0 being the topmost frame, i.e. the innermost function.
19339 The @code{$pc} value for that frame.
19343 File name of the source file where the function lives.
19345 Line number corresponding to the @code{$pc}.
19348 If invoked without arguments, this command prints a backtrace for the
19349 whole stack. If given two integer arguments, it shows the frames whose
19350 levels are between the two arguments (inclusive). If the two arguments
19351 are equal, it shows the single frame at the corresponding level.
19353 @subsubheading @value{GDBN} Command
19355 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
19357 @subsubheading Example
19359 Full stack backtrace:
19365 [frame=@{level="0",addr="0x0001076c",func="foo",
19366 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="11"@},
19367 frame=@{level="1",addr="0x000107a4",func="foo",
19368 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19369 frame=@{level="2",addr="0x000107a4",func="foo",
19370 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19371 frame=@{level="3",addr="0x000107a4",func="foo",
19372 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19373 frame=@{level="4",addr="0x000107a4",func="foo",
19374 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19375 frame=@{level="5",addr="0x000107a4",func="foo",
19376 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19377 frame=@{level="6",addr="0x000107a4",func="foo",
19378 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19379 frame=@{level="7",addr="0x000107a4",func="foo",
19380 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19381 frame=@{level="8",addr="0x000107a4",func="foo",
19382 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19383 frame=@{level="9",addr="0x000107a4",func="foo",
19384 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19385 frame=@{level="10",addr="0x000107a4",func="foo",
19386 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19387 frame=@{level="11",addr="0x00010738",func="main",
19388 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="4"@}]
19392 Show frames between @var{low_frame} and @var{high_frame}:
19396 -stack-list-frames 3 5
19398 [frame=@{level="3",addr="0x000107a4",func="foo",
19399 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19400 frame=@{level="4",addr="0x000107a4",func="foo",
19401 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@},
19402 frame=@{level="5",addr="0x000107a4",func="foo",
19403 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19407 Show a single frame:
19411 -stack-list-frames 3 3
19413 [frame=@{level="3",addr="0x000107a4",func="foo",
19414 file="recursive2.c",fullname="/home/foo/bar/devo/myproject/recursive2.c",line="14"@}]
19419 @subheading The @code{-stack-list-locals} Command
19420 @findex -stack-list-locals
19422 @subsubheading Synopsis
19425 -stack-list-locals @var{print-values}
19428 Display the local variable names for the current frame. With an
19429 argument of 0 or @code{--no-values}, prints only the names of the variables.
19430 With argument of 1 or @code{--all-values}, prints also their values. With
19431 argument of 2 or @code{--simple-values}, prints the name, type and value for
19432 simple data types and the name and type for arrays, structures and
19433 unions. In this last case, the idea is that the user can see the
19434 value of simple data types immediately and he can create variable
19435 objects for other data types if he wishes to explore their values in
19438 @subsubheading @value{GDBN} Command
19440 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
19442 @subsubheading Example
19446 -stack-list-locals 0
19447 ^done,locals=[name="A",name="B",name="C"]
19449 -stack-list-locals --all-values
19450 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
19451 @{name="C",value="@{1, 2, 3@}"@}]
19452 -stack-list-locals --simple-values
19453 ^done,locals=[@{name="A",type="int",value="1"@},
19454 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
19459 @subheading The @code{-stack-select-frame} Command
19460 @findex -stack-select-frame
19462 @subsubheading Synopsis
19465 -stack-select-frame @var{framenum}
19468 Change the current frame. Select a different frame @var{framenum} on
19471 @subsubheading @value{GDBN} Command
19473 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
19474 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
19476 @subsubheading Example
19480 -stack-select-frame 2
19485 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19486 @node GDB/MI Symbol Query
19487 @section @sc{gdb/mi} Symbol Query Commands
19490 @subheading The @code{-symbol-info-address} Command
19491 @findex -symbol-info-address
19493 @subsubheading Synopsis
19496 -symbol-info-address @var{symbol}
19499 Describe where @var{symbol} is stored.
19501 @subsubheading @value{GDBN} Command
19503 The corresponding @value{GDBN} command is @samp{info address}.
19505 @subsubheading Example
19509 @subheading The @code{-symbol-info-file} Command
19510 @findex -symbol-info-file
19512 @subsubheading Synopsis
19518 Show the file for the symbol.
19520 @subsubheading @value{GDBN} Command
19522 There's no equivalent @value{GDBN} command. @code{gdbtk} has
19523 @samp{gdb_find_file}.
19525 @subsubheading Example
19529 @subheading The @code{-symbol-info-function} Command
19530 @findex -symbol-info-function
19532 @subsubheading Synopsis
19535 -symbol-info-function
19538 Show which function the symbol lives in.
19540 @subsubheading @value{GDBN} Command
19542 @samp{gdb_get_function} in @code{gdbtk}.
19544 @subsubheading Example
19548 @subheading The @code{-symbol-info-line} Command
19549 @findex -symbol-info-line
19551 @subsubheading Synopsis
19557 Show the core addresses of the code for a source line.
19559 @subsubheading @value{GDBN} Command
19561 The corresponding @value{GDBN} command is @samp{info line}.
19562 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
19564 @subsubheading Example
19568 @subheading The @code{-symbol-info-symbol} Command
19569 @findex -symbol-info-symbol
19571 @subsubheading Synopsis
19574 -symbol-info-symbol @var{addr}
19577 Describe what symbol is at location @var{addr}.
19579 @subsubheading @value{GDBN} Command
19581 The corresponding @value{GDBN} command is @samp{info symbol}.
19583 @subsubheading Example
19587 @subheading The @code{-symbol-list-functions} Command
19588 @findex -symbol-list-functions
19590 @subsubheading Synopsis
19593 -symbol-list-functions
19596 List the functions in the executable.
19598 @subsubheading @value{GDBN} Command
19600 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
19601 @samp{gdb_search} in @code{gdbtk}.
19603 @subsubheading Example
19607 @subheading The @code{-symbol-list-lines} Command
19608 @findex -symbol-list-lines
19610 @subsubheading Synopsis
19613 -symbol-list-lines @var{filename}
19616 Print the list of lines that contain code and their associated program
19617 addresses for the given source filename. The entries are sorted in
19618 ascending PC order.
19620 @subsubheading @value{GDBN} Command
19622 There is no corresponding @value{GDBN} command.
19624 @subsubheading Example
19627 -symbol-list-lines basics.c
19628 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
19633 @subheading The @code{-symbol-list-types} Command
19634 @findex -symbol-list-types
19636 @subsubheading Synopsis
19642 List all the type names.
19644 @subsubheading @value{GDBN} Command
19646 The corresponding commands are @samp{info types} in @value{GDBN},
19647 @samp{gdb_search} in @code{gdbtk}.
19649 @subsubheading Example
19653 @subheading The @code{-symbol-list-variables} Command
19654 @findex -symbol-list-variables
19656 @subsubheading Synopsis
19659 -symbol-list-variables
19662 List all the global and static variable names.
19664 @subsubheading @value{GDBN} Command
19666 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
19668 @subsubheading Example
19672 @subheading The @code{-symbol-locate} Command
19673 @findex -symbol-locate
19675 @subsubheading Synopsis
19681 @subsubheading @value{GDBN} Command
19683 @samp{gdb_loc} in @code{gdbtk}.
19685 @subsubheading Example
19689 @subheading The @code{-symbol-type} Command
19690 @findex -symbol-type
19692 @subsubheading Synopsis
19695 -symbol-type @var{variable}
19698 Show type of @var{variable}.
19700 @subsubheading @value{GDBN} Command
19702 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
19703 @samp{gdb_obj_variable}.
19705 @subsubheading Example
19709 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
19710 @node GDB/MI Target Manipulation
19711 @section @sc{gdb/mi} Target Manipulation Commands
19714 @subheading The @code{-target-attach} Command
19715 @findex -target-attach
19717 @subsubheading Synopsis
19720 -target-attach @var{pid} | @var{file}
19723 Attach to a process @var{pid} or a file @var{file} outside of @value{GDBN}.
19725 @subsubheading @value{GDBN} command
19727 The corresponding @value{GDBN} command is @samp{attach}.
19729 @subsubheading Example
19733 @subheading The @code{-target-compare-sections} Command
19734 @findex -target-compare-sections
19736 @subsubheading Synopsis
19739 -target-compare-sections [ @var{section} ]
19742 Compare data of section @var{section} on target to the exec file.
19743 Without the argument, all sections are compared.
19745 @subsubheading @value{GDBN} Command
19747 The @value{GDBN} equivalent is @samp{compare-sections}.
19749 @subsubheading Example
19753 @subheading The @code{-target-detach} Command
19754 @findex -target-detach
19756 @subsubheading Synopsis
19762 Disconnect from the remote target. There's no output.
19764 @subsubheading @value{GDBN} command
19766 The corresponding @value{GDBN} command is @samp{detach}.
19768 @subsubheading Example
19778 @subheading The @code{-target-disconnect} Command
19779 @findex -target-disconnect
19781 @subsubheading Synopsis
19787 Disconnect from the remote target. There's no output.
19789 @subsubheading @value{GDBN} command
19791 The corresponding @value{GDBN} command is @samp{disconnect}.
19793 @subsubheading Example
19803 @subheading The @code{-target-download} Command
19804 @findex -target-download
19806 @subsubheading Synopsis
19812 Loads the executable onto the remote target.
19813 It prints out an update message every half second, which includes the fields:
19817 The name of the section.
19819 The size of what has been sent so far for that section.
19821 The size of the section.
19823 The total size of what was sent so far (the current and the previous sections).
19825 The size of the overall executable to download.
19829 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
19830 @sc{gdb/mi} Output Syntax}).
19832 In addition, it prints the name and size of the sections, as they are
19833 downloaded. These messages include the following fields:
19837 The name of the section.
19839 The size of the section.
19841 The size of the overall executable to download.
19845 At the end, a summary is printed.
19847 @subsubheading @value{GDBN} Command
19849 The corresponding @value{GDBN} command is @samp{load}.
19851 @subsubheading Example
19853 Note: each status message appears on a single line. Here the messages
19854 have been broken down so that they can fit onto a page.
19859 +download,@{section=".text",section-size="6668",total-size="9880"@}
19860 +download,@{section=".text",section-sent="512",section-size="6668",
19861 total-sent="512",total-size="9880"@}
19862 +download,@{section=".text",section-sent="1024",section-size="6668",
19863 total-sent="1024",total-size="9880"@}
19864 +download,@{section=".text",section-sent="1536",section-size="6668",
19865 total-sent="1536",total-size="9880"@}
19866 +download,@{section=".text",section-sent="2048",section-size="6668",
19867 total-sent="2048",total-size="9880"@}
19868 +download,@{section=".text",section-sent="2560",section-size="6668",
19869 total-sent="2560",total-size="9880"@}
19870 +download,@{section=".text",section-sent="3072",section-size="6668",
19871 total-sent="3072",total-size="9880"@}
19872 +download,@{section=".text",section-sent="3584",section-size="6668",
19873 total-sent="3584",total-size="9880"@}
19874 +download,@{section=".text",section-sent="4096",section-size="6668",
19875 total-sent="4096",total-size="9880"@}
19876 +download,@{section=".text",section-sent="4608",section-size="6668",
19877 total-sent="4608",total-size="9880"@}
19878 +download,@{section=".text",section-sent="5120",section-size="6668",
19879 total-sent="5120",total-size="9880"@}
19880 +download,@{section=".text",section-sent="5632",section-size="6668",
19881 total-sent="5632",total-size="9880"@}
19882 +download,@{section=".text",section-sent="6144",section-size="6668",
19883 total-sent="6144",total-size="9880"@}
19884 +download,@{section=".text",section-sent="6656",section-size="6668",
19885 total-sent="6656",total-size="9880"@}
19886 +download,@{section=".init",section-size="28",total-size="9880"@}
19887 +download,@{section=".fini",section-size="28",total-size="9880"@}
19888 +download,@{section=".data",section-size="3156",total-size="9880"@}
19889 +download,@{section=".data",section-sent="512",section-size="3156",
19890 total-sent="7236",total-size="9880"@}
19891 +download,@{section=".data",section-sent="1024",section-size="3156",
19892 total-sent="7748",total-size="9880"@}
19893 +download,@{section=".data",section-sent="1536",section-size="3156",
19894 total-sent="8260",total-size="9880"@}
19895 +download,@{section=".data",section-sent="2048",section-size="3156",
19896 total-sent="8772",total-size="9880"@}
19897 +download,@{section=".data",section-sent="2560",section-size="3156",
19898 total-sent="9284",total-size="9880"@}
19899 +download,@{section=".data",section-sent="3072",section-size="3156",
19900 total-sent="9796",total-size="9880"@}
19901 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
19907 @subheading The @code{-target-exec-status} Command
19908 @findex -target-exec-status
19910 @subsubheading Synopsis
19913 -target-exec-status
19916 Provide information on the state of the target (whether it is running or
19917 not, for instance).
19919 @subsubheading @value{GDBN} Command
19921 There's no equivalent @value{GDBN} command.
19923 @subsubheading Example
19927 @subheading The @code{-target-list-available-targets} Command
19928 @findex -target-list-available-targets
19930 @subsubheading Synopsis
19933 -target-list-available-targets
19936 List the possible targets to connect to.
19938 @subsubheading @value{GDBN} Command
19940 The corresponding @value{GDBN} command is @samp{help target}.
19942 @subsubheading Example
19946 @subheading The @code{-target-list-current-targets} Command
19947 @findex -target-list-current-targets
19949 @subsubheading Synopsis
19952 -target-list-current-targets
19955 Describe the current target.
19957 @subsubheading @value{GDBN} Command
19959 The corresponding information is printed by @samp{info file} (among
19962 @subsubheading Example
19966 @subheading The @code{-target-list-parameters} Command
19967 @findex -target-list-parameters
19969 @subsubheading Synopsis
19972 -target-list-parameters
19977 @subsubheading @value{GDBN} Command
19981 @subsubheading Example
19985 @subheading The @code{-target-select} Command
19986 @findex -target-select
19988 @subsubheading Synopsis
19991 -target-select @var{type} @var{parameters @dots{}}
19994 Connect @value{GDBN} to the remote target. This command takes two args:
19998 The type of target, for instance @samp{async}, @samp{remote}, etc.
19999 @item @var{parameters}
20000 Device names, host names and the like. @xref{Target Commands, ,
20001 Commands for managing targets}, for more details.
20004 The output is a connection notification, followed by the address at
20005 which the target program is, in the following form:
20008 ^connected,addr="@var{address}",func="@var{function name}",
20009 args=[@var{arg list}]
20012 @subsubheading @value{GDBN} Command
20014 The corresponding @value{GDBN} command is @samp{target}.
20016 @subsubheading Example
20020 -target-select async /dev/ttya
20021 ^connected,addr="0xfe00a300",func="??",args=[]
20025 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20026 @node GDB/MI Thread Commands
20027 @section @sc{gdb/mi} Thread Commands
20030 @subheading The @code{-thread-info} Command
20031 @findex -thread-info
20033 @subsubheading Synopsis
20039 @subsubheading @value{GDBN} command
20043 @subsubheading Example
20047 @subheading The @code{-thread-list-all-threads} Command
20048 @findex -thread-list-all-threads
20050 @subsubheading Synopsis
20053 -thread-list-all-threads
20056 @subsubheading @value{GDBN} Command
20058 The equivalent @value{GDBN} command is @samp{info threads}.
20060 @subsubheading Example
20064 @subheading The @code{-thread-list-ids} Command
20065 @findex -thread-list-ids
20067 @subsubheading Synopsis
20073 Produces a list of the currently known @value{GDBN} thread ids. At the
20074 end of the list it also prints the total number of such threads.
20076 @subsubheading @value{GDBN} Command
20078 Part of @samp{info threads} supplies the same information.
20080 @subsubheading Example
20082 No threads present, besides the main process:
20087 ^done,thread-ids=@{@},number-of-threads="0"
20097 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20098 number-of-threads="3"
20103 @subheading The @code{-thread-select} Command
20104 @findex -thread-select
20106 @subsubheading Synopsis
20109 -thread-select @var{threadnum}
20112 Make @var{threadnum} the current thread. It prints the number of the new
20113 current thread, and the topmost frame for that thread.
20115 @subsubheading @value{GDBN} Command
20117 The corresponding @value{GDBN} command is @samp{thread}.
20119 @subsubheading Example
20126 *stopped,reason="end-stepping-range",thread-id="2",line="187",
20127 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
20131 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
20132 number-of-threads="3"
20135 ^done,new-thread-id="3",
20136 frame=@{level="0",func="vprintf",
20137 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
20138 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
20142 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20143 @node GDB/MI Tracepoint Commands
20144 @section @sc{gdb/mi} Tracepoint Commands
20146 The tracepoint commands are not yet implemented.
20148 @c @subheading -trace-actions
20150 @c @subheading -trace-delete
20152 @c @subheading -trace-disable
20154 @c @subheading -trace-dump
20156 @c @subheading -trace-enable
20158 @c @subheading -trace-exists
20160 @c @subheading -trace-find
20162 @c @subheading -trace-frame-number
20164 @c @subheading -trace-info
20166 @c @subheading -trace-insert
20168 @c @subheading -trace-list
20170 @c @subheading -trace-pass-count
20172 @c @subheading -trace-save
20174 @c @subheading -trace-start
20176 @c @subheading -trace-stop
20179 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
20180 @node GDB/MI Variable Objects
20181 @section @sc{gdb/mi} Variable Objects
20184 @subheading Motivation for Variable Objects in @sc{gdb/mi}
20186 For the implementation of a variable debugger window (locals, watched
20187 expressions, etc.), we are proposing the adaptation of the existing code
20188 used by @code{Insight}.
20190 The two main reasons for that are:
20194 It has been proven in practice (it is already on its second generation).
20197 It will shorten development time (needless to say how important it is
20201 The original interface was designed to be used by Tcl code, so it was
20202 slightly changed so it could be used through @sc{gdb/mi}. This section
20203 describes the @sc{gdb/mi} operations that will be available and gives some
20204 hints about their use.
20206 @emph{Note}: In addition to the set of operations described here, we
20207 expect the @sc{gui} implementation of a variable window to require, at
20208 least, the following operations:
20211 @item @code{-gdb-show} @code{output-radix}
20212 @item @code{-stack-list-arguments}
20213 @item @code{-stack-list-locals}
20214 @item @code{-stack-select-frame}
20217 @subheading Introduction to Variable Objects in @sc{gdb/mi}
20219 @cindex variable objects in @sc{gdb/mi}
20220 The basic idea behind variable objects is the creation of a named object
20221 to represent a variable, an expression, a memory location or even a CPU
20222 register. For each object created, a set of operations is available for
20223 examining or changing its properties.
20225 Furthermore, complex data types, such as C structures, are represented
20226 in a tree format. For instance, the @code{struct} type variable is the
20227 root and the children will represent the struct members. If a child
20228 is itself of a complex type, it will also have children of its own.
20229 Appropriate language differences are handled for C, C@t{++} and Java.
20231 When returning the actual values of the objects, this facility allows
20232 for the individual selection of the display format used in the result
20233 creation. It can be chosen among: binary, decimal, hexadecimal, octal
20234 and natural. Natural refers to a default format automatically
20235 chosen based on the variable type (like decimal for an @code{int}, hex
20236 for pointers, etc.).
20238 The following is the complete set of @sc{gdb/mi} operations defined to
20239 access this functionality:
20241 @multitable @columnfractions .4 .6
20242 @item @strong{Operation}
20243 @tab @strong{Description}
20245 @item @code{-var-create}
20246 @tab create a variable object
20247 @item @code{-var-delete}
20248 @tab delete the variable object and its children
20249 @item @code{-var-set-format}
20250 @tab set the display format of this variable
20251 @item @code{-var-show-format}
20252 @tab show the display format of this variable
20253 @item @code{-var-info-num-children}
20254 @tab tells how many children this object has
20255 @item @code{-var-list-children}
20256 @tab return a list of the object's children
20257 @item @code{-var-info-type}
20258 @tab show the type of this variable object
20259 @item @code{-var-info-expression}
20260 @tab print what this variable object represents
20261 @item @code{-var-show-attributes}
20262 @tab is this variable editable? does it exist here?
20263 @item @code{-var-evaluate-expression}
20264 @tab get the value of this variable
20265 @item @code{-var-assign}
20266 @tab set the value of this variable
20267 @item @code{-var-update}
20268 @tab update the variable and its children
20271 In the next subsection we describe each operation in detail and suggest
20272 how it can be used.
20274 @subheading Description And Use of Operations on Variable Objects
20276 @subheading The @code{-var-create} Command
20277 @findex -var-create
20279 @subsubheading Synopsis
20282 -var-create @{@var{name} | "-"@}
20283 @{@var{frame-addr} | "*"@} @var{expression}
20286 This operation creates a variable object, which allows the monitoring of
20287 a variable, the result of an expression, a memory cell or a CPU
20290 The @var{name} parameter is the string by which the object can be
20291 referenced. It must be unique. If @samp{-} is specified, the varobj
20292 system will generate a string ``varNNNNNN'' automatically. It will be
20293 unique provided that one does not specify @var{name} on that format.
20294 The command fails if a duplicate name is found.
20296 The frame under which the expression should be evaluated can be
20297 specified by @var{frame-addr}. A @samp{*} indicates that the current
20298 frame should be used.
20300 @var{expression} is any expression valid on the current language set (must not
20301 begin with a @samp{*}), or one of the following:
20305 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
20308 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
20311 @samp{$@var{regname}} --- a CPU register name
20314 @subsubheading Result
20316 This operation returns the name, number of children and the type of the
20317 object created. Type is returned as a string as the ones generated by
20318 the @value{GDBN} CLI:
20321 name="@var{name}",numchild="N",type="@var{type}"
20325 @subheading The @code{-var-delete} Command
20326 @findex -var-delete
20328 @subsubheading Synopsis
20331 -var-delete @var{name}
20334 Deletes a previously created variable object and all of its children.
20336 Returns an error if the object @var{name} is not found.
20339 @subheading The @code{-var-set-format} Command
20340 @findex -var-set-format
20342 @subsubheading Synopsis
20345 -var-set-format @var{name} @var{format-spec}
20348 Sets the output format for the value of the object @var{name} to be
20351 The syntax for the @var{format-spec} is as follows:
20354 @var{format-spec} @expansion{}
20355 @{binary | decimal | hexadecimal | octal | natural@}
20359 @subheading The @code{-var-show-format} Command
20360 @findex -var-show-format
20362 @subsubheading Synopsis
20365 -var-show-format @var{name}
20368 Returns the format used to display the value of the object @var{name}.
20371 @var{format} @expansion{}
20376 @subheading The @code{-var-info-num-children} Command
20377 @findex -var-info-num-children
20379 @subsubheading Synopsis
20382 -var-info-num-children @var{name}
20385 Returns the number of children of a variable object @var{name}:
20392 @subheading The @code{-var-list-children} Command
20393 @findex -var-list-children
20395 @subsubheading Synopsis
20398 -var-list-children [@var{print-values}] @var{name}
20401 Returns a list of the children of the specified variable object. With
20402 just the variable object name as an argument or with an optional
20403 preceding argument of 0 or @code{--no-values}, prints only the names of the
20404 variables. With an optional preceding argument of 1 or @code{--all-values},
20405 also prints their values.
20407 @subsubheading Example
20411 -var-list-children n
20412 numchild=@var{n},children=[@{name=@var{name},
20413 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
20415 -var-list-children --all-values n
20416 numchild=@var{n},children=[@{name=@var{name},
20417 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
20421 @subheading The @code{-var-info-type} Command
20422 @findex -var-info-type
20424 @subsubheading Synopsis
20427 -var-info-type @var{name}
20430 Returns the type of the specified variable @var{name}. The type is
20431 returned as a string in the same format as it is output by the
20435 type=@var{typename}
20439 @subheading The @code{-var-info-expression} Command
20440 @findex -var-info-expression
20442 @subsubheading Synopsis
20445 -var-info-expression @var{name}
20448 Returns what is represented by the variable object @var{name}:
20451 lang=@var{lang-spec},exp=@var{expression}
20455 where @var{lang-spec} is @code{@{"C" | "C++" | "Java"@}}.
20457 @subheading The @code{-var-show-attributes} Command
20458 @findex -var-show-attributes
20460 @subsubheading Synopsis
20463 -var-show-attributes @var{name}
20466 List attributes of the specified variable object @var{name}:
20469 status=@var{attr} [ ( ,@var{attr} )* ]
20473 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
20475 @subheading The @code{-var-evaluate-expression} Command
20476 @findex -var-evaluate-expression
20478 @subsubheading Synopsis
20481 -var-evaluate-expression @var{name}
20484 Evaluates the expression that is represented by the specified variable
20485 object and returns its value as a string in the current format specified
20492 Note that one must invoke @code{-var-list-children} for a variable
20493 before the value of a child variable can be evaluated.
20495 @subheading The @code{-var-assign} Command
20496 @findex -var-assign
20498 @subsubheading Synopsis
20501 -var-assign @var{name} @var{expression}
20504 Assigns the value of @var{expression} to the variable object specified
20505 by @var{name}. The object must be @samp{editable}. If the variable's
20506 value is altered by the assign, the variable will show up in any
20507 subsequent @code{-var-update} list.
20509 @subsubheading Example
20517 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
20521 @subheading The @code{-var-update} Command
20522 @findex -var-update
20524 @subsubheading Synopsis
20527 -var-update @{@var{name} | "*"@}
20530 Update the value of the variable object @var{name} by evaluating its
20531 expression after fetching all the new values from memory or registers.
20532 A @samp{*} causes all existing variable objects to be updated.
20536 @chapter @value{GDBN} Annotations
20538 This chapter describes annotations in @value{GDBN}. Annotations were
20539 designed to interface @value{GDBN} to graphical user interfaces or other
20540 similar programs which want to interact with @value{GDBN} at a
20541 relatively high level.
20543 The annotation mechanism has largely been superseeded by @sc{gdb/mi}
20547 This is Edition @value{EDITION}, @value{DATE}.
20551 * Annotations Overview:: What annotations are; the general syntax.
20552 * Server Prefix:: Issuing a command without affecting user state.
20553 * Prompting:: Annotations marking @value{GDBN}'s need for input.
20554 * Errors:: Annotations for error messages.
20555 * Invalidation:: Some annotations describe things now invalid.
20556 * Annotations for Running::
20557 Whether the program is running, how it stopped, etc.
20558 * Source Annotations:: Annotations describing source code.
20561 @node Annotations Overview
20562 @section What is an Annotation?
20563 @cindex annotations
20565 Annotations start with a newline character, two @samp{control-z}
20566 characters, and the name of the annotation. If there is no additional
20567 information associated with this annotation, the name of the annotation
20568 is followed immediately by a newline. If there is additional
20569 information, the name of the annotation is followed by a space, the
20570 additional information, and a newline. The additional information
20571 cannot contain newline characters.
20573 Any output not beginning with a newline and two @samp{control-z}
20574 characters denotes literal output from @value{GDBN}. Currently there is
20575 no need for @value{GDBN} to output a newline followed by two
20576 @samp{control-z} characters, but if there was such a need, the
20577 annotations could be extended with an @samp{escape} annotation which
20578 means those three characters as output.
20580 The annotation @var{level}, which is specified using the
20581 @option{--annotate} command line option (@pxref{Mode Options}), controls
20582 how much information @value{GDBN} prints together with its prompt,
20583 values of expressions, source lines, and other types of output. Level 0
20584 is for no anntations, level 1 is for use when @value{GDBN} is run as a
20585 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
20586 for programs that control @value{GDBN}, and level 2 annotations have
20587 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
20588 Interface, annotate, GDB's Obsolete Annotations}).
20591 @kindex set annotate
20592 @item set annotate @var{level}
20593 The @value{GDB} command @code{set annotate} sets the level of
20594 annotations to the specified @var{level}.
20596 @item show annotate
20597 @kindex show annotate
20598 Show the current annotation level.
20601 This chapter describes level 3 annotations.
20603 A simple example of starting up @value{GDBN} with annotations is:
20606 $ @kbd{gdb --annotate=3}
20608 Copyright 2003 Free Software Foundation, Inc.
20609 GDB is free software, covered by the GNU General Public License,
20610 and you are welcome to change it and/or distribute copies of it
20611 under certain conditions.
20612 Type "show copying" to see the conditions.
20613 There is absolutely no warranty for GDB. Type "show warranty"
20615 This GDB was configured as "i386-pc-linux-gnu"
20626 Here @samp{quit} is input to @value{GDBN}; the rest is output from
20627 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
20628 denotes a @samp{control-z} character) are annotations; the rest is
20629 output from @value{GDBN}.
20631 @node Server Prefix
20632 @section The Server Prefix
20633 @cindex server prefix for annotations
20635 To issue a command to @value{GDBN} without affecting certain aspects of
20636 the state which is seen by users, prefix it with @samp{server }. This
20637 means that this command will not affect the command history, nor will it
20638 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
20639 pressed on a line by itself.
20641 The server prefix does not affect the recording of values into the value
20642 history; to print a value without recording it into the value history,
20643 use the @code{output} command instead of the @code{print} command.
20646 @section Annotation for @value{GDBN} Input
20648 @cindex annotations for prompts
20649 When @value{GDBN} prompts for input, it annotates this fact so it is possible
20650 to know when to send output, when the output from a given command is
20653 Different kinds of input each have a different @dfn{input type}. Each
20654 input type has three annotations: a @code{pre-} annotation, which
20655 denotes the beginning of any prompt which is being output, a plain
20656 annotation, which denotes the end of the prompt, and then a @code{post-}
20657 annotation which denotes the end of any echo which may (or may not) be
20658 associated with the input. For example, the @code{prompt} input type
20659 features the following annotations:
20667 The input types are
20672 @findex post-prompt
20674 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
20676 @findex pre-commands
20678 @findex post-commands
20680 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
20681 command. The annotations are repeated for each command which is input.
20683 @findex pre-overload-choice
20684 @findex overload-choice
20685 @findex post-overload-choice
20686 @item overload-choice
20687 When @value{GDBN} wants the user to select between various overloaded functions.
20693 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
20695 @findex pre-prompt-for-continue
20696 @findex prompt-for-continue
20697 @findex post-prompt-for-continue
20698 @item prompt-for-continue
20699 When @value{GDBN} is asking the user to press return to continue. Note: Don't
20700 expect this to work well; instead use @code{set height 0} to disable
20701 prompting. This is because the counting of lines is buggy in the
20702 presence of annotations.
20707 @cindex annotations for errors, warnings and interrupts
20714 This annotation occurs right before @value{GDBN} responds to an interrupt.
20721 This annotation occurs right before @value{GDBN} responds to an error.
20723 Quit and error annotations indicate that any annotations which @value{GDBN} was
20724 in the middle of may end abruptly. For example, if a
20725 @code{value-history-begin} annotation is followed by a @code{error}, one
20726 cannot expect to receive the matching @code{value-history-end}. One
20727 cannot expect not to receive it either, however; an error annotation
20728 does not necessarily mean that @value{GDBN} is immediately returning all the way
20731 @findex error-begin
20732 A quit or error annotation may be preceded by
20738 Any output between that and the quit or error annotation is the error
20741 Warning messages are not yet annotated.
20742 @c If we want to change that, need to fix warning(), type_error(),
20743 @c range_error(), and possibly other places.
20746 @section Invalidation Notices
20748 @cindex annotations for invalidation messages
20749 The following annotations say that certain pieces of state may have
20753 @findex frames-invalid
20754 @item ^Z^Zframes-invalid
20756 The frames (for example, output from the @code{backtrace} command) may
20759 @findex breakpoints-invalid
20760 @item ^Z^Zbreakpoints-invalid
20762 The breakpoints may have changed. For example, the user just added or
20763 deleted a breakpoint.
20766 @node Annotations for Running
20767 @section Running the Program
20768 @cindex annotations for running programs
20772 When the program starts executing due to a @value{GDBN} command such as
20773 @code{step} or @code{continue},
20779 is output. When the program stops,
20785 is output. Before the @code{stopped} annotation, a variety of
20786 annotations describe how the program stopped.
20790 @item ^Z^Zexited @var{exit-status}
20791 The program exited, and @var{exit-status} is the exit status (zero for
20792 successful exit, otherwise nonzero).
20795 @findex signal-name
20796 @findex signal-name-end
20797 @findex signal-string
20798 @findex signal-string-end
20799 @item ^Z^Zsignalled
20800 The program exited with a signal. After the @code{^Z^Zsignalled}, the
20801 annotation continues:
20807 ^Z^Zsignal-name-end
20811 ^Z^Zsignal-string-end
20816 where @var{name} is the name of the signal, such as @code{SIGILL} or
20817 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
20818 as @code{Illegal Instruction} or @code{Segmentation fault}.
20819 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
20820 user's benefit and have no particular format.
20824 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
20825 just saying that the program received the signal, not that it was
20826 terminated with it.
20829 @item ^Z^Zbreakpoint @var{number}
20830 The program hit breakpoint number @var{number}.
20833 @item ^Z^Zwatchpoint @var{number}
20834 The program hit watchpoint number @var{number}.
20837 @node Source Annotations
20838 @section Displaying Source
20839 @cindex annotations for source display
20842 The following annotation is used instead of displaying source code:
20845 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
20848 where @var{filename} is an absolute file name indicating which source
20849 file, @var{line} is the line number within that file (where 1 is the
20850 first line in the file), @var{character} is the character position
20851 within the file (where 0 is the first character in the file) (for most
20852 debug formats this will necessarily point to the beginning of a line),
20853 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
20854 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
20855 @var{addr} is the address in the target program associated with the
20856 source which is being displayed. @var{addr} is in the form @samp{0x}
20857 followed by one or more lowercase hex digits (note that this does not
20858 depend on the language).
20861 @chapter Reporting Bugs in @value{GDBN}
20862 @cindex bugs in @value{GDBN}
20863 @cindex reporting bugs in @value{GDBN}
20865 Your bug reports play an essential role in making @value{GDBN} reliable.
20867 Reporting a bug may help you by bringing a solution to your problem, or it
20868 may not. But in any case the principal function of a bug report is to help
20869 the entire community by making the next version of @value{GDBN} work better. Bug
20870 reports are your contribution to the maintenance of @value{GDBN}.
20872 In order for a bug report to serve its purpose, you must include the
20873 information that enables us to fix the bug.
20876 * Bug Criteria:: Have you found a bug?
20877 * Bug Reporting:: How to report bugs
20881 @section Have you found a bug?
20882 @cindex bug criteria
20884 If you are not sure whether you have found a bug, here are some guidelines:
20887 @cindex fatal signal
20888 @cindex debugger crash
20889 @cindex crash of debugger
20891 If the debugger gets a fatal signal, for any input whatever, that is a
20892 @value{GDBN} bug. Reliable debuggers never crash.
20894 @cindex error on valid input
20896 If @value{GDBN} produces an error message for valid input, that is a
20897 bug. (Note that if you're cross debugging, the problem may also be
20898 somewhere in the connection to the target.)
20900 @cindex invalid input
20902 If @value{GDBN} does not produce an error message for invalid input,
20903 that is a bug. However, you should note that your idea of
20904 ``invalid input'' might be our idea of ``an extension'' or ``support
20905 for traditional practice''.
20908 If you are an experienced user of debugging tools, your suggestions
20909 for improvement of @value{GDBN} are welcome in any case.
20912 @node Bug Reporting
20913 @section How to report bugs
20914 @cindex bug reports
20915 @cindex @value{GDBN} bugs, reporting
20917 A number of companies and individuals offer support for @sc{gnu} products.
20918 If you obtained @value{GDBN} from a support organization, we recommend you
20919 contact that organization first.
20921 You can find contact information for many support companies and
20922 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
20924 @c should add a web page ref...
20926 In any event, we also recommend that you submit bug reports for
20927 @value{GDBN}. The prefered method is to submit them directly using
20928 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
20929 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
20932 @strong{Do not send bug reports to @samp{info-gdb}, or to
20933 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
20934 not want to receive bug reports. Those that do have arranged to receive
20937 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
20938 serves as a repeater. The mailing list and the newsgroup carry exactly
20939 the same messages. Often people think of posting bug reports to the
20940 newsgroup instead of mailing them. This appears to work, but it has one
20941 problem which can be crucial: a newsgroup posting often lacks a mail
20942 path back to the sender. Thus, if we need to ask for more information,
20943 we may be unable to reach you. For this reason, it is better to send
20944 bug reports to the mailing list.
20946 The fundamental principle of reporting bugs usefully is this:
20947 @strong{report all the facts}. If you are not sure whether to state a
20948 fact or leave it out, state it!
20950 Often people omit facts because they think they know what causes the
20951 problem and assume that some details do not matter. Thus, you might
20952 assume that the name of the variable you use in an example does not matter.
20953 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
20954 stray memory reference which happens to fetch from the location where that
20955 name is stored in memory; perhaps, if the name were different, the contents
20956 of that location would fool the debugger into doing the right thing despite
20957 the bug. Play it safe and give a specific, complete example. That is the
20958 easiest thing for you to do, and the most helpful.
20960 Keep in mind that the purpose of a bug report is to enable us to fix the
20961 bug. It may be that the bug has been reported previously, but neither
20962 you nor we can know that unless your bug report is complete and
20965 Sometimes people give a few sketchy facts and ask, ``Does this ring a
20966 bell?'' Those bug reports are useless, and we urge everyone to
20967 @emph{refuse to respond to them} except to chide the sender to report
20970 To enable us to fix the bug, you should include all these things:
20974 The version of @value{GDBN}. @value{GDBN} announces it if you start
20975 with no arguments; you can also print it at any time using @code{show
20978 Without this, we will not know whether there is any point in looking for
20979 the bug in the current version of @value{GDBN}.
20982 The type of machine you are using, and the operating system name and
20986 What compiler (and its version) was used to compile @value{GDBN}---e.g.
20987 ``@value{GCC}--2.8.1''.
20990 What compiler (and its version) was used to compile the program you are
20991 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
20992 C Compiler''. For GCC, you can say @code{gcc --version} to get this
20993 information; for other compilers, see the documentation for those
20997 The command arguments you gave the compiler to compile your example and
20998 observe the bug. For example, did you use @samp{-O}? To guarantee
20999 you will not omit something important, list them all. A copy of the
21000 Makefile (or the output from make) is sufficient.
21002 If we were to try to guess the arguments, we would probably guess wrong
21003 and then we might not encounter the bug.
21006 A complete input script, and all necessary source files, that will
21010 A description of what behavior you observe that you believe is
21011 incorrect. For example, ``It gets a fatal signal.''
21013 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
21014 will certainly notice it. But if the bug is incorrect output, we might
21015 not notice unless it is glaringly wrong. You might as well not give us
21016 a chance to make a mistake.
21018 Even if the problem you experience is a fatal signal, you should still
21019 say so explicitly. Suppose something strange is going on, such as, your
21020 copy of @value{GDBN} is out of synch, or you have encountered a bug in
21021 the C library on your system. (This has happened!) Your copy might
21022 crash and ours would not. If you told us to expect a crash, then when
21023 ours fails to crash, we would know that the bug was not happening for
21024 us. If you had not told us to expect a crash, then we would not be able
21025 to draw any conclusion from our observations.
21028 @cindex recording a session script
21029 To collect all this information, you can use a session recording program
21030 such as @command{script}, which is available on many Unix systems.
21031 Just run your @value{GDBN} session inside @command{script} and then
21032 include the @file{typescript} file with your bug report.
21034 Another way to record a @value{GDBN} session is to run @value{GDBN}
21035 inside Emacs and then save the entire buffer to a file.
21038 If you wish to suggest changes to the @value{GDBN} source, send us context
21039 diffs. If you even discuss something in the @value{GDBN} source, refer to
21040 it by context, not by line number.
21042 The line numbers in our development sources will not match those in your
21043 sources. Your line numbers would convey no useful information to us.
21047 Here are some things that are not necessary:
21051 A description of the envelope of the bug.
21053 Often people who encounter a bug spend a lot of time investigating
21054 which changes to the input file will make the bug go away and which
21055 changes will not affect it.
21057 This is often time consuming and not very useful, because the way we
21058 will find the bug is by running a single example under the debugger
21059 with breakpoints, not by pure deduction from a series of examples.
21060 We recommend that you save your time for something else.
21062 Of course, if you can find a simpler example to report @emph{instead}
21063 of the original one, that is a convenience for us. Errors in the
21064 output will be easier to spot, running under the debugger will take
21065 less time, and so on.
21067 However, simplification is not vital; if you do not want to do this,
21068 report the bug anyway and send us the entire test case you used.
21071 A patch for the bug.
21073 A patch for the bug does help us if it is a good one. But do not omit
21074 the necessary information, such as the test case, on the assumption that
21075 a patch is all we need. We might see problems with your patch and decide
21076 to fix the problem another way, or we might not understand it at all.
21078 Sometimes with a program as complicated as @value{GDBN} it is very hard to
21079 construct an example that will make the program follow a certain path
21080 through the code. If you do not send us the example, we will not be able
21081 to construct one, so we will not be able to verify that the bug is fixed.
21083 And if we cannot understand what bug you are trying to fix, or why your
21084 patch should be an improvement, we will not install it. A test case will
21085 help us to understand.
21088 A guess about what the bug is or what it depends on.
21090 Such guesses are usually wrong. Even we cannot guess right about such
21091 things without first using the debugger to find the facts.
21094 @c The readline documentation is distributed with the readline code
21095 @c and consists of the two following files:
21097 @c inc-hist.texinfo
21098 @c Use -I with makeinfo to point to the appropriate directory,
21099 @c environment var TEXINPUTS with TeX.
21100 @include rluser.texinfo
21101 @include inc-hist.texinfo
21104 @node Formatting Documentation
21105 @appendix Formatting Documentation
21107 @cindex @value{GDBN} reference card
21108 @cindex reference card
21109 The @value{GDBN} 4 release includes an already-formatted reference card, ready
21110 for printing with PostScript or Ghostscript, in the @file{gdb}
21111 subdirectory of the main source directory@footnote{In
21112 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
21113 release.}. If you can use PostScript or Ghostscript with your printer,
21114 you can print the reference card immediately with @file{refcard.ps}.
21116 The release also includes the source for the reference card. You
21117 can format it, using @TeX{}, by typing:
21123 The @value{GDBN} reference card is designed to print in @dfn{landscape}
21124 mode on US ``letter'' size paper;
21125 that is, on a sheet 11 inches wide by 8.5 inches
21126 high. You will need to specify this form of printing as an option to
21127 your @sc{dvi} output program.
21129 @cindex documentation
21131 All the documentation for @value{GDBN} comes as part of the machine-readable
21132 distribution. The documentation is written in Texinfo format, which is
21133 a documentation system that uses a single source file to produce both
21134 on-line information and a printed manual. You can use one of the Info
21135 formatting commands to create the on-line version of the documentation
21136 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
21138 @value{GDBN} includes an already formatted copy of the on-line Info
21139 version of this manual in the @file{gdb} subdirectory. The main Info
21140 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
21141 subordinate files matching @samp{gdb.info*} in the same directory. If
21142 necessary, you can print out these files, or read them with any editor;
21143 but they are easier to read using the @code{info} subsystem in @sc{gnu}
21144 Emacs or the standalone @code{info} program, available as part of the
21145 @sc{gnu} Texinfo distribution.
21147 If you want to format these Info files yourself, you need one of the
21148 Info formatting programs, such as @code{texinfo-format-buffer} or
21151 If you have @code{makeinfo} installed, and are in the top level
21152 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
21153 version @value{GDBVN}), you can make the Info file by typing:
21160 If you want to typeset and print copies of this manual, you need @TeX{},
21161 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
21162 Texinfo definitions file.
21164 @TeX{} is a typesetting program; it does not print files directly, but
21165 produces output files called @sc{dvi} files. To print a typeset
21166 document, you need a program to print @sc{dvi} files. If your system
21167 has @TeX{} installed, chances are it has such a program. The precise
21168 command to use depends on your system; @kbd{lpr -d} is common; another
21169 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
21170 require a file name without any extension or a @samp{.dvi} extension.
21172 @TeX{} also requires a macro definitions file called
21173 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
21174 written in Texinfo format. On its own, @TeX{} cannot either read or
21175 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
21176 and is located in the @file{gdb-@var{version-number}/texinfo}
21179 If you have @TeX{} and a @sc{dvi} printer program installed, you can
21180 typeset and print this manual. First switch to the the @file{gdb}
21181 subdirectory of the main source directory (for example, to
21182 @file{gdb-@value{GDBVN}/gdb}) and type:
21188 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
21190 @node Installing GDB
21191 @appendix Installing @value{GDBN}
21192 @cindex configuring @value{GDBN}
21193 @cindex installation
21194 @cindex configuring @value{GDBN}, and source tree subdirectories
21196 @value{GDBN} comes with a @code{configure} script that automates the process
21197 of preparing @value{GDBN} for installation; you can then use @code{make} to
21198 build the @code{gdb} program.
21200 @c irrelevant in info file; it's as current as the code it lives with.
21201 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
21202 look at the @file{README} file in the sources; we may have improved the
21203 installation procedures since publishing this manual.}
21206 The @value{GDBN} distribution includes all the source code you need for
21207 @value{GDBN} in a single directory, whose name is usually composed by
21208 appending the version number to @samp{gdb}.
21210 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
21211 @file{gdb-@value{GDBVN}} directory. That directory contains:
21214 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
21215 script for configuring @value{GDBN} and all its supporting libraries
21217 @item gdb-@value{GDBVN}/gdb
21218 the source specific to @value{GDBN} itself
21220 @item gdb-@value{GDBVN}/bfd
21221 source for the Binary File Descriptor library
21223 @item gdb-@value{GDBVN}/include
21224 @sc{gnu} include files
21226 @item gdb-@value{GDBVN}/libiberty
21227 source for the @samp{-liberty} free software library
21229 @item gdb-@value{GDBVN}/opcodes
21230 source for the library of opcode tables and disassemblers
21232 @item gdb-@value{GDBVN}/readline
21233 source for the @sc{gnu} command-line interface
21235 @item gdb-@value{GDBVN}/glob
21236 source for the @sc{gnu} filename pattern-matching subroutine
21238 @item gdb-@value{GDBVN}/mmalloc
21239 source for the @sc{gnu} memory-mapped malloc package
21242 The simplest way to configure and build @value{GDBN} is to run @code{configure}
21243 from the @file{gdb-@var{version-number}} source directory, which in
21244 this example is the @file{gdb-@value{GDBVN}} directory.
21246 First switch to the @file{gdb-@var{version-number}} source directory
21247 if you are not already in it; then run @code{configure}. Pass the
21248 identifier for the platform on which @value{GDBN} will run as an
21254 cd gdb-@value{GDBVN}
21255 ./configure @var{host}
21260 where @var{host} is an identifier such as @samp{sun4} or
21261 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
21262 (You can often leave off @var{host}; @code{configure} tries to guess the
21263 correct value by examining your system.)
21265 Running @samp{configure @var{host}} and then running @code{make} builds the
21266 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
21267 libraries, then @code{gdb} itself. The configured source files, and the
21268 binaries, are left in the corresponding source directories.
21271 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
21272 system does not recognize this automatically when you run a different
21273 shell, you may need to run @code{sh} on it explicitly:
21276 sh configure @var{host}
21279 If you run @code{configure} from a directory that contains source
21280 directories for multiple libraries or programs, such as the
21281 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
21282 creates configuration files for every directory level underneath (unless
21283 you tell it not to, with the @samp{--norecursion} option).
21285 You should run the @code{configure} script from the top directory in the
21286 source tree, the @file{gdb-@var{version-number}} directory. If you run
21287 @code{configure} from one of the subdirectories, you will configure only
21288 that subdirectory. That is usually not what you want. In particular,
21289 if you run the first @code{configure} from the @file{gdb} subdirectory
21290 of the @file{gdb-@var{version-number}} directory, you will omit the
21291 configuration of @file{bfd}, @file{readline}, and other sibling
21292 directories of the @file{gdb} subdirectory. This leads to build errors
21293 about missing include files such as @file{bfd/bfd.h}.
21295 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
21296 However, you should make sure that the shell on your path (named by
21297 the @samp{SHELL} environment variable) is publicly readable. Remember
21298 that @value{GDBN} uses the shell to start your program---some systems refuse to
21299 let @value{GDBN} debug child processes whose programs are not readable.
21302 * Separate Objdir:: Compiling @value{GDBN} in another directory
21303 * Config Names:: Specifying names for hosts and targets
21304 * Configure Options:: Summary of options for configure
21307 @node Separate Objdir
21308 @section Compiling @value{GDBN} in another directory
21310 If you want to run @value{GDBN} versions for several host or target machines,
21311 you need a different @code{gdb} compiled for each combination of
21312 host and target. @code{configure} is designed to make this easy by
21313 allowing you to generate each configuration in a separate subdirectory,
21314 rather than in the source directory. If your @code{make} program
21315 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
21316 @code{make} in each of these directories builds the @code{gdb}
21317 program specified there.
21319 To build @code{gdb} in a separate directory, run @code{configure}
21320 with the @samp{--srcdir} option to specify where to find the source.
21321 (You also need to specify a path to find @code{configure}
21322 itself from your working directory. If the path to @code{configure}
21323 would be the same as the argument to @samp{--srcdir}, you can leave out
21324 the @samp{--srcdir} option; it is assumed.)
21326 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
21327 separate directory for a Sun 4 like this:
21331 cd gdb-@value{GDBVN}
21334 ../gdb-@value{GDBVN}/configure sun4
21339 When @code{configure} builds a configuration using a remote source
21340 directory, it creates a tree for the binaries with the same structure
21341 (and using the same names) as the tree under the source directory. In
21342 the example, you'd find the Sun 4 library @file{libiberty.a} in the
21343 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
21344 @file{gdb-sun4/gdb}.
21346 Make sure that your path to the @file{configure} script has just one
21347 instance of @file{gdb} in it. If your path to @file{configure} looks
21348 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
21349 one subdirectory of @value{GDBN}, not the whole package. This leads to
21350 build errors about missing include files such as @file{bfd/bfd.h}.
21352 One popular reason to build several @value{GDBN} configurations in separate
21353 directories is to configure @value{GDBN} for cross-compiling (where
21354 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
21355 programs that run on another machine---the @dfn{target}).
21356 You specify a cross-debugging target by
21357 giving the @samp{--target=@var{target}} option to @code{configure}.
21359 When you run @code{make} to build a program or library, you must run
21360 it in a configured directory---whatever directory you were in when you
21361 called @code{configure} (or one of its subdirectories).
21363 The @code{Makefile} that @code{configure} generates in each source
21364 directory also runs recursively. If you type @code{make} in a source
21365 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
21366 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
21367 will build all the required libraries, and then build GDB.
21369 When you have multiple hosts or targets configured in separate
21370 directories, you can run @code{make} on them in parallel (for example,
21371 if they are NFS-mounted on each of the hosts); they will not interfere
21375 @section Specifying names for hosts and targets
21377 The specifications used for hosts and targets in the @code{configure}
21378 script are based on a three-part naming scheme, but some short predefined
21379 aliases are also supported. The full naming scheme encodes three pieces
21380 of information in the following pattern:
21383 @var{architecture}-@var{vendor}-@var{os}
21386 For example, you can use the alias @code{sun4} as a @var{host} argument,
21387 or as the value for @var{target} in a @code{--target=@var{target}}
21388 option. The equivalent full name is @samp{sparc-sun-sunos4}.
21390 The @code{configure} script accompanying @value{GDBN} does not provide
21391 any query facility to list all supported host and target names or
21392 aliases. @code{configure} calls the Bourne shell script
21393 @code{config.sub} to map abbreviations to full names; you can read the
21394 script, if you wish, or you can use it to test your guesses on
21395 abbreviations---for example:
21398 % sh config.sub i386-linux
21400 % sh config.sub alpha-linux
21401 alpha-unknown-linux-gnu
21402 % sh config.sub hp9k700
21404 % sh config.sub sun4
21405 sparc-sun-sunos4.1.1
21406 % sh config.sub sun3
21407 m68k-sun-sunos4.1.1
21408 % sh config.sub i986v
21409 Invalid configuration `i986v': machine `i986v' not recognized
21413 @code{config.sub} is also distributed in the @value{GDBN} source
21414 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
21416 @node Configure Options
21417 @section @code{configure} options
21419 Here is a summary of the @code{configure} options and arguments that
21420 are most often useful for building @value{GDBN}. @code{configure} also has
21421 several other options not listed here. @inforef{What Configure
21422 Does,,configure.info}, for a full explanation of @code{configure}.
21425 configure @r{[}--help@r{]}
21426 @r{[}--prefix=@var{dir}@r{]}
21427 @r{[}--exec-prefix=@var{dir}@r{]}
21428 @r{[}--srcdir=@var{dirname}@r{]}
21429 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
21430 @r{[}--target=@var{target}@r{]}
21435 You may introduce options with a single @samp{-} rather than
21436 @samp{--} if you prefer; but you may abbreviate option names if you use
21441 Display a quick summary of how to invoke @code{configure}.
21443 @item --prefix=@var{dir}
21444 Configure the source to install programs and files under directory
21447 @item --exec-prefix=@var{dir}
21448 Configure the source to install programs under directory
21451 @c avoid splitting the warning from the explanation:
21453 @item --srcdir=@var{dirname}
21454 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
21455 @code{make} that implements the @code{VPATH} feature.}@*
21456 Use this option to make configurations in directories separate from the
21457 @value{GDBN} source directories. Among other things, you can use this to
21458 build (or maintain) several configurations simultaneously, in separate
21459 directories. @code{configure} writes configuration specific files in
21460 the current directory, but arranges for them to use the source in the
21461 directory @var{dirname}. @code{configure} creates directories under
21462 the working directory in parallel to the source directories below
21465 @item --norecursion
21466 Configure only the directory level where @code{configure} is executed; do not
21467 propagate configuration to subdirectories.
21469 @item --target=@var{target}
21470 Configure @value{GDBN} for cross-debugging programs running on the specified
21471 @var{target}. Without this option, @value{GDBN} is configured to debug
21472 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
21474 There is no convenient way to generate a list of all available targets.
21476 @item @var{host} @dots{}
21477 Configure @value{GDBN} to run on the specified @var{host}.
21479 There is no convenient way to generate a list of all available hosts.
21482 There are many other options available as well, but they are generally
21483 needed for special purposes only.
21485 @node Maintenance Commands
21486 @appendix Maintenance Commands
21487 @cindex maintenance commands
21488 @cindex internal commands
21490 In addition to commands intended for @value{GDBN} users, @value{GDBN}
21491 includes a number of commands intended for @value{GDBN} developers,
21492 that are not documented elsewhere in this manual. These commands are
21493 provided here for reference. (For commands that turn on debugging
21494 messages, see @ref{Debugging Output}.)
21497 @kindex maint agent
21498 @item maint agent @var{expression}
21499 Translate the given @var{expression} into remote agent bytecodes.
21500 This command is useful for debugging the Agent Expression mechanism
21501 (@pxref{Agent Expressions}).
21503 @kindex maint info breakpoints
21504 @item @anchor{maint info breakpoints}maint info breakpoints
21505 Using the same format as @samp{info breakpoints}, display both the
21506 breakpoints you've set explicitly, and those @value{GDBN} is using for
21507 internal purposes. Internal breakpoints are shown with negative
21508 breakpoint numbers. The type column identifies what kind of breakpoint
21513 Normal, explicitly set breakpoint.
21516 Normal, explicitly set watchpoint.
21519 Internal breakpoint, used to handle correctly stepping through
21520 @code{longjmp} calls.
21522 @item longjmp resume
21523 Internal breakpoint at the target of a @code{longjmp}.
21526 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
21529 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
21532 Shared library events.
21536 @kindex maint check-symtabs
21537 @item maint check-symtabs
21538 Check the consistency of psymtabs and symtabs.
21540 @kindex maint cplus first_component
21541 @item maint cplus first_component @var{name}
21542 Print the first C@t{++} class/namespace component of @var{name}.
21544 @kindex maint cplus namespace
21545 @item maint cplus namespace
21546 Print the list of possible C@t{++} namespaces.
21548 @kindex maint demangle
21549 @item maint demangle @var{name}
21550 Demangle a C@t{++} or Objective-C manled @var{name}.
21552 @kindex maint deprecate
21553 @kindex maint undeprecate
21554 @cindex deprecated commands
21555 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
21556 @itemx maint undeprecate @var{command}
21557 Deprecate or undeprecate the named @var{command}. Deprecated commands
21558 cause @value{GDBN} to issue a warning when you use them. The optional
21559 argument @var{replacement} says which newer command should be used in
21560 favor of the deprecated one; if it is given, @value{GDBN} will mention
21561 the replacement as part of the warning.
21563 @kindex maint dump-me
21564 @item maint dump-me
21565 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
21566 Cause a fatal signal in the debugger and force it to dump its core.
21567 This is supported only on systems which support aborting a program
21568 with the @code{SIGQUIT} signal.
21570 @kindex maint internal-error
21571 @kindex maint internal-warning
21572 @item maint internal-error @r{[}@var{message-text}@r{]}
21573 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
21574 Cause @value{GDBN} to call the internal function @code{internal_error}
21575 or @code{internal_warning} and hence behave as though an internal error
21576 or internal warning has been detected. In addition to reporting the
21577 internal problem, these functions give the user the opportunity to
21578 either quit @value{GDBN} or create a core file of the current
21579 @value{GDBN} session.
21581 These commands take an optional parameter @var{message-text} that is
21582 used as the text of the error or warning message.
21584 Here's an example of using @code{indernal-error}:
21587 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
21588 @dots{}/maint.c:121: internal-error: testing, 1, 2
21589 A problem internal to GDB has been detected. Further
21590 debugging may prove unreliable.
21591 Quit this debugging session? (y or n) @kbd{n}
21592 Create a core file? (y or n) @kbd{n}
21596 @kindex maint packet
21597 @item maint packet @var{text}
21598 If @value{GDBN} is talking to an inferior via the serial protocol,
21599 then this command sends the string @var{text} to the inferior, and
21600 displays the response packet. @value{GDBN} supplies the initial
21601 @samp{$} character, the terminating @samp{#} character, and the
21604 @kindex maint print architecture
21605 @item maint print architecture @r{[}@var{file}@r{]}
21606 Print the entire architecture configuration. The optional argument
21607 @var{file} names the file where the output goes.
21609 @kindex maint print dummy-frames
21610 @item maint print dummy-frames
21611 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
21614 (@value{GDBP}) @kbd{b add}
21616 (@value{GDBP}) @kbd{print add(2,3)}
21617 Breakpoint 2, add (a=2, b=3) at @dots{}
21619 The program being debugged stopped while in a function called from GDB.
21621 (@value{GDBP}) @kbd{maint print dummy-frames}
21622 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
21623 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
21624 call_lo=0x01014000 call_hi=0x01014001
21628 Takes an optional file parameter.
21630 @kindex maint print registers
21631 @kindex maint print raw-registers
21632 @kindex maint print cooked-registers
21633 @kindex maint print register-groups
21634 @item maint print registers @r{[}@var{file}@r{]}
21635 @itemx maint print raw-registers @r{[}@var{file}@r{]}
21636 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
21637 @itemx maint print register-groups @r{[}@var{file}@r{]}
21638 Print @value{GDBN}'s internal register data structures.
21640 The command @code{maint print raw-registers} includes the contents of
21641 the raw register cache; the command @code{maint print cooked-registers}
21642 includes the (cooked) value of all registers; and the command
21643 @code{maint print register-groups} includes the groups that each
21644 register is a member of. @xref{Registers,, Registers, gdbint,
21645 @value{GDBN} Internals}.
21647 These commands take an optional parameter, a file name to which to
21648 write the information.
21650 @kindex maint print reggroups
21651 @item maint print reggroups @r{[}@var{file}@r{]}
21652 Print @value{GDBN}'s internal register group data structures. The
21653 optional argument @var{file} tells to what file to write the
21656 The register groups info looks like this:
21659 (@value{GDBP}) @kbd{maint print reggroups}
21672 This command forces @value{GDBN} to flush its internal register cache.
21674 @kindex maint print objfiles
21675 @cindex info for known object files
21676 @item maint print objfiles
21677 Print a dump of all known object files. For each object file, this
21678 command prints its name, address in memory, and all of its psymtabs
21681 @kindex maint print statistics
21682 @cindex bcache statistics
21683 @item maint print statistics
21684 This command prints, for each object file in the program, various data
21685 about that object file followed by the byte cache (@dfn{bcache})
21686 statistics for the object file. The objfile data includes the number
21687 of minimal, partical, full, and stabs symbols, the number of types
21688 defined by the objfile, the number of as yet unexpanded psym tables,
21689 the number of line tables and string tables, and the amount of memory
21690 used by the various tables. The bcache statistics include the counts,
21691 sizes, and counts of duplicates of all and unique objects, max,
21692 average, and median entry size, total memory used and its overhead and
21693 savings, and various measures of the hash table size and chain
21696 @kindex maint print type
21697 @cindex type chain of a data type
21698 @item maint print type @var{expr}
21699 Print the type chain for a type specified by @var{expr}. The argument
21700 can be either a type name or a symbol. If it is a symbol, the type of
21701 that symbol is described. The type chain produced by this command is
21702 a recursive definition of the data type as stored in @value{GDBN}'s
21703 data structures, including its flags and contained types.
21705 @kindex maint set dwarf2 max-cache-age
21706 @kindex maint show dwarf2 max-cache-age
21707 @item maint set dwarf2 max-cache-age
21708 @itemx maint show dwarf2 max-cache-age
21709 Control the DWARF 2 compilation unit cache.
21711 @cindex DWARF 2 compilation units cache
21712 In object files with inter-compilation-unit references, such as those
21713 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
21714 reader needs to frequently refer to previously read compilation units.
21715 This setting controls how long a compilation unit will remain in the
21716 cache if it is not referenced. A higher limit means that cached
21717 compilation units will be stored in memory longer, and more total
21718 memory will be used. Setting it to zero disables caching, which will
21719 slow down @value{GDBN} startup, but reduce memory consumption.
21721 @kindex maint set profile
21722 @kindex maint show profile
21723 @cindex profiling GDB
21724 @item maint set profile
21725 @itemx maint show profile
21726 Control profiling of @value{GDBN}.
21728 Profiling will be disabled until you use the @samp{maint set profile}
21729 command to enable it. When you enable profiling, the system will begin
21730 collecting timing and execution count data; when you disable profiling or
21731 exit @value{GDBN}, the results will be written to a log file. Remember that
21732 if you use profiling, @value{GDBN} will overwrite the profiling log file
21733 (often called @file{gmon.out}). If you have a record of important profiling
21734 data in a @file{gmon.out} file, be sure to move it to a safe location.
21736 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
21737 compiled with the @samp{-pg} compiler option.
21739 @kindex maint show-debug-regs
21740 @cindex x86 hardware debug registers
21741 @item maint show-debug-regs
21742 Control whether to show variables that mirror the x86 hardware debug
21743 registers. Use @code{ON} to enable, @code{OFF} to disable. If
21744 enabled, the debug registers values are shown when GDB inserts or
21745 removes a hardware breakpoint or watchpoint, and when the inferior
21746 triggers a hardware-assisted breakpoint or watchpoint.
21748 @kindex maint space
21749 @cindex memory used by commands
21751 Control whether to display memory usage for each command. If set to a
21752 nonzero value, @value{GDBN} will display how much memory each command
21753 took, following the command's own output. This can also be requested
21754 by invoking @value{GDBN} with the @option{--statistics} command-line
21755 switch (@pxref{Mode Options}).
21758 @cindex time of command execution
21760 Control whether to display the execution time for each command. If
21761 set to a nonzero value, @value{GDBN} will display how much time it
21762 took to execute each command, following the command's own output.
21763 This can also be requested by invoking @value{GDBN} with the
21764 @option{--statistics} command-line switch (@pxref{Mode Options}).
21766 @kindex maint translate-address
21767 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
21768 Find the symbol stored at the location specified by the address
21769 @var{addr} and an optional section name @var{section}. If found,
21770 @value{GDBN} prints the name of the closest symbol and an offset from
21771 the symbol's location to the specified address. This is similar to
21772 the @code{info address} command (@pxref{Symbols}), except that this
21773 command also allows to find symbols in other sections.
21777 The following command is useful for non-interactive invocations of
21778 @value{GDBN}, such as in the test suite.
21781 @item set watchdog @var{nsec}
21782 @kindex set watchdog
21783 @cindex watchdog timer
21784 @cindex timeout for commands
21785 Set the maximum number of seconds @value{GDBN} will wait for the
21786 target operation to finish. If this time expires, @value{GDBN}
21787 reports and error and the command is aborted.
21789 @item show watchdog
21790 Show the current setting of the target wait timeout.
21793 @node Remote Protocol
21794 @appendix @value{GDBN} Remote Serial Protocol
21799 * Stop Reply Packets::
21800 * General Query Packets::
21801 * Register Packet Format::
21803 * File-I/O remote protocol extension::
21809 There may be occasions when you need to know something about the
21810 protocol---for example, if there is only one serial port to your target
21811 machine, you might want your program to do something special if it
21812 recognizes a packet meant for @value{GDBN}.
21814 In the examples below, @samp{->} and @samp{<-} are used to indicate
21815 transmitted and received data respectfully.
21817 @cindex protocol, @value{GDBN} remote serial
21818 @cindex serial protocol, @value{GDBN} remote
21819 @cindex remote serial protocol
21820 All @value{GDBN} commands and responses (other than acknowledgments) are
21821 sent as a @var{packet}. A @var{packet} is introduced with the character
21822 @samp{$}, the actual @var{packet-data}, and the terminating character
21823 @samp{#} followed by a two-digit @var{checksum}:
21826 @code{$}@var{packet-data}@code{#}@var{checksum}
21830 @cindex checksum, for @value{GDBN} remote
21832 The two-digit @var{checksum} is computed as the modulo 256 sum of all
21833 characters between the leading @samp{$} and the trailing @samp{#} (an
21834 eight bit unsigned checksum).
21836 Implementors should note that prior to @value{GDBN} 5.0 the protocol
21837 specification also included an optional two-digit @var{sequence-id}:
21840 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
21843 @cindex sequence-id, for @value{GDBN} remote
21845 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
21846 has never output @var{sequence-id}s. Stubs that handle packets added
21847 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
21849 @cindex acknowledgment, for @value{GDBN} remote
21850 When either the host or the target machine receives a packet, the first
21851 response expected is an acknowledgment: either @samp{+} (to indicate
21852 the package was received correctly) or @samp{-} (to request
21856 -> @code{$}@var{packet-data}@code{#}@var{checksum}
21861 The host (@value{GDBN}) sends @var{command}s, and the target (the
21862 debugging stub incorporated in your program) sends a @var{response}. In
21863 the case of step and continue @var{command}s, the response is only sent
21864 when the operation has completed (the target has again stopped).
21866 @var{packet-data} consists of a sequence of characters with the
21867 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
21870 Fields within the packet should be separated using @samp{,} @samp{;} or
21871 @cindex remote protocol, field separator
21872 @samp{:}. Except where otherwise noted all numbers are represented in
21873 @sc{hex} with leading zeros suppressed.
21875 Implementors should note that prior to @value{GDBN} 5.0, the character
21876 @samp{:} could not appear as the third character in a packet (as it
21877 would potentially conflict with the @var{sequence-id}).
21879 Response @var{data} can be run-length encoded to save space. A @samp{*}
21880 means that the next character is an @sc{ascii} encoding giving a repeat count
21881 which stands for that many repetitions of the character preceding the
21882 @samp{*}. The encoding is @code{n+29}, yielding a printable character
21883 where @code{n >=3} (which is where rle starts to win). The printable
21884 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
21885 value greater than 126 should not be used.
21892 means the same as "0000".
21894 The error response returned for some packets includes a two character
21895 error number. That number is not well defined.
21897 For any @var{command} not supported by the stub, an empty response
21898 (@samp{$#00}) should be returned. That way it is possible to extend the
21899 protocol. A newer @value{GDBN} can tell if a packet is supported based
21902 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
21903 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
21909 The following table provides a complete list of all currently defined
21910 @var{command}s and their corresponding response @var{data}.
21911 @xref{File-I/O remote protocol extension}, for details about the File
21912 I/O extension of the remote protocol.
21916 @item @code{!} --- extended mode
21917 @cindex @code{!} packet
21919 Enable extended mode. In extended mode, the remote server is made
21920 persistent. The @samp{R} packet is used to restart the program being
21926 The remote target both supports and has enabled extended mode.
21929 @item @code{?} --- last signal
21930 @cindex @code{?} packet
21932 Indicate the reason the target halted. The reply is the same as for
21936 @xref{Stop Reply Packets}, for the reply specifications.
21938 @item @code{a} --- reserved
21940 Reserved for future use.
21942 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
21943 @cindex @code{A} packet
21945 Initialized @samp{argv[]} array passed into program. @var{arglen}
21946 specifies the number of bytes in the hex encoded byte stream @var{arg}.
21947 See @code{gdbserver} for more details.
21955 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
21956 @cindex @code{b} packet
21958 Change the serial line speed to @var{baud}.
21960 JTC: @emph{When does the transport layer state change? When it's
21961 received, or after the ACK is transmitted. In either case, there are
21962 problems if the command or the acknowledgment packet is dropped.}
21964 Stan: @emph{If people really wanted to add something like this, and get
21965 it working for the first time, they ought to modify ser-unix.c to send
21966 some kind of out-of-band message to a specially-setup stub and have the
21967 switch happen "in between" packets, so that from remote protocol's point
21968 of view, nothing actually happened.}
21970 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
21971 @cindex @code{B} packet
21973 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
21974 breakpoint at @var{addr}.
21976 This packet has been replaced by the @samp{Z} and @samp{z} packets
21977 (@pxref{insert breakpoint or watchpoint packet}).
21979 @item @code{c}@var{addr} --- continue
21980 @cindex @code{c} packet
21982 @var{addr} is address to resume. If @var{addr} is omitted, resume at
21986 @xref{Stop Reply Packets}, for the reply specifications.
21988 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
21989 @cindex @code{C} packet
21991 Continue with signal @var{sig} (hex signal number). If
21992 @code{;}@var{addr} is omitted, resume at same address.
21995 @xref{Stop Reply Packets}, for the reply specifications.
21997 @item @code{d} --- toggle debug @strong{(deprecated)}
21998 @cindex @code{d} packet
22002 @item @code{D} --- detach
22003 @cindex @code{D} packet
22005 Detach @value{GDBN} from the remote system. Sent to the remote target
22006 before @value{GDBN} disconnects via the @code{detach} command.
22010 @item @emph{no response}
22011 @value{GDBN} does not check for any response after sending this packet.
22014 @item @code{e} --- reserved
22016 Reserved for future use.
22018 @item @code{E} --- reserved
22020 Reserved for future use.
22022 @item @code{f} --- reserved
22024 Reserved for future use.
22026 @item @code{F}@var{RC}@code{,}@var{EE}@code{,}@var{CF}@code{;}@var{XX} --- Reply to target's F packet.
22027 @cindex @code{F} packet
22029 This packet is send by @value{GDBN} as reply to a @code{F} request packet
22030 sent by the target. This is part of the File-I/O protocol extension.
22031 @xref{File-I/O remote protocol extension}, for the specification.
22033 @item @code{g} --- read registers
22034 @anchor{read registers packet}
22035 @cindex @code{g} packet
22037 Read general registers.
22041 @item @var{XX@dots{}}
22042 Each byte of register data is described by two hex digits. The bytes
22043 with the register are transmitted in target byte order. The size of
22044 each register and their position within the @samp{g} @var{packet} are
22045 determined by the @value{GDBN} internal macros
22046 @var{DEPRECATED_REGISTER_RAW_SIZE} and @var{REGISTER_NAME} macros. The
22047 specification of several standard @code{g} packets is specified below.
22052 @item @code{G}@var{XX@dots{}} --- write regs
22053 @cindex @code{G} packet
22055 @xref{read registers packet}, for a description of the @var{XX@dots{}}
22066 @item @code{h} --- reserved
22068 Reserved for future use.
22070 @item @code{H}@var{c}@var{t@dots{}} --- set thread
22071 @cindex @code{H} packet
22073 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
22074 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
22075 should be @samp{c} for step and continue operations, @samp{g} for other
22076 operations. The thread designator @var{t@dots{}} may be -1, meaning all
22077 the threads, a thread number, or zero which means pick any thread.
22088 @c 'H': How restrictive (or permissive) is the thread model. If a
22089 @c thread is selected and stopped, are other threads allowed
22090 @c to continue to execute? As I mentioned above, I think the
22091 @c semantics of each command when a thread is selected must be
22092 @c described. For example:
22094 @c 'g': If the stub supports threads and a specific thread is
22095 @c selected, returns the register block from that thread;
22096 @c otherwise returns current registers.
22098 @c 'G' If the stub supports threads and a specific thread is
22099 @c selected, sets the registers of the register block of
22100 @c that thread; otherwise sets current registers.
22102 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
22103 @anchor{cycle step packet}
22104 @cindex @code{i} packet
22106 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
22107 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
22108 step starting at that address.
22110 @item @code{I} --- signal then cycle step @strong{(reserved)}
22111 @cindex @code{I} packet
22113 @xref{step with signal packet}. @xref{cycle step packet}.
22115 @item @code{j} --- reserved
22117 Reserved for future use.
22119 @item @code{J} --- reserved
22121 Reserved for future use.
22123 @item @code{k} --- kill request
22124 @cindex @code{k} packet
22126 FIXME: @emph{There is no description of how to operate when a specific
22127 thread context has been selected (i.e.@: does 'k' kill only that
22130 @item @code{K} --- reserved
22132 Reserved for future use.
22134 @item @code{l} --- reserved
22136 Reserved for future use.
22138 @item @code{L} --- reserved
22140 Reserved for future use.
22142 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
22143 @cindex @code{m} packet
22145 Read @var{length} bytes of memory starting at address @var{addr}.
22146 Neither @value{GDBN} nor the stub assume that sized memory transfers are
22147 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
22148 transfer mechanism is needed.}
22152 @item @var{XX@dots{}}
22153 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
22154 to read only part of the data. Neither @value{GDBN} nor the stub assume
22155 that sized memory transfers are assumed using word aligned
22156 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
22162 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
22163 @cindex @code{M} packet
22165 Write @var{length} bytes of memory starting at address @var{addr}.
22166 @var{XX@dots{}} is the data.
22173 for an error (this includes the case where only part of the data was
22177 @item @code{n} --- reserved
22179 Reserved for future use.
22181 @item @code{N} --- reserved
22183 Reserved for future use.
22185 @item @code{o} --- reserved
22187 Reserved for future use.
22189 @item @code{O} --- reserved
22191 @item @code{p}@var{hex number of register} --- read register packet
22192 @cindex @code{p} packet
22194 @xref{read registers packet}, for a description of how the returned
22195 register value is encoded.
22199 @item @var{XX@dots{}}
22200 the register's value
22204 Indicating an unrecognized @var{query}.
22207 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
22208 @anchor{write register packet}
22209 @cindex @code{P} packet
22211 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
22212 digits for each byte in the register (target byte order).
22222 @item @code{q}@var{query} --- general query
22223 @anchor{general query packet}
22224 @cindex @code{q} packet
22226 Request info about @var{query}. In general @value{GDBN} queries have a
22227 leading upper case letter. Custom vendor queries should use a company
22228 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
22229 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
22230 that they match the full @var{query} name.
22234 @item @var{XX@dots{}}
22235 Hex encoded data from query. The reply can not be empty.
22239 Indicating an unrecognized @var{query}.
22242 @item @code{Q}@var{var}@code{=}@var{val} --- general set
22243 @cindex @code{Q} packet
22245 Set value of @var{var} to @var{val}.
22247 @xref{general query packet}, for a discussion of naming conventions.
22249 @item @code{r} --- reset @strong{(deprecated)}
22250 @cindex @code{r} packet
22252 Reset the entire system.
22254 @item @code{R}@var{XX} --- remote restart
22255 @cindex @code{R} packet
22257 Restart the program being debugged. @var{XX}, while needed, is ignored.
22258 This packet is only available in extended mode.
22262 @item @emph{no reply}
22263 The @samp{R} packet has no reply.
22266 @item @code{s}@var{addr} --- step
22267 @cindex @code{s} packet
22269 @var{addr} is address to resume. If @var{addr} is omitted, resume at
22273 @xref{Stop Reply Packets}, for the reply specifications.
22275 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
22276 @anchor{step with signal packet}
22277 @cindex @code{S} packet
22279 Like @samp{C} but step not continue.
22282 @xref{Stop Reply Packets}, for the reply specifications.
22284 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
22285 @cindex @code{t} packet
22287 Search backwards starting at address @var{addr} for a match with pattern
22288 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
22289 @var{addr} must be at least 3 digits.
22291 @item @code{T}@var{XX} --- thread alive
22292 @cindex @code{T} packet
22294 Find out if the thread XX is alive.
22299 thread is still alive
22304 @item @code{u} --- reserved
22306 Reserved for future use.
22308 @item @code{U} --- reserved
22310 Reserved for future use.
22312 @item @code{v} --- verbose packet prefix
22314 Packets starting with @code{v} are identified by a multi-letter name,
22315 up to the first @code{;} or @code{?} (or the end of the packet).
22317 @item @code{vCont}[;@var{action}[@code{:}@var{tid}]]... --- extended resume
22318 @cindex @code{vCont} packet
22320 Resume the inferior. Different actions may be specified for each thread.
22321 If an action is specified with no @var{tid}, then it is applied to any
22322 threads that don't have a specific action specified; if no default action is
22323 specified then other threads should remain stopped. Specifying multiple
22324 default actions is an error; specifying no actions is also an error.
22325 Thread IDs are specified in hexadecimal. Currently supported actions are:
22331 Continue with signal @var{sig}. @var{sig} should be two hex digits.
22335 Step with signal @var{sig}. @var{sig} should be two hex digits.
22338 The optional @var{addr} argument normally associated with these packets is
22339 not supported in @code{vCont}.
22342 @xref{Stop Reply Packets}, for the reply specifications.
22344 @item @code{vCont?} --- extended resume query
22345 @cindex @code{vCont?} packet
22347 Query support for the @code{vCont} packet.
22351 @item @code{vCont}[;@var{action}]...
22352 The @code{vCont} packet is supported. Each @var{action} is a supported
22353 command in the @code{vCont} packet.
22355 The @code{vCont} packet is not supported.
22358 @item @code{V} --- reserved
22360 Reserved for future use.
22362 @item @code{w} --- reserved
22364 Reserved for future use.
22366 @item @code{W} --- reserved
22368 Reserved for future use.
22370 @item @code{x} --- reserved
22372 Reserved for future use.
22374 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
22375 @cindex @code{X} packet
22377 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
22378 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
22379 escaped using @code{0x7d}, and then XORed with @code{0x20}.
22380 For example, @code{0x7d} would be transmitted as @code{0x7d 0x5d}.
22390 @item @code{y} --- reserved
22392 Reserved for future use.
22394 @item @code{Y} reserved
22396 Reserved for future use.
22398 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
22399 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
22400 @anchor{insert breakpoint or watchpoint packet}
22401 @cindex @code{z} packet
22402 @cindex @code{Z} packets
22404 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
22405 watchpoint starting at address @var{address} and covering the next
22406 @var{length} bytes.
22408 Each breakpoint and watchpoint packet @var{type} is documented
22411 @emph{Implementation notes: A remote target shall return an empty string
22412 for an unrecognized breakpoint or watchpoint packet @var{type}. A
22413 remote target shall support either both or neither of a given
22414 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
22415 avoid potential problems with duplicate packets, the operations should
22416 be implemented in an idempotent way.}
22418 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
22419 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
22420 @cindex @code{z0} packet
22421 @cindex @code{Z0} packet
22423 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
22424 @code{addr} of size @code{length}.
22426 A memory breakpoint is implemented by replacing the instruction at
22427 @var{addr} with a software breakpoint or trap instruction. The
22428 @code{length} is used by targets that indicates the size of the
22429 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
22430 @sc{mips} can insert either a 2 or 4 byte breakpoint).
22432 @emph{Implementation note: It is possible for a target to copy or move
22433 code that contains memory breakpoints (e.g., when implementing
22434 overlays). The behavior of this packet, in the presence of such a
22435 target, is not defined.}
22447 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
22448 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
22449 @cindex @code{z1} packet
22450 @cindex @code{Z1} packet
22452 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
22453 address @code{addr} of size @code{length}.
22455 A hardware breakpoint is implemented using a mechanism that is not
22456 dependant on being able to modify the target's memory.
22458 @emph{Implementation note: A hardware breakpoint is not affected by code
22471 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
22472 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
22473 @cindex @code{z2} packet
22474 @cindex @code{Z2} packet
22476 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
22488 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
22489 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
22490 @cindex @code{z3} packet
22491 @cindex @code{Z3} packet
22493 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
22505 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
22506 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
22507 @cindex @code{z4} packet
22508 @cindex @code{Z4} packet
22510 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
22524 @node Stop Reply Packets
22525 @section Stop Reply Packets
22526 @cindex stop reply packets
22528 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
22529 receive any of the below as a reply. In the case of the @samp{C},
22530 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
22531 when the target halts. In the below the exact meaning of @samp{signal
22532 number} is poorly defined. In general one of the UNIX signal numbering
22533 conventions is used.
22538 @var{AA} is the signal number
22540 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
22541 @cindex @code{T} packet reply
22543 @var{AA} = two hex digit signal number; @var{n...} = register number
22544 (hex), @var{r...} = target byte ordered register contents, size defined
22545 by @code{DEPRECATED_REGISTER_RAW_SIZE}; @var{n...} = @samp{thread},
22546 @var{r...} = thread process ID, this is a hex integer; @var{n...} =
22547 (@samp{watch} | @samp{rwatch} | @samp{awatch}, @var{r...} = data
22548 address, this is a hex integer; @var{n...} = other string not starting
22549 with valid hex digit. @value{GDBN} should ignore this @var{n...},
22550 @var{r...} pair and go on to the next. This way we can extend the
22555 The process exited, and @var{AA} is the exit status. This is only
22556 applicable to certain targets.
22560 The process terminated with signal @var{AA}.
22562 @item O@var{XX@dots{}}
22564 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
22565 any time while the program is running and the debugger should continue
22566 to wait for @samp{W}, @samp{T}, etc.
22568 @item F@var{call-id}@code{,}@var{parameter@dots{}}
22570 @var{call-id} is the identifier which says which host system call should
22571 be called. This is just the name of the function. Translation into the
22572 correct system call is only applicable as it's defined in @value{GDBN}.
22573 @xref{File-I/O remote protocol extension}, for a list of implemented
22576 @var{parameter@dots{}} is a list of parameters as defined for this very
22579 The target replies with this packet when it expects @value{GDBN} to call
22580 a host system call on behalf of the target. @value{GDBN} replies with
22581 an appropriate @code{F} packet and keeps up waiting for the next reply
22582 packet from the target. The latest @samp{C}, @samp{c}, @samp{S} or
22583 @samp{s} action is expected to be continued.
22584 @xref{File-I/O remote protocol extension}, for more details.
22588 @node General Query Packets
22589 @section General Query Packets
22590 @cindex remote query requests
22592 The following set and query packets have already been defined.
22596 @item @code{q}@code{C} --- current thread
22597 @cindex current thread, remote request
22598 @cindex @code{qC} packet
22599 Return the current thread id.
22603 @item @code{QC}@var{pid}
22604 Where @var{pid} is an unsigned hexidecimal process id.
22606 Any other reply implies the old pid.
22609 @item @code{q}@code{fThreadInfo} -- all thread ids
22610 @cindex list active threads, remote request
22611 @cindex @code{qfThreadInfo} packet
22612 @code{q}@code{sThreadInfo}
22614 Obtain a list of active thread ids from the target (OS). Since there
22615 may be too many active threads to fit into one reply packet, this query
22616 works iteratively: it may require more than one query/reply sequence to
22617 obtain the entire list of threads. The first query of the sequence will
22618 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
22619 sequence will be the @code{qs}@code{ThreadInfo} query.
22621 NOTE: replaces the @code{qL} query (see below).
22625 @item @code{m}@var{id}
22627 @item @code{m}@var{id},@var{id}@dots{}
22628 a comma-separated list of thread ids
22630 (lower case 'el') denotes end of list.
22633 In response to each query, the target will reply with a list of one or
22634 more thread ids, in big-endian unsigned hex, separated by commas.
22635 @value{GDBN} will respond to each reply with a request for more thread
22636 ids (using the @code{qs} form of the query), until the target responds
22637 with @code{l} (lower-case el, for @code{'last'}).
22639 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
22640 @cindex thread attributes info, remote request
22641 @cindex @code{qThreadExtraInfo} packet
22642 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
22643 string description of a thread's attributes from the target OS. This
22644 string may contain anything that the target OS thinks is interesting for
22645 @value{GDBN} to tell the user about the thread. The string is displayed
22646 in @value{GDBN}'s @samp{info threads} display. Some examples of
22647 possible thread extra info strings are ``Runnable'', or ``Blocked on
22652 @item @var{XX@dots{}}
22653 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
22654 the printable string containing the extra information about the thread's
22658 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
22660 Obtain thread information from RTOS. Where: @var{startflag} (one hex
22661 digit) is one to indicate the first query and zero to indicate a
22662 subsequent query; @var{threadcount} (two hex digits) is the maximum
22663 number of threads the response packet can contain; and @var{nextthread}
22664 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
22665 returned in the response as @var{argthread}.
22667 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
22672 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
22673 Where: @var{count} (two hex digits) is the number of threads being
22674 returned; @var{done} (one hex digit) is zero to indicate more threads
22675 and one indicates no further threads; @var{argthreadid} (eight hex
22676 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
22677 is a sequence of thread IDs from the target. @var{threadid} (eight hex
22678 digits). See @code{remote.c:parse_threadlist_response()}.
22681 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
22682 @cindex CRC of memory block, remote request
22683 @cindex @code{qCRC} packet
22686 @item @code{E}@var{NN}
22687 An error (such as memory fault)
22688 @item @code{C}@var{CRC32}
22689 A 32 bit cyclic redundancy check of the specified memory region.
22692 @item @code{q}@code{Offsets} --- query sect offs
22693 @cindex section offsets, remote request
22694 @cindex @code{qOffsets} packet
22695 Get section offsets that the target used when re-locating the downloaded
22696 image. @emph{Note: while a @code{Bss} offset is included in the
22697 response, @value{GDBN} ignores this and instead applies the @code{Data}
22698 offset to the @code{Bss} section.}
22702 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
22705 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
22706 @cindex thread information, remote request
22707 @cindex @code{qP} packet
22708 Returns information on @var{threadid}. Where: @var{mode} is a hex
22709 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
22716 See @code{remote.c:remote_unpack_thread_info_response()}.
22718 @item @code{q}@code{Rcmd,}@var{command} --- remote command
22719 @cindex execute remote command, remote request
22720 @cindex @code{qRcmd} packet
22721 @var{command} (hex encoded) is passed to the local interpreter for
22722 execution. Invalid commands should be reported using the output string.
22723 Before the final result packet, the target may also respond with a
22724 number of intermediate @code{O}@var{output} console output packets.
22725 @emph{Implementors should note that providing access to a stubs's
22726 interpreter may have security implications}.
22731 A command response with no output.
22733 A command response with the hex encoded output string @var{OUTPUT}.
22734 @item @code{E}@var{NN}
22735 Indicate a badly formed request.
22737 When @samp{q}@samp{Rcmd} is not recognized.
22740 @item @code{qSymbol::} --- symbol lookup
22741 @cindex symbol lookup, remote request
22742 @cindex @code{qSymbol} packet
22743 Notify the target that @value{GDBN} is prepared to serve symbol lookup
22744 requests. Accept requests from the target for the values of symbols.
22749 The target does not need to look up any (more) symbols.
22750 @item @code{qSymbol:}@var{sym_name}
22751 The target requests the value of symbol @var{sym_name} (hex encoded).
22752 @value{GDBN} may provide the value by using the
22753 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
22756 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
22758 Set the value of @var{sym_name} to @var{sym_value}.
22760 @var{sym_name} (hex encoded) is the name of a symbol whose value the
22761 target has previously requested.
22763 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
22764 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
22770 The target does not need to look up any (more) symbols.
22771 @item @code{qSymbol:}@var{sym_name}
22772 The target requests the value of a new symbol @var{sym_name} (hex
22773 encoded). @value{GDBN} will continue to supply the values of symbols
22774 (if available), until the target ceases to request them.
22777 @item @code{qPart}:@var{object}:@code{read}:@var{annex}:@var{offset},@var{length} --- read special data
22778 @cindex read special object, remote request
22779 @cindex @code{qPart} packet
22780 Read uninterpreted bytes from the target's special data area
22781 identified by the keyword @code{object}.
22782 Request @var{length} bytes starting at @var{offset} bytes into the data.
22783 The content and encoding of @var{annex} is specific to the object;
22784 it can supply additional details about what data to access.
22786 Here are the specific requests of this form defined so far.
22787 All @samp{@code{qPart}:@var{object}:@code{read}:@dots{}}
22788 requests use the same reply formats, listed below.
22791 @item @code{qPart}:@code{auxv}:@code{read}::@var{offset},@var{length}
22792 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
22793 auxiliary vector}, and see @ref{Remote configuration,
22794 read-aux-vector-packet}. Note @var{annex} must be empty.
22800 The @var{offset} in the request is at the end of the data.
22801 There is no more data to be read.
22803 @item @var{XX@dots{}}
22804 Hex encoded data bytes read.
22805 This may be fewer bytes than the @var{length} in the request.
22808 The request was malformed, or @var{annex} was invalid.
22810 @item @code{E}@var{nn}
22811 The offset was invalid, or there was an error encountered reading the data.
22812 @var{nn} is a hex-encoded @code{errno} value.
22814 @item @code{""} (empty)
22815 An empty reply indicates the @var{object} or @var{annex} string was not
22816 recognized by the stub.
22819 @item @code{qPart}:@var{object}:@code{write}:@var{annex}:@var{offset}:@var{data@dots{}}
22820 @cindex write data into object, remote request
22821 Write uninterpreted bytes into the target's special data area
22822 identified by the keyword @code{object},
22823 starting at @var{offset} bytes into the data.
22824 @var{data@dots{}} is the hex-encoded data to be written.
22825 The content and encoding of @var{annex} is specific to the object;
22826 it can supply additional details about what data to access.
22828 No requests of this form are presently in use. This specification
22829 serves as a placeholder to document the common format that new
22830 specific request specifications ought to use.
22835 @var{nn} (hex encoded) is the number of bytes written.
22836 This may be fewer bytes than supplied in the request.
22839 The request was malformed, or @var{annex} was invalid.
22841 @item @code{E}@var{nn}
22842 The offset was invalid, or there was an error encountered writing the data.
22843 @var{nn} is a hex-encoded @code{errno} value.
22845 @item @code{""} (empty)
22846 An empty reply indicates the @var{object} or @var{annex} string was not
22847 recognized by the stub, or that the object does not support writing.
22850 @item @code{qPart}:@var{object}:@var{operation}:@dots{}
22851 Requests of this form may be added in the future. When a stub does
22852 not recognize the @var{object} keyword, or its support for
22853 @var{object} does not recognize the @var{operation} keyword,
22854 the stub must respond with an empty packet.
22856 @item @code{qGetTLSAddr}:@var{thread-id},@var{offset},@var{lm} --- get thread local storage address
22857 @cindex get thread-local storage address, remote request
22858 @cindex @code{qGetTLSAddr} packet
22859 Fetch the address associated with thread local storage specified
22860 by @var{thread-id}, @var{offset}, and @var{lm}.
22862 @var{thread-id} is the (big endian, hex encoded) thread id associated with the
22863 thread for which to fetch the TLS address.
22865 @var{offset} is the (big endian, hex encoded) offset associated with the
22866 thread local variable. (This offset is obtained from the debug
22867 information associated with the variable.)
22869 @var{lm} is the (big endian, hex encoded) OS/ABI specific encoding of the
22870 the load module associated with the thread local storage. For example,
22871 a @sc{gnu}/Linux system will pass the link map address of the shared
22872 object associated with the thread local storage under consideration.
22873 Other operating environments may choose to represent the load module
22874 differently, so the precise meaning of this parameter will vary.
22878 @item @var{XX@dots{}}
22879 Hex encoded (big endian) bytes representing the address of the thread
22880 local storage requested.
22882 @item @code{E}@var{nn} (where @var{nn} are hex digits)
22885 @item @code{""} (empty)
22886 An empty reply indicates that @code{qGetTLSAddr} is not supported by the stub.
22889 Use of this request packet is controlled by the @code{set remote
22890 get-thread-local-storage-address} command (@pxref{Remote
22891 configuration, set remote get-thread-local-storage-address}).
22895 @node Register Packet Format
22896 @section Register Packet Format
22898 The following @samp{g}/@samp{G} packets have previously been defined.
22899 In the below, some thirty-two bit registers are transferred as
22900 sixty-four bits. Those registers should be zero/sign extended (which?)
22901 to fill the space allocated. Register bytes are transfered in target
22902 byte order. The two nibbles within a register byte are transfered
22903 most-significant - least-significant.
22909 All registers are transfered as thirty-two bit quantities in the order:
22910 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
22911 registers; fsr; fir; fp.
22915 All registers are transfered as sixty-four bit quantities (including
22916 thirty-two bit registers such as @code{sr}). The ordering is the same
22924 Example sequence of a target being re-started. Notice how the restart
22925 does not get any direct output:
22930 @emph{target restarts}
22933 <- @code{T001:1234123412341234}
22937 Example sequence of a target being stepped by a single instruction:
22940 -> @code{G1445@dots{}}
22945 <- @code{T001:1234123412341234}
22949 <- @code{1455@dots{}}
22953 @node File-I/O remote protocol extension
22954 @section File-I/O remote protocol extension
22955 @cindex File-I/O remote protocol extension
22958 * File-I/O Overview::
22959 * Protocol basics::
22960 * The F request packet::
22961 * The F reply packet::
22962 * Memory transfer::
22963 * The Ctrl-C message::
22965 * The isatty call::
22966 * The system call::
22967 * List of supported calls::
22968 * Protocol specific representation of datatypes::
22970 * File-I/O Examples::
22973 @node File-I/O Overview
22974 @subsection File-I/O Overview
22975 @cindex file-i/o overview
22977 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
22978 target to use the host's file system and console I/O when calling various
22979 system calls. System calls on the target system are translated into a
22980 remote protocol packet to the host system which then performs the needed
22981 actions and returns with an adequate response packet to the target system.
22982 This simulates file system operations even on targets that lack file systems.
22984 The protocol is defined host- and target-system independent. It uses
22985 its own independent representation of datatypes and values. Both,
22986 @value{GDBN} and the target's @value{GDBN} stub are responsible for
22987 translating the system dependent values into the unified protocol values
22988 when data is transmitted.
22990 The communication is synchronous. A system call is possible only
22991 when GDB is waiting for the @samp{C}, @samp{c}, @samp{S} or @samp{s}
22992 packets. While @value{GDBN} handles the request for a system call,
22993 the target is stopped to allow deterministic access to the target's
22994 memory. Therefore File-I/O is not interuptible by target signals. It
22995 is possible to interrupt File-I/O by a user interrupt (Ctrl-C), though.
22997 The target's request to perform a host system call does not finish
22998 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
22999 after finishing the system call, the target returns to continuing the
23000 previous activity (continue, step). No additional continue or step
23001 request from @value{GDBN} is required.
23004 (@value{GDBP}) continue
23005 <- target requests 'system call X'
23006 target is stopped, @value{GDBN} executes system call
23007 -> GDB returns result
23008 ... target continues, GDB returns to wait for the target
23009 <- target hits breakpoint and sends a Txx packet
23012 The protocol is only used for files on the host file system and
23013 for I/O on the console. Character or block special devices, pipes,
23014 named pipes or sockets or any other communication method on the host
23015 system are not supported by this protocol.
23017 @node Protocol basics
23018 @subsection Protocol basics
23019 @cindex protocol basics, file-i/o
23021 The File-I/O protocol uses the @code{F} packet, as request as well
23022 as as reply packet. Since a File-I/O system call can only occur when
23023 @value{GDBN} is waiting for the continuing or stepping target, the
23024 File-I/O request is a reply that @value{GDBN} has to expect as a result
23025 of a former @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
23026 This @code{F} packet contains all information needed to allow @value{GDBN}
23027 to call the appropriate host system call:
23031 A unique identifier for the requested system call.
23034 All parameters to the system call. Pointers are given as addresses
23035 in the target memory address space. Pointers to strings are given as
23036 pointer/length pair. Numerical values are given as they are.
23037 Numerical control values are given in a protocol specific representation.
23041 At that point @value{GDBN} has to perform the following actions.
23045 If parameter pointer values are given, which point to data needed as input
23046 to a system call, @value{GDBN} requests this data from the target with a
23047 standard @code{m} packet request. This additional communication has to be
23048 expected by the target implementation and is handled as any other @code{m}
23052 @value{GDBN} translates all value from protocol representation to host
23053 representation as needed. Datatypes are coerced into the host types.
23056 @value{GDBN} calls the system call
23059 It then coerces datatypes back to protocol representation.
23062 If pointer parameters in the request packet point to buffer space in which
23063 a system call is expected to copy data to, the data is transmitted to the
23064 target using a @code{M} or @code{X} packet. This packet has to be expected
23065 by the target implementation and is handled as any other @code{M} or @code{X}
23070 Eventually @value{GDBN} replies with another @code{F} packet which contains all
23071 necessary information for the target to continue. This at least contains
23078 @code{errno}, if has been changed by the system call.
23085 After having done the needed type and value coercion, the target continues
23086 the latest continue or step action.
23088 @node The F request packet
23089 @subsection The @code{F} request packet
23090 @cindex file-i/o request packet
23091 @cindex @code{F} request packet
23093 The @code{F} request packet has the following format:
23098 @code{F}@var{call-id}@code{,}@var{parameter@dots{}}
23101 @var{call-id} is the identifier to indicate the host system call to be called.
23102 This is just the name of the function.
23104 @var{parameter@dots{}} are the parameters to the system call.
23108 Parameters are hexadecimal integer values, either the real values in case
23109 of scalar datatypes, as pointers to target buffer space in case of compound
23110 datatypes and unspecified memory areas or as pointer/length pairs in case
23111 of string parameters. These are appended to the call-id, each separated
23112 from its predecessor by a comma. All values are transmitted in ASCII
23113 string representation, pointer/length pairs separated by a slash.
23115 @node The F reply packet
23116 @subsection The @code{F} reply packet
23117 @cindex file-i/o reply packet
23118 @cindex @code{F} reply packet
23120 The @code{F} reply packet has the following format:
23125 @code{F}@var{retcode}@code{,}@var{errno}@code{,}@var{Ctrl-C flag}@code{;}@var{call specific attachment}
23128 @var{retcode} is the return code of the system call as hexadecimal value.
23130 @var{errno} is the errno set by the call, in protocol specific representation.
23131 This parameter can be omitted if the call was successful.
23133 @var{Ctrl-C flag} is only send if the user requested a break. In this
23134 case, @var{errno} must be send as well, even if the call was successful.
23135 The @var{Ctrl-C flag} itself consists of the character 'C':
23142 or, if the call was interupted before the host call has been performed:
23149 assuming 4 is the protocol specific representation of @code{EINTR}.
23153 @node Memory transfer
23154 @subsection Memory transfer
23155 @cindex memory transfer, in file-i/o protocol
23157 Structured data which is transferred using a memory read or write as e.g.@:
23158 a @code{struct stat} is expected to be in a protocol specific format with
23159 all scalar multibyte datatypes being big endian. This should be done by
23160 the target before the @code{F} packet is sent resp.@: by @value{GDBN} before
23161 it transfers memory to the target. Transferred pointers to structured
23162 data should point to the already coerced data at any time.
23164 @node The Ctrl-C message
23165 @subsection The Ctrl-C message
23166 @cindex ctrl-c message, in file-i/o protocol
23168 A special case is, if the @var{Ctrl-C flag} is set in the @value{GDBN}
23169 reply packet. In this case the target should behave, as if it had
23170 gotten a break message. The meaning for the target is ``system call
23171 interupted by @code{SIGINT}''. Consequentially, the target should actually stop
23172 (as with a break message) and return to @value{GDBN} with a @code{T02}
23173 packet. In this case, it's important for the target to know, in which
23174 state the system call was interrupted. Since this action is by design
23175 not an atomic operation, we have to differ between two cases:
23179 The system call hasn't been performed on the host yet.
23182 The system call on the host has been finished.
23186 These two states can be distinguished by the target by the value of the
23187 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
23188 call hasn't been performed. This is equivalent to the @code{EINTR} handling
23189 on POSIX systems. In any other case, the target may presume that the
23190 system call has been finished --- successful or not --- and should behave
23191 as if the break message arrived right after the system call.
23193 @value{GDBN} must behave reliable. If the system call has not been called
23194 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
23195 @code{errno} in the packet. If the system call on the host has been finished
23196 before the user requests a break, the full action must be finshed by
23197 @value{GDBN}. This requires sending @code{M} or @code{X} packets as they fit.
23198 The @code{F} packet may only be send when either nothing has happened
23199 or the full action has been completed.
23202 @subsection Console I/O
23203 @cindex console i/o as part of file-i/o
23205 By default and if not explicitely closed by the target system, the file
23206 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
23207 on the @value{GDBN} console is handled as any other file output operation
23208 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
23209 by @value{GDBN} so that after the target read request from file descriptor
23210 0 all following typing is buffered until either one of the following
23215 The user presses @kbd{Ctrl-C}. The behaviour is as explained above, the
23217 system call is treated as finished.
23220 The user presses @kbd{Enter}. This is treated as end of input with a trailing
23224 The user presses @kbd{Ctrl-D}. This is treated as end of input. No trailing
23225 character, especially no Ctrl-D is appended to the input.
23229 If the user has typed more characters as fit in the buffer given to
23230 the read call, the trailing characters are buffered in @value{GDBN} until
23231 either another @code{read(0, @dots{})} is requested by the target or debugging
23232 is stopped on users request.
23234 @node The isatty call
23235 @subsection The @samp{isatty} function call
23236 @cindex isatty call, file-i/o protocol
23238 A special case in this protocol is the library call @code{isatty} which
23239 is implemented as its own call inside of this protocol. It returns
23240 1 to the target if the file descriptor given as parameter is attached
23241 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
23242 would require implementing @code{ioctl} and would be more complex than
23245 @node The system call
23246 @subsection The @samp{system} function call
23247 @cindex system call, file-i/o protocol
23249 The other special case in this protocol is the @code{system} call which
23250 is implemented as its own call, too. @value{GDBN} is taking over the full
23251 task of calling the necessary host calls to perform the @code{system}
23252 call. The return value of @code{system} is simplified before it's returned
23253 to the target. Basically, the only signal transmitted back is @code{EINTR}
23254 in case the user pressed @kbd{Ctrl-C}. Otherwise the return value consists
23255 entirely of the exit status of the called command.
23257 Due to security concerns, the @code{system} call is by default refused
23258 by @value{GDBN}. The user has to allow this call explicitly with the
23259 @kbd{set remote system-call-allowed 1} command.
23262 @item set remote system-call-allowed
23263 @kindex set remote system-call-allowed
23264 Control whether to allow the @code{system} calls in the File I/O
23265 protocol for the remote target. The default is zero (disabled).
23267 @item show remote system-call-allowed
23268 @kindex show remote system-call-allowed
23269 Show the current setting of system calls for the remote File I/O
23273 @node List of supported calls
23274 @subsection List of supported calls
23275 @cindex list of supported file-i/o calls
23292 @unnumberedsubsubsec open
23293 @cindex open, file-i/o system call
23297 int open(const char *pathname, int flags);
23298 int open(const char *pathname, int flags, mode_t mode);
23301 Fopen,pathptr/len,flags,mode
23305 @code{flags} is the bitwise or of the following values:
23309 If the file does not exist it will be created. The host
23310 rules apply as far as file ownership and time stamps
23314 When used with O_CREAT, if the file already exists it is
23315 an error and open() fails.
23318 If the file already exists and the open mode allows
23319 writing (O_RDWR or O_WRONLY is given) it will be
23320 truncated to length 0.
23323 The file is opened in append mode.
23326 The file is opened for reading only.
23329 The file is opened for writing only.
23332 The file is opened for reading and writing.
23335 Each other bit is silently ignored.
23340 @code{mode} is the bitwise or of the following values:
23344 User has read permission.
23347 User has write permission.
23350 Group has read permission.
23353 Group has write permission.
23356 Others have read permission.
23359 Others have write permission.
23362 Each other bit is silently ignored.
23367 @exdent Return value:
23368 open returns the new file descriptor or -1 if an error
23376 pathname already exists and O_CREAT and O_EXCL were used.
23379 pathname refers to a directory.
23382 The requested access is not allowed.
23385 pathname was too long.
23388 A directory component in pathname does not exist.
23391 pathname refers to a device, pipe, named pipe or socket.
23394 pathname refers to a file on a read-only filesystem and
23395 write access was requested.
23398 pathname is an invalid pointer value.
23401 No space on device to create the file.
23404 The process already has the maximum number of files open.
23407 The limit on the total number of files open on the system
23411 The call was interrupted by the user.
23415 @unnumberedsubsubsec close
23416 @cindex close, file-i/o system call
23425 @exdent Return value:
23426 close returns zero on success, or -1 if an error occurred.
23433 fd isn't a valid open file descriptor.
23436 The call was interrupted by the user.
23440 @unnumberedsubsubsec read
23441 @cindex read, file-i/o system call
23445 int read(int fd, void *buf, unsigned int count);
23448 Fread,fd,bufptr,count
23450 @exdent Return value:
23451 On success, the number of bytes read is returned.
23452 Zero indicates end of file. If count is zero, read
23453 returns zero as well. On error, -1 is returned.
23460 fd is not a valid file descriptor or is not open for
23464 buf is an invalid pointer value.
23467 The call was interrupted by the user.
23471 @unnumberedsubsubsec write
23472 @cindex write, file-i/o system call
23476 int write(int fd, const void *buf, unsigned int count);
23479 Fwrite,fd,bufptr,count
23481 @exdent Return value:
23482 On success, the number of bytes written are returned.
23483 Zero indicates nothing was written. On error, -1
23491 fd is not a valid file descriptor or is not open for
23495 buf is an invalid pointer value.
23498 An attempt was made to write a file that exceeds the
23499 host specific maximum file size allowed.
23502 No space on device to write the data.
23505 The call was interrupted by the user.
23509 @unnumberedsubsubsec lseek
23510 @cindex lseek, file-i/o system call
23514 long lseek (int fd, long offset, int flag);
23517 Flseek,fd,offset,flag
23520 @code{flag} is one of:
23524 The offset is set to offset bytes.
23527 The offset is set to its current location plus offset
23531 The offset is set to the size of the file plus offset
23536 @exdent Return value:
23537 On success, the resulting unsigned offset in bytes from
23538 the beginning of the file is returned. Otherwise, a
23539 value of -1 is returned.
23546 fd is not a valid open file descriptor.
23549 fd is associated with the @value{GDBN} console.
23552 flag is not a proper value.
23555 The call was interrupted by the user.
23559 @unnumberedsubsubsec rename
23560 @cindex rename, file-i/o system call
23564 int rename(const char *oldpath, const char *newpath);
23567 Frename,oldpathptr/len,newpathptr/len
23569 @exdent Return value:
23570 On success, zero is returned. On error, -1 is returned.
23577 newpath is an existing directory, but oldpath is not a
23581 newpath is a non-empty directory.
23584 oldpath or newpath is a directory that is in use by some
23588 An attempt was made to make a directory a subdirectory
23592 A component used as a directory in oldpath or new
23593 path is not a directory. Or oldpath is a directory
23594 and newpath exists but is not a directory.
23597 oldpathptr or newpathptr are invalid pointer values.
23600 No access to the file or the path of the file.
23604 oldpath or newpath was too long.
23607 A directory component in oldpath or newpath does not exist.
23610 The file is on a read-only filesystem.
23613 The device containing the file has no room for the new
23617 The call was interrupted by the user.
23621 @unnumberedsubsubsec unlink
23622 @cindex unlink, file-i/o system call
23626 int unlink(const char *pathname);
23629 Funlink,pathnameptr/len
23631 @exdent Return value:
23632 On success, zero is returned. On error, -1 is returned.
23639 No access to the file or the path of the file.
23642 The system does not allow unlinking of directories.
23645 The file pathname cannot be unlinked because it's
23646 being used by another process.
23649 pathnameptr is an invalid pointer value.
23652 pathname was too long.
23655 A directory component in pathname does not exist.
23658 A component of the path is not a directory.
23661 The file is on a read-only filesystem.
23664 The call was interrupted by the user.
23668 @unnumberedsubsubsec stat/fstat
23669 @cindex fstat, file-i/o system call
23670 @cindex stat, file-i/o system call
23674 int stat(const char *pathname, struct stat *buf);
23675 int fstat(int fd, struct stat *buf);
23678 Fstat,pathnameptr/len,bufptr
23681 @exdent Return value:
23682 On success, zero is returned. On error, -1 is returned.
23689 fd is not a valid open file.
23692 A directory component in pathname does not exist or the
23693 path is an empty string.
23696 A component of the path is not a directory.
23699 pathnameptr is an invalid pointer value.
23702 No access to the file or the path of the file.
23705 pathname was too long.
23708 The call was interrupted by the user.
23712 @unnumberedsubsubsec gettimeofday
23713 @cindex gettimeofday, file-i/o system call
23717 int gettimeofday(struct timeval *tv, void *tz);
23720 Fgettimeofday,tvptr,tzptr
23722 @exdent Return value:
23723 On success, 0 is returned, -1 otherwise.
23730 tz is a non-NULL pointer.
23733 tvptr and/or tzptr is an invalid pointer value.
23737 @unnumberedsubsubsec isatty
23738 @cindex isatty, file-i/o system call
23742 int isatty(int fd);
23747 @exdent Return value:
23748 Returns 1 if fd refers to the @value{GDBN} console, 0 otherwise.
23755 The call was interrupted by the user.
23759 @unnumberedsubsubsec system
23760 @cindex system, file-i/o system call
23764 int system(const char *command);
23767 Fsystem,commandptr/len
23769 @exdent Return value:
23770 The value returned is -1 on error and the return status
23771 of the command otherwise. Only the exit status of the
23772 command is returned, which is extracted from the hosts
23773 system return value by calling WEXITSTATUS(retval).
23774 In case /bin/sh could not be executed, 127 is returned.
23781 The call was interrupted by the user.
23784 @node Protocol specific representation of datatypes
23785 @subsection Protocol specific representation of datatypes
23786 @cindex protocol specific representation of datatypes, in file-i/o protocol
23789 * Integral datatypes::
23795 @node Integral datatypes
23796 @unnumberedsubsubsec Integral datatypes
23797 @cindex integral datatypes, in file-i/o protocol
23799 The integral datatypes used in the system calls are
23802 int@r{,} unsigned int@r{,} long@r{,} unsigned long@r{,} mode_t @r{and} time_t
23805 @code{Int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
23806 implemented as 32 bit values in this protocol.
23808 @code{Long} and @code{unsigned long} are implemented as 64 bit types.
23810 @xref{Limits}, for corresponding MIN and MAX values (similar to those
23811 in @file{limits.h}) to allow range checking on host and target.
23813 @code{time_t} datatypes are defined as seconds since the Epoch.
23815 All integral datatypes transferred as part of a memory read or write of a
23816 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
23819 @node Pointer values
23820 @unnumberedsubsubsec Pointer values
23821 @cindex pointer values, in file-i/o protocol
23823 Pointers to target data are transmitted as they are. An exception
23824 is made for pointers to buffers for which the length isn't
23825 transmitted as part of the function call, namely strings. Strings
23826 are transmitted as a pointer/length pair, both as hex values, e.g.@:
23833 which is a pointer to data of length 18 bytes at position 0x1aaf.
23834 The length is defined as the full string length in bytes, including
23835 the trailing null byte. Example:
23838 ``hello, world'' at address 0x123456
23849 @unnumberedsubsubsec struct stat
23850 @cindex struct stat, in file-i/o protocol
23852 The buffer of type struct stat used by the target and @value{GDBN} is defined
23857 unsigned int st_dev; /* device */
23858 unsigned int st_ino; /* inode */
23859 mode_t st_mode; /* protection */
23860 unsigned int st_nlink; /* number of hard links */
23861 unsigned int st_uid; /* user ID of owner */
23862 unsigned int st_gid; /* group ID of owner */
23863 unsigned int st_rdev; /* device type (if inode device) */
23864 unsigned long st_size; /* total size, in bytes */
23865 unsigned long st_blksize; /* blocksize for filesystem I/O */
23866 unsigned long st_blocks; /* number of blocks allocated */
23867 time_t st_atime; /* time of last access */
23868 time_t st_mtime; /* time of last modification */
23869 time_t st_ctime; /* time of last change */
23873 The integral datatypes are conforming to the definitions given in the
23874 approriate section (see @ref{Integral datatypes}, for details) so this
23875 structure is of size 64 bytes.
23877 The values of several fields have a restricted meaning and/or
23884 st_ino: No valid meaning for the target. Transmitted unchanged.
23886 st_mode: Valid mode bits are described in Appendix C. Any other
23887 bits have currently no meaning for the target.
23889 st_uid: No valid meaning for the target. Transmitted unchanged.
23891 st_gid: No valid meaning for the target. Transmitted unchanged.
23893 st_rdev: No valid meaning for the target. Transmitted unchanged.
23895 st_atime, st_mtime, st_ctime:
23896 These values have a host and file system dependent
23897 accuracy. Especially on Windows hosts the file systems
23898 don't support exact timing values.
23901 The target gets a struct stat of the above representation and is
23902 responsible to coerce it to the target representation before
23905 Note that due to size differences between the host and target
23906 representation of stat members, these members could eventually
23907 get truncated on the target.
23909 @node struct timeval
23910 @unnumberedsubsubsec struct timeval
23911 @cindex struct timeval, in file-i/o protocol
23913 The buffer of type struct timeval used by the target and @value{GDBN}
23914 is defined as follows:
23918 time_t tv_sec; /* second */
23919 long tv_usec; /* microsecond */
23923 The integral datatypes are conforming to the definitions given in the
23924 approriate section (see @ref{Integral datatypes}, for details) so this
23925 structure is of size 8 bytes.
23928 @subsection Constants
23929 @cindex constants, in file-i/o protocol
23931 The following values are used for the constants inside of the
23932 protocol. @value{GDBN} and target are resposible to translate these
23933 values before and after the call as needed.
23944 @unnumberedsubsubsec Open flags
23945 @cindex open flags, in file-i/o protocol
23947 All values are given in hexadecimal representation.
23959 @node mode_t values
23960 @unnumberedsubsubsec mode_t values
23961 @cindex mode_t values, in file-i/o protocol
23963 All values are given in octal representation.
23980 @unnumberedsubsubsec Errno values
23981 @cindex errno values, in file-i/o protocol
23983 All values are given in decimal representation.
24008 EUNKNOWN is used as a fallback error value if a host system returns
24009 any error value not in the list of supported error numbers.
24012 @unnumberedsubsubsec Lseek flags
24013 @cindex lseek flags, in file-i/o protocol
24022 @unnumberedsubsubsec Limits
24023 @cindex limits, in file-i/o protocol
24025 All values are given in decimal representation.
24028 INT_MIN -2147483648
24030 UINT_MAX 4294967295
24031 LONG_MIN -9223372036854775808
24032 LONG_MAX 9223372036854775807
24033 ULONG_MAX 18446744073709551615
24036 @node File-I/O Examples
24037 @subsection File-I/O Examples
24038 @cindex file-i/o examples
24040 Example sequence of a write call, file descriptor 3, buffer is at target
24041 address 0x1234, 6 bytes should be written:
24044 <- @code{Fwrite,3,1234,6}
24045 @emph{request memory read from target}
24048 @emph{return "6 bytes written"}
24052 Example sequence of a read call, file descriptor 3, buffer is at target
24053 address 0x1234, 6 bytes should be read:
24056 <- @code{Fread,3,1234,6}
24057 @emph{request memory write to target}
24058 -> @code{X1234,6:XXXXXX}
24059 @emph{return "6 bytes read"}
24063 Example sequence of a read call, call fails on the host due to invalid
24064 file descriptor (EBADF):
24067 <- @code{Fread,3,1234,6}
24071 Example sequence of a read call, user presses Ctrl-C before syscall on
24075 <- @code{Fread,3,1234,6}
24080 Example sequence of a read call, user presses Ctrl-C after syscall on
24084 <- @code{Fread,3,1234,6}
24085 -> @code{X1234,6:XXXXXX}
24089 @include agentexpr.texi
24103 % I think something like @colophon should be in texinfo. In the
24105 \long\def\colophon{\hbox to0pt{}\vfill
24106 \centerline{The body of this manual is set in}
24107 \centerline{\fontname\tenrm,}
24108 \centerline{with headings in {\bf\fontname\tenbf}}
24109 \centerline{and examples in {\tt\fontname\tentt}.}
24110 \centerline{{\it\fontname\tenit\/},}
24111 \centerline{{\bf\fontname\tenbf}, and}
24112 \centerline{{\sl\fontname\tensl\/}}
24113 \centerline{are used for emphasis.}\vfill}
24115 % Blame: doc@cygnus.com, 1991.