1 \input texinfo @c -*-texinfo-*-
2 @c Copyright 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,
3 @c 1999, 2000, 2001, 2002
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!
33 @c !!set GDB manual's revision date
36 @c !!set GDB edit command default editor
39 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
41 @c This is a dir.info fragment to support semi-automated addition of
42 @c manuals to an info tree.
43 @dircategory Programming & development tools.
45 * Gdb: (gdb). The @sc{gnu} debugger.
49 This file documents the @sc{gnu} debugger @value{GDBN}.
52 This is the @value{EDITION} Edition, @value{DATE},
53 of @cite{Debugging with @value{GDBN}: the @sc{gnu} Source-Level Debugger}
54 for @value{GDBN} Version @value{GDBVN}.
56 Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998,@*
57 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
59 Permission is granted to copy, distribute and/or modify this document
60 under the terms of the GNU Free Documentation License, Version 1.1 or
61 any later version published by the Free Software Foundation; with the
62 Invariant Sections being ``Free Software'' and ``Free Software Needs
63 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
64 and with the Back-Cover Texts as in (a) below.
66 (a) The Free Software Foundation's Back-Cover Text is: ``You have
67 freedom to copy and modify this GNU Manual, like GNU software. Copies
68 published by the Free Software Foundation raise funds for GNU
73 @title Debugging with @value{GDBN}
74 @subtitle The @sc{gnu} Source-Level Debugger
76 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
77 @subtitle @value{DATE}
78 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
82 \hfill (Send bugs and comments on @value{GDBN} to bug-gdb\@gnu.org.)\par
83 \hfill {\it Debugging with @value{GDBN}}\par
84 \hfill \TeX{}info \texinfoversion\par
88 @vskip 0pt plus 1filll
89 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
90 1996, 1998, 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
92 Published by the Free Software Foundation @*
93 59 Temple Place - Suite 330, @*
94 Boston, MA 02111-1307 USA @*
97 Permission is granted to copy, distribute and/or modify this document
98 under the terms of the GNU Free Documentation License, Version 1.1 or
99 any later version published by the Free Software Foundation; with the
100 Invariant Sections being ``Free Software'' and ``Free Software Needs
101 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
102 and with the Back-Cover Texts as in (a) below.
104 (a) The Free Software Foundation's Back-Cover Text is: ``You have
105 freedom to copy and modify this GNU Manual, like GNU software. Copies
106 published by the Free Software Foundation raise funds for GNU
112 @node Top, Summary, (dir), (dir)
114 @top Debugging with @value{GDBN}
116 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
118 This is the @value{EDITION} Edition, @value{DATE}, for @value{GDBN} Version
121 Copyright (C) 1988-2002 Free Software Foundation, Inc.
124 * Summary:: Summary of @value{GDBN}
125 * Sample Session:: A sample @value{GDBN} session
127 * Invocation:: Getting in and out of @value{GDBN}
128 * Commands:: @value{GDBN} commands
129 * Running:: Running programs under @value{GDBN}
130 * Stopping:: Stopping and continuing
131 * Stack:: Examining the stack
132 * Source:: Examining source files
133 * Data:: Examining data
134 * Macros:: Preprocessor Macros
135 * Tracepoints:: Debugging remote targets non-intrusively
136 * Overlays:: Debugging programs that use overlays
138 * Languages:: Using @value{GDBN} with different languages
140 * Symbols:: Examining the symbol table
141 * Altering:: Altering execution
142 * GDB Files:: @value{GDBN} files
143 * Targets:: Specifying a debugging target
144 * Remote Debugging:: Debugging remote programs
145 * Configurations:: Configuration-specific information
146 * Controlling GDB:: Controlling @value{GDBN}
147 * Sequences:: Canned sequences of commands
148 * TUI:: @value{GDBN} Text User Interface
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 * Copying:: GNU General Public License says
162 how you can copy and share GDB
163 * GNU Free Documentation License:: The license for this documentation
172 @unnumbered Summary of @value{GDBN}
174 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
175 going on ``inside'' another program while it executes---or what another
176 program was doing at the moment it crashed.
178 @value{GDBN} can do four main kinds of things (plus other things in support of
179 these) to help you catch bugs in the act:
183 Start your program, specifying anything that might affect its behavior.
186 Make your program stop on specified conditions.
189 Examine what has happened, when your program has stopped.
192 Change things in your program, so you can experiment with correcting the
193 effects of one bug and go on to learn about another.
196 You can use @value{GDBN} to debug programs written in C and C++.
197 For more information, see @ref{Support,,Supported languages}.
198 For more information, see @ref{C,,C and C++}.
200 @c OBSOLETE @cindex Chill
203 @c OBSOLETE and Chill
204 is partial. For information on Modula-2, see @ref{Modula-2,,Modula-2}.
205 @c OBSOLETE For information on Chill, see @ref{Chill}.
208 Debugging Pascal programs which use sets, subranges, file variables, or
209 nested functions does not currently work. @value{GDBN} does not support
210 entering expressions, printing values, or similar features using Pascal
214 @value{GDBN} can be used to debug programs written in Fortran, although
215 it may be necessary to refer to some variables with a trailing
219 * Free Software:: Freely redistributable software
220 * Contributors:: Contributors to GDB
224 @unnumberedsec Free software
226 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
227 General Public License
228 (GPL). The GPL gives you the freedom to copy or adapt a licensed
229 program---but every person getting a copy also gets with it the
230 freedom to modify that copy (which means that they must get access to
231 the source code), and the freedom to distribute further copies.
232 Typical software companies use copyrights to limit your freedoms; the
233 Free Software Foundation uses the GPL to preserve these freedoms.
235 Fundamentally, the General Public License is a license which says that
236 you have these freedoms and that you cannot take these freedoms away
239 @unnumberedsec Free Software Needs Free Documentation
241 The biggest deficiency in the free software community today is not in
242 the software---it is the lack of good free documentation that we can
243 include with the free software. Many of our most important
244 programs do not come with free reference manuals and free introductory
245 texts. Documentation is an essential part of any software package;
246 when an important free software package does not come with a free
247 manual and a free tutorial, that is a major gap. We have many such
250 Consider Perl, for instance. The tutorial manuals that people
251 normally use are non-free. How did this come about? Because the
252 authors of those manuals published them with restrictive terms---no
253 copying, no modification, source files not available---which exclude
254 them from the free software world.
256 That wasn't the first time this sort of thing happened, and it was far
257 from the last. Many times we have heard a GNU user eagerly describe a
258 manual that he is writing, his intended contribution to the community,
259 only to learn that he had ruined everything by signing a publication
260 contract to make it non-free.
262 Free documentation, like free software, is a matter of freedom, not
263 price. The problem with the non-free manual is not that publishers
264 charge a price for printed copies---that in itself is fine. (The Free
265 Software Foundation sells printed copies of manuals, too.) The
266 problem is the restrictions on the use of the manual. Free manuals
267 are available in source code form, and give you permission to copy and
268 modify. Non-free manuals do not allow this.
270 The criteria of freedom for a free manual are roughly the same as for
271 free software. Redistribution (including the normal kinds of
272 commercial redistribution) must be permitted, so that the manual can
273 accompany every copy of the program, both on-line and on paper.
275 Permission for modification of the technical content is crucial too.
276 When people modify the software, adding or changing features, if they
277 are conscientious they will change the manual too---so they can
278 provide accurate and clear documentation for the modified program. A
279 manual that leaves you no choice but to write a new manual to document
280 a changed version of the program is not really available to our
283 Some kinds of limits on the way modification is handled are
284 acceptable. For example, requirements to preserve the original
285 author's copyright notice, the distribution terms, or the list of
286 authors, are ok. It is also no problem to require modified versions
287 to include notice that they were modified. Even entire sections that
288 may not be deleted or changed are acceptable, as long as they deal
289 with nontechnical topics (like this one). These kinds of restrictions
290 are acceptable because they don't obstruct the community's normal use
293 However, it must be possible to modify all the @emph{technical}
294 content of the manual, and then distribute the result in all the usual
295 media, through all the usual channels. Otherwise, the restrictions
296 obstruct the use of the manual, it is not free, and we need another
297 manual to replace it.
299 Please spread the word about this issue. Our community continues to
300 lose manuals to proprietary publishing. If we spread the word that
301 free software needs free reference manuals and free tutorials, perhaps
302 the next person who wants to contribute by writing documentation will
303 realize, before it is too late, that only free manuals contribute to
304 the free software community.
306 If you are writing documentation, please insist on publishing it under
307 the GNU Free Documentation License or another free documentation
308 license. Remember that this decision requires your approval---you
309 don't have to let the publisher decide. Some commercial publishers
310 will use a free license if you insist, but they will not propose the
311 option; it is up to you to raise the issue and say firmly that this is
312 what you want. If the publisher you are dealing with refuses, please
313 try other publishers. If you're not sure whether a proposed license
314 is free, write to @email{licensing@@gnu.org}.
316 You can encourage commercial publishers to sell more free, copylefted
317 manuals and tutorials by buying them, and particularly by buying
318 copies from the publishers that paid for their writing or for major
319 improvements. Meanwhile, try to avoid buying non-free documentation
320 at all. Check the distribution terms of a manual before you buy it,
321 and insist that whoever seeks your business must respect your freedom.
322 Check the history of the book, and try to reward the publishers that
323 have paid or pay the authors to work on it.
325 The Free Software Foundation maintains a list of free documentation
326 published by other publishers, at
327 @url{http://www.fsf.org/doc/other-free-books.html}.
330 @unnumberedsec Contributors to @value{GDBN}
332 Richard Stallman was the original author of @value{GDBN}, and of many
333 other @sc{gnu} programs. Many others have contributed to its
334 development. This section attempts to credit major contributors. One
335 of the virtues of free software is that everyone is free to contribute
336 to it; with regret, we cannot actually acknowledge everyone here. The
337 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
338 blow-by-blow account.
340 Changes much prior to version 2.0 are lost in the mists of time.
343 @emph{Plea:} Additions to this section are particularly welcome. If you
344 or your friends (or enemies, to be evenhanded) have been unfairly
345 omitted from this list, we would like to add your names!
348 So that they may not regard their many labors as thankless, we
349 particularly thank those who shepherded @value{GDBN} through major
351 Andrew Cagney (releases 5.3, 5.2, 5.1 and 5.0);
352 Jim Blandy (release 4.18);
353 Jason Molenda (release 4.17);
354 Stan Shebs (release 4.14);
355 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
356 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
357 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
358 Jim Kingdon (releases 3.5, 3.4, and 3.3);
359 and Randy Smith (releases 3.2, 3.1, and 3.0).
361 Richard Stallman, assisted at various times by Peter TerMaat, Chris
362 Hanson, and Richard Mlynarik, handled releases through 2.8.
364 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
365 in @value{GDBN}, with significant additional contributions from Per
366 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
367 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
368 much general update work leading to release 3.0).
370 @value{GDBN} uses the BFD subroutine library to examine multiple
371 object-file formats; BFD was a joint project of David V.
372 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
374 David Johnson wrote the original COFF support; Pace Willison did
375 the original support for encapsulated COFF.
377 Brent Benson of Harris Computer Systems contributed DWARF2 support.
379 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
380 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
382 Jean-Daniel Fekete contributed Sun 386i support.
383 Chris Hanson improved the HP9000 support.
384 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
385 David Johnson contributed Encore Umax support.
386 Jyrki Kuoppala contributed Altos 3068 support.
387 Jeff Law contributed HP PA and SOM support.
388 Keith Packard contributed NS32K support.
389 Doug Rabson contributed Acorn Risc Machine support.
390 Bob Rusk contributed Harris Nighthawk CX-UX support.
391 Chris Smith contributed Convex support (and Fortran debugging).
392 Jonathan Stone contributed Pyramid support.
393 Michael Tiemann contributed SPARC support.
394 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
395 Pace Willison contributed Intel 386 support.
396 Jay Vosburgh contributed Symmetry support.
398 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
400 Rich Schaefer and Peter Schauer helped with support of SunOS shared
403 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
404 about several machine instruction sets.
406 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
407 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
408 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
409 and RDI targets, respectively.
411 Brian Fox is the author of the readline libraries providing
412 command-line editing and command history.
414 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
415 Modula-2 support, and contributed the Languages chapter of this manual.
417 Fred Fish wrote most of the support for Unix System Vr4.
418 He also enhanced the command-completion support to cover C@t{++} overloaded
421 Hitachi America, Ltd. sponsored the support for H8/300, H8/500, and
424 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
426 Mitsubishi sponsored the support for D10V, D30V, and M32R/D processors.
428 Toshiba sponsored the support for the TX39 Mips processor.
430 Matsushita sponsored the support for the MN10200 and MN10300 processors.
432 Fujitsu sponsored the support for SPARClite and FR30 processors.
434 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
437 Michael Snyder added support for tracepoints.
439 Stu Grossman wrote gdbserver.
441 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
442 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
444 The following people at the Hewlett-Packard Company contributed
445 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
446 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
447 compiler, and the terminal user interface: Ben Krepp, Richard Title,
448 John Bishop, Susan Macchia, Kathy Mann, Satish Pai, India Paul, Steve
449 Rehrauer, and Elena Zannoni. Kim Haase provided HP-specific
450 information in this manual.
452 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
453 Robert Hoehne made significant contributions to the DJGPP port.
455 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
456 development since 1991. Cygnus engineers who have worked on @value{GDBN}
457 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
458 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
459 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
460 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
461 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
462 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
463 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
464 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
465 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
466 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
467 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
468 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
469 Zuhn have made contributions both large and small.
471 Jim Blandy added support for preprocessor macros, while working for Red
475 @chapter A Sample @value{GDBN} Session
477 You can use this manual at your leisure to read all about @value{GDBN}.
478 However, a handful of commands are enough to get started using the
479 debugger. This chapter illustrates those commands.
482 In this sample session, we emphasize user input like this: @b{input},
483 to make it easier to pick out from the surrounding output.
486 @c FIXME: this example may not be appropriate for some configs, where
487 @c FIXME...primary interest is in remote use.
489 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
490 processor) exhibits the following bug: sometimes, when we change its
491 quote strings from the default, the commands used to capture one macro
492 definition within another stop working. In the following short @code{m4}
493 session, we define a macro @code{foo} which expands to @code{0000}; we
494 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
495 same thing. However, when we change the open quote string to
496 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
497 procedure fails to define a new synonym @code{baz}:
506 @b{define(bar,defn(`foo'))}
510 @b{changequote(<QUOTE>,<UNQUOTE>)}
512 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
515 m4: End of input: 0: fatal error: EOF in string
519 Let us use @value{GDBN} to try to see what is going on.
522 $ @b{@value{GDBP} m4}
523 @c FIXME: this falsifies the exact text played out, to permit smallbook
524 @c FIXME... format to come out better.
525 @value{GDBN} is free software and you are welcome to distribute copies
526 of it under certain conditions; type "show copying" to see
528 There is absolutely no warranty for @value{GDBN}; type "show warranty"
531 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
536 @value{GDBN} reads only enough symbol data to know where to find the
537 rest when needed; as a result, the first prompt comes up very quickly.
538 We now tell @value{GDBN} to use a narrower display width than usual, so
539 that examples fit in this manual.
542 (@value{GDBP}) @b{set width 70}
546 We need to see how the @code{m4} built-in @code{changequote} works.
547 Having looked at the source, we know the relevant subroutine is
548 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
549 @code{break} command.
552 (@value{GDBP}) @b{break m4_changequote}
553 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
557 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
558 control; as long as control does not reach the @code{m4_changequote}
559 subroutine, the program runs as usual:
562 (@value{GDBP}) @b{run}
563 Starting program: /work/Editorial/gdb/gnu/m4/m4
571 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
572 suspends execution of @code{m4}, displaying information about the
573 context where it stops.
576 @b{changequote(<QUOTE>,<UNQUOTE>)}
578 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
580 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
584 Now we use the command @code{n} (@code{next}) to advance execution to
585 the next line of the current function.
589 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
594 @code{set_quotes} looks like a promising subroutine. We can go into it
595 by using the command @code{s} (@code{step}) instead of @code{next}.
596 @code{step} goes to the next line to be executed in @emph{any}
597 subroutine, so it steps into @code{set_quotes}.
601 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
603 530 if (lquote != def_lquote)
607 The display that shows the subroutine where @code{m4} is now
608 suspended (and its arguments) is called a stack frame display. It
609 shows a summary of the stack. We can use the @code{backtrace}
610 command (which can also be spelled @code{bt}), to see where we are
611 in the stack as a whole: the @code{backtrace} command displays a
612 stack frame for each active subroutine.
615 (@value{GDBP}) @b{bt}
616 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
618 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
620 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
621 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
623 #4 0x79dc in expand_input () at macro.c:40
624 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
628 We step through a few more lines to see what happens. The first two
629 times, we can use @samp{s}; the next two times we use @code{n} to avoid
630 falling into the @code{xstrdup} subroutine.
634 0x3b5c 532 if (rquote != def_rquote)
636 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
637 def_lquote : xstrdup(lq);
639 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
642 538 len_lquote = strlen(rquote);
646 The last line displayed looks a little odd; we can examine the variables
647 @code{lquote} and @code{rquote} to see if they are in fact the new left
648 and right quotes we specified. We use the command @code{p}
649 (@code{print}) to see their values.
652 (@value{GDBP}) @b{p lquote}
653 $1 = 0x35d40 "<QUOTE>"
654 (@value{GDBP}) @b{p rquote}
655 $2 = 0x35d50 "<UNQUOTE>"
659 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
660 To look at some context, we can display ten lines of source
661 surrounding the current line with the @code{l} (@code{list}) command.
667 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
669 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
672 538 len_lquote = strlen(rquote);
673 539 len_rquote = strlen(lquote);
680 Let us step past the two lines that set @code{len_lquote} and
681 @code{len_rquote}, and then examine the values of those variables.
685 539 len_rquote = strlen(lquote);
688 (@value{GDBP}) @b{p len_lquote}
690 (@value{GDBP}) @b{p len_rquote}
695 That certainly looks wrong, assuming @code{len_lquote} and
696 @code{len_rquote} are meant to be the lengths of @code{lquote} and
697 @code{rquote} respectively. We can set them to better values using
698 the @code{p} command, since it can print the value of
699 any expression---and that expression can include subroutine calls and
703 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
705 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
710 Is that enough to fix the problem of using the new quotes with the
711 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
712 executing with the @code{c} (@code{continue}) command, and then try the
713 example that caused trouble initially:
719 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
726 Success! The new quotes now work just as well as the default ones. The
727 problem seems to have been just the two typos defining the wrong
728 lengths. We allow @code{m4} exit by giving it an EOF as input:
732 Program exited normally.
736 The message @samp{Program exited normally.} is from @value{GDBN}; it
737 indicates @code{m4} has finished executing. We can end our @value{GDBN}
738 session with the @value{GDBN} @code{quit} command.
741 (@value{GDBP}) @b{quit}
745 @chapter Getting In and Out of @value{GDBN}
747 This chapter discusses how to start @value{GDBN}, and how to get out of it.
751 type @samp{@value{GDBP}} to start @value{GDBN}.
753 type @kbd{quit} or @kbd{C-d} to exit.
757 * Invoking GDB:: How to start @value{GDBN}
758 * Quitting GDB:: How to quit @value{GDBN}
759 * Shell Commands:: How to use shell commands inside @value{GDBN}
763 @section Invoking @value{GDBN}
765 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
766 @value{GDBN} reads commands from the terminal until you tell it to exit.
768 You can also run @code{@value{GDBP}} with a variety of arguments and options,
769 to specify more of your debugging environment at the outset.
771 The command-line options described here are designed
772 to cover a variety of situations; in some environments, some of these
773 options may effectively be unavailable.
775 The most usual way to start @value{GDBN} is with one argument,
776 specifying an executable program:
779 @value{GDBP} @var{program}
783 You can also start with both an executable program and a core file
787 @value{GDBP} @var{program} @var{core}
790 You can, instead, specify a process ID as a second argument, if you want
791 to debug a running process:
794 @value{GDBP} @var{program} 1234
798 would attach @value{GDBN} to process @code{1234} (unless you also have a file
799 named @file{1234}; @value{GDBN} does check for a core file first).
801 Taking advantage of the second command-line argument requires a fairly
802 complete operating system; when you use @value{GDBN} as a remote
803 debugger attached to a bare board, there may not be any notion of
804 ``process'', and there is often no way to get a core dump. @value{GDBN}
805 will warn you if it is unable to attach or to read core dumps.
807 You can optionally have @code{@value{GDBP}} pass any arguments after the
808 executable file to the inferior using @code{--args}. This option stops
811 gdb --args gcc -O2 -c foo.c
813 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
814 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
816 You can run @code{@value{GDBP}} without printing the front material, which describes
817 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
824 You can further control how @value{GDBN} starts up by using command-line
825 options. @value{GDBN} itself can remind you of the options available.
835 to display all available options and briefly describe their use
836 (@samp{@value{GDBP} -h} is a shorter equivalent).
838 All options and command line arguments you give are processed
839 in sequential order. The order makes a difference when the
840 @samp{-x} option is used.
844 * File Options:: Choosing files
845 * Mode Options:: Choosing modes
849 @subsection Choosing files
851 When @value{GDBN} starts, it reads any arguments other than options as
852 specifying an executable file and core file (or process ID). This is
853 the same as if the arguments were specified by the @samp{-se} and
854 @samp{-c} (or @samp{-p} options respectively. (@value{GDBN} reads the
855 first argument that does not have an associated option flag as
856 equivalent to the @samp{-se} option followed by that argument; and the
857 second argument that does not have an associated option flag, if any, as
858 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
859 If the second argument begins with a decimal digit, @value{GDBN} will
860 first attempt to attach to it as a process, and if that fails, attempt
861 to open it as a corefile. If you have a corefile whose name begins with
862 a digit, you can prevent @value{GDBN} from treating it as a pid by
863 prefixing it with @file{./}, eg. @file{./12345}.
865 If @value{GDBN} has not been configured to included core file support,
866 such as for most embedded targets, then it will complain about a second
867 argument and ignore it.
869 Many options have both long and short forms; both are shown in the
870 following list. @value{GDBN} also recognizes the long forms if you truncate
871 them, so long as enough of the option is present to be unambiguous.
872 (If you prefer, you can flag option arguments with @samp{--} rather
873 than @samp{-}, though we illustrate the more usual convention.)
875 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
876 @c way, both those who look for -foo and --foo in the index, will find
880 @item -symbols @var{file}
882 @cindex @code{--symbols}
884 Read symbol table from file @var{file}.
886 @item -exec @var{file}
888 @cindex @code{--exec}
890 Use file @var{file} as the executable file to execute when appropriate,
891 and for examining pure data in conjunction with a core dump.
895 Read symbol table from file @var{file} and use it as the executable
898 @item -core @var{file}
900 @cindex @code{--core}
902 Use file @var{file} as a core dump to examine.
904 @item -c @var{number}
905 @item -pid @var{number}
906 @itemx -p @var{number}
909 Connect to process ID @var{number}, as with the @code{attach} command.
910 If there is no such process, @value{GDBN} will attempt to open a core
911 file named @var{number}.
913 @item -command @var{file}
915 @cindex @code{--command}
917 Execute @value{GDBN} commands from file @var{file}. @xref{Command
918 Files,, Command files}.
920 @item -directory @var{directory}
921 @itemx -d @var{directory}
922 @cindex @code{--directory}
924 Add @var{directory} to the path to search for source files.
928 @cindex @code{--mapped}
930 @emph{Warning: this option depends on operating system facilities that are not
931 supported on all systems.}@*
932 If memory-mapped files are available on your system through the @code{mmap}
933 system call, you can use this option
934 to have @value{GDBN} write the symbols from your
935 program into a reusable file in the current directory. If the program you are debugging is
936 called @file{/tmp/fred}, the mapped symbol file is @file{/tmp/fred.syms}.
937 Future @value{GDBN} debugging sessions notice the presence of this file,
938 and can quickly map in symbol information from it, rather than reading
939 the symbol table from the executable program.
941 The @file{.syms} file is specific to the host machine where @value{GDBN}
942 is run. It holds an exact image of the internal @value{GDBN} symbol
943 table. It cannot be shared across multiple host platforms.
947 @cindex @code{--readnow}
949 Read each symbol file's entire symbol table immediately, rather than
950 the default, which is to read it incrementally as it is needed.
951 This makes startup slower, but makes future operations faster.
955 You typically combine the @code{-mapped} and @code{-readnow} options in
956 order to build a @file{.syms} file that contains complete symbol
957 information. (@xref{Files,,Commands to specify files}, for information
958 on @file{.syms} files.) A simple @value{GDBN} invocation to do nothing
959 but build a @file{.syms} file for future use is:
962 gdb -batch -nx -mapped -readnow programname
966 @subsection Choosing modes
968 You can run @value{GDBN} in various alternative modes---for example, in
969 batch mode or quiet mode.
976 Do not execute commands found in any initialization files. Normally,
977 @value{GDBN} executes the commands in these files after all the command
978 options and arguments have been processed. @xref{Command Files,,Command
984 @cindex @code{--quiet}
985 @cindex @code{--silent}
987 ``Quiet''. Do not print the introductory and copyright messages. These
988 messages are also suppressed in batch mode.
991 @cindex @code{--batch}
992 Run in batch mode. Exit with status @code{0} after processing all the
993 command files specified with @samp{-x} (and all commands from
994 initialization files, if not inhibited with @samp{-n}). Exit with
995 nonzero status if an error occurs in executing the @value{GDBN} commands
996 in the command files.
998 Batch mode may be useful for running @value{GDBN} as a filter, for
999 example to download and run a program on another computer; in order to
1000 make this more useful, the message
1003 Program exited normally.
1007 (which is ordinarily issued whenever a program running under
1008 @value{GDBN} control terminates) is not issued when running in batch
1013 @cindex @code{--nowindows}
1015 ``No windows''. If @value{GDBN} comes with a graphical user interface
1016 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1017 interface. If no GUI is available, this option has no effect.
1021 @cindex @code{--windows}
1023 If @value{GDBN} includes a GUI, then this option requires it to be
1026 @item -cd @var{directory}
1028 Run @value{GDBN} using @var{directory} as its working directory,
1029 instead of the current directory.
1033 @cindex @code{--fullname}
1035 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1036 subprocess. It tells @value{GDBN} to output the full file name and line
1037 number in a standard, recognizable fashion each time a stack frame is
1038 displayed (which includes each time your program stops). This
1039 recognizable format looks like two @samp{\032} characters, followed by
1040 the file name, line number and character position separated by colons,
1041 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1042 @samp{\032} characters as a signal to display the source code for the
1046 @cindex @code{--epoch}
1047 The Epoch Emacs-@value{GDBN} interface sets this option when it runs
1048 @value{GDBN} as a subprocess. It tells @value{GDBN} to modify its print
1049 routines so as to allow Epoch to display values of expressions in a
1052 @item -annotate @var{level}
1053 @cindex @code{--annotate}
1054 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1055 effect is identical to using @samp{set annotate @var{level}}
1056 (@pxref{Annotations}).
1057 Annotation level controls how much information does @value{GDBN} print
1058 together with its prompt, values of expressions, source lines, and other
1059 types of output. Level 0 is the normal, level 1 is for use when
1060 @value{GDBN} is run as a subprocess of @sc{gnu} Emacs, level 2 is the
1061 maximum annotation suitable for programs that control @value{GDBN}.
1064 @cindex @code{--async}
1065 Use the asynchronous event loop for the command-line interface.
1066 @value{GDBN} processes all events, such as user keyboard input, via a
1067 special event loop. This allows @value{GDBN} to accept and process user
1068 commands in parallel with the debugged process being
1069 run@footnote{@value{GDBN} built with @sc{djgpp} tools for
1070 MS-DOS/MS-Windows supports this mode of operation, but the event loop is
1071 suspended when the debuggee runs.}, so you don't need to wait for
1072 control to return to @value{GDBN} before you type the next command.
1073 (@emph{Note:} as of version 5.1, the target side of the asynchronous
1074 operation is not yet in place, so @samp{-async} does not work fully
1076 @c FIXME: when the target side of the event loop is done, the above NOTE
1077 @c should be removed.
1079 When the standard input is connected to a terminal device, @value{GDBN}
1080 uses the asynchronous event loop by default, unless disabled by the
1081 @samp{-noasync} option.
1084 @cindex @code{--noasync}
1085 Disable the asynchronous event loop for the command-line interface.
1088 @cindex @code{--args}
1089 Change interpretation of command line so that arguments following the
1090 executable file are passed as command line arguments to the inferior.
1091 This option stops option processing.
1093 @item -baud @var{bps}
1095 @cindex @code{--baud}
1097 Set the line speed (baud rate or bits per second) of any serial
1098 interface used by @value{GDBN} for remote debugging.
1100 @item -tty @var{device}
1101 @itemx -t @var{device}
1102 @cindex @code{--tty}
1104 Run using @var{device} for your program's standard input and output.
1105 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1107 @c resolve the situation of these eventually
1109 @cindex @code{--tui}
1110 Activate the Terminal User Interface when starting.
1111 The Terminal User Interface manages several text windows on the terminal,
1112 showing source, assembly, registers and @value{GDBN} command outputs
1113 (@pxref{TUI, ,@value{GDBN} Text User Interface}).
1114 Do not use this option if you run @value{GDBN} from Emacs
1115 (@pxref{Emacs, ,Using @value{GDBN} under @sc{gnu} Emacs}).
1118 @c @cindex @code{--xdb}
1119 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1120 @c For information, see the file @file{xdb_trans.html}, which is usually
1121 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1124 @item -interpreter @var{interp}
1125 @cindex @code{--interpreter}
1126 Use the interpreter @var{interp} for interface with the controlling
1127 program or device. This option is meant to be set by programs which
1128 communicate with @value{GDBN} using it as a back end.
1130 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1131 @value{GDBN} to use the current @dfn{@sc{gdb/mi} interface}
1132 (@pxref{GDB/MI, , The @sc{gdb/mi} Interface}). The previous @sc{gdb/mi}
1133 interface, included in @value{GDBN} version 5.3, can be selected with
1134 @samp{--interpreter=mi1}. Earlier @sc{gdb/mi} interfaces
1138 @cindex @code{--write}
1139 Open the executable and core files for both reading and writing. This
1140 is equivalent to the @samp{set write on} command inside @value{GDBN}
1144 @cindex @code{--statistics}
1145 This option causes @value{GDBN} to print statistics about time and
1146 memory usage after it completes each command and returns to the prompt.
1149 @cindex @code{--version}
1150 This option causes @value{GDBN} to print its version number and
1151 no-warranty blurb, and exit.
1156 @section Quitting @value{GDBN}
1157 @cindex exiting @value{GDBN}
1158 @cindex leaving @value{GDBN}
1161 @kindex quit @r{[}@var{expression}@r{]}
1162 @kindex q @r{(@code{quit})}
1163 @item quit @r{[}@var{expression}@r{]}
1165 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1166 @code{q}), or type an end-of-file character (usually @kbd{C-d}). If you
1167 do not supply @var{expression}, @value{GDBN} will terminate normally;
1168 otherwise it will terminate using the result of @var{expression} as the
1173 An interrupt (often @kbd{C-c}) does not exit from @value{GDBN}, but rather
1174 terminates the action of any @value{GDBN} command that is in progress and
1175 returns to @value{GDBN} command level. It is safe to type the interrupt
1176 character at any time because @value{GDBN} does not allow it to take effect
1177 until a time when it is safe.
1179 If you have been using @value{GDBN} to control an attached process or
1180 device, you can release it with the @code{detach} command
1181 (@pxref{Attach, ,Debugging an already-running process}).
1183 @node Shell Commands
1184 @section Shell commands
1186 If you need to execute occasional shell commands during your
1187 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1188 just use the @code{shell} command.
1192 @cindex shell escape
1193 @item shell @var{command string}
1194 Invoke a standard shell to execute @var{command string}.
1195 If it exists, the environment variable @code{SHELL} determines which
1196 shell to run. Otherwise @value{GDBN} uses the default shell
1197 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1200 The utility @code{make} is often needed in development environments.
1201 You do not have to use the @code{shell} command for this purpose in
1206 @cindex calling make
1207 @item make @var{make-args}
1208 Execute the @code{make} program with the specified
1209 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1213 @chapter @value{GDBN} Commands
1215 You can abbreviate a @value{GDBN} command to the first few letters of the command
1216 name, if that abbreviation is unambiguous; and you can repeat certain
1217 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1218 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1219 show you the alternatives available, if there is more than one possibility).
1222 * Command Syntax:: How to give commands to @value{GDBN}
1223 * Completion:: Command completion
1224 * Help:: How to ask @value{GDBN} for help
1227 @node Command Syntax
1228 @section Command syntax
1230 A @value{GDBN} command is a single line of input. There is no limit on
1231 how long it can be. It starts with a command name, which is followed by
1232 arguments whose meaning depends on the command name. For example, the
1233 command @code{step} accepts an argument which is the number of times to
1234 step, as in @samp{step 5}. You can also use the @code{step} command
1235 with no arguments. Some commands do not allow any arguments.
1237 @cindex abbreviation
1238 @value{GDBN} command names may always be truncated if that abbreviation is
1239 unambiguous. Other possible command abbreviations are listed in the
1240 documentation for individual commands. In some cases, even ambiguous
1241 abbreviations are allowed; for example, @code{s} is specially defined as
1242 equivalent to @code{step} even though there are other commands whose
1243 names start with @code{s}. You can test abbreviations by using them as
1244 arguments to the @code{help} command.
1246 @cindex repeating commands
1247 @kindex RET @r{(repeat last command)}
1248 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1249 repeat the previous command. Certain commands (for example, @code{run})
1250 will not repeat this way; these are commands whose unintentional
1251 repetition might cause trouble and which you are unlikely to want to
1254 The @code{list} and @code{x} commands, when you repeat them with
1255 @key{RET}, construct new arguments rather than repeating
1256 exactly as typed. This permits easy scanning of source or memory.
1258 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1259 output, in a way similar to the common utility @code{more}
1260 (@pxref{Screen Size,,Screen size}). Since it is easy to press one
1261 @key{RET} too many in this situation, @value{GDBN} disables command
1262 repetition after any command that generates this sort of display.
1264 @kindex # @r{(a comment)}
1266 Any text from a @kbd{#} to the end of the line is a comment; it does
1267 nothing. This is useful mainly in command files (@pxref{Command
1268 Files,,Command files}).
1270 @cindex repeating command sequences
1271 @kindex C-o @r{(operate-and-get-next)}
1272 The @kbd{C-o} binding is useful for repeating a complex sequence of
1273 commands. This command accepts the current line, like @kbd{RET}, and
1274 then fetches the next line relative to the current line from the history
1278 @section Command completion
1281 @cindex word completion
1282 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1283 only one possibility; it can also show you what the valid possibilities
1284 are for the next word in a command, at any time. This works for @value{GDBN}
1285 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1287 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1288 of a word. If there is only one possibility, @value{GDBN} fills in the
1289 word, and waits for you to finish the command (or press @key{RET} to
1290 enter it). For example, if you type
1292 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1293 @c complete accuracy in these examples; space introduced for clarity.
1294 @c If texinfo enhancements make it unnecessary, it would be nice to
1295 @c replace " @key" by "@key" in the following...
1297 (@value{GDBP}) info bre @key{TAB}
1301 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1302 the only @code{info} subcommand beginning with @samp{bre}:
1305 (@value{GDBP}) info breakpoints
1309 You can either press @key{RET} at this point, to run the @code{info
1310 breakpoints} command, or backspace and enter something else, if
1311 @samp{breakpoints} does not look like the command you expected. (If you
1312 were sure you wanted @code{info breakpoints} in the first place, you
1313 might as well just type @key{RET} immediately after @samp{info bre},
1314 to exploit command abbreviations rather than command completion).
1316 If there is more than one possibility for the next word when you press
1317 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1318 characters and try again, or just press @key{TAB} a second time;
1319 @value{GDBN} displays all the possible completions for that word. For
1320 example, you might want to set a breakpoint on a subroutine whose name
1321 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1322 just sounds the bell. Typing @key{TAB} again displays all the
1323 function names in your program that begin with those characters, for
1327 (@value{GDBP}) b make_ @key{TAB}
1328 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1329 make_a_section_from_file make_environ
1330 make_abs_section make_function_type
1331 make_blockvector make_pointer_type
1332 make_cleanup make_reference_type
1333 make_command make_symbol_completion_list
1334 (@value{GDBP}) b make_
1338 After displaying the available possibilities, @value{GDBN} copies your
1339 partial input (@samp{b make_} in the example) so you can finish the
1342 If you just want to see the list of alternatives in the first place, you
1343 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1344 means @kbd{@key{META} ?}. You can type this either by holding down a
1345 key designated as the @key{META} shift on your keyboard (if there is
1346 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1348 @cindex quotes in commands
1349 @cindex completion of quoted strings
1350 Sometimes the string you need, while logically a ``word'', may contain
1351 parentheses or other characters that @value{GDBN} normally excludes from
1352 its notion of a word. To permit word completion to work in this
1353 situation, you may enclose words in @code{'} (single quote marks) in
1354 @value{GDBN} commands.
1356 The most likely situation where you might need this is in typing the
1357 name of a C@t{++} function. This is because C@t{++} allows function
1358 overloading (multiple definitions of the same function, distinguished
1359 by argument type). For example, when you want to set a breakpoint you
1360 may need to distinguish whether you mean the version of @code{name}
1361 that takes an @code{int} parameter, @code{name(int)}, or the version
1362 that takes a @code{float} parameter, @code{name(float)}. To use the
1363 word-completion facilities in this situation, type a single quote
1364 @code{'} at the beginning of the function name. This alerts
1365 @value{GDBN} that it may need to consider more information than usual
1366 when you press @key{TAB} or @kbd{M-?} to request word completion:
1369 (@value{GDBP}) b 'bubble( @kbd{M-?}
1370 bubble(double,double) bubble(int,int)
1371 (@value{GDBP}) b 'bubble(
1374 In some cases, @value{GDBN} can tell that completing a name requires using
1375 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1376 completing as much as it can) if you do not type the quote in the first
1380 (@value{GDBP}) b bub @key{TAB}
1381 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1382 (@value{GDBP}) b 'bubble(
1386 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1387 you have not yet started typing the argument list when you ask for
1388 completion on an overloaded symbol.
1390 For more information about overloaded functions, see @ref{C plus plus
1391 expressions, ,C@t{++} expressions}. You can use the command @code{set
1392 overload-resolution off} to disable overload resolution;
1393 see @ref{Debugging C plus plus, ,@value{GDBN} features for C@t{++}}.
1397 @section Getting help
1398 @cindex online documentation
1401 You can always ask @value{GDBN} itself for information on its commands,
1402 using the command @code{help}.
1405 @kindex h @r{(@code{help})}
1408 You can use @code{help} (abbreviated @code{h}) with no arguments to
1409 display a short list of named classes of commands:
1413 List of classes of commands:
1415 aliases -- Aliases of other commands
1416 breakpoints -- Making program stop at certain points
1417 data -- Examining data
1418 files -- Specifying and examining files
1419 internals -- Maintenance commands
1420 obscure -- Obscure features
1421 running -- Running the program
1422 stack -- Examining the stack
1423 status -- Status inquiries
1424 support -- Support facilities
1425 tracepoints -- Tracing of program execution without@*
1426 stopping the program
1427 user-defined -- User-defined commands
1429 Type "help" followed by a class name for a list of
1430 commands in that class.
1431 Type "help" followed by command name for full
1433 Command name abbreviations are allowed if unambiguous.
1436 @c the above line break eliminates huge line overfull...
1438 @item help @var{class}
1439 Using one of the general help classes as an argument, you can get a
1440 list of the individual commands in that class. For example, here is the
1441 help display for the class @code{status}:
1444 (@value{GDBP}) help status
1449 @c Line break in "show" line falsifies real output, but needed
1450 @c to fit in smallbook page size.
1451 info -- Generic command for showing things
1452 about the program being debugged
1453 show -- Generic command for showing things
1456 Type "help" followed by command name for full
1458 Command name abbreviations are allowed if unambiguous.
1462 @item help @var{command}
1463 With a command name as @code{help} argument, @value{GDBN} displays a
1464 short paragraph on how to use that command.
1467 @item apropos @var{args}
1468 The @code{apropos @var{args}} command searches through all of the @value{GDBN}
1469 commands, and their documentation, for the regular expression specified in
1470 @var{args}. It prints out all matches found. For example:
1481 set symbol-reloading -- Set dynamic symbol table reloading
1482 multiple times in one run
1483 show symbol-reloading -- Show dynamic symbol table reloading
1484 multiple times in one run
1489 @item complete @var{args}
1490 The @code{complete @var{args}} command lists all the possible completions
1491 for the beginning of a command. Use @var{args} to specify the beginning of the
1492 command you want completed. For example:
1498 @noindent results in:
1509 @noindent This is intended for use by @sc{gnu} Emacs.
1512 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1513 and @code{show} to inquire about the state of your program, or the state
1514 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1515 manual introduces each of them in the appropriate context. The listings
1516 under @code{info} and under @code{show} in the Index point to
1517 all the sub-commands. @xref{Index}.
1522 @kindex i @r{(@code{info})}
1524 This command (abbreviated @code{i}) is for describing the state of your
1525 program. For example, you can list the arguments given to your program
1526 with @code{info args}, list the registers currently in use with @code{info
1527 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1528 You can get a complete list of the @code{info} sub-commands with
1529 @w{@code{help info}}.
1533 You can assign the result of an expression to an environment variable with
1534 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1535 @code{set prompt $}.
1539 In contrast to @code{info}, @code{show} is for describing the state of
1540 @value{GDBN} itself.
1541 You can change most of the things you can @code{show}, by using the
1542 related command @code{set}; for example, you can control what number
1543 system is used for displays with @code{set radix}, or simply inquire
1544 which is currently in use with @code{show radix}.
1547 To display all the settable parameters and their current
1548 values, you can use @code{show} with no arguments; you may also use
1549 @code{info set}. Both commands produce the same display.
1550 @c FIXME: "info set" violates the rule that "info" is for state of
1551 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1552 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1556 Here are three miscellaneous @code{show} subcommands, all of which are
1557 exceptional in lacking corresponding @code{set} commands:
1560 @kindex show version
1561 @cindex version number
1563 Show what version of @value{GDBN} is running. You should include this
1564 information in @value{GDBN} bug-reports. If multiple versions of
1565 @value{GDBN} are in use at your site, you may need to determine which
1566 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1567 commands are introduced, and old ones may wither away. Also, many
1568 system vendors ship variant versions of @value{GDBN}, and there are
1569 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1570 The version number is the same as the one announced when you start
1573 @kindex show copying
1575 Display information about permission for copying @value{GDBN}.
1577 @kindex show warranty
1579 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1580 if your version of @value{GDBN} comes with one.
1585 @chapter Running Programs Under @value{GDBN}
1587 When you run a program under @value{GDBN}, you must first generate
1588 debugging information when you compile it.
1590 You may start @value{GDBN} with its arguments, if any, in an environment
1591 of your choice. If you are doing native debugging, you may redirect
1592 your program's input and output, debug an already running process, or
1593 kill a child process.
1596 * Compilation:: Compiling for debugging
1597 * Starting:: Starting your program
1598 * Arguments:: Your program's arguments
1599 * Environment:: Your program's environment
1601 * Working Directory:: Your program's working directory
1602 * Input/Output:: Your program's input and output
1603 * Attach:: Debugging an already-running process
1604 * Kill Process:: Killing the child process
1606 * Threads:: Debugging programs with multiple threads
1607 * Processes:: Debugging programs with multiple processes
1611 @section Compiling for debugging
1613 In order to debug a program effectively, you need to generate
1614 debugging information when you compile it. This debugging information
1615 is stored in the object file; it describes the data type of each
1616 variable or function and the correspondence between source line numbers
1617 and addresses in the executable code.
1619 To request debugging information, specify the @samp{-g} option when you run
1622 Most compilers do not include information about preprocessor macros in
1623 the debugging information if you specify the @option{-g} flag alone,
1624 because this information is rather large. Version 3.1 of @value{NGCC},
1625 the @sc{gnu} C compiler, provides macro information if you specify the
1626 options @option{-gdwarf-2} and @option{-g3}; the former option requests
1627 debugging information in the Dwarf 2 format, and the latter requests
1628 ``extra information''. In the future, we hope to find more compact ways
1629 to represent macro information, so that it can be included with
1632 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1633 options together. Using those compilers, you cannot generate optimized
1634 executables containing debugging information.
1636 @value{NGCC}, the @sc{gnu} C compiler, supports @samp{-g} with or
1637 without @samp{-O}, making it possible to debug optimized code. We
1638 recommend that you @emph{always} use @samp{-g} whenever you compile a
1639 program. You may think your program is correct, but there is no sense
1640 in pushing your luck.
1642 @cindex optimized code, debugging
1643 @cindex debugging optimized code
1644 When you debug a program compiled with @samp{-g -O}, remember that the
1645 optimizer is rearranging your code; the debugger shows you what is
1646 really there. Do not be too surprised when the execution path does not
1647 exactly match your source file! An extreme example: if you define a
1648 variable, but never use it, @value{GDBN} never sees that
1649 variable---because the compiler optimizes it out of existence.
1651 Some things do not work as well with @samp{-g -O} as with just
1652 @samp{-g}, particularly on machines with instruction scheduling. If in
1653 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1654 please report it to us as a bug (including a test case!).
1656 Older versions of the @sc{gnu} C compiler permitted a variant option
1657 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1658 format; if your @sc{gnu} C compiler has this option, do not use it.
1662 @section Starting your program
1668 @kindex r @r{(@code{run})}
1671 Use the @code{run} command to start your program under @value{GDBN}.
1672 You must first specify the program name (except on VxWorks) with an
1673 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1674 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1675 (@pxref{Files, ,Commands to specify files}).
1679 If you are running your program in an execution environment that
1680 supports processes, @code{run} creates an inferior process and makes
1681 that process run your program. (In environments without processes,
1682 @code{run} jumps to the start of your program.)
1684 The execution of a program is affected by certain information it
1685 receives from its superior. @value{GDBN} provides ways to specify this
1686 information, which you must do @emph{before} starting your program. (You
1687 can change it after starting your program, but such changes only affect
1688 your program the next time you start it.) This information may be
1689 divided into four categories:
1692 @item The @emph{arguments.}
1693 Specify the arguments to give your program as the arguments of the
1694 @code{run} command. If a shell is available on your target, the shell
1695 is used to pass the arguments, so that you may use normal conventions
1696 (such as wildcard expansion or variable substitution) in describing
1698 In Unix systems, you can control which shell is used with the
1699 @code{SHELL} environment variable.
1700 @xref{Arguments, ,Your program's arguments}.
1702 @item The @emph{environment.}
1703 Your program normally inherits its environment from @value{GDBN}, but you can
1704 use the @value{GDBN} commands @code{set environment} and @code{unset
1705 environment} to change parts of the environment that affect
1706 your program. @xref{Environment, ,Your program's environment}.
1708 @item The @emph{working directory.}
1709 Your program inherits its working directory from @value{GDBN}. You can set
1710 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
1711 @xref{Working Directory, ,Your program's working directory}.
1713 @item The @emph{standard input and output.}
1714 Your program normally uses the same device for standard input and
1715 standard output as @value{GDBN} is using. You can redirect input and output
1716 in the @code{run} command line, or you can use the @code{tty} command to
1717 set a different device for your program.
1718 @xref{Input/Output, ,Your program's input and output}.
1721 @emph{Warning:} While input and output redirection work, you cannot use
1722 pipes to pass the output of the program you are debugging to another
1723 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
1727 When you issue the @code{run} command, your program begins to execute
1728 immediately. @xref{Stopping, ,Stopping and continuing}, for discussion
1729 of how to arrange for your program to stop. Once your program has
1730 stopped, you may call functions in your program, using the @code{print}
1731 or @code{call} commands. @xref{Data, ,Examining Data}.
1733 If the modification time of your symbol file has changed since the last
1734 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
1735 table, and reads it again. When it does this, @value{GDBN} tries to retain
1736 your current breakpoints.
1739 @section Your program's arguments
1741 @cindex arguments (to your program)
1742 The arguments to your program can be specified by the arguments of the
1744 They are passed to a shell, which expands wildcard characters and
1745 performs redirection of I/O, and thence to your program. Your
1746 @code{SHELL} environment variable (if it exists) specifies what shell
1747 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
1748 the default shell (@file{/bin/sh} on Unix).
1750 On non-Unix systems, the program is usually invoked directly by
1751 @value{GDBN}, which emulates I/O redirection via the appropriate system
1752 calls, and the wildcard characters are expanded by the startup code of
1753 the program, not by the shell.
1755 @code{run} with no arguments uses the same arguments used by the previous
1756 @code{run}, or those set by the @code{set args} command.
1761 Specify the arguments to be used the next time your program is run. If
1762 @code{set args} has no arguments, @code{run} executes your program
1763 with no arguments. Once you have run your program with arguments,
1764 using @code{set args} before the next @code{run} is the only way to run
1765 it again without arguments.
1769 Show the arguments to give your program when it is started.
1773 @section Your program's environment
1775 @cindex environment (of your program)
1776 The @dfn{environment} consists of a set of environment variables and
1777 their values. Environment variables conventionally record such things as
1778 your user name, your home directory, your terminal type, and your search
1779 path for programs to run. Usually you set up environment variables with
1780 the shell and they are inherited by all the other programs you run. When
1781 debugging, it can be useful to try running your program with a modified
1782 environment without having to start @value{GDBN} over again.
1786 @item path @var{directory}
1787 Add @var{directory} to the front of the @code{PATH} environment variable
1788 (the search path for executables) that will be passed to your program.
1789 The value of @code{PATH} used by @value{GDBN} does not change.
1790 You may specify several directory names, separated by whitespace or by a
1791 system-dependent separator character (@samp{:} on Unix, @samp{;} on
1792 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
1793 is moved to the front, so it is searched sooner.
1795 You can use the string @samp{$cwd} to refer to whatever is the current
1796 working directory at the time @value{GDBN} searches the path. If you
1797 use @samp{.} instead, it refers to the directory where you executed the
1798 @code{path} command. @value{GDBN} replaces @samp{.} in the
1799 @var{directory} argument (with the current path) before adding
1800 @var{directory} to the search path.
1801 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1802 @c document that, since repeating it would be a no-op.
1806 Display the list of search paths for executables (the @code{PATH}
1807 environment variable).
1809 @kindex show environment
1810 @item show environment @r{[}@var{varname}@r{]}
1811 Print the value of environment variable @var{varname} to be given to
1812 your program when it starts. If you do not supply @var{varname},
1813 print the names and values of all environment variables to be given to
1814 your program. You can abbreviate @code{environment} as @code{env}.
1816 @kindex set environment
1817 @item set environment @var{varname} @r{[}=@var{value}@r{]}
1818 Set environment variable @var{varname} to @var{value}. The value
1819 changes for your program only, not for @value{GDBN} itself. @var{value} may
1820 be any string; the values of environment variables are just strings, and
1821 any interpretation is supplied by your program itself. The @var{value}
1822 parameter is optional; if it is eliminated, the variable is set to a
1824 @c "any string" here does not include leading, trailing
1825 @c blanks. Gnu asks: does anyone care?
1827 For example, this command:
1834 tells the debugged program, when subsequently run, that its user is named
1835 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1836 are not actually required.)
1838 @kindex unset environment
1839 @item unset environment @var{varname}
1840 Remove variable @var{varname} from the environment to be passed to your
1841 program. This is different from @samp{set env @var{varname} =};
1842 @code{unset environment} removes the variable from the environment,
1843 rather than assigning it an empty value.
1846 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
1848 by your @code{SHELL} environment variable if it exists (or
1849 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
1850 that runs an initialization file---such as @file{.cshrc} for C-shell, or
1851 @file{.bashrc} for BASH---any variables you set in that file affect
1852 your program. You may wish to move setting of environment variables to
1853 files that are only run when you sign on, such as @file{.login} or
1856 @node Working Directory
1857 @section Your program's working directory
1859 @cindex working directory (of your program)
1860 Each time you start your program with @code{run}, it inherits its
1861 working directory from the current working directory of @value{GDBN}.
1862 The @value{GDBN} working directory is initially whatever it inherited
1863 from its parent process (typically the shell), but you can specify a new
1864 working directory in @value{GDBN} with the @code{cd} command.
1866 The @value{GDBN} working directory also serves as a default for the commands
1867 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
1872 @item cd @var{directory}
1873 Set the @value{GDBN} working directory to @var{directory}.
1877 Print the @value{GDBN} working directory.
1881 @section Your program's input and output
1886 By default, the program you run under @value{GDBN} does input and output to
1887 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
1888 to its own terminal modes to interact with you, but it records the terminal
1889 modes your program was using and switches back to them when you continue
1890 running your program.
1893 @kindex info terminal
1895 Displays information recorded by @value{GDBN} about the terminal modes your
1899 You can redirect your program's input and/or output using shell
1900 redirection with the @code{run} command. For example,
1907 starts your program, diverting its output to the file @file{outfile}.
1910 @cindex controlling terminal
1911 Another way to specify where your program should do input and output is
1912 with the @code{tty} command. This command accepts a file name as
1913 argument, and causes this file to be the default for future @code{run}
1914 commands. It also resets the controlling terminal for the child
1915 process, for future @code{run} commands. For example,
1922 directs that processes started with subsequent @code{run} commands
1923 default to do input and output on the terminal @file{/dev/ttyb} and have
1924 that as their controlling terminal.
1926 An explicit redirection in @code{run} overrides the @code{tty} command's
1927 effect on the input/output device, but not its effect on the controlling
1930 When you use the @code{tty} command or redirect input in the @code{run}
1931 command, only the input @emph{for your program} is affected. The input
1932 for @value{GDBN} still comes from your terminal.
1935 @section Debugging an already-running process
1940 @item attach @var{process-id}
1941 This command attaches to a running process---one that was started
1942 outside @value{GDBN}. (@code{info files} shows your active
1943 targets.) The command takes as argument a process ID. The usual way to
1944 find out the process-id of a Unix process is with the @code{ps} utility,
1945 or with the @samp{jobs -l} shell command.
1947 @code{attach} does not repeat if you press @key{RET} a second time after
1948 executing the command.
1951 To use @code{attach}, your program must be running in an environment
1952 which supports processes; for example, @code{attach} does not work for
1953 programs on bare-board targets that lack an operating system. You must
1954 also have permission to send the process a signal.
1956 When you use @code{attach}, the debugger finds the program running in
1957 the process first by looking in the current working directory, then (if
1958 the program is not found) by using the source file search path
1959 (@pxref{Source Path, ,Specifying source directories}). You can also use
1960 the @code{file} command to load the program. @xref{Files, ,Commands to
1963 The first thing @value{GDBN} does after arranging to debug the specified
1964 process is to stop it. You can examine and modify an attached process
1965 with all the @value{GDBN} commands that are ordinarily available when
1966 you start processes with @code{run}. You can insert breakpoints; you
1967 can step and continue; you can modify storage. If you would rather the
1968 process continue running, you may use the @code{continue} command after
1969 attaching @value{GDBN} to the process.
1974 When you have finished debugging the attached process, you can use the
1975 @code{detach} command to release it from @value{GDBN} control. Detaching
1976 the process continues its execution. After the @code{detach} command,
1977 that process and @value{GDBN} become completely independent once more, and you
1978 are ready to @code{attach} another process or start one with @code{run}.
1979 @code{detach} does not repeat if you press @key{RET} again after
1980 executing the command.
1983 If you exit @value{GDBN} or use the @code{run} command while you have an
1984 attached process, you kill that process. By default, @value{GDBN} asks
1985 for confirmation if you try to do either of these things; you can
1986 control whether or not you need to confirm by using the @code{set
1987 confirm} command (@pxref{Messages/Warnings, ,Optional warnings and
1991 @section Killing the child process
1996 Kill the child process in which your program is running under @value{GDBN}.
1999 This command is useful if you wish to debug a core dump instead of a
2000 running process. @value{GDBN} ignores any core dump file while your program
2003 On some operating systems, a program cannot be executed outside @value{GDBN}
2004 while you have breakpoints set on it inside @value{GDBN}. You can use the
2005 @code{kill} command in this situation to permit running your program
2006 outside the debugger.
2008 The @code{kill} command is also useful if you wish to recompile and
2009 relink your program, since on many systems it is impossible to modify an
2010 executable file while it is running in a process. In this case, when you
2011 next type @code{run}, @value{GDBN} notices that the file has changed, and
2012 reads the symbol table again (while trying to preserve your current
2013 breakpoint settings).
2016 @section Debugging programs with multiple threads
2018 @cindex threads of execution
2019 @cindex multiple threads
2020 @cindex switching threads
2021 In some operating systems, such as HP-UX and Solaris, a single program
2022 may have more than one @dfn{thread} of execution. The precise semantics
2023 of threads differ from one operating system to another, but in general
2024 the threads of a single program are akin to multiple processes---except
2025 that they share one address space (that is, they can all examine and
2026 modify the same variables). On the other hand, each thread has its own
2027 registers and execution stack, and perhaps private memory.
2029 @value{GDBN} provides these facilities for debugging multi-thread
2033 @item automatic notification of new threads
2034 @item @samp{thread @var{threadno}}, a command to switch among threads
2035 @item @samp{info threads}, a command to inquire about existing threads
2036 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2037 a command to apply a command to a list of threads
2038 @item thread-specific breakpoints
2042 @emph{Warning:} These facilities are not yet available on every
2043 @value{GDBN} configuration where the operating system supports threads.
2044 If your @value{GDBN} does not support threads, these commands have no
2045 effect. For example, a system without thread support shows no output
2046 from @samp{info threads}, and always rejects the @code{thread} command,
2050 (@value{GDBP}) info threads
2051 (@value{GDBP}) thread 1
2052 Thread ID 1 not known. Use the "info threads" command to
2053 see the IDs of currently known threads.
2055 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2056 @c doesn't support threads"?
2059 @cindex focus of debugging
2060 @cindex current thread
2061 The @value{GDBN} thread debugging facility allows you to observe all
2062 threads while your program runs---but whenever @value{GDBN} takes
2063 control, one thread in particular is always the focus of debugging.
2064 This thread is called the @dfn{current thread}. Debugging commands show
2065 program information from the perspective of the current thread.
2067 @cindex @code{New} @var{systag} message
2068 @cindex thread identifier (system)
2069 @c FIXME-implementors!! It would be more helpful if the [New...] message
2070 @c included GDB's numeric thread handle, so you could just go to that
2071 @c thread without first checking `info threads'.
2072 Whenever @value{GDBN} detects a new thread in your program, it displays
2073 the target system's identification for the thread with a message in the
2074 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2075 whose form varies depending on the particular system. For example, on
2076 LynxOS, you might see
2079 [New process 35 thread 27]
2083 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2084 the @var{systag} is simply something like @samp{process 368}, with no
2087 @c FIXME!! (1) Does the [New...] message appear even for the very first
2088 @c thread of a program, or does it only appear for the
2089 @c second---i.e.@: when it becomes obvious we have a multithread
2091 @c (2) *Is* there necessarily a first thread always? Or do some
2092 @c multithread systems permit starting a program with multiple
2093 @c threads ab initio?
2095 @cindex thread number
2096 @cindex thread identifier (GDB)
2097 For debugging purposes, @value{GDBN} associates its own thread
2098 number---always a single integer---with each thread in your program.
2101 @kindex info threads
2103 Display a summary of all threads currently in your
2104 program. @value{GDBN} displays for each thread (in this order):
2107 @item the thread number assigned by @value{GDBN}
2109 @item the target system's thread identifier (@var{systag})
2111 @item the current stack frame summary for that thread
2115 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2116 indicates the current thread.
2120 @c end table here to get a little more width for example
2123 (@value{GDBP}) info threads
2124 3 process 35 thread 27 0x34e5 in sigpause ()
2125 2 process 35 thread 23 0x34e5 in sigpause ()
2126 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2132 @cindex thread number
2133 @cindex thread identifier (GDB)
2134 For debugging purposes, @value{GDBN} associates its own thread
2135 number---a small integer assigned in thread-creation order---with each
2136 thread in your program.
2138 @cindex @code{New} @var{systag} message, on HP-UX
2139 @cindex thread identifier (system), on HP-UX
2140 @c FIXME-implementors!! It would be more helpful if the [New...] message
2141 @c included GDB's numeric thread handle, so you could just go to that
2142 @c thread without first checking `info threads'.
2143 Whenever @value{GDBN} detects a new thread in your program, it displays
2144 both @value{GDBN}'s thread number and the target system's identification for the thread with a message in the
2145 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2146 whose form varies depending on the particular system. For example, on
2150 [New thread 2 (system thread 26594)]
2154 when @value{GDBN} notices a new thread.
2157 @kindex info threads
2159 Display a summary of all threads currently in your
2160 program. @value{GDBN} displays for each thread (in this order):
2163 @item the thread number assigned by @value{GDBN}
2165 @item the target system's thread identifier (@var{systag})
2167 @item the current stack frame summary for that thread
2171 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2172 indicates the current thread.
2176 @c end table here to get a little more width for example
2179 (@value{GDBP}) info threads
2180 * 3 system thread 26607 worker (wptr=0x7b09c318 "@@") \@*
2182 2 system thread 26606 0x7b0030d8 in __ksleep () \@*
2183 from /usr/lib/libc.2
2184 1 system thread 27905 0x7b003498 in _brk () \@*
2185 from /usr/lib/libc.2
2189 @kindex thread @var{threadno}
2190 @item thread @var{threadno}
2191 Make thread number @var{threadno} the current thread. The command
2192 argument @var{threadno} is the internal @value{GDBN} thread number, as
2193 shown in the first field of the @samp{info threads} display.
2194 @value{GDBN} responds by displaying the system identifier of the thread
2195 you selected, and its current stack frame summary:
2198 @c FIXME!! This example made up; find a @value{GDBN} w/threads and get real one
2199 (@value{GDBP}) thread 2
2200 [Switching to process 35 thread 23]
2201 0x34e5 in sigpause ()
2205 As with the @samp{[New @dots{}]} message, the form of the text after
2206 @samp{Switching to} depends on your system's conventions for identifying
2209 @kindex thread apply
2210 @item thread apply [@var{threadno}] [@var{all}] @var{args}
2211 The @code{thread apply} command allows you to apply a command to one or
2212 more threads. Specify the numbers of the threads that you want affected
2213 with the command argument @var{threadno}. @var{threadno} is the internal
2214 @value{GDBN} thread number, as shown in the first field of the @samp{info
2215 threads} display. To apply a command to all threads, use
2216 @code{thread apply all} @var{args}.
2219 @cindex automatic thread selection
2220 @cindex switching threads automatically
2221 @cindex threads, automatic switching
2222 Whenever @value{GDBN} stops your program, due to a breakpoint or a
2223 signal, it automatically selects the thread where that breakpoint or
2224 signal happened. @value{GDBN} alerts you to the context switch with a
2225 message of the form @samp{[Switching to @var{systag}]} to identify the
2228 @xref{Thread Stops,,Stopping and starting multi-thread programs}, for
2229 more information about how @value{GDBN} behaves when you stop and start
2230 programs with multiple threads.
2232 @xref{Set Watchpoints,,Setting watchpoints}, for information about
2233 watchpoints in programs with multiple threads.
2236 @section Debugging programs with multiple processes
2238 @cindex fork, debugging programs which call
2239 @cindex multiple processes
2240 @cindex processes, multiple
2241 On most systems, @value{GDBN} has no special support for debugging
2242 programs which create additional processes using the @code{fork}
2243 function. When a program forks, @value{GDBN} will continue to debug the
2244 parent process and the child process will run unimpeded. If you have
2245 set a breakpoint in any code which the child then executes, the child
2246 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2247 will cause it to terminate.
2249 However, if you want to debug the child process there is a workaround
2250 which isn't too painful. Put a call to @code{sleep} in the code which
2251 the child process executes after the fork. It may be useful to sleep
2252 only if a certain environment variable is set, or a certain file exists,
2253 so that the delay need not occur when you don't want to run @value{GDBN}
2254 on the child. While the child is sleeping, use the @code{ps} program to
2255 get its process ID. Then tell @value{GDBN} (a new invocation of
2256 @value{GDBN} if you are also debugging the parent process) to attach to
2257 the child process (@pxref{Attach}). From that point on you can debug
2258 the child process just like any other process which you attached to.
2260 On HP-UX (11.x and later only?), @value{GDBN} provides support for
2261 debugging programs that create additional processes using the
2262 @code{fork} or @code{vfork} function.
2264 By default, when a program forks, @value{GDBN} will continue to debug
2265 the parent process and the child process will run unimpeded.
2267 If you want to follow the child process instead of the parent process,
2268 use the command @w{@code{set follow-fork-mode}}.
2271 @kindex set follow-fork-mode
2272 @item set follow-fork-mode @var{mode}
2273 Set the debugger response to a program call of @code{fork} or
2274 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
2275 process. The @var{mode} can be:
2279 The original process is debugged after a fork. The child process runs
2280 unimpeded. This is the default.
2283 The new process is debugged after a fork. The parent process runs
2287 The debugger will ask for one of the above choices.
2290 @item show follow-fork-mode
2291 Display the current debugger response to a @code{fork} or @code{vfork} call.
2294 If you ask to debug a child process and a @code{vfork} is followed by an
2295 @code{exec}, @value{GDBN} executes the new target up to the first
2296 breakpoint in the new target. If you have a breakpoint set on
2297 @code{main} in your original program, the breakpoint will also be set on
2298 the child process's @code{main}.
2300 When a child process is spawned by @code{vfork}, you cannot debug the
2301 child or parent until an @code{exec} call completes.
2303 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
2304 call executes, the new target restarts. To restart the parent process,
2305 use the @code{file} command with the parent executable name as its
2308 You can use the @code{catch} command to make @value{GDBN} stop whenever
2309 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
2310 Catchpoints, ,Setting catchpoints}.
2313 @chapter Stopping and Continuing
2315 The principal purposes of using a debugger are so that you can stop your
2316 program before it terminates; or so that, if your program runs into
2317 trouble, you can investigate and find out why.
2319 Inside @value{GDBN}, your program may stop for any of several reasons,
2320 such as a signal, a breakpoint, or reaching a new line after a
2321 @value{GDBN} command such as @code{step}. You may then examine and
2322 change variables, set new breakpoints or remove old ones, and then
2323 continue execution. Usually, the messages shown by @value{GDBN} provide
2324 ample explanation of the status of your program---but you can also
2325 explicitly request this information at any time.
2328 @kindex info program
2330 Display information about the status of your program: whether it is
2331 running or not, what process it is, and why it stopped.
2335 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
2336 * Continuing and Stepping:: Resuming execution
2338 * Thread Stops:: Stopping and starting multi-thread programs
2342 @section Breakpoints, watchpoints, and catchpoints
2345 A @dfn{breakpoint} makes your program stop whenever a certain point in
2346 the program is reached. For each breakpoint, you can add conditions to
2347 control in finer detail whether your program stops. You can set
2348 breakpoints with the @code{break} command and its variants (@pxref{Set
2349 Breaks, ,Setting breakpoints}), to specify the place where your program
2350 should stop by line number, function name or exact address in the
2353 In HP-UX, SunOS 4.x, SVR4, and Alpha OSF/1 configurations, you can set
2354 breakpoints in shared libraries before the executable is run. There is
2355 a minor limitation on HP-UX systems: you must wait until the executable
2356 is run in order to set breakpoints in shared library routines that are
2357 not called directly by the program (for example, routines that are
2358 arguments in a @code{pthread_create} call).
2361 @cindex memory tracing
2362 @cindex breakpoint on memory address
2363 @cindex breakpoint on variable modification
2364 A @dfn{watchpoint} is a special breakpoint that stops your program
2365 when the value of an expression changes. You must use a different
2366 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
2367 watchpoints}), but aside from that, you can manage a watchpoint like
2368 any other breakpoint: you enable, disable, and delete both breakpoints
2369 and watchpoints using the same commands.
2371 You can arrange to have values from your program displayed automatically
2372 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
2376 @cindex breakpoint on events
2377 A @dfn{catchpoint} is another special breakpoint that stops your program
2378 when a certain kind of event occurs, such as the throwing of a C@t{++}
2379 exception or the loading of a library. As with watchpoints, you use a
2380 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
2381 catchpoints}), but aside from that, you can manage a catchpoint like any
2382 other breakpoint. (To stop when your program receives a signal, use the
2383 @code{handle} command; see @ref{Signals, ,Signals}.)
2385 @cindex breakpoint numbers
2386 @cindex numbers for breakpoints
2387 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
2388 catchpoint when you create it; these numbers are successive integers
2389 starting with one. In many of the commands for controlling various
2390 features of breakpoints you use the breakpoint number to say which
2391 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
2392 @dfn{disabled}; if disabled, it has no effect on your program until you
2395 @cindex breakpoint ranges
2396 @cindex ranges of breakpoints
2397 Some @value{GDBN} commands accept a range of breakpoints on which to
2398 operate. A breakpoint range is either a single breakpoint number, like
2399 @samp{5}, or two such numbers, in increasing order, separated by a
2400 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
2401 all breakpoint in that range are operated on.
2404 * Set Breaks:: Setting breakpoints
2405 * Set Watchpoints:: Setting watchpoints
2406 * Set Catchpoints:: Setting catchpoints
2407 * Delete Breaks:: Deleting breakpoints
2408 * Disabling:: Disabling breakpoints
2409 * Conditions:: Break conditions
2410 * Break Commands:: Breakpoint command lists
2411 * Breakpoint Menus:: Breakpoint menus
2412 * Error in Breakpoints:: ``Cannot insert breakpoints''
2416 @subsection Setting breakpoints
2418 @c FIXME LMB what does GDB do if no code on line of breakpt?
2419 @c consider in particular declaration with/without initialization.
2421 @c FIXME 2 is there stuff on this already? break at fun start, already init?
2424 @kindex b @r{(@code{break})}
2425 @vindex $bpnum@r{, convenience variable}
2426 @cindex latest breakpoint
2427 Breakpoints are set with the @code{break} command (abbreviated
2428 @code{b}). The debugger convenience variable @samp{$bpnum} records the
2429 number of the breakpoint you've set most recently; see @ref{Convenience
2430 Vars,, Convenience variables}, for a discussion of what you can do with
2431 convenience variables.
2433 You have several ways to say where the breakpoint should go.
2436 @item break @var{function}
2437 Set a breakpoint at entry to function @var{function}.
2438 When using source languages that permit overloading of symbols, such as
2439 C@t{++}, @var{function} may refer to more than one possible place to break.
2440 @xref{Breakpoint Menus,,Breakpoint menus}, for a discussion of that situation.
2442 @item break +@var{offset}
2443 @itemx break -@var{offset}
2444 Set a breakpoint some number of lines forward or back from the position
2445 at which execution stopped in the currently selected @dfn{stack frame}.
2446 (@xref{Frames, ,Frames}, for a description of stack frames.)
2448 @item break @var{linenum}
2449 Set a breakpoint at line @var{linenum} in the current source file.
2450 The current source file is the last file whose source text was printed.
2451 The breakpoint will stop your program just before it executes any of the
2454 @item break @var{filename}:@var{linenum}
2455 Set a breakpoint at line @var{linenum} in source file @var{filename}.
2457 @item break @var{filename}:@var{function}
2458 Set a breakpoint at entry to function @var{function} found in file
2459 @var{filename}. Specifying a file name as well as a function name is
2460 superfluous except when multiple files contain similarly named
2463 @item break *@var{address}
2464 Set a breakpoint at address @var{address}. You can use this to set
2465 breakpoints in parts of your program which do not have debugging
2466 information or source files.
2469 When called without any arguments, @code{break} sets a breakpoint at
2470 the next instruction to be executed in the selected stack frame
2471 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
2472 innermost, this makes your program stop as soon as control
2473 returns to that frame. This is similar to the effect of a
2474 @code{finish} command in the frame inside the selected frame---except
2475 that @code{finish} does not leave an active breakpoint. If you use
2476 @code{break} without an argument in the innermost frame, @value{GDBN} stops
2477 the next time it reaches the current location; this may be useful
2480 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
2481 least one instruction has been executed. If it did not do this, you
2482 would be unable to proceed past a breakpoint without first disabling the
2483 breakpoint. This rule applies whether or not the breakpoint already
2484 existed when your program stopped.
2486 @item break @dots{} if @var{cond}
2487 Set a breakpoint with condition @var{cond}; evaluate the expression
2488 @var{cond} each time the breakpoint is reached, and stop only if the
2489 value is nonzero---that is, if @var{cond} evaluates as true.
2490 @samp{@dots{}} stands for one of the possible arguments described
2491 above (or no argument) specifying where to break. @xref{Conditions,
2492 ,Break conditions}, for more information on breakpoint conditions.
2495 @item tbreak @var{args}
2496 Set a breakpoint enabled only for one stop. @var{args} are the
2497 same as for the @code{break} command, and the breakpoint is set in the same
2498 way, but the breakpoint is automatically deleted after the first time your
2499 program stops there. @xref{Disabling, ,Disabling breakpoints}.
2502 @item hbreak @var{args}
2503 Set a hardware-assisted breakpoint. @var{args} are the same as for the
2504 @code{break} command and the breakpoint is set in the same way, but the
2505 breakpoint requires hardware support and some target hardware may not
2506 have this support. The main purpose of this is EPROM/ROM code
2507 debugging, so you can set a breakpoint at an instruction without
2508 changing the instruction. This can be used with the new trap-generation
2509 provided by SPARClite DSU and some x86-based targets. These targets
2510 will generate traps when a program accesses some data or instruction
2511 address that is assigned to the debug registers. However the hardware
2512 breakpoint registers can take a limited number of breakpoints. For
2513 example, on the DSU, only two data breakpoints can be set at a time, and
2514 @value{GDBN} will reject this command if more than two are used. Delete
2515 or disable unused hardware breakpoints before setting new ones
2516 (@pxref{Disabling, ,Disabling}). @xref{Conditions, ,Break conditions}.
2519 @item thbreak @var{args}
2520 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
2521 are the same as for the @code{hbreak} command and the breakpoint is set in
2522 the same way. However, like the @code{tbreak} command,
2523 the breakpoint is automatically deleted after the
2524 first time your program stops there. Also, like the @code{hbreak}
2525 command, the breakpoint requires hardware support and some target hardware
2526 may not have this support. @xref{Disabling, ,Disabling breakpoints}.
2527 See also @ref{Conditions, ,Break conditions}.
2530 @cindex regular expression
2531 @item rbreak @var{regex}
2532 Set breakpoints on all functions matching the regular expression
2533 @var{regex}. This command sets an unconditional breakpoint on all
2534 matches, printing a list of all breakpoints it set. Once these
2535 breakpoints are set, they are treated just like the breakpoints set with
2536 the @code{break} command. You can delete them, disable them, or make
2537 them conditional the same way as any other breakpoint.
2539 The syntax of the regular expression is the standard one used with tools
2540 like @file{grep}. Note that this is different from the syntax used by
2541 shells, so for instance @code{foo*} matches all functions that include
2542 an @code{fo} followed by zero or more @code{o}s. There is an implicit
2543 @code{.*} leading and trailing the regular expression you supply, so to
2544 match only functions that begin with @code{foo}, use @code{^foo}.
2546 When debugging C@t{++} programs, @code{rbreak} is useful for setting
2547 breakpoints on overloaded functions that are not members of any special
2550 @kindex info breakpoints
2551 @cindex @code{$_} and @code{info breakpoints}
2552 @item info breakpoints @r{[}@var{n}@r{]}
2553 @itemx info break @r{[}@var{n}@r{]}
2554 @itemx info watchpoints @r{[}@var{n}@r{]}
2555 Print a table of all breakpoints, watchpoints, and catchpoints set and
2556 not deleted, with the following columns for each breakpoint:
2559 @item Breakpoint Numbers
2561 Breakpoint, watchpoint, or catchpoint.
2563 Whether the breakpoint is marked to be disabled or deleted when hit.
2564 @item Enabled or Disabled
2565 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
2566 that are not enabled.
2568 Where the breakpoint is in your program, as a memory address.
2570 Where the breakpoint is in the source for your program, as a file and
2575 If a breakpoint is conditional, @code{info break} shows the condition on
2576 the line following the affected breakpoint; breakpoint commands, if any,
2577 are listed after that.
2580 @code{info break} with a breakpoint
2581 number @var{n} as argument lists only that breakpoint. The
2582 convenience variable @code{$_} and the default examining-address for
2583 the @code{x} command are set to the address of the last breakpoint
2584 listed (@pxref{Memory, ,Examining memory}).
2587 @code{info break} displays a count of the number of times the breakpoint
2588 has been hit. This is especially useful in conjunction with the
2589 @code{ignore} command. You can ignore a large number of breakpoint
2590 hits, look at the breakpoint info to see how many times the breakpoint
2591 was hit, and then run again, ignoring one less than that number. This
2592 will get you quickly to the last hit of that breakpoint.
2595 @value{GDBN} allows you to set any number of breakpoints at the same place in
2596 your program. There is nothing silly or meaningless about this. When
2597 the breakpoints are conditional, this is even useful
2598 (@pxref{Conditions, ,Break conditions}).
2600 @cindex negative breakpoint numbers
2601 @cindex internal @value{GDBN} breakpoints
2602 @value{GDBN} itself sometimes sets breakpoints in your program for
2603 special purposes, such as proper handling of @code{longjmp} (in C
2604 programs). These internal breakpoints are assigned negative numbers,
2605 starting with @code{-1}; @samp{info breakpoints} does not display them.
2606 You can see these breakpoints with the @value{GDBN} maintenance command
2607 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
2610 @node Set Watchpoints
2611 @subsection Setting watchpoints
2613 @cindex setting watchpoints
2614 @cindex software watchpoints
2615 @cindex hardware watchpoints
2616 You can use a watchpoint to stop execution whenever the value of an
2617 expression changes, without having to predict a particular place where
2620 Depending on your system, watchpoints may be implemented in software or
2621 hardware. @value{GDBN} does software watchpointing by single-stepping your
2622 program and testing the variable's value each time, which is hundreds of
2623 times slower than normal execution. (But this may still be worth it, to
2624 catch errors where you have no clue what part of your program is the
2627 On some systems, such as HP-UX, @sc{gnu}/Linux and some other x86-based targets,
2628 @value{GDBN} includes support for
2629 hardware watchpoints, which do not slow down the running of your
2634 @item watch @var{expr}
2635 Set a watchpoint for an expression. @value{GDBN} will break when @var{expr}
2636 is written into by the program and its value changes.
2639 @item rwatch @var{expr}
2640 Set a watchpoint that will break when watch @var{expr} is read by the program.
2643 @item awatch @var{expr}
2644 Set a watchpoint that will break when @var{expr} is either read or written into
2647 @kindex info watchpoints
2648 @item info watchpoints
2649 This command prints a list of watchpoints, breakpoints, and catchpoints;
2650 it is the same as @code{info break}.
2653 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
2654 watchpoints execute very quickly, and the debugger reports a change in
2655 value at the exact instruction where the change occurs. If @value{GDBN}
2656 cannot set a hardware watchpoint, it sets a software watchpoint, which
2657 executes more slowly and reports the change in value at the next
2658 statement, not the instruction, after the change occurs.
2660 When you issue the @code{watch} command, @value{GDBN} reports
2663 Hardware watchpoint @var{num}: @var{expr}
2667 if it was able to set a hardware watchpoint.
2669 Currently, the @code{awatch} and @code{rwatch} commands can only set
2670 hardware watchpoints, because accesses to data that don't change the
2671 value of the watched expression cannot be detected without examining
2672 every instruction as it is being executed, and @value{GDBN} does not do
2673 that currently. If @value{GDBN} finds that it is unable to set a
2674 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
2675 will print a message like this:
2678 Expression cannot be implemented with read/access watchpoint.
2681 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
2682 data type of the watched expression is wider than what a hardware
2683 watchpoint on the target machine can handle. For example, some systems
2684 can only watch regions that are up to 4 bytes wide; on such systems you
2685 cannot set hardware watchpoints for an expression that yields a
2686 double-precision floating-point number (which is typically 8 bytes
2687 wide). As a work-around, it might be possible to break the large region
2688 into a series of smaller ones and watch them with separate watchpoints.
2690 If you set too many hardware watchpoints, @value{GDBN} might be unable
2691 to insert all of them when you resume the execution of your program.
2692 Since the precise number of active watchpoints is unknown until such
2693 time as the program is about to be resumed, @value{GDBN} might not be
2694 able to warn you about this when you set the watchpoints, and the
2695 warning will be printed only when the program is resumed:
2698 Hardware watchpoint @var{num}: Could not insert watchpoint
2702 If this happens, delete or disable some of the watchpoints.
2704 The SPARClite DSU will generate traps when a program accesses some data
2705 or instruction address that is assigned to the debug registers. For the
2706 data addresses, DSU facilitates the @code{watch} command. However the
2707 hardware breakpoint registers can only take two data watchpoints, and
2708 both watchpoints must be the same kind. For example, you can set two
2709 watchpoints with @code{watch} commands, two with @code{rwatch} commands,
2710 @strong{or} two with @code{awatch} commands, but you cannot set one
2711 watchpoint with one command and the other with a different command.
2712 @value{GDBN} will reject the command if you try to mix watchpoints.
2713 Delete or disable unused watchpoint commands before setting new ones.
2715 If you call a function interactively using @code{print} or @code{call},
2716 any watchpoints you have set will be inactive until @value{GDBN} reaches another
2717 kind of breakpoint or the call completes.
2719 @value{GDBN} automatically deletes watchpoints that watch local
2720 (automatic) variables, or expressions that involve such variables, when
2721 they go out of scope, that is, when the execution leaves the block in
2722 which these variables were defined. In particular, when the program
2723 being debugged terminates, @emph{all} local variables go out of scope,
2724 and so only watchpoints that watch global variables remain set. If you
2725 rerun the program, you will need to set all such watchpoints again. One
2726 way of doing that would be to set a code breakpoint at the entry to the
2727 @code{main} function and when it breaks, set all the watchpoints.
2730 @cindex watchpoints and threads
2731 @cindex threads and watchpoints
2732 @emph{Warning:} In multi-thread programs, watchpoints have only limited
2733 usefulness. With the current watchpoint implementation, @value{GDBN}
2734 can only watch the value of an expression @emph{in a single thread}. If
2735 you are confident that the expression can only change due to the current
2736 thread's activity (and if you are also confident that no other thread
2737 can become current), then you can use watchpoints as usual. However,
2738 @value{GDBN} may not notice when a non-current thread's activity changes
2741 @c FIXME: this is almost identical to the previous paragraph.
2742 @emph{HP-UX Warning:} In multi-thread programs, software watchpoints
2743 have only limited usefulness. If @value{GDBN} creates a software
2744 watchpoint, it can only watch the value of an expression @emph{in a
2745 single thread}. If you are confident that the expression can only
2746 change due to the current thread's activity (and if you are also
2747 confident that no other thread can become current), then you can use
2748 software watchpoints as usual. However, @value{GDBN} may not notice
2749 when a non-current thread's activity changes the expression. (Hardware
2750 watchpoints, in contrast, watch an expression in all threads.)
2753 @node Set Catchpoints
2754 @subsection Setting catchpoints
2755 @cindex catchpoints, setting
2756 @cindex exception handlers
2757 @cindex event handling
2759 You can use @dfn{catchpoints} to cause the debugger to stop for certain
2760 kinds of program events, such as C@t{++} exceptions or the loading of a
2761 shared library. Use the @code{catch} command to set a catchpoint.
2765 @item catch @var{event}
2766 Stop when @var{event} occurs. @var{event} can be any of the following:
2770 The throwing of a C@t{++} exception.
2774 The catching of a C@t{++} exception.
2778 A call to @code{exec}. This is currently only available for HP-UX.
2782 A call to @code{fork}. This is currently only available for HP-UX.
2786 A call to @code{vfork}. This is currently only available for HP-UX.
2789 @itemx load @var{libname}
2791 The dynamic loading of any shared library, or the loading of the library
2792 @var{libname}. This is currently only available for HP-UX.
2795 @itemx unload @var{libname}
2796 @kindex catch unload
2797 The unloading of any dynamically loaded shared library, or the unloading
2798 of the library @var{libname}. This is currently only available for HP-UX.
2801 @item tcatch @var{event}
2802 Set a catchpoint that is enabled only for one stop. The catchpoint is
2803 automatically deleted after the first time the event is caught.
2807 Use the @code{info break} command to list the current catchpoints.
2809 There are currently some limitations to C@t{++} exception handling
2810 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
2814 If you call a function interactively, @value{GDBN} normally returns
2815 control to you when the function has finished executing. If the call
2816 raises an exception, however, the call may bypass the mechanism that
2817 returns control to you and cause your program either to abort or to
2818 simply continue running until it hits a breakpoint, catches a signal
2819 that @value{GDBN} is listening for, or exits. This is the case even if
2820 you set a catchpoint for the exception; catchpoints on exceptions are
2821 disabled within interactive calls.
2824 You cannot raise an exception interactively.
2827 You cannot install an exception handler interactively.
2830 @cindex raise exceptions
2831 Sometimes @code{catch} is not the best way to debug exception handling:
2832 if you need to know exactly where an exception is raised, it is better to
2833 stop @emph{before} the exception handler is called, since that way you
2834 can see the stack before any unwinding takes place. If you set a
2835 breakpoint in an exception handler instead, it may not be easy to find
2836 out where the exception was raised.
2838 To stop just before an exception handler is called, you need some
2839 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
2840 raised by calling a library function named @code{__raise_exception}
2841 which has the following ANSI C interface:
2844 /* @var{addr} is where the exception identifier is stored.
2845 @var{id} is the exception identifier. */
2846 void __raise_exception (void **addr, void *id);
2850 To make the debugger catch all exceptions before any stack
2851 unwinding takes place, set a breakpoint on @code{__raise_exception}
2852 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and exceptions}).
2854 With a conditional breakpoint (@pxref{Conditions, ,Break conditions})
2855 that depends on the value of @var{id}, you can stop your program when
2856 a specific exception is raised. You can use multiple conditional
2857 breakpoints to stop your program when any of a number of exceptions are
2862 @subsection Deleting breakpoints
2864 @cindex clearing breakpoints, watchpoints, catchpoints
2865 @cindex deleting breakpoints, watchpoints, catchpoints
2866 It is often necessary to eliminate a breakpoint, watchpoint, or
2867 catchpoint once it has done its job and you no longer want your program
2868 to stop there. This is called @dfn{deleting} the breakpoint. A
2869 breakpoint that has been deleted no longer exists; it is forgotten.
2871 With the @code{clear} command you can delete breakpoints according to
2872 where they are in your program. With the @code{delete} command you can
2873 delete individual breakpoints, watchpoints, or catchpoints by specifying
2874 their breakpoint numbers.
2876 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
2877 automatically ignores breakpoints on the first instruction to be executed
2878 when you continue execution without changing the execution address.
2883 Delete any breakpoints at the next instruction to be executed in the
2884 selected stack frame (@pxref{Selection, ,Selecting a frame}). When
2885 the innermost frame is selected, this is a good way to delete a
2886 breakpoint where your program just stopped.
2888 @item clear @var{function}
2889 @itemx clear @var{filename}:@var{function}
2890 Delete any breakpoints set at entry to the function @var{function}.
2892 @item clear @var{linenum}
2893 @itemx clear @var{filename}:@var{linenum}
2894 Delete any breakpoints set at or within the code of the specified line.
2896 @cindex delete breakpoints
2898 @kindex d @r{(@code{delete})}
2899 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2900 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
2901 ranges specified as arguments. If no argument is specified, delete all
2902 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
2903 confirm off}). You can abbreviate this command as @code{d}.
2907 @subsection Disabling breakpoints
2909 @kindex disable breakpoints
2910 @kindex enable breakpoints
2911 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
2912 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
2913 it had been deleted, but remembers the information on the breakpoint so
2914 that you can @dfn{enable} it again later.
2916 You disable and enable breakpoints, watchpoints, and catchpoints with
2917 the @code{enable} and @code{disable} commands, optionally specifying one
2918 or more breakpoint numbers as arguments. Use @code{info break} or
2919 @code{info watch} to print a list of breakpoints, watchpoints, and
2920 catchpoints if you do not know which numbers to use.
2922 A breakpoint, watchpoint, or catchpoint can have any of four different
2923 states of enablement:
2927 Enabled. The breakpoint stops your program. A breakpoint set
2928 with the @code{break} command starts out in this state.
2930 Disabled. The breakpoint has no effect on your program.
2932 Enabled once. The breakpoint stops your program, but then becomes
2935 Enabled for deletion. The breakpoint stops your program, but
2936 immediately after it does so it is deleted permanently. A breakpoint
2937 set with the @code{tbreak} command starts out in this state.
2940 You can use the following commands to enable or disable breakpoints,
2941 watchpoints, and catchpoints:
2944 @kindex disable breakpoints
2946 @kindex dis @r{(@code{disable})}
2947 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2948 Disable the specified breakpoints---or all breakpoints, if none are
2949 listed. A disabled breakpoint has no effect but is not forgotten. All
2950 options such as ignore-counts, conditions and commands are remembered in
2951 case the breakpoint is enabled again later. You may abbreviate
2952 @code{disable} as @code{dis}.
2954 @kindex enable breakpoints
2956 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
2957 Enable the specified breakpoints (or all defined breakpoints). They
2958 become effective once again in stopping your program.
2960 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
2961 Enable the specified breakpoints temporarily. @value{GDBN} disables any
2962 of these breakpoints immediately after stopping your program.
2964 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
2965 Enable the specified breakpoints to work once, then die. @value{GDBN}
2966 deletes any of these breakpoints as soon as your program stops there.
2969 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
2970 @c confusing: tbreak is also initially enabled.
2971 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
2972 ,Setting breakpoints}), breakpoints that you set are initially enabled;
2973 subsequently, they become disabled or enabled only when you use one of
2974 the commands above. (The command @code{until} can set and delete a
2975 breakpoint of its own, but it does not change the state of your other
2976 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
2980 @subsection Break conditions
2981 @cindex conditional breakpoints
2982 @cindex breakpoint conditions
2984 @c FIXME what is scope of break condition expr? Context where wanted?
2985 @c in particular for a watchpoint?
2986 The simplest sort of breakpoint breaks every time your program reaches a
2987 specified place. You can also specify a @dfn{condition} for a
2988 breakpoint. A condition is just a Boolean expression in your
2989 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
2990 a condition evaluates the expression each time your program reaches it,
2991 and your program stops only if the condition is @emph{true}.
2993 This is the converse of using assertions for program validation; in that
2994 situation, you want to stop when the assertion is violated---that is,
2995 when the condition is false. In C, if you want to test an assertion expressed
2996 by the condition @var{assert}, you should set the condition
2997 @samp{! @var{assert}} on the appropriate breakpoint.
2999 Conditions are also accepted for watchpoints; you may not need them,
3000 since a watchpoint is inspecting the value of an expression anyhow---but
3001 it might be simpler, say, to just set a watchpoint on a variable name,
3002 and specify a condition that tests whether the new value is an interesting
3005 Break conditions can have side effects, and may even call functions in
3006 your program. This can be useful, for example, to activate functions
3007 that log program progress, or to use your own print functions to
3008 format special data structures. The effects are completely predictable
3009 unless there is another enabled breakpoint at the same address. (In
3010 that case, @value{GDBN} might see the other breakpoint first and stop your
3011 program without checking the condition of this one.) Note that
3012 breakpoint commands are usually more convenient and flexible than break
3014 purpose of performing side effects when a breakpoint is reached
3015 (@pxref{Break Commands, ,Breakpoint command lists}).
3017 Break conditions can be specified when a breakpoint is set, by using
3018 @samp{if} in the arguments to the @code{break} command. @xref{Set
3019 Breaks, ,Setting breakpoints}. They can also be changed at any time
3020 with the @code{condition} command.
3022 You can also use the @code{if} keyword with the @code{watch} command.
3023 The @code{catch} command does not recognize the @code{if} keyword;
3024 @code{condition} is the only way to impose a further condition on a
3029 @item condition @var{bnum} @var{expression}
3030 Specify @var{expression} as the break condition for breakpoint,
3031 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
3032 breakpoint @var{bnum} stops your program only if the value of
3033 @var{expression} is true (nonzero, in C). When you use
3034 @code{condition}, @value{GDBN} checks @var{expression} immediately for
3035 syntactic correctness, and to determine whether symbols in it have
3036 referents in the context of your breakpoint. If @var{expression} uses
3037 symbols not referenced in the context of the breakpoint, @value{GDBN}
3038 prints an error message:
3041 No symbol "foo" in current context.
3046 not actually evaluate @var{expression} at the time the @code{condition}
3047 command (or a command that sets a breakpoint with a condition, like
3048 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
3050 @item condition @var{bnum}
3051 Remove the condition from breakpoint number @var{bnum}. It becomes
3052 an ordinary unconditional breakpoint.
3055 @cindex ignore count (of breakpoint)
3056 A special case of a breakpoint condition is to stop only when the
3057 breakpoint has been reached a certain number of times. This is so
3058 useful that there is a special way to do it, using the @dfn{ignore
3059 count} of the breakpoint. Every breakpoint has an ignore count, which
3060 is an integer. Most of the time, the ignore count is zero, and
3061 therefore has no effect. But if your program reaches a breakpoint whose
3062 ignore count is positive, then instead of stopping, it just decrements
3063 the ignore count by one and continues. As a result, if the ignore count
3064 value is @var{n}, the breakpoint does not stop the next @var{n} times
3065 your program reaches it.
3069 @item ignore @var{bnum} @var{count}
3070 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
3071 The next @var{count} times the breakpoint is reached, your program's
3072 execution does not stop; other than to decrement the ignore count, @value{GDBN}
3075 To make the breakpoint stop the next time it is reached, specify
3078 When you use @code{continue} to resume execution of your program from a
3079 breakpoint, you can specify an ignore count directly as an argument to
3080 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
3081 Stepping,,Continuing and stepping}.
3083 If a breakpoint has a positive ignore count and a condition, the
3084 condition is not checked. Once the ignore count reaches zero,
3085 @value{GDBN} resumes checking the condition.
3087 You could achieve the effect of the ignore count with a condition such
3088 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
3089 is decremented each time. @xref{Convenience Vars, ,Convenience
3093 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
3096 @node Break Commands
3097 @subsection Breakpoint command lists
3099 @cindex breakpoint commands
3100 You can give any breakpoint (or watchpoint or catchpoint) a series of
3101 commands to execute when your program stops due to that breakpoint. For
3102 example, you might want to print the values of certain expressions, or
3103 enable other breakpoints.
3108 @item commands @r{[}@var{bnum}@r{]}
3109 @itemx @dots{} @var{command-list} @dots{}
3111 Specify a list of commands for breakpoint number @var{bnum}. The commands
3112 themselves appear on the following lines. Type a line containing just
3113 @code{end} to terminate the commands.
3115 To remove all commands from a breakpoint, type @code{commands} and
3116 follow it immediately with @code{end}; that is, give no commands.
3118 With no @var{bnum} argument, @code{commands} refers to the last
3119 breakpoint, watchpoint, or catchpoint set (not to the breakpoint most
3120 recently encountered).
3123 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
3124 disabled within a @var{command-list}.
3126 You can use breakpoint commands to start your program up again. Simply
3127 use the @code{continue} command, or @code{step}, or any other command
3128 that resumes execution.
3130 Any other commands in the command list, after a command that resumes
3131 execution, are ignored. This is because any time you resume execution
3132 (even with a simple @code{next} or @code{step}), you may encounter
3133 another breakpoint---which could have its own command list, leading to
3134 ambiguities about which list to execute.
3137 If the first command you specify in a command list is @code{silent}, the
3138 usual message about stopping at a breakpoint is not printed. This may
3139 be desirable for breakpoints that are to print a specific message and
3140 then continue. If none of the remaining commands print anything, you
3141 see no sign that the breakpoint was reached. @code{silent} is
3142 meaningful only at the beginning of a breakpoint command list.
3144 The commands @code{echo}, @code{output}, and @code{printf} allow you to
3145 print precisely controlled output, and are often useful in silent
3146 breakpoints. @xref{Output, ,Commands for controlled output}.
3148 For example, here is how you could use breakpoint commands to print the
3149 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
3155 printf "x is %d\n",x
3160 One application for breakpoint commands is to compensate for one bug so
3161 you can test for another. Put a breakpoint just after the erroneous line
3162 of code, give it a condition to detect the case in which something
3163 erroneous has been done, and give it commands to assign correct values
3164 to any variables that need them. End with the @code{continue} command
3165 so that your program does not stop, and start with the @code{silent}
3166 command so that no output is produced. Here is an example:
3177 @node Breakpoint Menus
3178 @subsection Breakpoint menus
3180 @cindex symbol overloading
3182 Some programming languages (notably C@t{++}) permit a single function name
3183 to be defined several times, for application in different contexts.
3184 This is called @dfn{overloading}. When a function name is overloaded,
3185 @samp{break @var{function}} is not enough to tell @value{GDBN} where you want
3186 a breakpoint. If you realize this is a problem, you can use
3187 something like @samp{break @var{function}(@var{types})} to specify which
3188 particular version of the function you want. Otherwise, @value{GDBN} offers
3189 you a menu of numbered choices for different possible breakpoints, and
3190 waits for your selection with the prompt @samp{>}. The first two
3191 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
3192 sets a breakpoint at each definition of @var{function}, and typing
3193 @kbd{0} aborts the @code{break} command without setting any new
3196 For example, the following session excerpt shows an attempt to set a
3197 breakpoint at the overloaded symbol @code{String::after}.
3198 We choose three particular definitions of that function name:
3200 @c FIXME! This is likely to change to show arg type lists, at least
3203 (@value{GDBP}) b String::after
3206 [2] file:String.cc; line number:867
3207 [3] file:String.cc; line number:860
3208 [4] file:String.cc; line number:875
3209 [5] file:String.cc; line number:853
3210 [6] file:String.cc; line number:846
3211 [7] file:String.cc; line number:735
3213 Breakpoint 1 at 0xb26c: file String.cc, line 867.
3214 Breakpoint 2 at 0xb344: file String.cc, line 875.
3215 Breakpoint 3 at 0xafcc: file String.cc, line 846.
3216 Multiple breakpoints were set.
3217 Use the "delete" command to delete unwanted
3223 @c @ifclear BARETARGET
3224 @node Error in Breakpoints
3225 @subsection ``Cannot insert breakpoints''
3227 @c FIXME!! 14/6/95 Is there a real example of this? Let's use it.
3229 Under some operating systems, breakpoints cannot be used in a program if
3230 any other process is running that program. In this situation,
3231 attempting to run or continue a program with a breakpoint causes
3232 @value{GDBN} to print an error message:
3235 Cannot insert breakpoints.
3236 The same program may be running in another process.
3239 When this happens, you have three ways to proceed:
3243 Remove or disable the breakpoints, then continue.
3246 Suspend @value{GDBN}, and copy the file containing your program to a new
3247 name. Resume @value{GDBN} and use the @code{exec-file} command to specify
3248 that @value{GDBN} should run your program under that name.
3249 Then start your program again.
3252 Relink your program so that the text segment is nonsharable, using the
3253 linker option @samp{-N}. The operating system limitation may not apply
3254 to nonsharable executables.
3258 A similar message can be printed if you request too many active
3259 hardware-assisted breakpoints and watchpoints:
3261 @c FIXME: the precise wording of this message may change; the relevant
3262 @c source change is not committed yet (Sep 3, 1999).
3264 Stopped; cannot insert breakpoints.
3265 You may have requested too many hardware breakpoints and watchpoints.
3269 This message is printed when you attempt to resume the program, since
3270 only then @value{GDBN} knows exactly how many hardware breakpoints and
3271 watchpoints it needs to insert.
3273 When this message is printed, you need to disable or remove some of the
3274 hardware-assisted breakpoints and watchpoints, and then continue.
3277 @node Continuing and Stepping
3278 @section Continuing and stepping
3282 @cindex resuming execution
3283 @dfn{Continuing} means resuming program execution until your program
3284 completes normally. In contrast, @dfn{stepping} means executing just
3285 one more ``step'' of your program, where ``step'' may mean either one
3286 line of source code, or one machine instruction (depending on what
3287 particular command you use). Either when continuing or when stepping,
3288 your program may stop even sooner, due to a breakpoint or a signal. (If
3289 it stops due to a signal, you may want to use @code{handle}, or use
3290 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
3294 @kindex c @r{(@code{continue})}
3295 @kindex fg @r{(resume foreground execution)}
3296 @item continue @r{[}@var{ignore-count}@r{]}
3297 @itemx c @r{[}@var{ignore-count}@r{]}
3298 @itemx fg @r{[}@var{ignore-count}@r{]}
3299 Resume program execution, at the address where your program last stopped;
3300 any breakpoints set at that address are bypassed. The optional argument
3301 @var{ignore-count} allows you to specify a further number of times to
3302 ignore a breakpoint at this location; its effect is like that of
3303 @code{ignore} (@pxref{Conditions, ,Break conditions}).
3305 The argument @var{ignore-count} is meaningful only when your program
3306 stopped due to a breakpoint. At other times, the argument to
3307 @code{continue} is ignored.
3309 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
3310 debugged program is deemed to be the foreground program) are provided
3311 purely for convenience, and have exactly the same behavior as
3315 To resume execution at a different place, you can use @code{return}
3316 (@pxref{Returning, ,Returning from a function}) to go back to the
3317 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
3318 different address}) to go to an arbitrary location in your program.
3320 A typical technique for using stepping is to set a breakpoint
3321 (@pxref{Breakpoints, ,Breakpoints; watchpoints; and catchpoints}) at the
3322 beginning of the function or the section of your program where a problem
3323 is believed to lie, run your program until it stops at that breakpoint,
3324 and then step through the suspect area, examining the variables that are
3325 interesting, until you see the problem happen.
3329 @kindex s @r{(@code{step})}
3331 Continue running your program until control reaches a different source
3332 line, then stop it and return control to @value{GDBN}. This command is
3333 abbreviated @code{s}.
3336 @c "without debugging information" is imprecise; actually "without line
3337 @c numbers in the debugging information". (gcc -g1 has debugging info but
3338 @c not line numbers). But it seems complex to try to make that
3339 @c distinction here.
3340 @emph{Warning:} If you use the @code{step} command while control is
3341 within a function that was compiled without debugging information,
3342 execution proceeds until control reaches a function that does have
3343 debugging information. Likewise, it will not step into a function which
3344 is compiled without debugging information. To step through functions
3345 without debugging information, use the @code{stepi} command, described
3349 The @code{step} command only stops at the first instruction of a source
3350 line. This prevents the multiple stops that could otherwise occur in
3351 @code{switch} statements, @code{for} loops, etc. @code{step} continues
3352 to stop if a function that has debugging information is called within
3353 the line. In other words, @code{step} @emph{steps inside} any functions
3354 called within the line.
3356 Also, the @code{step} command only enters a function if there is line
3357 number information for the function. Otherwise it acts like the
3358 @code{next} command. This avoids problems when using @code{cc -gl}
3359 on MIPS machines. Previously, @code{step} entered subroutines if there
3360 was any debugging information about the routine.
3362 @item step @var{count}
3363 Continue running as in @code{step}, but do so @var{count} times. If a
3364 breakpoint is reached, or a signal not related to stepping occurs before
3365 @var{count} steps, stepping stops right away.
3368 @kindex n @r{(@code{next})}
3369 @item next @r{[}@var{count}@r{]}
3370 Continue to the next source line in the current (innermost) stack frame.
3371 This is similar to @code{step}, but function calls that appear within
3372 the line of code are executed without stopping. Execution stops when
3373 control reaches a different line of code at the original stack level
3374 that was executing when you gave the @code{next} command. This command
3375 is abbreviated @code{n}.
3377 An argument @var{count} is a repeat count, as for @code{step}.
3380 @c FIX ME!! Do we delete this, or is there a way it fits in with
3381 @c the following paragraph? --- Vctoria
3383 @c @code{next} within a function that lacks debugging information acts like
3384 @c @code{step}, but any function calls appearing within the code of the
3385 @c function are executed without stopping.
3387 The @code{next} command only stops at the first instruction of a
3388 source line. This prevents multiple stops that could otherwise occur in
3389 @code{switch} statements, @code{for} loops, etc.
3391 @kindex set step-mode
3393 @cindex functions without line info, and stepping
3394 @cindex stepping into functions with no line info
3395 @itemx set step-mode on
3396 The @code{set step-mode on} command causes the @code{step} command to
3397 stop at the first instruction of a function which contains no debug line
3398 information rather than stepping over it.
3400 This is useful in cases where you may be interested in inspecting the
3401 machine instructions of a function which has no symbolic info and do not
3402 want @value{GDBN} to automatically skip over this function.
3404 @item set step-mode off
3405 Causes the @code{step} command to step over any functions which contains no
3406 debug information. This is the default.
3410 Continue running until just after function in the selected stack frame
3411 returns. Print the returned value (if any).
3413 Contrast this with the @code{return} command (@pxref{Returning,
3414 ,Returning from a function}).
3417 @kindex u @r{(@code{until})}
3420 Continue running until a source line past the current line, in the
3421 current stack frame, is reached. This command is used to avoid single
3422 stepping through a loop more than once. It is like the @code{next}
3423 command, except that when @code{until} encounters a jump, it
3424 automatically continues execution until the program counter is greater
3425 than the address of the jump.
3427 This means that when you reach the end of a loop after single stepping
3428 though it, @code{until} makes your program continue execution until it
3429 exits the loop. In contrast, a @code{next} command at the end of a loop
3430 simply steps back to the beginning of the loop, which forces you to step
3431 through the next iteration.
3433 @code{until} always stops your program if it attempts to exit the current
3436 @code{until} may produce somewhat counterintuitive results if the order
3437 of machine code does not match the order of the source lines. For
3438 example, in the following excerpt from a debugging session, the @code{f}
3439 (@code{frame}) command shows that execution is stopped at line
3440 @code{206}; yet when we use @code{until}, we get to line @code{195}:
3444 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
3446 (@value{GDBP}) until
3447 195 for ( ; argc > 0; NEXTARG) @{
3450 This happened because, for execution efficiency, the compiler had
3451 generated code for the loop closure test at the end, rather than the
3452 start, of the loop---even though the test in a C @code{for}-loop is
3453 written before the body of the loop. The @code{until} command appeared
3454 to step back to the beginning of the loop when it advanced to this
3455 expression; however, it has not really gone to an earlier
3456 statement---not in terms of the actual machine code.
3458 @code{until} with no argument works by means of single
3459 instruction stepping, and hence is slower than @code{until} with an
3462 @item until @var{location}
3463 @itemx u @var{location}
3464 Continue running your program until either the specified location is
3465 reached, or the current stack frame returns. @var{location} is any of
3466 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
3467 ,Setting breakpoints}). This form of the command uses breakpoints,
3468 and hence is quicker than @code{until} without an argument.
3471 @kindex si @r{(@code{stepi})}
3473 @itemx stepi @var{arg}
3475 Execute one machine instruction, then stop and return to the debugger.
3477 It is often useful to do @samp{display/i $pc} when stepping by machine
3478 instructions. This makes @value{GDBN} automatically display the next
3479 instruction to be executed, each time your program stops. @xref{Auto
3480 Display,, Automatic display}.
3482 An argument is a repeat count, as in @code{step}.
3486 @kindex ni @r{(@code{nexti})}
3488 @itemx nexti @var{arg}
3490 Execute one machine instruction, but if it is a function call,
3491 proceed until the function returns.
3493 An argument is a repeat count, as in @code{next}.
3500 A signal is an asynchronous event that can happen in a program. The
3501 operating system defines the possible kinds of signals, and gives each
3502 kind a name and a number. For example, in Unix @code{SIGINT} is the
3503 signal a program gets when you type an interrupt character (often @kbd{C-c});
3504 @code{SIGSEGV} is the signal a program gets from referencing a place in
3505 memory far away from all the areas in use; @code{SIGALRM} occurs when
3506 the alarm clock timer goes off (which happens only if your program has
3507 requested an alarm).
3509 @cindex fatal signals
3510 Some signals, including @code{SIGALRM}, are a normal part of the
3511 functioning of your program. Others, such as @code{SIGSEGV}, indicate
3512 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
3513 program has not specified in advance some other way to handle the signal.
3514 @code{SIGINT} does not indicate an error in your program, but it is normally
3515 fatal so it can carry out the purpose of the interrupt: to kill the program.
3517 @value{GDBN} has the ability to detect any occurrence of a signal in your
3518 program. You can tell @value{GDBN} in advance what to do for each kind of
3521 @cindex handling signals
3522 Normally, @value{GDBN} is set up to let the non-erroneous signals like
3523 @code{SIGALRM} be silently passed to your program
3524 (so as not to interfere with their role in the program's functioning)
3525 but to stop your program immediately whenever an error signal happens.
3526 You can change these settings with the @code{handle} command.
3529 @kindex info signals
3532 Print a table of all the kinds of signals and how @value{GDBN} has been told to
3533 handle each one. You can use this to see the signal numbers of all
3534 the defined types of signals.
3536 @code{info handle} is an alias for @code{info signals}.
3539 @item handle @var{signal} @var{keywords}@dots{}
3540 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
3541 can be the number of a signal or its name (with or without the
3542 @samp{SIG} at the beginning); a list of signal numbers of the form
3543 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
3544 known signals. The @var{keywords} say what change to make.
3548 The keywords allowed by the @code{handle} command can be abbreviated.
3549 Their full names are:
3553 @value{GDBN} should not stop your program when this signal happens. It may
3554 still print a message telling you that the signal has come in.
3557 @value{GDBN} should stop your program when this signal happens. This implies
3558 the @code{print} keyword as well.
3561 @value{GDBN} should print a message when this signal happens.
3564 @value{GDBN} should not mention the occurrence of the signal at all. This
3565 implies the @code{nostop} keyword as well.
3569 @value{GDBN} should allow your program to see this signal; your program
3570 can handle the signal, or else it may terminate if the signal is fatal
3571 and not handled. @code{pass} and @code{noignore} are synonyms.
3575 @value{GDBN} should not allow your program to see this signal.
3576 @code{nopass} and @code{ignore} are synonyms.
3580 When a signal stops your program, the signal is not visible to the
3582 continue. Your program sees the signal then, if @code{pass} is in
3583 effect for the signal in question @emph{at that time}. In other words,
3584 after @value{GDBN} reports a signal, you can use the @code{handle}
3585 command with @code{pass} or @code{nopass} to control whether your
3586 program sees that signal when you continue.
3588 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
3589 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
3590 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
3593 You can also use the @code{signal} command to prevent your program from
3594 seeing a signal, or cause it to see a signal it normally would not see,
3595 or to give it any signal at any time. For example, if your program stopped
3596 due to some sort of memory reference error, you might store correct
3597 values into the erroneous variables and continue, hoping to see more
3598 execution; but your program would probably terminate immediately as
3599 a result of the fatal signal once it saw the signal. To prevent this,
3600 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
3604 @section Stopping and starting multi-thread programs
3606 When your program has multiple threads (@pxref{Threads,, Debugging
3607 programs with multiple threads}), you can choose whether to set
3608 breakpoints on all threads, or on a particular thread.
3611 @cindex breakpoints and threads
3612 @cindex thread breakpoints
3613 @kindex break @dots{} thread @var{threadno}
3614 @item break @var{linespec} thread @var{threadno}
3615 @itemx break @var{linespec} thread @var{threadno} if @dots{}
3616 @var{linespec} specifies source lines; there are several ways of
3617 writing them, but the effect is always to specify some source line.
3619 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
3620 to specify that you only want @value{GDBN} to stop the program when a
3621 particular thread reaches this breakpoint. @var{threadno} is one of the
3622 numeric thread identifiers assigned by @value{GDBN}, shown in the first
3623 column of the @samp{info threads} display.
3625 If you do not specify @samp{thread @var{threadno}} when you set a
3626 breakpoint, the breakpoint applies to @emph{all} threads of your
3629 You can use the @code{thread} qualifier on conditional breakpoints as
3630 well; in this case, place @samp{thread @var{threadno}} before the
3631 breakpoint condition, like this:
3634 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
3639 @cindex stopped threads
3640 @cindex threads, stopped
3641 Whenever your program stops under @value{GDBN} for any reason,
3642 @emph{all} threads of execution stop, not just the current thread. This
3643 allows you to examine the overall state of the program, including
3644 switching between threads, without worrying that things may change
3647 @cindex continuing threads
3648 @cindex threads, continuing
3649 Conversely, whenever you restart the program, @emph{all} threads start
3650 executing. @emph{This is true even when single-stepping} with commands
3651 like @code{step} or @code{next}.
3653 In particular, @value{GDBN} cannot single-step all threads in lockstep.
3654 Since thread scheduling is up to your debugging target's operating
3655 system (not controlled by @value{GDBN}), other threads may
3656 execute more than one statement while the current thread completes a
3657 single step. Moreover, in general other threads stop in the middle of a
3658 statement, rather than at a clean statement boundary, when the program
3661 You might even find your program stopped in another thread after
3662 continuing or even single-stepping. This happens whenever some other
3663 thread runs into a breakpoint, a signal, or an exception before the
3664 first thread completes whatever you requested.
3666 On some OSes, you can lock the OS scheduler and thus allow only a single
3670 @item set scheduler-locking @var{mode}
3671 Set the scheduler locking mode. If it is @code{off}, then there is no
3672 locking and any thread may run at any time. If @code{on}, then only the
3673 current thread may run when the inferior is resumed. The @code{step}
3674 mode optimizes for single-stepping. It stops other threads from
3675 ``seizing the prompt'' by preempting the current thread while you are
3676 stepping. Other threads will only rarely (or never) get a chance to run
3677 when you step. They are more likely to run when you @samp{next} over a
3678 function call, and they are completely free to run when you use commands
3679 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
3680 thread hits a breakpoint during its timeslice, they will never steal the
3681 @value{GDBN} prompt away from the thread that you are debugging.
3683 @item show scheduler-locking
3684 Display the current scheduler locking mode.
3689 @chapter Examining the Stack
3691 When your program has stopped, the first thing you need to know is where it
3692 stopped and how it got there.
3695 Each time your program performs a function call, information about the call
3697 That information includes the location of the call in your program,
3698 the arguments of the call,
3699 and the local variables of the function being called.
3700 The information is saved in a block of data called a @dfn{stack frame}.
3701 The stack frames are allocated in a region of memory called the @dfn{call
3704 When your program stops, the @value{GDBN} commands for examining the
3705 stack allow you to see all of this information.
3707 @cindex selected frame
3708 One of the stack frames is @dfn{selected} by @value{GDBN} and many
3709 @value{GDBN} commands refer implicitly to the selected frame. In
3710 particular, whenever you ask @value{GDBN} for the value of a variable in
3711 your program, the value is found in the selected frame. There are
3712 special @value{GDBN} commands to select whichever frame you are
3713 interested in. @xref{Selection, ,Selecting a frame}.
3715 When your program stops, @value{GDBN} automatically selects the
3716 currently executing frame and describes it briefly, similar to the
3717 @code{frame} command (@pxref{Frame Info, ,Information about a frame}).
3720 * Frames:: Stack frames
3721 * Backtrace:: Backtraces
3722 * Selection:: Selecting a frame
3723 * Frame Info:: Information on a frame
3728 @section Stack frames
3730 @cindex frame, definition
3732 The call stack is divided up into contiguous pieces called @dfn{stack
3733 frames}, or @dfn{frames} for short; each frame is the data associated
3734 with one call to one function. The frame contains the arguments given
3735 to the function, the function's local variables, and the address at
3736 which the function is executing.
3738 @cindex initial frame
3739 @cindex outermost frame
3740 @cindex innermost frame
3741 When your program is started, the stack has only one frame, that of the
3742 function @code{main}. This is called the @dfn{initial} frame or the
3743 @dfn{outermost} frame. Each time a function is called, a new frame is
3744 made. Each time a function returns, the frame for that function invocation
3745 is eliminated. If a function is recursive, there can be many frames for
3746 the same function. The frame for the function in which execution is
3747 actually occurring is called the @dfn{innermost} frame. This is the most
3748 recently created of all the stack frames that still exist.
3750 @cindex frame pointer
3751 Inside your program, stack frames are identified by their addresses. A
3752 stack frame consists of many bytes, each of which has its own address; each
3753 kind of computer has a convention for choosing one byte whose
3754 address serves as the address of the frame. Usually this address is kept
3755 in a register called the @dfn{frame pointer register} while execution is
3756 going on in that frame.
3758 @cindex frame number
3759 @value{GDBN} assigns numbers to all existing stack frames, starting with
3760 zero for the innermost frame, one for the frame that called it,
3761 and so on upward. These numbers do not really exist in your program;
3762 they are assigned by @value{GDBN} to give you a way of designating stack
3763 frames in @value{GDBN} commands.
3765 @c The -fomit-frame-pointer below perennially causes hbox overflow
3766 @c underflow problems.
3767 @cindex frameless execution
3768 Some compilers provide a way to compile functions so that they operate
3769 without stack frames. (For example, the @value{GCC} option
3771 @samp{-fomit-frame-pointer}
3773 generates functions without a frame.)
3774 This is occasionally done with heavily used library functions to save
3775 the frame setup time. @value{GDBN} has limited facilities for dealing
3776 with these function invocations. If the innermost function invocation
3777 has no stack frame, @value{GDBN} nevertheless regards it as though
3778 it had a separate frame, which is numbered zero as usual, allowing
3779 correct tracing of the function call chain. However, @value{GDBN} has
3780 no provision for frameless functions elsewhere in the stack.
3783 @kindex frame@r{, command}
3784 @cindex current stack frame
3785 @item frame @var{args}
3786 The @code{frame} command allows you to move from one stack frame to another,
3787 and to print the stack frame you select. @var{args} may be either the
3788 address of the frame or the stack frame number. Without an argument,
3789 @code{frame} prints the current stack frame.
3791 @kindex select-frame
3792 @cindex selecting frame silently
3794 The @code{select-frame} command allows you to move from one stack frame
3795 to another without printing the frame. This is the silent version of
3804 @cindex stack traces
3805 A backtrace is a summary of how your program got where it is. It shows one
3806 line per frame, for many frames, starting with the currently executing
3807 frame (frame zero), followed by its caller (frame one), and on up the
3812 @kindex bt @r{(@code{backtrace})}
3815 Print a backtrace of the entire stack: one line per frame for all
3816 frames in the stack.
3818 You can stop the backtrace at any time by typing the system interrupt
3819 character, normally @kbd{C-c}.
3821 @item backtrace @var{n}
3823 Similar, but print only the innermost @var{n} frames.
3825 @item backtrace -@var{n}
3827 Similar, but print only the outermost @var{n} frames.
3832 @kindex info s @r{(@code{info stack})}
3833 The names @code{where} and @code{info stack} (abbreviated @code{info s})
3834 are additional aliases for @code{backtrace}.
3836 Each line in the backtrace shows the frame number and the function name.
3837 The program counter value is also shown---unless you use @code{set
3838 print address off}. The backtrace also shows the source file name and
3839 line number, as well as the arguments to the function. The program
3840 counter value is omitted if it is at the beginning of the code for that
3843 Here is an example of a backtrace. It was made with the command
3844 @samp{bt 3}, so it shows the innermost three frames.
3848 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
3850 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
3851 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
3853 (More stack frames follow...)
3858 The display for frame zero does not begin with a program counter
3859 value, indicating that your program has stopped at the beginning of the
3860 code for line @code{993} of @code{builtin.c}.
3863 @section Selecting a frame
3865 Most commands for examining the stack and other data in your program work on
3866 whichever stack frame is selected at the moment. Here are the commands for
3867 selecting a stack frame; all of them finish by printing a brief description
3868 of the stack frame just selected.
3871 @kindex frame@r{, selecting}
3872 @kindex f @r{(@code{frame})}
3875 Select frame number @var{n}. Recall that frame zero is the innermost
3876 (currently executing) frame, frame one is the frame that called the
3877 innermost one, and so on. The highest-numbered frame is the one for
3880 @item frame @var{addr}
3882 Select the frame at address @var{addr}. This is useful mainly if the
3883 chaining of stack frames has been damaged by a bug, making it
3884 impossible for @value{GDBN} to assign numbers properly to all frames. In
3885 addition, this can be useful when your program has multiple stacks and
3886 switches between them.
3888 On the SPARC architecture, @code{frame} needs two addresses to
3889 select an arbitrary frame: a frame pointer and a stack pointer.
3891 On the MIPS and Alpha architecture, it needs two addresses: a stack
3892 pointer and a program counter.
3894 On the 29k architecture, it needs three addresses: a register stack
3895 pointer, a program counter, and a memory stack pointer.
3896 @c note to future updaters: this is conditioned on a flag
3897 @c SETUP_ARBITRARY_FRAME in the tm-*.h files. The above is up to date
3898 @c as of 27 Jan 1994.
3902 Move @var{n} frames up the stack. For positive numbers @var{n}, this
3903 advances toward the outermost frame, to higher frame numbers, to frames
3904 that have existed longer. @var{n} defaults to one.
3907 @kindex do @r{(@code{down})}
3909 Move @var{n} frames down the stack. For positive numbers @var{n}, this
3910 advances toward the innermost frame, to lower frame numbers, to frames
3911 that were created more recently. @var{n} defaults to one. You may
3912 abbreviate @code{down} as @code{do}.
3915 All of these commands end by printing two lines of output describing the
3916 frame. The first line shows the frame number, the function name, the
3917 arguments, and the source file and line number of execution in that
3918 frame. The second line shows the text of that source line.
3926 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
3928 10 read_input_file (argv[i]);
3932 After such a printout, the @code{list} command with no arguments
3933 prints ten lines centered on the point of execution in the frame.
3934 You can also edit the program at the point of execution with your favorite
3935 editing program by typing @code{edit}.
3936 @xref{List, ,Printing source lines},
3940 @kindex down-silently
3942 @item up-silently @var{n}
3943 @itemx down-silently @var{n}
3944 These two commands are variants of @code{up} and @code{down},
3945 respectively; they differ in that they do their work silently, without
3946 causing display of the new frame. They are intended primarily for use
3947 in @value{GDBN} command scripts, where the output might be unnecessary and
3952 @section Information about a frame
3954 There are several other commands to print information about the selected
3960 When used without any argument, this command does not change which
3961 frame is selected, but prints a brief description of the currently
3962 selected stack frame. It can be abbreviated @code{f}. With an
3963 argument, this command is used to select a stack frame.
3964 @xref{Selection, ,Selecting a frame}.
3967 @kindex info f @r{(@code{info frame})}
3970 This command prints a verbose description of the selected stack frame,
3975 the address of the frame
3977 the address of the next frame down (called by this frame)
3979 the address of the next frame up (caller of this frame)
3981 the language in which the source code corresponding to this frame is written
3983 the address of the frame's arguments
3985 the address of the frame's local variables
3987 the program counter saved in it (the address of execution in the caller frame)
3989 which registers were saved in the frame
3992 @noindent The verbose description is useful when
3993 something has gone wrong that has made the stack format fail to fit
3994 the usual conventions.
3996 @item info frame @var{addr}
3997 @itemx info f @var{addr}
3998 Print a verbose description of the frame at address @var{addr}, without
3999 selecting that frame. The selected frame remains unchanged by this
4000 command. This requires the same kind of address (more than one for some
4001 architectures) that you specify in the @code{frame} command.
4002 @xref{Selection, ,Selecting a frame}.
4006 Print the arguments of the selected frame, each on a separate line.
4010 Print the local variables of the selected frame, each on a separate
4011 line. These are all variables (declared either static or automatic)
4012 accessible at the point of execution of the selected frame.
4015 @cindex catch exceptions, list active handlers
4016 @cindex exception handlers, how to list
4018 Print a list of all the exception handlers that are active in the
4019 current stack frame at the current point of execution. To see other
4020 exception handlers, visit the associated frame (using the @code{up},
4021 @code{down}, or @code{frame} commands); then type @code{info catch}.
4022 @xref{Set Catchpoints, , Setting catchpoints}.
4028 @chapter Examining Source Files
4030 @value{GDBN} can print parts of your program's source, since the debugging
4031 information recorded in the program tells @value{GDBN} what source files were
4032 used to build it. When your program stops, @value{GDBN} spontaneously prints
4033 the line where it stopped. Likewise, when you select a stack frame
4034 (@pxref{Selection, ,Selecting a frame}), @value{GDBN} prints the line where
4035 execution in that frame has stopped. You can print other portions of
4036 source files by explicit command.
4038 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
4039 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
4040 @value{GDBN} under @sc{gnu} Emacs}.
4043 * List:: Printing source lines
4044 * Edit:: Editing source files
4045 * Search:: Searching source files
4046 * Source Path:: Specifying source directories
4047 * Machine Code:: Source and machine code
4051 @section Printing source lines
4054 @kindex l @r{(@code{list})}
4055 To print lines from a source file, use the @code{list} command
4056 (abbreviated @code{l}). By default, ten lines are printed.
4057 There are several ways to specify what part of the file you want to print.
4059 Here are the forms of the @code{list} command most commonly used:
4062 @item list @var{linenum}
4063 Print lines centered around line number @var{linenum} in the
4064 current source file.
4066 @item list @var{function}
4067 Print lines centered around the beginning of function
4071 Print more lines. If the last lines printed were printed with a
4072 @code{list} command, this prints lines following the last lines
4073 printed; however, if the last line printed was a solitary line printed
4074 as part of displaying a stack frame (@pxref{Stack, ,Examining the
4075 Stack}), this prints lines centered around that line.
4078 Print lines just before the lines last printed.
4081 By default, @value{GDBN} prints ten source lines with any of these forms of
4082 the @code{list} command. You can change this using @code{set listsize}:
4085 @kindex set listsize
4086 @item set listsize @var{count}
4087 Make the @code{list} command display @var{count} source lines (unless
4088 the @code{list} argument explicitly specifies some other number).
4090 @kindex show listsize
4092 Display the number of lines that @code{list} prints.
4095 Repeating a @code{list} command with @key{RET} discards the argument,
4096 so it is equivalent to typing just @code{list}. This is more useful
4097 than listing the same lines again. An exception is made for an
4098 argument of @samp{-}; that argument is preserved in repetition so that
4099 each repetition moves up in the source file.
4102 In general, the @code{list} command expects you to supply zero, one or two
4103 @dfn{linespecs}. Linespecs specify source lines; there are several ways
4104 of writing them, but the effect is always to specify some source line.
4105 Here is a complete description of the possible arguments for @code{list}:
4108 @item list @var{linespec}
4109 Print lines centered around the line specified by @var{linespec}.
4111 @item list @var{first},@var{last}
4112 Print lines from @var{first} to @var{last}. Both arguments are
4115 @item list ,@var{last}
4116 Print lines ending with @var{last}.
4118 @item list @var{first},
4119 Print lines starting with @var{first}.
4122 Print lines just after the lines last printed.
4125 Print lines just before the lines last printed.
4128 As described in the preceding table.
4131 Here are the ways of specifying a single source line---all the
4136 Specifies line @var{number} of the current source file.
4137 When a @code{list} command has two linespecs, this refers to
4138 the same source file as the first linespec.
4141 Specifies the line @var{offset} lines after the last line printed.
4142 When used as the second linespec in a @code{list} command that has
4143 two, this specifies the line @var{offset} lines down from the
4147 Specifies the line @var{offset} lines before the last line printed.
4149 @item @var{filename}:@var{number}
4150 Specifies line @var{number} in the source file @var{filename}.
4152 @item @var{function}
4153 Specifies the line that begins the body of the function @var{function}.
4154 For example: in C, this is the line with the open brace.
4156 @item @var{filename}:@var{function}
4157 Specifies the line of the open-brace that begins the body of the
4158 function @var{function} in the file @var{filename}. You only need the
4159 file name with a function name to avoid ambiguity when there are
4160 identically named functions in different source files.
4162 @item *@var{address}
4163 Specifies the line containing the program address @var{address}.
4164 @var{address} may be any expression.
4168 @section Editing source files
4169 @cindex editing source files
4172 @kindex e @r{(@code{edit})}
4173 To edit the lines in a source file, use the @code{edit} command.
4174 The editing program of your choice
4175 is invoked with the current line set to
4176 the active line in the program.
4177 Alternatively, there are several ways to specify what part of the file you
4178 want to print if you want to see other parts of the program.
4180 Here are the forms of the @code{edit} command most commonly used:
4184 Edit the current source file at the active line number in the program.
4186 @item edit @var{number}
4187 Edit the current source file with @var{number} as the active line number.
4189 @item edit @var{function}
4190 Edit the file containing @var{function} at the beginning of its definition.
4192 @item edit @var{filename}:@var{number}
4193 Specifies line @var{number} in the source file @var{filename}.
4195 @item edit @var{filename}:@var{function}
4196 Specifies the line that begins the body of the
4197 function @var{function} in the file @var{filename}. You only need the
4198 file name with a function name to avoid ambiguity when there are
4199 identically named functions in different source files.
4201 @item edit *@var{address}
4202 Specifies the line containing the program address @var{address}.
4203 @var{address} may be any expression.
4206 @subsection Choosing your editor
4207 You can customize @value{GDBN} to use any editor you want
4209 The only restriction is that your editor (say @code{ex}), recognizes the
4210 following command-line syntax:
4212 ex +@var{number} file
4214 The optional numeric value +@var{number} designates the active line in
4215 the file.}. By default, it is @value{EDITOR}, but you can change this
4216 by setting the environment variable @code{EDITOR} before using
4217 @value{GDBN}. For example, to configure @value{GDBN} to use the
4218 @code{vi} editor, you could use these commands with the @code{sh} shell:
4224 or in the @code{csh} shell,
4226 setenv EDITOR /usr/bin/vi
4231 @section Searching source files
4233 @kindex reverse-search
4235 There are two commands for searching through the current source file for a
4240 @kindex forward-search
4241 @item forward-search @var{regexp}
4242 @itemx search @var{regexp}
4243 The command @samp{forward-search @var{regexp}} checks each line,
4244 starting with the one following the last line listed, for a match for
4245 @var{regexp}. It lists the line that is found. You can use the
4246 synonym @samp{search @var{regexp}} or abbreviate the command name as
4249 @item reverse-search @var{regexp}
4250 The command @samp{reverse-search @var{regexp}} checks each line, starting
4251 with the one before the last line listed and going backward, for a match
4252 for @var{regexp}. It lists the line that is found. You can abbreviate
4253 this command as @code{rev}.
4257 @section Specifying source directories
4260 @cindex directories for source files
4261 Executable programs sometimes do not record the directories of the source
4262 files from which they were compiled, just the names. Even when they do,
4263 the directories could be moved between the compilation and your debugging
4264 session. @value{GDBN} has a list of directories to search for source files;
4265 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
4266 it tries all the directories in the list, in the order they are present
4267 in the list, until it finds a file with the desired name. Note that
4268 the executable search path is @emph{not} used for this purpose. Neither is
4269 the current working directory, unless it happens to be in the source
4272 If @value{GDBN} cannot find a source file in the source path, and the
4273 object program records a directory, @value{GDBN} tries that directory
4274 too. If the source path is empty, and there is no record of the
4275 compilation directory, @value{GDBN} looks in the current directory as a
4278 Whenever you reset or rearrange the source path, @value{GDBN} clears out
4279 any information it has cached about where source files are found and where
4280 each line is in the file.
4284 When you start @value{GDBN}, its source path includes only @samp{cdir}
4285 and @samp{cwd}, in that order.
4286 To add other directories, use the @code{directory} command.
4289 @item directory @var{dirname} @dots{}
4290 @item dir @var{dirname} @dots{}
4291 Add directory @var{dirname} to the front of the source path. Several
4292 directory names may be given to this command, separated by @samp{:}
4293 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
4294 part of absolute file names) or
4295 whitespace. You may specify a directory that is already in the source
4296 path; this moves it forward, so @value{GDBN} searches it sooner.
4300 @vindex $cdir@r{, convenience variable}
4301 @vindex $cwdr@r{, convenience variable}
4302 @cindex compilation directory
4303 @cindex current directory
4304 @cindex working directory
4305 @cindex directory, current
4306 @cindex directory, compilation
4307 You can use the string @samp{$cdir} to refer to the compilation
4308 directory (if one is recorded), and @samp{$cwd} to refer to the current
4309 working directory. @samp{$cwd} is not the same as @samp{.}---the former
4310 tracks the current working directory as it changes during your @value{GDBN}
4311 session, while the latter is immediately expanded to the current
4312 directory at the time you add an entry to the source path.
4315 Reset the source path to empty again. This requires confirmation.
4317 @c RET-repeat for @code{directory} is explicitly disabled, but since
4318 @c repeating it would be a no-op we do not say that. (thanks to RMS)
4320 @item show directories
4321 @kindex show directories
4322 Print the source path: show which directories it contains.
4325 If your source path is cluttered with directories that are no longer of
4326 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
4327 versions of source. You can correct the situation as follows:
4331 Use @code{directory} with no argument to reset the source path to empty.
4334 Use @code{directory} with suitable arguments to reinstall the
4335 directories you want in the source path. You can add all the
4336 directories in one command.
4340 @section Source and machine code
4342 You can use the command @code{info line} to map source lines to program
4343 addresses (and vice versa), and the command @code{disassemble} to display
4344 a range of addresses as machine instructions. When run under @sc{gnu} Emacs
4345 mode, the @code{info line} command causes the arrow to point to the
4346 line specified. Also, @code{info line} prints addresses in symbolic form as
4351 @item info line @var{linespec}
4352 Print the starting and ending addresses of the compiled code for
4353 source line @var{linespec}. You can specify source lines in any of
4354 the ways understood by the @code{list} command (@pxref{List, ,Printing
4358 For example, we can use @code{info line} to discover the location of
4359 the object code for the first line of function
4360 @code{m4_changequote}:
4362 @c FIXME: I think this example should also show the addresses in
4363 @c symbolic form, as they usually would be displayed.
4365 (@value{GDBP}) info line m4_changequote
4366 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
4370 We can also inquire (using @code{*@var{addr}} as the form for
4371 @var{linespec}) what source line covers a particular address:
4373 (@value{GDBP}) info line *0x63ff
4374 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
4377 @cindex @code{$_} and @code{info line}
4378 @kindex x@r{(examine), and} info line
4379 After @code{info line}, the default address for the @code{x} command
4380 is changed to the starting address of the line, so that @samp{x/i} is
4381 sufficient to begin examining the machine code (@pxref{Memory,
4382 ,Examining memory}). Also, this address is saved as the value of the
4383 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
4388 @cindex assembly instructions
4389 @cindex instructions, assembly
4390 @cindex machine instructions
4391 @cindex listing machine instructions
4393 This specialized command dumps a range of memory as machine
4394 instructions. The default memory range is the function surrounding the
4395 program counter of the selected frame. A single argument to this
4396 command is a program counter value; @value{GDBN} dumps the function
4397 surrounding this value. Two arguments specify a range of addresses
4398 (first inclusive, second exclusive) to dump.
4401 The following example shows the disassembly of a range of addresses of
4402 HP PA-RISC 2.0 code:
4405 (@value{GDBP}) disas 0x32c4 0x32e4
4406 Dump of assembler code from 0x32c4 to 0x32e4:
4407 0x32c4 <main+204>: addil 0,dp
4408 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
4409 0x32cc <main+212>: ldil 0x3000,r31
4410 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
4411 0x32d4 <main+220>: ldo 0(r31),rp
4412 0x32d8 <main+224>: addil -0x800,dp
4413 0x32dc <main+228>: ldo 0x588(r1),r26
4414 0x32e0 <main+232>: ldil 0x3000,r31
4415 End of assembler dump.
4418 Some architectures have more than one commonly-used set of instruction
4419 mnemonics or other syntax.
4422 @kindex set disassembly-flavor
4423 @cindex assembly instructions
4424 @cindex instructions, assembly
4425 @cindex machine instructions
4426 @cindex listing machine instructions
4427 @cindex Intel disassembly flavor
4428 @cindex AT&T disassembly flavor
4429 @item set disassembly-flavor @var{instruction-set}
4430 Select the instruction set to use when disassembling the
4431 program via the @code{disassemble} or @code{x/i} commands.
4433 Currently this command is only defined for the Intel x86 family. You
4434 can set @var{instruction-set} to either @code{intel} or @code{att}.
4435 The default is @code{att}, the AT&T flavor used by default by Unix
4436 assemblers for x86-based targets.
4441 @chapter Examining Data
4443 @cindex printing data
4444 @cindex examining data
4447 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
4448 @c document because it is nonstandard... Under Epoch it displays in a
4449 @c different window or something like that.
4450 The usual way to examine data in your program is with the @code{print}
4451 command (abbreviated @code{p}), or its synonym @code{inspect}. It
4452 evaluates and prints the value of an expression of the language your
4453 program is written in (@pxref{Languages, ,Using @value{GDBN} with
4454 Different Languages}).
4457 @item print @var{expr}
4458 @itemx print /@var{f} @var{expr}
4459 @var{expr} is an expression (in the source language). By default the
4460 value of @var{expr} is printed in a format appropriate to its data type;
4461 you can choose a different format by specifying @samp{/@var{f}}, where
4462 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
4466 @itemx print /@var{f}
4467 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
4468 @dfn{value history}; @pxref{Value History, ,Value history}). This allows you to
4469 conveniently inspect the same value in an alternative format.
4472 A more low-level way of examining data is with the @code{x} command.
4473 It examines data in memory at a specified address and prints it in a
4474 specified format. @xref{Memory, ,Examining memory}.
4476 If you are interested in information about types, or about how the
4477 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
4478 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
4482 * Expressions:: Expressions
4483 * Variables:: Program variables
4484 * Arrays:: Artificial arrays
4485 * Output Formats:: Output formats
4486 * Memory:: Examining memory
4487 * Auto Display:: Automatic display
4488 * Print Settings:: Print settings
4489 * Value History:: Value history
4490 * Convenience Vars:: Convenience variables
4491 * Registers:: Registers
4492 * Floating Point Hardware:: Floating point hardware
4493 * Vector Unit:: Vector Unit
4494 * Memory Region Attributes:: Memory region attributes
4495 * Dump/Restore Files:: Copy between memory and a file
4496 * Character Sets:: Debugging programs that use a different
4497 character set than GDB does
4501 @section Expressions
4504 @code{print} and many other @value{GDBN} commands accept an expression and
4505 compute its value. Any kind of constant, variable or operator defined
4506 by the programming language you are using is valid in an expression in
4507 @value{GDBN}. This includes conditional expressions, function calls,
4508 casts, and string constants. It also includes preprocessor macros, if
4509 you compiled your program to include this information; see
4512 @value{GDBN} supports array constants in expressions input by
4513 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
4514 you can use the command @code{print @{1, 2, 3@}} to build up an array in
4515 memory that is @code{malloc}ed in the target program.
4517 Because C is so widespread, most of the expressions shown in examples in
4518 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
4519 Languages}, for information on how to use expressions in other
4522 In this section, we discuss operators that you can use in @value{GDBN}
4523 expressions regardless of your programming language.
4525 Casts are supported in all languages, not just in C, because it is so
4526 useful to cast a number into a pointer in order to examine a structure
4527 at that address in memory.
4528 @c FIXME: casts supported---Mod2 true?
4530 @value{GDBN} supports these operators, in addition to those common
4531 to programming languages:
4535 @samp{@@} is a binary operator for treating parts of memory as arrays.
4536 @xref{Arrays, ,Artificial arrays}, for more information.
4539 @samp{::} allows you to specify a variable in terms of the file or
4540 function where it is defined. @xref{Variables, ,Program variables}.
4542 @cindex @{@var{type}@}
4543 @cindex type casting memory
4544 @cindex memory, viewing as typed object
4545 @cindex casts, to view memory
4546 @item @{@var{type}@} @var{addr}
4547 Refers to an object of type @var{type} stored at address @var{addr} in
4548 memory. @var{addr} may be any expression whose value is an integer or
4549 pointer (but parentheses are required around binary operators, just as in
4550 a cast). This construct is allowed regardless of what kind of data is
4551 normally supposed to reside at @var{addr}.
4555 @section Program variables
4557 The most common kind of expression to use is the name of a variable
4560 Variables in expressions are understood in the selected stack frame
4561 (@pxref{Selection, ,Selecting a frame}); they must be either:
4565 global (or file-static)
4572 visible according to the scope rules of the
4573 programming language from the point of execution in that frame
4576 @noindent This means that in the function
4591 you can examine and use the variable @code{a} whenever your program is
4592 executing within the function @code{foo}, but you can only use or
4593 examine the variable @code{b} while your program is executing inside
4594 the block where @code{b} is declared.
4596 @cindex variable name conflict
4597 There is an exception: you can refer to a variable or function whose
4598 scope is a single source file even if the current execution point is not
4599 in this file. But it is possible to have more than one such variable or
4600 function with the same name (in different source files). If that
4601 happens, referring to that name has unpredictable effects. If you wish,
4602 you can specify a static variable in a particular function or file,
4603 using the colon-colon notation:
4605 @cindex colon-colon, context for variables/functions
4607 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
4608 @cindex @code{::}, context for variables/functions
4611 @var{file}::@var{variable}
4612 @var{function}::@var{variable}
4616 Here @var{file} or @var{function} is the name of the context for the
4617 static @var{variable}. In the case of file names, you can use quotes to
4618 make sure @value{GDBN} parses the file name as a single word---for example,
4619 to print a global value of @code{x} defined in @file{f2.c}:
4622 (@value{GDBP}) p 'f2.c'::x
4625 @cindex C@t{++} scope resolution
4626 This use of @samp{::} is very rarely in conflict with the very similar
4627 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
4628 scope resolution operator in @value{GDBN} expressions.
4629 @c FIXME: Um, so what happens in one of those rare cases where it's in
4632 @cindex wrong values
4633 @cindex variable values, wrong
4635 @emph{Warning:} Occasionally, a local variable may appear to have the
4636 wrong value at certain points in a function---just after entry to a new
4637 scope, and just before exit.
4639 You may see this problem when you are stepping by machine instructions.
4640 This is because, on most machines, it takes more than one instruction to
4641 set up a stack frame (including local variable definitions); if you are
4642 stepping by machine instructions, variables may appear to have the wrong
4643 values until the stack frame is completely built. On exit, it usually
4644 also takes more than one machine instruction to destroy a stack frame;
4645 after you begin stepping through that group of instructions, local
4646 variable definitions may be gone.
4648 This may also happen when the compiler does significant optimizations.
4649 To be sure of always seeing accurate values, turn off all optimization
4652 @cindex ``No symbol "foo" in current context''
4653 Another possible effect of compiler optimizations is to optimize
4654 unused variables out of existence, or assign variables to registers (as
4655 opposed to memory addresses). Depending on the support for such cases
4656 offered by the debug info format used by the compiler, @value{GDBN}
4657 might not be able to display values for such local variables. If that
4658 happens, @value{GDBN} will print a message like this:
4661 No symbol "foo" in current context.
4664 To solve such problems, either recompile without optimizations, or use a
4665 different debug info format, if the compiler supports several such
4666 formats. For example, @value{NGCC}, the @sc{gnu} C/C@t{++} compiler usually
4667 supports the @samp{-gstabs} option. @samp{-gstabs} produces debug info
4668 in a format that is superior to formats such as COFF. You may be able
4669 to use DWARF2 (@samp{-gdwarf-2}), which is also an effective form for
4670 debug info. See @ref{Debugging Options,,Options for Debugging Your
4671 Program or @sc{gnu} CC, gcc.info, Using @sc{gnu} CC}, for more
4676 @section Artificial arrays
4678 @cindex artificial array
4679 @kindex @@@r{, referencing memory as an array}
4680 It is often useful to print out several successive objects of the
4681 same type in memory; a section of an array, or an array of
4682 dynamically determined size for which only a pointer exists in the
4685 You can do this by referring to a contiguous span of memory as an
4686 @dfn{artificial array}, using the binary operator @samp{@@}. The left
4687 operand of @samp{@@} should be the first element of the desired array
4688 and be an individual object. The right operand should be the desired length
4689 of the array. The result is an array value whose elements are all of
4690 the type of the left argument. The first element is actually the left
4691 argument; the second element comes from bytes of memory immediately
4692 following those that hold the first element, and so on. Here is an
4693 example. If a program says
4696 int *array = (int *) malloc (len * sizeof (int));
4700 you can print the contents of @code{array} with
4706 The left operand of @samp{@@} must reside in memory. Array values made
4707 with @samp{@@} in this way behave just like other arrays in terms of
4708 subscripting, and are coerced to pointers when used in expressions.
4709 Artificial arrays most often appear in expressions via the value history
4710 (@pxref{Value History, ,Value history}), after printing one out.
4712 Another way to create an artificial array is to use a cast.
4713 This re-interprets a value as if it were an array.
4714 The value need not be in memory:
4716 (@value{GDBP}) p/x (short[2])0x12345678
4717 $1 = @{0x1234, 0x5678@}
4720 As a convenience, if you leave the array length out (as in
4721 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
4722 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
4724 (@value{GDBP}) p/x (short[])0x12345678
4725 $2 = @{0x1234, 0x5678@}
4728 Sometimes the artificial array mechanism is not quite enough; in
4729 moderately complex data structures, the elements of interest may not
4730 actually be adjacent---for example, if you are interested in the values
4731 of pointers in an array. One useful work-around in this situation is
4732 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
4733 variables}) as a counter in an expression that prints the first
4734 interesting value, and then repeat that expression via @key{RET}. For
4735 instance, suppose you have an array @code{dtab} of pointers to
4736 structures, and you are interested in the values of a field @code{fv}
4737 in each structure. Here is an example of what you might type:
4747 @node Output Formats
4748 @section Output formats
4750 @cindex formatted output
4751 @cindex output formats
4752 By default, @value{GDBN} prints a value according to its data type. Sometimes
4753 this is not what you want. For example, you might want to print a number
4754 in hex, or a pointer in decimal. Or you might want to view data in memory
4755 at a certain address as a character string or as an instruction. To do
4756 these things, specify an @dfn{output format} when you print a value.
4758 The simplest use of output formats is to say how to print a value
4759 already computed. This is done by starting the arguments of the
4760 @code{print} command with a slash and a format letter. The format
4761 letters supported are:
4765 Regard the bits of the value as an integer, and print the integer in
4769 Print as integer in signed decimal.
4772 Print as integer in unsigned decimal.
4775 Print as integer in octal.
4778 Print as integer in binary. The letter @samp{t} stands for ``two''.
4779 @footnote{@samp{b} cannot be used because these format letters are also
4780 used with the @code{x} command, where @samp{b} stands for ``byte'';
4781 see @ref{Memory,,Examining memory}.}
4784 @cindex unknown address, locating
4785 @cindex locate address
4786 Print as an address, both absolute in hexadecimal and as an offset from
4787 the nearest preceding symbol. You can use this format used to discover
4788 where (in what function) an unknown address is located:
4791 (@value{GDBP}) p/a 0x54320
4792 $3 = 0x54320 <_initialize_vx+396>
4796 The command @code{info symbol 0x54320} yields similar results.
4797 @xref{Symbols, info symbol}.
4800 Regard as an integer and print it as a character constant.
4803 Regard the bits of the value as a floating point number and print
4804 using typical floating point syntax.
4807 For example, to print the program counter in hex (@pxref{Registers}), type
4814 Note that no space is required before the slash; this is because command
4815 names in @value{GDBN} cannot contain a slash.
4817 To reprint the last value in the value history with a different format,
4818 you can use the @code{print} command with just a format and no
4819 expression. For example, @samp{p/x} reprints the last value in hex.
4822 @section Examining memory
4824 You can use the command @code{x} (for ``examine'') to examine memory in
4825 any of several formats, independently of your program's data types.
4827 @cindex examining memory
4829 @kindex x @r{(examine memory)}
4830 @item x/@var{nfu} @var{addr}
4833 Use the @code{x} command to examine memory.
4836 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
4837 much memory to display and how to format it; @var{addr} is an
4838 expression giving the address where you want to start displaying memory.
4839 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
4840 Several commands set convenient defaults for @var{addr}.
4843 @item @var{n}, the repeat count
4844 The repeat count is a decimal integer; the default is 1. It specifies
4845 how much memory (counting by units @var{u}) to display.
4846 @c This really is **decimal**; unaffected by 'set radix' as of GDB
4849 @item @var{f}, the display format
4850 The display format is one of the formats used by @code{print},
4851 @samp{s} (null-terminated string), or @samp{i} (machine instruction).
4852 The default is @samp{x} (hexadecimal) initially.
4853 The default changes each time you use either @code{x} or @code{print}.
4855 @item @var{u}, the unit size
4856 The unit size is any of
4862 Halfwords (two bytes).
4864 Words (four bytes). This is the initial default.
4866 Giant words (eight bytes).
4869 Each time you specify a unit size with @code{x}, that size becomes the
4870 default unit the next time you use @code{x}. (For the @samp{s} and
4871 @samp{i} formats, the unit size is ignored and is normally not written.)
4873 @item @var{addr}, starting display address
4874 @var{addr} is the address where you want @value{GDBN} to begin displaying
4875 memory. The expression need not have a pointer value (though it may);
4876 it is always interpreted as an integer address of a byte of memory.
4877 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
4878 @var{addr} is usually just after the last address examined---but several
4879 other commands also set the default address: @code{info breakpoints} (to
4880 the address of the last breakpoint listed), @code{info line} (to the
4881 starting address of a line), and @code{print} (if you use it to display
4882 a value from memory).
4885 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
4886 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
4887 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
4888 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
4889 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
4891 Since the letters indicating unit sizes are all distinct from the
4892 letters specifying output formats, you do not have to remember whether
4893 unit size or format comes first; either order works. The output
4894 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
4895 (However, the count @var{n} must come first; @samp{wx4} does not work.)
4897 Even though the unit size @var{u} is ignored for the formats @samp{s}
4898 and @samp{i}, you might still want to use a count @var{n}; for example,
4899 @samp{3i} specifies that you want to see three machine instructions,
4900 including any operands. The command @code{disassemble} gives an
4901 alternative way of inspecting machine instructions; see @ref{Machine
4902 Code,,Source and machine code}.
4904 All the defaults for the arguments to @code{x} are designed to make it
4905 easy to continue scanning memory with minimal specifications each time
4906 you use @code{x}. For example, after you have inspected three machine
4907 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
4908 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
4909 the repeat count @var{n} is used again; the other arguments default as
4910 for successive uses of @code{x}.
4912 @cindex @code{$_}, @code{$__}, and value history
4913 The addresses and contents printed by the @code{x} command are not saved
4914 in the value history because there is often too much of them and they
4915 would get in the way. Instead, @value{GDBN} makes these values available for
4916 subsequent use in expressions as values of the convenience variables
4917 @code{$_} and @code{$__}. After an @code{x} command, the last address
4918 examined is available for use in expressions in the convenience variable
4919 @code{$_}. The contents of that address, as examined, are available in
4920 the convenience variable @code{$__}.
4922 If the @code{x} command has a repeat count, the address and contents saved
4923 are from the last memory unit printed; this is not the same as the last
4924 address printed if several units were printed on the last line of output.
4927 @section Automatic display
4928 @cindex automatic display
4929 @cindex display of expressions
4931 If you find that you want to print the value of an expression frequently
4932 (to see how it changes), you might want to add it to the @dfn{automatic
4933 display list} so that @value{GDBN} prints its value each time your program stops.
4934 Each expression added to the list is given a number to identify it;
4935 to remove an expression from the list, you specify that number.
4936 The automatic display looks like this:
4940 3: bar[5] = (struct hack *) 0x3804
4944 This display shows item numbers, expressions and their current values. As with
4945 displays you request manually using @code{x} or @code{print}, you can
4946 specify the output format you prefer; in fact, @code{display} decides
4947 whether to use @code{print} or @code{x} depending on how elaborate your
4948 format specification is---it uses @code{x} if you specify a unit size,
4949 or one of the two formats (@samp{i} and @samp{s}) that are only
4950 supported by @code{x}; otherwise it uses @code{print}.
4954 @item display @var{expr}
4955 Add the expression @var{expr} to the list of expressions to display
4956 each time your program stops. @xref{Expressions, ,Expressions}.
4958 @code{display} does not repeat if you press @key{RET} again after using it.
4960 @item display/@var{fmt} @var{expr}
4961 For @var{fmt} specifying only a display format and not a size or
4962 count, add the expression @var{expr} to the auto-display list but
4963 arrange to display it each time in the specified format @var{fmt}.
4964 @xref{Output Formats,,Output formats}.
4966 @item display/@var{fmt} @var{addr}
4967 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
4968 number of units, add the expression @var{addr} as a memory address to
4969 be examined each time your program stops. Examining means in effect
4970 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining memory}.
4973 For example, @samp{display/i $pc} can be helpful, to see the machine
4974 instruction about to be executed each time execution stops (@samp{$pc}
4975 is a common name for the program counter; @pxref{Registers, ,Registers}).
4978 @kindex delete display
4980 @item undisplay @var{dnums}@dots{}
4981 @itemx delete display @var{dnums}@dots{}
4982 Remove item numbers @var{dnums} from the list of expressions to display.
4984 @code{undisplay} does not repeat if you press @key{RET} after using it.
4985 (Otherwise you would just get the error @samp{No display number @dots{}}.)
4987 @kindex disable display
4988 @item disable display @var{dnums}@dots{}
4989 Disable the display of item numbers @var{dnums}. A disabled display
4990 item is not printed automatically, but is not forgotten. It may be
4991 enabled again later.
4993 @kindex enable display
4994 @item enable display @var{dnums}@dots{}
4995 Enable display of item numbers @var{dnums}. It becomes effective once
4996 again in auto display of its expression, until you specify otherwise.
4999 Display the current values of the expressions on the list, just as is
5000 done when your program stops.
5002 @kindex info display
5004 Print the list of expressions previously set up to display
5005 automatically, each one with its item number, but without showing the
5006 values. This includes disabled expressions, which are marked as such.
5007 It also includes expressions which would not be displayed right now
5008 because they refer to automatic variables not currently available.
5011 If a display expression refers to local variables, then it does not make
5012 sense outside the lexical context for which it was set up. Such an
5013 expression is disabled when execution enters a context where one of its
5014 variables is not defined. For example, if you give the command
5015 @code{display last_char} while inside a function with an argument
5016 @code{last_char}, @value{GDBN} displays this argument while your program
5017 continues to stop inside that function. When it stops elsewhere---where
5018 there is no variable @code{last_char}---the display is disabled
5019 automatically. The next time your program stops where @code{last_char}
5020 is meaningful, you can enable the display expression once again.
5022 @node Print Settings
5023 @section Print settings
5025 @cindex format options
5026 @cindex print settings
5027 @value{GDBN} provides the following ways to control how arrays, structures,
5028 and symbols are printed.
5031 These settings are useful for debugging programs in any language:
5034 @kindex set print address
5035 @item set print address
5036 @itemx set print address on
5037 @value{GDBN} prints memory addresses showing the location of stack
5038 traces, structure values, pointer values, breakpoints, and so forth,
5039 even when it also displays the contents of those addresses. The default
5040 is @code{on}. For example, this is what a stack frame display looks like with
5041 @code{set print address on}:
5046 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
5048 530 if (lquote != def_lquote)
5052 @item set print address off
5053 Do not print addresses when displaying their contents. For example,
5054 this is the same stack frame displayed with @code{set print address off}:
5058 (@value{GDBP}) set print addr off
5060 #0 set_quotes (lq="<<", rq=">>") at input.c:530
5061 530 if (lquote != def_lquote)
5065 You can use @samp{set print address off} to eliminate all machine
5066 dependent displays from the @value{GDBN} interface. For example, with
5067 @code{print address off}, you should get the same text for backtraces on
5068 all machines---whether or not they involve pointer arguments.
5070 @kindex show print address
5071 @item show print address
5072 Show whether or not addresses are to be printed.
5075 When @value{GDBN} prints a symbolic address, it normally prints the
5076 closest earlier symbol plus an offset. If that symbol does not uniquely
5077 identify the address (for example, it is a name whose scope is a single
5078 source file), you may need to clarify. One way to do this is with
5079 @code{info line}, for example @samp{info line *0x4537}. Alternately,
5080 you can set @value{GDBN} to print the source file and line number when
5081 it prints a symbolic address:
5084 @kindex set print symbol-filename
5085 @item set print symbol-filename on
5086 Tell @value{GDBN} to print the source file name and line number of a
5087 symbol in the symbolic form of an address.
5089 @item set print symbol-filename off
5090 Do not print source file name and line number of a symbol. This is the
5093 @kindex show print symbol-filename
5094 @item show print symbol-filename
5095 Show whether or not @value{GDBN} will print the source file name and
5096 line number of a symbol in the symbolic form of an address.
5099 Another situation where it is helpful to show symbol filenames and line
5100 numbers is when disassembling code; @value{GDBN} shows you the line
5101 number and source file that corresponds to each instruction.
5103 Also, you may wish to see the symbolic form only if the address being
5104 printed is reasonably close to the closest earlier symbol:
5107 @kindex set print max-symbolic-offset
5108 @item set print max-symbolic-offset @var{max-offset}
5109 Tell @value{GDBN} to only display the symbolic form of an address if the
5110 offset between the closest earlier symbol and the address is less than
5111 @var{max-offset}. The default is 0, which tells @value{GDBN}
5112 to always print the symbolic form of an address if any symbol precedes it.
5114 @kindex show print max-symbolic-offset
5115 @item show print max-symbolic-offset
5116 Ask how large the maximum offset is that @value{GDBN} prints in a
5120 @cindex wild pointer, interpreting
5121 @cindex pointer, finding referent
5122 If you have a pointer and you are not sure where it points, try
5123 @samp{set print symbol-filename on}. Then you can determine the name
5124 and source file location of the variable where it points, using
5125 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
5126 For example, here @value{GDBN} shows that a variable @code{ptt} points
5127 at another variable @code{t}, defined in @file{hi2.c}:
5130 (@value{GDBP}) set print symbol-filename on
5131 (@value{GDBP}) p/a ptt
5132 $4 = 0xe008 <t in hi2.c>
5136 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
5137 does not show the symbol name and filename of the referent, even with
5138 the appropriate @code{set print} options turned on.
5141 Other settings control how different kinds of objects are printed:
5144 @kindex set print array
5145 @item set print array
5146 @itemx set print array on
5147 Pretty print arrays. This format is more convenient to read,
5148 but uses more space. The default is off.
5150 @item set print array off
5151 Return to compressed format for arrays.
5153 @kindex show print array
5154 @item show print array
5155 Show whether compressed or pretty format is selected for displaying
5158 @kindex set print elements
5159 @item set print elements @var{number-of-elements}
5160 Set a limit on how many elements of an array @value{GDBN} will print.
5161 If @value{GDBN} is printing a large array, it stops printing after it has
5162 printed the number of elements set by the @code{set print elements} command.
5163 This limit also applies to the display of strings.
5164 When @value{GDBN} starts, this limit is set to 200.
5165 Setting @var{number-of-elements} to zero means that the printing is unlimited.
5167 @kindex show print elements
5168 @item show print elements
5169 Display the number of elements of a large array that @value{GDBN} will print.
5170 If the number is 0, then the printing is unlimited.
5172 @kindex set print null-stop
5173 @item set print null-stop
5174 Cause @value{GDBN} to stop printing the characters of an array when the first
5175 @sc{null} is encountered. This is useful when large arrays actually
5176 contain only short strings.
5179 @kindex set print pretty
5180 @item set print pretty on
5181 Cause @value{GDBN} to print structures in an indented format with one member
5182 per line, like this:
5197 @item set print pretty off
5198 Cause @value{GDBN} to print structures in a compact format, like this:
5202 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
5203 meat = 0x54 "Pork"@}
5208 This is the default format.
5210 @kindex show print pretty
5211 @item show print pretty
5212 Show which format @value{GDBN} is using to print structures.
5214 @kindex set print sevenbit-strings
5215 @item set print sevenbit-strings on
5216 Print using only seven-bit characters; if this option is set,
5217 @value{GDBN} displays any eight-bit characters (in strings or
5218 character values) using the notation @code{\}@var{nnn}. This setting is
5219 best if you are working in English (@sc{ascii}) and you use the
5220 high-order bit of characters as a marker or ``meta'' bit.
5222 @item set print sevenbit-strings off
5223 Print full eight-bit characters. This allows the use of more
5224 international character sets, and is the default.
5226 @kindex show print sevenbit-strings
5227 @item show print sevenbit-strings
5228 Show whether or not @value{GDBN} is printing only seven-bit characters.
5230 @kindex set print union
5231 @item set print union on
5232 Tell @value{GDBN} to print unions which are contained in structures. This
5233 is the default setting.
5235 @item set print union off
5236 Tell @value{GDBN} not to print unions which are contained in structures.
5238 @kindex show print union
5239 @item show print union
5240 Ask @value{GDBN} whether or not it will print unions which are contained in
5243 For example, given the declarations
5246 typedef enum @{Tree, Bug@} Species;
5247 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
5248 typedef enum @{Caterpillar, Cocoon, Butterfly@}
5259 struct thing foo = @{Tree, @{Acorn@}@};
5263 with @code{set print union on} in effect @samp{p foo} would print
5266 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
5270 and with @code{set print union off} in effect it would print
5273 $1 = @{it = Tree, form = @{...@}@}
5279 These settings are of interest when debugging C@t{++} programs:
5283 @kindex set print demangle
5284 @item set print demangle
5285 @itemx set print demangle on
5286 Print C@t{++} names in their source form rather than in the encoded
5287 (``mangled'') form passed to the assembler and linker for type-safe
5288 linkage. The default is on.
5290 @kindex show print demangle
5291 @item show print demangle
5292 Show whether C@t{++} names are printed in mangled or demangled form.
5294 @kindex set print asm-demangle
5295 @item set print asm-demangle
5296 @itemx set print asm-demangle on
5297 Print C@t{++} names in their source form rather than their mangled form, even
5298 in assembler code printouts such as instruction disassemblies.
5301 @kindex show print asm-demangle
5302 @item show print asm-demangle
5303 Show whether C@t{++} names in assembly listings are printed in mangled
5306 @kindex set demangle-style
5307 @cindex C@t{++} symbol decoding style
5308 @cindex symbol decoding style, C@t{++}
5309 @item set demangle-style @var{style}
5310 Choose among several encoding schemes used by different compilers to
5311 represent C@t{++} names. The choices for @var{style} are currently:
5315 Allow @value{GDBN} to choose a decoding style by inspecting your program.
5318 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
5319 This is the default.
5322 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
5325 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
5328 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
5329 @strong{Warning:} this setting alone is not sufficient to allow
5330 debugging @code{cfront}-generated executables. @value{GDBN} would
5331 require further enhancement to permit that.
5334 If you omit @var{style}, you will see a list of possible formats.
5336 @kindex show demangle-style
5337 @item show demangle-style
5338 Display the encoding style currently in use for decoding C@t{++} symbols.
5340 @kindex set print object
5341 @item set print object
5342 @itemx set print object on
5343 When displaying a pointer to an object, identify the @emph{actual}
5344 (derived) type of the object rather than the @emph{declared} type, using
5345 the virtual function table.
5347 @item set print object off
5348 Display only the declared type of objects, without reference to the
5349 virtual function table. This is the default setting.
5351 @kindex show print object
5352 @item show print object
5353 Show whether actual, or declared, object types are displayed.
5355 @kindex set print static-members
5356 @item set print static-members
5357 @itemx set print static-members on
5358 Print static members when displaying a C@t{++} object. The default is on.
5360 @item set print static-members off
5361 Do not print static members when displaying a C@t{++} object.
5363 @kindex show print static-members
5364 @item show print static-members
5365 Show whether C@t{++} static members are printed, or not.
5367 @c These don't work with HP ANSI C++ yet.
5368 @kindex set print vtbl
5369 @item set print vtbl
5370 @itemx set print vtbl on
5371 Pretty print C@t{++} virtual function tables. The default is off.
5372 (The @code{vtbl} commands do not work on programs compiled with the HP
5373 ANSI C@t{++} compiler (@code{aCC}).)
5375 @item set print vtbl off
5376 Do not pretty print C@t{++} virtual function tables.
5378 @kindex show print vtbl
5379 @item show print vtbl
5380 Show whether C@t{++} virtual function tables are pretty printed, or not.
5384 @section Value history
5386 @cindex value history
5387 Values printed by the @code{print} command are saved in the @value{GDBN}
5388 @dfn{value history}. This allows you to refer to them in other expressions.
5389 Values are kept until the symbol table is re-read or discarded
5390 (for example with the @code{file} or @code{symbol-file} commands).
5391 When the symbol table changes, the value history is discarded,
5392 since the values may contain pointers back to the types defined in the
5397 @cindex history number
5398 The values printed are given @dfn{history numbers} by which you can
5399 refer to them. These are successive integers starting with one.
5400 @code{print} shows you the history number assigned to a value by
5401 printing @samp{$@var{num} = } before the value; here @var{num} is the
5404 To refer to any previous value, use @samp{$} followed by the value's
5405 history number. The way @code{print} labels its output is designed to
5406 remind you of this. Just @code{$} refers to the most recent value in
5407 the history, and @code{$$} refers to the value before that.
5408 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
5409 is the value just prior to @code{$$}, @code{$$1} is equivalent to
5410 @code{$$}, and @code{$$0} is equivalent to @code{$}.
5412 For example, suppose you have just printed a pointer to a structure and
5413 want to see the contents of the structure. It suffices to type
5419 If you have a chain of structures where the component @code{next} points
5420 to the next one, you can print the contents of the next one with this:
5427 You can print successive links in the chain by repeating this
5428 command---which you can do by just typing @key{RET}.
5430 Note that the history records values, not expressions. If the value of
5431 @code{x} is 4 and you type these commands:
5439 then the value recorded in the value history by the @code{print} command
5440 remains 4 even though the value of @code{x} has changed.
5445 Print the last ten values in the value history, with their item numbers.
5446 This is like @samp{p@ $$9} repeated ten times, except that @code{show
5447 values} does not change the history.
5449 @item show values @var{n}
5450 Print ten history values centered on history item number @var{n}.
5453 Print ten history values just after the values last printed. If no more
5454 values are available, @code{show values +} produces no display.
5457 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
5458 same effect as @samp{show values +}.
5460 @node Convenience Vars
5461 @section Convenience variables
5463 @cindex convenience variables
5464 @value{GDBN} provides @dfn{convenience variables} that you can use within
5465 @value{GDBN} to hold on to a value and refer to it later. These variables
5466 exist entirely within @value{GDBN}; they are not part of your program, and
5467 setting a convenience variable has no direct effect on further execution
5468 of your program. That is why you can use them freely.
5470 Convenience variables are prefixed with @samp{$}. Any name preceded by
5471 @samp{$} can be used for a convenience variable, unless it is one of
5472 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
5473 (Value history references, in contrast, are @emph{numbers} preceded
5474 by @samp{$}. @xref{Value History, ,Value history}.)
5476 You can save a value in a convenience variable with an assignment
5477 expression, just as you would set a variable in your program.
5481 set $foo = *object_ptr
5485 would save in @code{$foo} the value contained in the object pointed to by
5488 Using a convenience variable for the first time creates it, but its
5489 value is @code{void} until you assign a new value. You can alter the
5490 value with another assignment at any time.
5492 Convenience variables have no fixed types. You can assign a convenience
5493 variable any type of value, including structures and arrays, even if
5494 that variable already has a value of a different type. The convenience
5495 variable, when used as an expression, has the type of its current value.
5498 @kindex show convenience
5499 @item show convenience
5500 Print a list of convenience variables used so far, and their values.
5501 Abbreviated @code{show conv}.
5504 One of the ways to use a convenience variable is as a counter to be
5505 incremented or a pointer to be advanced. For example, to print
5506 a field from successive elements of an array of structures:
5510 print bar[$i++]->contents
5514 Repeat that command by typing @key{RET}.
5516 Some convenience variables are created automatically by @value{GDBN} and given
5517 values likely to be useful.
5520 @vindex $_@r{, convenience variable}
5522 The variable @code{$_} is automatically set by the @code{x} command to
5523 the last address examined (@pxref{Memory, ,Examining memory}). Other
5524 commands which provide a default address for @code{x} to examine also
5525 set @code{$_} to that address; these commands include @code{info line}
5526 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
5527 except when set by the @code{x} command, in which case it is a pointer
5528 to the type of @code{$__}.
5530 @vindex $__@r{, convenience variable}
5532 The variable @code{$__} is automatically set by the @code{x} command
5533 to the value found in the last address examined. Its type is chosen
5534 to match the format in which the data was printed.
5537 @vindex $_exitcode@r{, convenience variable}
5538 The variable @code{$_exitcode} is automatically set to the exit code when
5539 the program being debugged terminates.
5542 On HP-UX systems, if you refer to a function or variable name that
5543 begins with a dollar sign, @value{GDBN} searches for a user or system
5544 name first, before it searches for a convenience variable.
5550 You can refer to machine register contents, in expressions, as variables
5551 with names starting with @samp{$}. The names of registers are different
5552 for each machine; use @code{info registers} to see the names used on
5556 @kindex info registers
5557 @item info registers
5558 Print the names and values of all registers except floating-point
5559 registers (in the selected stack frame).
5561 @kindex info all-registers
5562 @cindex floating point registers
5563 @item info all-registers
5564 Print the names and values of all registers, including floating-point
5567 @item info registers @var{regname} @dots{}
5568 Print the @dfn{relativized} value of each specified register @var{regname}.
5569 As discussed in detail below, register values are normally relative to
5570 the selected stack frame. @var{regname} may be any register name valid on
5571 the machine you are using, with or without the initial @samp{$}.
5574 @value{GDBN} has four ``standard'' register names that are available (in
5575 expressions) on most machines---whenever they do not conflict with an
5576 architecture's canonical mnemonics for registers. The register names
5577 @code{$pc} and @code{$sp} are used for the program counter register and
5578 the stack pointer. @code{$fp} is used for a register that contains a
5579 pointer to the current stack frame, and @code{$ps} is used for a
5580 register that contains the processor status. For example,
5581 you could print the program counter in hex with
5588 or print the instruction to be executed next with
5595 or add four to the stack pointer@footnote{This is a way of removing
5596 one word from the stack, on machines where stacks grow downward in
5597 memory (most machines, nowadays). This assumes that the innermost
5598 stack frame is selected; setting @code{$sp} is not allowed when other
5599 stack frames are selected. To pop entire frames off the stack,
5600 regardless of machine architecture, use @code{return};
5601 see @ref{Returning, ,Returning from a function}.} with
5607 Whenever possible, these four standard register names are available on
5608 your machine even though the machine has different canonical mnemonics,
5609 so long as there is no conflict. The @code{info registers} command
5610 shows the canonical names. For example, on the SPARC, @code{info
5611 registers} displays the processor status register as @code{$psr} but you
5612 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
5613 is an alias for the @sc{eflags} register.
5615 @value{GDBN} always considers the contents of an ordinary register as an
5616 integer when the register is examined in this way. Some machines have
5617 special registers which can hold nothing but floating point; these
5618 registers are considered to have floating point values. There is no way
5619 to refer to the contents of an ordinary register as floating point value
5620 (although you can @emph{print} it as a floating point value with
5621 @samp{print/f $@var{regname}}).
5623 Some registers have distinct ``raw'' and ``virtual'' data formats. This
5624 means that the data format in which the register contents are saved by
5625 the operating system is not the same one that your program normally
5626 sees. For example, the registers of the 68881 floating point
5627 coprocessor are always saved in ``extended'' (raw) format, but all C
5628 programs expect to work with ``double'' (virtual) format. In such
5629 cases, @value{GDBN} normally works with the virtual format only (the format
5630 that makes sense for your program), but the @code{info registers} command
5631 prints the data in both formats.
5633 Normally, register values are relative to the selected stack frame
5634 (@pxref{Selection, ,Selecting a frame}). This means that you get the
5635 value that the register would contain if all stack frames farther in
5636 were exited and their saved registers restored. In order to see the
5637 true contents of hardware registers, you must select the innermost
5638 frame (with @samp{frame 0}).
5640 However, @value{GDBN} must deduce where registers are saved, from the machine
5641 code generated by your compiler. If some registers are not saved, or if
5642 @value{GDBN} is unable to locate the saved registers, the selected stack
5643 frame makes no difference.
5645 @node Floating Point Hardware
5646 @section Floating point hardware
5647 @cindex floating point
5649 Depending on the configuration, @value{GDBN} may be able to give
5650 you more information about the status of the floating point hardware.
5655 Display hardware-dependent information about the floating
5656 point unit. The exact contents and layout vary depending on the
5657 floating point chip. Currently, @samp{info float} is supported on
5658 the ARM and x86 machines.
5662 @section Vector Unit
5665 Depending on the configuration, @value{GDBN} may be able to give you
5666 more information about the status of the vector unit.
5671 Display information about the vector unit. The exact contents and
5672 layout vary depending on the hardware.
5675 @node Memory Region Attributes
5676 @section Memory region attributes
5677 @cindex memory region attributes
5679 @dfn{Memory region attributes} allow you to describe special handling
5680 required by regions of your target's memory. @value{GDBN} uses attributes
5681 to determine whether to allow certain types of memory accesses; whether to
5682 use specific width accesses; and whether to cache target memory.
5684 Defined memory regions can be individually enabled and disabled. When a
5685 memory region is disabled, @value{GDBN} uses the default attributes when
5686 accessing memory in that region. Similarly, if no memory regions have
5687 been defined, @value{GDBN} uses the default attributes when accessing
5690 When a memory region is defined, it is given a number to identify it;
5691 to enable, disable, or remove a memory region, you specify that number.
5695 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
5696 Define memory region bounded by @var{lower} and @var{upper} with
5697 attributes @var{attributes}@dots{}. Note that @var{upper} == 0 is a
5698 special case: it is treated as the the target's maximum memory address.
5699 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
5702 @item delete mem @var{nums}@dots{}
5703 Remove memory regions @var{nums}@dots{}.
5706 @item disable mem @var{nums}@dots{}
5707 Disable memory regions @var{nums}@dots{}.
5708 A disabled memory region is not forgotten.
5709 It may be enabled again later.
5712 @item enable mem @var{nums}@dots{}
5713 Enable memory regions @var{nums}@dots{}.
5717 Print a table of all defined memory regions, with the following columns
5721 @item Memory Region Number
5722 @item Enabled or Disabled.
5723 Enabled memory regions are marked with @samp{y}.
5724 Disabled memory regions are marked with @samp{n}.
5727 The address defining the inclusive lower bound of the memory region.
5730 The address defining the exclusive upper bound of the memory region.
5733 The list of attributes set for this memory region.
5738 @subsection Attributes
5740 @subsubsection Memory Access Mode
5741 The access mode attributes set whether @value{GDBN} may make read or
5742 write accesses to a memory region.
5744 While these attributes prevent @value{GDBN} from performing invalid
5745 memory accesses, they do nothing to prevent the target system, I/O DMA,
5746 etc. from accessing memory.
5750 Memory is read only.
5752 Memory is write only.
5754 Memory is read/write. This is the default.
5757 @subsubsection Memory Access Size
5758 The acccess size attributes tells @value{GDBN} to use specific sized
5759 accesses in the memory region. Often memory mapped device registers
5760 require specific sized accesses. If no access size attribute is
5761 specified, @value{GDBN} may use accesses of any size.
5765 Use 8 bit memory accesses.
5767 Use 16 bit memory accesses.
5769 Use 32 bit memory accesses.
5771 Use 64 bit memory accesses.
5774 @c @subsubsection Hardware/Software Breakpoints
5775 @c The hardware/software breakpoint attributes set whether @value{GDBN}
5776 @c will use hardware or software breakpoints for the internal breakpoints
5777 @c used by the step, next, finish, until, etc. commands.
5781 @c Always use hardware breakpoints
5782 @c @item swbreak (default)
5785 @subsubsection Data Cache
5786 The data cache attributes set whether @value{GDBN} will cache target
5787 memory. While this generally improves performance by reducing debug
5788 protocol overhead, it can lead to incorrect results because @value{GDBN}
5789 does not know about volatile variables or memory mapped device
5794 Enable @value{GDBN} to cache target memory.
5796 Disable @value{GDBN} from caching target memory. This is the default.
5799 @c @subsubsection Memory Write Verification
5800 @c The memory write verification attributes set whether @value{GDBN}
5801 @c will re-reads data after each write to verify the write was successful.
5805 @c @item noverify (default)
5808 @node Dump/Restore Files
5809 @section Copy between memory and a file
5810 @cindex dump/restore files
5811 @cindex append data to a file
5812 @cindex dump data to a file
5813 @cindex restore data from a file
5818 The commands @code{dump}, @code{append}, and @code{restore} are used
5819 for copying data between target memory and a file. Data is written
5820 into a file using @code{dump} or @code{append}, and restored from a
5821 file into memory by using @code{restore}. Files may be binary, srec,
5822 intel hex, or tekhex (but only binary files can be appended).
5826 @kindex append binary
5827 @item dump binary memory @var{filename} @var{start_addr} @var{end_addr}
5828 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5829 raw binary format file @var{filename}.
5831 @item append binary memory @var{filename} @var{start_addr} @var{end_addr}
5832 Append contents of memory from @var{start_addr} to @var{end_addr} to
5833 raw binary format file @var{filename}.
5835 @item dump binary value @var{filename} @var{expression}
5836 Dump value of @var{expression} into raw binary format file @var{filename}.
5838 @item append binary memory @var{filename} @var{expression}
5839 Append value of @var{expression} to raw binary format file @var{filename}.
5842 @item dump ihex memory @var{filename} @var{start_addr} @var{end_addr}
5843 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5844 intel hex format file @var{filename}.
5846 @item dump ihex value @var{filename} @var{expression}
5847 Dump value of @var{expression} into intel hex format file @var{filename}.
5850 @item dump srec memory @var{filename} @var{start_addr} @var{end_addr}
5851 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5852 srec format file @var{filename}.
5854 @item dump srec value @var{filename} @var{expression}
5855 Dump value of @var{expression} into srec format file @var{filename}.
5858 @item dump tekhex memory @var{filename} @var{start_addr} @var{end_addr}
5859 Dump contents of memory from @var{start_addr} to @var{end_addr} into
5860 tekhex format file @var{filename}.
5862 @item dump tekhex value @var{filename} @var{expression}
5863 Dump value of @var{expression} into tekhex format file @var{filename}.
5865 @item restore @var{filename} [@var{binary}] @var{bias} @var{start} @var{end}
5866 Restore the contents of file @var{filename} into memory. The @code{restore}
5867 command can automatically recognize any known bfd file format, except for
5868 raw binary. To restore a raw binary file you must use the optional argument
5869 @var{binary} after the filename.
5871 If @var{bias} is non-zero, its value will be added to the addresses
5872 contained in the file. Binary files always start at address zero, so
5873 they will be restored at address @var{bias}. Other bfd files have
5874 a built-in location; they will be restored at offset @var{bias}
5877 If @var{start} and/or @var{end} are non-zero, then only data between
5878 file offset @var{start} and file offset @var{end} will be restored.
5879 These offsets are relative to the addresses in the file, before
5880 the @var{bias} argument is applied.
5884 @node Character Sets
5885 @section Character Sets
5886 @cindex character sets
5888 @cindex translating between character sets
5889 @cindex host character set
5890 @cindex target character set
5892 If the program you are debugging uses a different character set to
5893 represent characters and strings than the one @value{GDBN} uses itself,
5894 @value{GDBN} can automatically translate between the character sets for
5895 you. The character set @value{GDBN} uses we call the @dfn{host
5896 character set}; the one the inferior program uses we call the
5897 @dfn{target character set}.
5899 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
5900 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
5901 remote protocol (@pxref{Remote,Remote Debugging}) to debug a program
5902 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
5903 then the host character set is Latin-1, and the target character set is
5904 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
5905 target-charset ebcdic-us}, then @value{GDBN} translates between
5906 @sc{ebcdic} and Latin 1 as you print character or string values, or use
5907 character and string literals in expressions.
5909 @value{GDBN} has no way to automatically recognize which character set
5910 the inferior program uses; you must tell it, using the @code{set
5911 target-charset} command, described below.
5913 Here are the commands for controlling @value{GDBN}'s character set
5917 @item set target-charset @var{charset}
5918 @kindex set target-charset
5919 Set the current target character set to @var{charset}. We list the
5920 character set names @value{GDBN} recognizes below, but if you invoke the
5921 @code{set target-charset} command with no argument, @value{GDBN} lists
5922 the character sets it supports.
5926 @item set host-charset @var{charset}
5927 @kindex set host-charset
5928 Set the current host character set to @var{charset}.
5930 By default, @value{GDBN} uses a host character set appropriate to the
5931 system it is running on; you can override that default using the
5932 @code{set host-charset} command.
5934 @value{GDBN} can only use certain character sets as its host character
5935 set. We list the character set names @value{GDBN} recognizes below, and
5936 indicate which can be host character sets, but if you invoke the
5937 @code{set host-charset} command with no argument, @value{GDBN} lists the
5938 character sets it supports, placing an asterisk (@samp{*}) after those
5939 it can use as a host character set.
5941 @item set charset @var{charset}
5943 Set the current host and target character sets to @var{charset}. If you
5944 invoke the @code{set charset} command with no argument, it lists the
5945 character sets it supports. @value{GDBN} can only use certain character
5946 sets as its host character set; it marks those in the list with an
5947 asterisk (@samp{*}).
5950 @itemx show host-charset
5951 @itemx show target-charset
5952 @kindex show charset
5953 @kindex show host-charset
5954 @kindex show target-charset
5955 Show the current host and target charsets. The @code{show host-charset}
5956 and @code{show target-charset} commands are synonyms for @code{show
5961 @value{GDBN} currently includes support for the following character
5967 @cindex ASCII character set
5968 Seven-bit U.S. @sc{ascii}. @value{GDBN} can use this as its host
5972 @cindex ISO 8859-1 character set
5973 @cindex ISO Latin 1 character set
5974 The ISO Latin 1 character set. This extends ASCII with accented
5975 characters needed for French, German, and Spanish. @value{GDBN} can use
5976 this as its host character set.
5980 @cindex EBCDIC character set
5981 @cindex IBM1047 character set
5982 Variants of the @sc{ebcdic} character set, used on some of IBM's
5983 mainframe operating systems. (@sc{gnu}/Linux on the S/390 uses U.S. @sc{ascii}.)
5984 @value{GDBN} cannot use these as its host character set.
5988 Note that these are all single-byte character sets. More work inside
5989 GDB is needed to support multi-byte or variable-width character
5990 encodings, like the UTF-8 and UCS-2 encodings of Unicode.
5992 Here is an example of @value{GDBN}'s character set support in action.
5993 Assume that the following source code has been placed in the file
5994 @file{charset-test.c}:
6000 = @{72, 101, 108, 108, 111, 44, 32, 119,
6001 111, 114, 108, 100, 33, 10, 0@};
6002 char ibm1047_hello[]
6003 = @{200, 133, 147, 147, 150, 107, 64, 166,
6004 150, 153, 147, 132, 90, 37, 0@};
6008 printf ("Hello, world!\n");
6012 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
6013 containing the string @samp{Hello, world!} followed by a newline,
6014 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
6016 We compile the program, and invoke the debugger on it:
6019 $ gcc -g charset-test.c -o charset-test
6020 $ gdb -nw charset-test
6021 GNU gdb 2001-12-19-cvs
6022 Copyright 2001 Free Software Foundation, Inc.
6027 We can use the @code{show charset} command to see what character sets
6028 @value{GDBN} is currently using to interpret and display characters and
6033 The current host and target character set is `iso-8859-1'.
6037 For the sake of printing this manual, let's use @sc{ascii} as our
6038 initial character set:
6040 (gdb) set charset ascii
6042 The current host and target character set is `ascii'.
6046 Let's assume that @sc{ascii} is indeed the correct character set for our
6047 host system --- in other words, let's assume that if @value{GDBN} prints
6048 characters using the @sc{ascii} character set, our terminal will display
6049 them properly. Since our current target character set is also
6050 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
6053 (gdb) print ascii_hello
6054 $1 = 0x401698 "Hello, world!\n"
6055 (gdb) print ascii_hello[0]
6060 @value{GDBN} uses the target character set for character and string
6061 literals you use in expressions:
6069 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
6072 @value{GDBN} relies on the user to tell it which character set the
6073 target program uses. If we print @code{ibm1047_hello} while our target
6074 character set is still @sc{ascii}, we get jibberish:
6077 (gdb) print ibm1047_hello
6078 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
6079 (gdb) print ibm1047_hello[0]
6084 If we invoke the @code{set target-charset} command without an argument,
6085 @value{GDBN} tells us the character sets it supports:
6088 (gdb) set target-charset
6089 Valid character sets are:
6094 * - can be used as a host character set
6097 We can select @sc{ibm1047} as our target character set, and examine the
6098 program's strings again. Now the @sc{ascii} string is wrong, but
6099 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
6100 target character set, @sc{ibm1047}, to the host character set,
6101 @sc{ascii}, and they display correctly:
6104 (gdb) set target-charset ibm1047
6106 The current host character set is `ascii'.
6107 The current target character set is `ibm1047'.
6108 (gdb) print ascii_hello
6109 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
6110 (gdb) print ascii_hello[0]
6112 (gdb) print ibm1047_hello
6113 $8 = 0x4016a8 "Hello, world!\n"
6114 (gdb) print ibm1047_hello[0]
6119 As above, @value{GDBN} uses the target character set for character and
6120 string literals you use in expressions:
6128 The IBM1047 character set uses the number 78 to encode the @samp{+}
6133 @chapter C Preprocessor Macros
6135 Some languages, such as C and C++, provide a way to define and invoke
6136 ``preprocessor macros'' which expand into strings of tokens.
6137 @value{GDBN} can evaluate expressions containing macro invocations, show
6138 the result of macro expansion, and show a macro's definition, including
6139 where it was defined.
6141 You may need to compile your program specially to provide @value{GDBN}
6142 with information about preprocessor macros. Most compilers do not
6143 include macros in their debugging information, even when you compile
6144 with the @option{-g} flag. @xref{Compilation}.
6146 A program may define a macro at one point, remove that definition later,
6147 and then provide a different definition after that. Thus, at different
6148 points in the program, a macro may have different definitions, or have
6149 no definition at all. If there is a current stack frame, @value{GDBN}
6150 uses the macros in scope at that frame's source code line. Otherwise,
6151 @value{GDBN} uses the macros in scope at the current listing location;
6154 At the moment, @value{GDBN} does not support the @code{##}
6155 token-splicing operator, the @code{#} stringification operator, or
6156 variable-arity macros.
6158 Whenever @value{GDBN} evaluates an expression, it always expands any
6159 macro invocations present in the expression. @value{GDBN} also provides
6160 the following commands for working with macros explicitly.
6164 @kindex macro expand
6165 @cindex macro expansion, showing the results of preprocessor
6166 @cindex preprocessor macro expansion, showing the results of
6167 @cindex expanding preprocessor macros
6168 @item macro expand @var{expression}
6169 @itemx macro exp @var{expression}
6170 Show the results of expanding all preprocessor macro invocations in
6171 @var{expression}. Since @value{GDBN} simply expands macros, but does
6172 not parse the result, @var{expression} need not be a valid expression;
6173 it can be any string of tokens.
6175 @kindex macro expand-once
6176 @item macro expand-once @var{expression}
6177 @itemx macro exp1 @var{expression}
6178 @i{(This command is not yet implemented.)} Show the results of
6179 expanding those preprocessor macro invocations that appear explicitly in
6180 @var{expression}. Macro invocations appearing in that expansion are
6181 left unchanged. This command allows you to see the effect of a
6182 particular macro more clearly, without being confused by further
6183 expansions. Since @value{GDBN} simply expands macros, but does not
6184 parse the result, @var{expression} need not be a valid expression; it
6185 can be any string of tokens.
6188 @cindex macro definition, showing
6189 @cindex definition, showing a macro's
6190 @item info macro @var{macro}
6191 Show the definition of the macro named @var{macro}, and describe the
6192 source location where that definition was established.
6194 @kindex macro define
6195 @cindex user-defined macros
6196 @cindex defining macros interactively
6197 @cindex macros, user-defined
6198 @item macro define @var{macro} @var{replacement-list}
6199 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
6200 @i{(This command is not yet implemented.)} Introduce a definition for a
6201 preprocessor macro named @var{macro}, invocations of which are replaced
6202 by the tokens given in @var{replacement-list}. The first form of this
6203 command defines an ``object-like'' macro, which takes no arguments; the
6204 second form defines a ``function-like'' macro, which takes the arguments
6205 given in @var{arglist}.
6207 A definition introduced by this command is in scope in every expression
6208 evaluated in @value{GDBN}, until it is removed with the @command{macro
6209 undef} command, described below. The definition overrides all
6210 definitions for @var{macro} present in the program being debugged, as
6211 well as any previous user-supplied definition.
6214 @item macro undef @var{macro}
6215 @i{(This command is not yet implemented.)} Remove any user-supplied
6216 definition for the macro named @var{macro}. This command only affects
6217 definitions provided with the @command{macro define} command, described
6218 above; it cannot remove definitions present in the program being
6223 @cindex macros, example of debugging with
6224 Here is a transcript showing the above commands in action. First, we
6225 show our source files:
6233 #define ADD(x) (M + x)
6238 printf ("Hello, world!\n");
6240 printf ("We're so creative.\n");
6242 printf ("Goodbye, world!\n");
6249 Now, we compile the program using the @sc{gnu} C compiler, @value{NGCC}.
6250 We pass the @option{-gdwarf-2} and @option{-g3} flags to ensure the
6251 compiler includes information about preprocessor macros in the debugging
6255 $ gcc -gdwarf-2 -g3 sample.c -o sample
6259 Now, we start @value{GDBN} on our sample program:
6263 GNU gdb 2002-05-06-cvs
6264 Copyright 2002 Free Software Foundation, Inc.
6265 GDB is free software, @dots{}
6269 We can expand macros and examine their definitions, even when the
6270 program is not running. @value{GDBN} uses the current listing position
6271 to decide which macro definitions are in scope:
6277 5 #define ADD(x) (M + x)
6282 10 printf ("Hello, world!\n");
6284 12 printf ("We're so creative.\n");
6285 (gdb) info macro ADD
6286 Defined at /home/jimb/gdb/macros/play/sample.c:5
6287 #define ADD(x) (M + x)
6289 Defined at /home/jimb/gdb/macros/play/sample.h:1
6290 included at /home/jimb/gdb/macros/play/sample.c:2
6292 (gdb) macro expand ADD(1)
6293 expands to: (42 + 1)
6294 (gdb) macro expand-once ADD(1)
6295 expands to: once (M + 1)
6299 In the example above, note that @command{macro expand-once} expands only
6300 the macro invocation explicit in the original text --- the invocation of
6301 @code{ADD} --- but does not expand the invocation of the macro @code{M},
6302 which was introduced by @code{ADD}.
6304 Once the program is running, GDB uses the macro definitions in force at
6305 the source line of the current stack frame:
6309 Breakpoint 1 at 0x8048370: file sample.c, line 10.
6311 Starting program: /home/jimb/gdb/macros/play/sample
6313 Breakpoint 1, main () at sample.c:10
6314 10 printf ("Hello, world!\n");
6318 At line 10, the definition of the macro @code{N} at line 9 is in force:
6322 Defined at /home/jimb/gdb/macros/play/sample.c:9
6324 (gdb) macro expand N Q M
6331 As we step over directives that remove @code{N}'s definition, and then
6332 give it a new definition, @value{GDBN} finds the definition (or lack
6333 thereof) in force at each point:
6338 12 printf ("We're so creative.\n");
6340 The symbol `N' has no definition as a C/C++ preprocessor macro
6341 at /home/jimb/gdb/macros/play/sample.c:12
6344 14 printf ("Goodbye, world!\n");
6346 Defined at /home/jimb/gdb/macros/play/sample.c:13
6348 (gdb) macro expand N Q M
6349 expands to: 1729 < 42
6357 @chapter Tracepoints
6358 @c This chapter is based on the documentation written by Michael
6359 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
6362 In some applications, it is not feasible for the debugger to interrupt
6363 the program's execution long enough for the developer to learn
6364 anything helpful about its behavior. If the program's correctness
6365 depends on its real-time behavior, delays introduced by a debugger
6366 might cause the program to change its behavior drastically, or perhaps
6367 fail, even when the code itself is correct. It is useful to be able
6368 to observe the program's behavior without interrupting it.
6370 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
6371 specify locations in the program, called @dfn{tracepoints}, and
6372 arbitrary expressions to evaluate when those tracepoints are reached.
6373 Later, using the @code{tfind} command, you can examine the values
6374 those expressions had when the program hit the tracepoints. The
6375 expressions may also denote objects in memory---structures or arrays,
6376 for example---whose values @value{GDBN} should record; while visiting
6377 a particular tracepoint, you may inspect those objects as if they were
6378 in memory at that moment. However, because @value{GDBN} records these
6379 values without interacting with you, it can do so quickly and
6380 unobtrusively, hopefully not disturbing the program's behavior.
6382 The tracepoint facility is currently available only for remote
6383 targets. @xref{Targets}. In addition, your remote target must know how
6384 to collect trace data. This functionality is implemented in the remote
6385 stub; however, none of the stubs distributed with @value{GDBN} support
6386 tracepoints as of this writing.
6388 This chapter describes the tracepoint commands and features.
6392 * Analyze Collected Data::
6393 * Tracepoint Variables::
6396 @node Set Tracepoints
6397 @section Commands to Set Tracepoints
6399 Before running such a @dfn{trace experiment}, an arbitrary number of
6400 tracepoints can be set. Like a breakpoint (@pxref{Set Breaks}), a
6401 tracepoint has a number assigned to it by @value{GDBN}. Like with
6402 breakpoints, tracepoint numbers are successive integers starting from
6403 one. Many of the commands associated with tracepoints take the
6404 tracepoint number as their argument, to identify which tracepoint to
6407 For each tracepoint, you can specify, in advance, some arbitrary set
6408 of data that you want the target to collect in the trace buffer when
6409 it hits that tracepoint. The collected data can include registers,
6410 local variables, or global data. Later, you can use @value{GDBN}
6411 commands to examine the values these data had at the time the
6414 This section describes commands to set tracepoints and associated
6415 conditions and actions.
6418 * Create and Delete Tracepoints::
6419 * Enable and Disable Tracepoints::
6420 * Tracepoint Passcounts::
6421 * Tracepoint Actions::
6422 * Listing Tracepoints::
6423 * Starting and Stopping Trace Experiment::
6426 @node Create and Delete Tracepoints
6427 @subsection Create and Delete Tracepoints
6430 @cindex set tracepoint
6433 The @code{trace} command is very similar to the @code{break} command.
6434 Its argument can be a source line, a function name, or an address in
6435 the target program. @xref{Set Breaks}. The @code{trace} command
6436 defines a tracepoint, which is a point in the target program where the
6437 debugger will briefly stop, collect some data, and then allow the
6438 program to continue. Setting a tracepoint or changing its commands
6439 doesn't take effect until the next @code{tstart} command; thus, you
6440 cannot change the tracepoint attributes once a trace experiment is
6443 Here are some examples of using the @code{trace} command:
6446 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
6448 (@value{GDBP}) @b{trace +2} // 2 lines forward
6450 (@value{GDBP}) @b{trace my_function} // first source line of function
6452 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
6454 (@value{GDBP}) @b{trace *0x2117c4} // an address
6458 You can abbreviate @code{trace} as @code{tr}.
6461 @cindex last tracepoint number
6462 @cindex recent tracepoint number
6463 @cindex tracepoint number
6464 The convenience variable @code{$tpnum} records the tracepoint number
6465 of the most recently set tracepoint.
6467 @kindex delete tracepoint
6468 @cindex tracepoint deletion
6469 @item delete tracepoint @r{[}@var{num}@r{]}
6470 Permanently delete one or more tracepoints. With no argument, the
6471 default is to delete all tracepoints.
6476 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
6478 (@value{GDBP}) @b{delete trace} // remove all tracepoints
6482 You can abbreviate this command as @code{del tr}.
6485 @node Enable and Disable Tracepoints
6486 @subsection Enable and Disable Tracepoints
6489 @kindex disable tracepoint
6490 @item disable tracepoint @r{[}@var{num}@r{]}
6491 Disable tracepoint @var{num}, or all tracepoints if no argument
6492 @var{num} is given. A disabled tracepoint will have no effect during
6493 the next trace experiment, but it is not forgotten. You can re-enable
6494 a disabled tracepoint using the @code{enable tracepoint} command.
6496 @kindex enable tracepoint
6497 @item enable tracepoint @r{[}@var{num}@r{]}
6498 Enable tracepoint @var{num}, or all tracepoints. The enabled
6499 tracepoints will become effective the next time a trace experiment is
6503 @node Tracepoint Passcounts
6504 @subsection Tracepoint Passcounts
6508 @cindex tracepoint pass count
6509 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
6510 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
6511 automatically stop a trace experiment. If a tracepoint's passcount is
6512 @var{n}, then the trace experiment will be automatically stopped on
6513 the @var{n}'th time that tracepoint is hit. If the tracepoint number
6514 @var{num} is not specified, the @code{passcount} command sets the
6515 passcount of the most recently defined tracepoint. If no passcount is
6516 given, the trace experiment will run until stopped explicitly by the
6522 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
6523 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
6525 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
6526 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
6527 (@value{GDBP}) @b{trace foo}
6528 (@value{GDBP}) @b{pass 3}
6529 (@value{GDBP}) @b{trace bar}
6530 (@value{GDBP}) @b{pass 2}
6531 (@value{GDBP}) @b{trace baz}
6532 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
6533 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
6534 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
6535 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
6539 @node Tracepoint Actions
6540 @subsection Tracepoint Action Lists
6544 @cindex tracepoint actions
6545 @item actions @r{[}@var{num}@r{]}
6546 This command will prompt for a list of actions to be taken when the
6547 tracepoint is hit. If the tracepoint number @var{num} is not
6548 specified, this command sets the actions for the one that was most
6549 recently defined (so that you can define a tracepoint and then say
6550 @code{actions} without bothering about its number). You specify the
6551 actions themselves on the following lines, one action at a time, and
6552 terminate the actions list with a line containing just @code{end}. So
6553 far, the only defined actions are @code{collect} and
6554 @code{while-stepping}.
6556 @cindex remove actions from a tracepoint
6557 To remove all actions from a tracepoint, type @samp{actions @var{num}}
6558 and follow it immediately with @samp{end}.
6561 (@value{GDBP}) @b{collect @var{data}} // collect some data
6563 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
6565 (@value{GDBP}) @b{end} // signals the end of actions.
6568 In the following example, the action list begins with @code{collect}
6569 commands indicating the things to be collected when the tracepoint is
6570 hit. Then, in order to single-step and collect additional data
6571 following the tracepoint, a @code{while-stepping} command is used,
6572 followed by the list of things to be collected while stepping. The
6573 @code{while-stepping} command is terminated by its own separate
6574 @code{end} command. Lastly, the action list is terminated by an
6578 (@value{GDBP}) @b{trace foo}
6579 (@value{GDBP}) @b{actions}
6580 Enter actions for tracepoint 1, one per line:
6589 @kindex collect @r{(tracepoints)}
6590 @item collect @var{expr1}, @var{expr2}, @dots{}
6591 Collect values of the given expressions when the tracepoint is hit.
6592 This command accepts a comma-separated list of any valid expressions.
6593 In addition to global, static, or local variables, the following
6594 special arguments are supported:
6598 collect all registers
6601 collect all function arguments
6604 collect all local variables.
6607 You can give several consecutive @code{collect} commands, each one
6608 with a single argument, or one @code{collect} command with several
6609 arguments separated by commas: the effect is the same.
6611 The command @code{info scope} (@pxref{Symbols, info scope}) is
6612 particularly useful for figuring out what data to collect.
6614 @kindex while-stepping @r{(tracepoints)}
6615 @item while-stepping @var{n}
6616 Perform @var{n} single-step traces after the tracepoint, collecting
6617 new data at each step. The @code{while-stepping} command is
6618 followed by the list of what to collect while stepping (followed by
6619 its own @code{end} command):
6623 > collect $regs, myglobal
6629 You may abbreviate @code{while-stepping} as @code{ws} or
6633 @node Listing Tracepoints
6634 @subsection Listing Tracepoints
6637 @kindex info tracepoints
6638 @cindex information about tracepoints
6639 @item info tracepoints @r{[}@var{num}@r{]}
6640 Display information about the tracepoint @var{num}. If you don't specify
6641 a tracepoint number, displays information about all the tracepoints
6642 defined so far. For each tracepoint, the following information is
6649 whether it is enabled or disabled
6653 its passcount as given by the @code{passcount @var{n}} command
6655 its step count as given by the @code{while-stepping @var{n}} command
6657 where in the source files is the tracepoint set
6659 its action list as given by the @code{actions} command
6663 (@value{GDBP}) @b{info trace}
6664 Num Enb Address PassC StepC What
6665 1 y 0x002117c4 0 0 <gdb_asm>
6666 2 y 0x0020dc64 0 0 in g_test at g_test.c:1375
6667 3 y 0x0020b1f4 0 0 in get_data at ../foo.c:41
6672 This command can be abbreviated @code{info tp}.
6675 @node Starting and Stopping Trace Experiment
6676 @subsection Starting and Stopping Trace Experiment
6680 @cindex start a new trace experiment
6681 @cindex collected data discarded
6683 This command takes no arguments. It starts the trace experiment, and
6684 begins collecting data. This has the side effect of discarding all
6685 the data collected in the trace buffer during the previous trace
6689 @cindex stop a running trace experiment
6691 This command takes no arguments. It ends the trace experiment, and
6692 stops collecting data.
6694 @strong{Note:} a trace experiment and data collection may stop
6695 automatically if any tracepoint's passcount is reached
6696 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
6699 @cindex status of trace data collection
6700 @cindex trace experiment, status of
6702 This command displays the status of the current trace data
6706 Here is an example of the commands we described so far:
6709 (@value{GDBP}) @b{trace gdb_c_test}
6710 (@value{GDBP}) @b{actions}
6711 Enter actions for tracepoint #1, one per line.
6712 > collect $regs,$locals,$args
6717 (@value{GDBP}) @b{tstart}
6718 [time passes @dots{}]
6719 (@value{GDBP}) @b{tstop}
6723 @node Analyze Collected Data
6724 @section Using the collected data
6726 After the tracepoint experiment ends, you use @value{GDBN} commands
6727 for examining the trace data. The basic idea is that each tracepoint
6728 collects a trace @dfn{snapshot} every time it is hit and another
6729 snapshot every time it single-steps. All these snapshots are
6730 consecutively numbered from zero and go into a buffer, and you can
6731 examine them later. The way you examine them is to @dfn{focus} on a
6732 specific trace snapshot. When the remote stub is focused on a trace
6733 snapshot, it will respond to all @value{GDBN} requests for memory and
6734 registers by reading from the buffer which belongs to that snapshot,
6735 rather than from @emph{real} memory or registers of the program being
6736 debugged. This means that @strong{all} @value{GDBN} commands
6737 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
6738 behave as if we were currently debugging the program state as it was
6739 when the tracepoint occurred. Any requests for data that are not in
6740 the buffer will fail.
6743 * tfind:: How to select a trace snapshot
6744 * tdump:: How to display all data for a snapshot
6745 * save-tracepoints:: How to save tracepoints for a future run
6749 @subsection @code{tfind @var{n}}
6752 @cindex select trace snapshot
6753 @cindex find trace snapshot
6754 The basic command for selecting a trace snapshot from the buffer is
6755 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
6756 counting from zero. If no argument @var{n} is given, the next
6757 snapshot is selected.
6759 Here are the various forms of using the @code{tfind} command.
6763 Find the first snapshot in the buffer. This is a synonym for
6764 @code{tfind 0} (since 0 is the number of the first snapshot).
6767 Stop debugging trace snapshots, resume @emph{live} debugging.
6770 Same as @samp{tfind none}.
6773 No argument means find the next trace snapshot.
6776 Find the previous trace snapshot before the current one. This permits
6777 retracing earlier steps.
6779 @item tfind tracepoint @var{num}
6780 Find the next snapshot associated with tracepoint @var{num}. Search
6781 proceeds forward from the last examined trace snapshot. If no
6782 argument @var{num} is given, it means find the next snapshot collected
6783 for the same tracepoint as the current snapshot.
6785 @item tfind pc @var{addr}
6786 Find the next snapshot associated with the value @var{addr} of the
6787 program counter. Search proceeds forward from the last examined trace
6788 snapshot. If no argument @var{addr} is given, it means find the next
6789 snapshot with the same value of PC as the current snapshot.
6791 @item tfind outside @var{addr1}, @var{addr2}
6792 Find the next snapshot whose PC is outside the given range of
6795 @item tfind range @var{addr1}, @var{addr2}
6796 Find the next snapshot whose PC is between @var{addr1} and
6797 @var{addr2}. @c FIXME: Is the range inclusive or exclusive?
6799 @item tfind line @r{[}@var{file}:@r{]}@var{n}
6800 Find the next snapshot associated with the source line @var{n}. If
6801 the optional argument @var{file} is given, refer to line @var{n} in
6802 that source file. Search proceeds forward from the last examined
6803 trace snapshot. If no argument @var{n} is given, it means find the
6804 next line other than the one currently being examined; thus saying
6805 @code{tfind line} repeatedly can appear to have the same effect as
6806 stepping from line to line in a @emph{live} debugging session.
6809 The default arguments for the @code{tfind} commands are specifically
6810 designed to make it easy to scan through the trace buffer. For
6811 instance, @code{tfind} with no argument selects the next trace
6812 snapshot, and @code{tfind -} with no argument selects the previous
6813 trace snapshot. So, by giving one @code{tfind} command, and then
6814 simply hitting @key{RET} repeatedly you can examine all the trace
6815 snapshots in order. Or, by saying @code{tfind -} and then hitting
6816 @key{RET} repeatedly you can examine the snapshots in reverse order.
6817 The @code{tfind line} command with no argument selects the snapshot
6818 for the next source line executed. The @code{tfind pc} command with
6819 no argument selects the next snapshot with the same program counter
6820 (PC) as the current frame. The @code{tfind tracepoint} command with
6821 no argument selects the next trace snapshot collected by the same
6822 tracepoint as the current one.
6824 In addition to letting you scan through the trace buffer manually,
6825 these commands make it easy to construct @value{GDBN} scripts that
6826 scan through the trace buffer and print out whatever collected data
6827 you are interested in. Thus, if we want to examine the PC, FP, and SP
6828 registers from each trace frame in the buffer, we can say this:
6831 (@value{GDBP}) @b{tfind start}
6832 (@value{GDBP}) @b{while ($trace_frame != -1)}
6833 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
6834 $trace_frame, $pc, $sp, $fp
6838 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
6839 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
6840 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
6841 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
6842 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
6843 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
6844 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
6845 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
6846 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
6847 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
6848 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
6851 Or, if we want to examine the variable @code{X} at each source line in
6855 (@value{GDBP}) @b{tfind start}
6856 (@value{GDBP}) @b{while ($trace_frame != -1)}
6857 > printf "Frame %d, X == %d\n", $trace_frame, X
6867 @subsection @code{tdump}
6869 @cindex dump all data collected at tracepoint
6870 @cindex tracepoint data, display
6872 This command takes no arguments. It prints all the data collected at
6873 the current trace snapshot.
6876 (@value{GDBP}) @b{trace 444}
6877 (@value{GDBP}) @b{actions}
6878 Enter actions for tracepoint #2, one per line:
6879 > collect $regs, $locals, $args, gdb_long_test
6882 (@value{GDBP}) @b{tstart}
6884 (@value{GDBP}) @b{tfind line 444}
6885 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
6887 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
6889 (@value{GDBP}) @b{tdump}
6890 Data collected at tracepoint 2, trace frame 1:
6891 d0 0xc4aa0085 -995491707
6895 d4 0x71aea3d 119204413
6900 a1 0x3000668 50333288
6903 a4 0x3000698 50333336
6905 fp 0x30bf3c 0x30bf3c
6906 sp 0x30bf34 0x30bf34
6908 pc 0x20b2c8 0x20b2c8
6912 p = 0x20e5b4 "gdb-test"
6919 gdb_long_test = 17 '\021'
6924 @node save-tracepoints
6925 @subsection @code{save-tracepoints @var{filename}}
6926 @kindex save-tracepoints
6927 @cindex save tracepoints for future sessions
6929 This command saves all current tracepoint definitions together with
6930 their actions and passcounts, into a file @file{@var{filename}}
6931 suitable for use in a later debugging session. To read the saved
6932 tracepoint definitions, use the @code{source} command (@pxref{Command
6935 @node Tracepoint Variables
6936 @section Convenience Variables for Tracepoints
6937 @cindex tracepoint variables
6938 @cindex convenience variables for tracepoints
6941 @vindex $trace_frame
6942 @item (int) $trace_frame
6943 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
6944 snapshot is selected.
6947 @item (int) $tracepoint
6948 The tracepoint for the current trace snapshot.
6951 @item (int) $trace_line
6952 The line number for the current trace snapshot.
6955 @item (char []) $trace_file
6956 The source file for the current trace snapshot.
6959 @item (char []) $trace_func
6960 The name of the function containing @code{$tracepoint}.
6963 Note: @code{$trace_file} is not suitable for use in @code{printf},
6964 use @code{output} instead.
6966 Here's a simple example of using these convenience variables for
6967 stepping through all the trace snapshots and printing some of their
6971 (@value{GDBP}) @b{tfind start}
6973 (@value{GDBP}) @b{while $trace_frame != -1}
6974 > output $trace_file
6975 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
6981 @chapter Debugging Programs That Use Overlays
6984 If your program is too large to fit completely in your target system's
6985 memory, you can sometimes use @dfn{overlays} to work around this
6986 problem. @value{GDBN} provides some support for debugging programs that
6990 * How Overlays Work:: A general explanation of overlays.
6991 * Overlay Commands:: Managing overlays in @value{GDBN}.
6992 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
6993 mapped by asking the inferior.
6994 * Overlay Sample Program:: A sample program using overlays.
6997 @node How Overlays Work
6998 @section How Overlays Work
6999 @cindex mapped overlays
7000 @cindex unmapped overlays
7001 @cindex load address, overlay's
7002 @cindex mapped address
7003 @cindex overlay area
7005 Suppose you have a computer whose instruction address space is only 64
7006 kilobytes long, but which has much more memory which can be accessed by
7007 other means: special instructions, segment registers, or memory
7008 management hardware, for example. Suppose further that you want to
7009 adapt a program which is larger than 64 kilobytes to run on this system.
7011 One solution is to identify modules of your program which are relatively
7012 independent, and need not call each other directly; call these modules
7013 @dfn{overlays}. Separate the overlays from the main program, and place
7014 their machine code in the larger memory. Place your main program in
7015 instruction memory, but leave at least enough space there to hold the
7016 largest overlay as well.
7018 Now, to call a function located in an overlay, you must first copy that
7019 overlay's machine code from the large memory into the space set aside
7020 for it in the instruction memory, and then jump to its entry point
7023 @c NB: In the below the mapped area's size is greater or equal to the
7024 @c size of all overlays. This is intentional to remind the developer
7025 @c that overlays don't necessarily need to be the same size.
7029 Data Instruction Larger
7030 Address Space Address Space Address Space
7031 +-----------+ +-----------+ +-----------+
7033 +-----------+ +-----------+ +-----------+<-- overlay 1
7034 | program | | main | .----| overlay 1 | load address
7035 | variables | | program | | +-----------+
7036 | and heap | | | | | |
7037 +-----------+ | | | +-----------+<-- overlay 2
7038 | | +-----------+ | | | load address
7039 +-----------+ | | | .-| overlay 2 |
7041 mapped --->+-----------+ | | +-----------+
7043 | overlay | <-' | | |
7044 | area | <---' +-----------+<-- overlay 3
7045 | | <---. | | load address
7046 +-----------+ `--| overlay 3 |
7053 @anchor{A code overlay}A code overlay
7057 The diagram (@pxref{A code overlay}) shows a system with separate data
7058 and instruction address spaces. To map an overlay, the program copies
7059 its code from the larger address space to the instruction address space.
7060 Since the overlays shown here all use the same mapped address, only one
7061 may be mapped at a time. For a system with a single address space for
7062 data and instructions, the diagram would be similar, except that the
7063 program variables and heap would share an address space with the main
7064 program and the overlay area.
7066 An overlay loaded into instruction memory and ready for use is called a
7067 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
7068 instruction memory. An overlay not present (or only partially present)
7069 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
7070 is its address in the larger memory. The mapped address is also called
7071 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
7072 called the @dfn{load memory address}, or @dfn{LMA}.
7074 Unfortunately, overlays are not a completely transparent way to adapt a
7075 program to limited instruction memory. They introduce a new set of
7076 global constraints you must keep in mind as you design your program:
7081 Before calling or returning to a function in an overlay, your program
7082 must make sure that overlay is actually mapped. Otherwise, the call or
7083 return will transfer control to the right address, but in the wrong
7084 overlay, and your program will probably crash.
7087 If the process of mapping an overlay is expensive on your system, you
7088 will need to choose your overlays carefully to minimize their effect on
7089 your program's performance.
7092 The executable file you load onto your system must contain each
7093 overlay's instructions, appearing at the overlay's load address, not its
7094 mapped address. However, each overlay's instructions must be relocated
7095 and its symbols defined as if the overlay were at its mapped address.
7096 You can use GNU linker scripts to specify different load and relocation
7097 addresses for pieces of your program; see @ref{Overlay Description,,,
7098 ld.info, Using ld: the GNU linker}.
7101 The procedure for loading executable files onto your system must be able
7102 to load their contents into the larger address space as well as the
7103 instruction and data spaces.
7107 The overlay system described above is rather simple, and could be
7108 improved in many ways:
7113 If your system has suitable bank switch registers or memory management
7114 hardware, you could use those facilities to make an overlay's load area
7115 contents simply appear at their mapped address in instruction space.
7116 This would probably be faster than copying the overlay to its mapped
7117 area in the usual way.
7120 If your overlays are small enough, you could set aside more than one
7121 overlay area, and have more than one overlay mapped at a time.
7124 You can use overlays to manage data, as well as instructions. In
7125 general, data overlays are even less transparent to your design than
7126 code overlays: whereas code overlays only require care when you call or
7127 return to functions, data overlays require care every time you access
7128 the data. Also, if you change the contents of a data overlay, you
7129 must copy its contents back out to its load address before you can copy a
7130 different data overlay into the same mapped area.
7135 @node Overlay Commands
7136 @section Overlay Commands
7138 To use @value{GDBN}'s overlay support, each overlay in your program must
7139 correspond to a separate section of the executable file. The section's
7140 virtual memory address and load memory address must be the overlay's
7141 mapped and load addresses. Identifying overlays with sections allows
7142 @value{GDBN} to determine the appropriate address of a function or
7143 variable, depending on whether the overlay is mapped or not.
7145 @value{GDBN}'s overlay commands all start with the word @code{overlay};
7146 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
7151 Disable @value{GDBN}'s overlay support. When overlay support is
7152 disabled, @value{GDBN} assumes that all functions and variables are
7153 always present at their mapped addresses. By default, @value{GDBN}'s
7154 overlay support is disabled.
7156 @item overlay manual
7157 @kindex overlay manual
7158 @cindex manual overlay debugging
7159 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
7160 relies on you to tell it which overlays are mapped, and which are not,
7161 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
7162 commands described below.
7164 @item overlay map-overlay @var{overlay}
7165 @itemx overlay map @var{overlay}
7166 @kindex overlay map-overlay
7167 @cindex map an overlay
7168 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
7169 be the name of the object file section containing the overlay. When an
7170 overlay is mapped, @value{GDBN} assumes it can find the overlay's
7171 functions and variables at their mapped addresses. @value{GDBN} assumes
7172 that any other overlays whose mapped ranges overlap that of
7173 @var{overlay} are now unmapped.
7175 @item overlay unmap-overlay @var{overlay}
7176 @itemx overlay unmap @var{overlay}
7177 @kindex overlay unmap-overlay
7178 @cindex unmap an overlay
7179 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
7180 must be the name of the object file section containing the overlay.
7181 When an overlay is unmapped, @value{GDBN} assumes it can find the
7182 overlay's functions and variables at their load addresses.
7185 @kindex overlay auto
7186 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
7187 consults a data structure the overlay manager maintains in the inferior
7188 to see which overlays are mapped. For details, see @ref{Automatic
7191 @item overlay load-target
7193 @kindex overlay load-target
7194 @cindex reloading the overlay table
7195 Re-read the overlay table from the inferior. Normally, @value{GDBN}
7196 re-reads the table @value{GDBN} automatically each time the inferior
7197 stops, so this command should only be necessary if you have changed the
7198 overlay mapping yourself using @value{GDBN}. This command is only
7199 useful when using automatic overlay debugging.
7201 @item overlay list-overlays
7203 @cindex listing mapped overlays
7204 Display a list of the overlays currently mapped, along with their mapped
7205 addresses, load addresses, and sizes.
7209 Normally, when @value{GDBN} prints a code address, it includes the name
7210 of the function the address falls in:
7214 $3 = @{int ()@} 0x11a0 <main>
7217 When overlay debugging is enabled, @value{GDBN} recognizes code in
7218 unmapped overlays, and prints the names of unmapped functions with
7219 asterisks around them. For example, if @code{foo} is a function in an
7220 unmapped overlay, @value{GDBN} prints it this way:
7224 No sections are mapped.
7226 $5 = @{int (int)@} 0x100000 <*foo*>
7229 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
7234 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
7235 mapped at 0x1016 - 0x104a
7237 $6 = @{int (int)@} 0x1016 <foo>
7240 When overlay debugging is enabled, @value{GDBN} can find the correct
7241 address for functions and variables in an overlay, whether or not the
7242 overlay is mapped. This allows most @value{GDBN} commands, like
7243 @code{break} and @code{disassemble}, to work normally, even on unmapped
7244 code. However, @value{GDBN}'s breakpoint support has some limitations:
7248 @cindex breakpoints in overlays
7249 @cindex overlays, setting breakpoints in
7250 You can set breakpoints in functions in unmapped overlays, as long as
7251 @value{GDBN} can write to the overlay at its load address.
7253 @value{GDBN} can not set hardware or simulator-based breakpoints in
7254 unmapped overlays. However, if you set a breakpoint at the end of your
7255 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
7256 you are using manual overlay management), @value{GDBN} will re-set its
7257 breakpoints properly.
7261 @node Automatic Overlay Debugging
7262 @section Automatic Overlay Debugging
7263 @cindex automatic overlay debugging
7265 @value{GDBN} can automatically track which overlays are mapped and which
7266 are not, given some simple co-operation from the overlay manager in the
7267 inferior. If you enable automatic overlay debugging with the
7268 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
7269 looks in the inferior's memory for certain variables describing the
7270 current state of the overlays.
7272 Here are the variables your overlay manager must define to support
7273 @value{GDBN}'s automatic overlay debugging:
7277 @item @code{_ovly_table}:
7278 This variable must be an array of the following structures:
7283 /* The overlay's mapped address. */
7286 /* The size of the overlay, in bytes. */
7289 /* The overlay's load address. */
7292 /* Non-zero if the overlay is currently mapped;
7294 unsigned long mapped;
7298 @item @code{_novlys}:
7299 This variable must be a four-byte signed integer, holding the total
7300 number of elements in @code{_ovly_table}.
7304 To decide whether a particular overlay is mapped or not, @value{GDBN}
7305 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
7306 @code{lma} members equal the VMA and LMA of the overlay's section in the
7307 executable file. When @value{GDBN} finds a matching entry, it consults
7308 the entry's @code{mapped} member to determine whether the overlay is
7311 In addition, your overlay manager may define a function called
7312 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
7313 will silently set a breakpoint there. If the overlay manager then
7314 calls this function whenever it has changed the overlay table, this
7315 will enable @value{GDBN} to accurately keep track of which overlays
7316 are in program memory, and update any breakpoints that may be set
7317 in overlays. This will allow breakpoints to work even if the
7318 overlays are kept in ROM or other non-writable memory while they
7319 are not being executed.
7321 @node Overlay Sample Program
7322 @section Overlay Sample Program
7323 @cindex overlay example program
7325 When linking a program which uses overlays, you must place the overlays
7326 at their load addresses, while relocating them to run at their mapped
7327 addresses. To do this, you must write a linker script (@pxref{Overlay
7328 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
7329 since linker scripts are specific to a particular host system, target
7330 architecture, and target memory layout, this manual cannot provide
7331 portable sample code demonstrating @value{GDBN}'s overlay support.
7333 However, the @value{GDBN} source distribution does contain an overlaid
7334 program, with linker scripts for a few systems, as part of its test
7335 suite. The program consists of the following files from
7336 @file{gdb/testsuite/gdb.base}:
7340 The main program file.
7342 A simple overlay manager, used by @file{overlays.c}.
7347 Overlay modules, loaded and used by @file{overlays.c}.
7350 Linker scripts for linking the test program on the @code{d10v-elf}
7351 and @code{m32r-elf} targets.
7354 You can build the test program using the @code{d10v-elf} GCC
7355 cross-compiler like this:
7358 $ d10v-elf-gcc -g -c overlays.c
7359 $ d10v-elf-gcc -g -c ovlymgr.c
7360 $ d10v-elf-gcc -g -c foo.c
7361 $ d10v-elf-gcc -g -c bar.c
7362 $ d10v-elf-gcc -g -c baz.c
7363 $ d10v-elf-gcc -g -c grbx.c
7364 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
7365 baz.o grbx.o -Wl,-Td10v.ld -o overlays
7368 The build process is identical for any other architecture, except that
7369 you must substitute the appropriate compiler and linker script for the
7370 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
7374 @chapter Using @value{GDBN} with Different Languages
7377 Although programming languages generally have common aspects, they are
7378 rarely expressed in the same manner. For instance, in ANSI C,
7379 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
7380 Modula-2, it is accomplished by @code{p^}. Values can also be
7381 represented (and displayed) differently. Hex numbers in C appear as
7382 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
7384 @cindex working language
7385 Language-specific information is built into @value{GDBN} for some languages,
7386 allowing you to express operations like the above in your program's
7387 native language, and allowing @value{GDBN} to output values in a manner
7388 consistent with the syntax of your program's native language. The
7389 language you use to build expressions is called the @dfn{working
7393 * Setting:: Switching between source languages
7394 * Show:: Displaying the language
7395 * Checks:: Type and range checks
7396 * Support:: Supported languages
7400 @section Switching between source languages
7402 There are two ways to control the working language---either have @value{GDBN}
7403 set it automatically, or select it manually yourself. You can use the
7404 @code{set language} command for either purpose. On startup, @value{GDBN}
7405 defaults to setting the language automatically. The working language is
7406 used to determine how expressions you type are interpreted, how values
7409 In addition to the working language, every source file that
7410 @value{GDBN} knows about has its own working language. For some object
7411 file formats, the compiler might indicate which language a particular
7412 source file is in. However, most of the time @value{GDBN} infers the
7413 language from the name of the file. The language of a source file
7414 controls whether C@t{++} names are demangled---this way @code{backtrace} can
7415 show each frame appropriately for its own language. There is no way to
7416 set the language of a source file from within @value{GDBN}, but you can
7417 set the language associated with a filename extension. @xref{Show, ,
7418 Displaying the language}.
7420 This is most commonly a problem when you use a program, such
7421 as @code{cfront} or @code{f2c}, that generates C but is written in
7422 another language. In that case, make the
7423 program use @code{#line} directives in its C output; that way
7424 @value{GDBN} will know the correct language of the source code of the original
7425 program, and will display that source code, not the generated C code.
7428 * Filenames:: Filename extensions and languages.
7429 * Manually:: Setting the working language manually
7430 * Automatically:: Having @value{GDBN} infer the source language
7434 @subsection List of filename extensions and languages
7436 If a source file name ends in one of the following extensions, then
7437 @value{GDBN} infers that its language is the one indicated.
7456 @c OBSOLETE @item .ch
7457 @c OBSOLETE @itemx .c186
7458 @c OBSOLETE @itemx .c286
7459 @c OBSOLETE CHILL source file
7462 Modula-2 source file
7466 Assembler source file. This actually behaves almost like C, but
7467 @value{GDBN} does not skip over function prologues when stepping.
7470 In addition, you may set the language associated with a filename
7471 extension. @xref{Show, , Displaying the language}.
7474 @subsection Setting the working language
7476 If you allow @value{GDBN} to set the language automatically,
7477 expressions are interpreted the same way in your debugging session and
7480 @kindex set language
7481 If you wish, you may set the language manually. To do this, issue the
7482 command @samp{set language @var{lang}}, where @var{lang} is the name of
7484 @code{c} or @code{modula-2}.
7485 For a list of the supported languages, type @samp{set language}.
7487 Setting the language manually prevents @value{GDBN} from updating the working
7488 language automatically. This can lead to confusion if you try
7489 to debug a program when the working language is not the same as the
7490 source language, when an expression is acceptable to both
7491 languages---but means different things. For instance, if the current
7492 source file were written in C, and @value{GDBN} was parsing Modula-2, a
7500 might not have the effect you intended. In C, this means to add
7501 @code{b} and @code{c} and place the result in @code{a}. The result
7502 printed would be the value of @code{a}. In Modula-2, this means to compare
7503 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
7506 @subsection Having @value{GDBN} infer the source language
7508 To have @value{GDBN} set the working language automatically, use
7509 @samp{set language local} or @samp{set language auto}. @value{GDBN}
7510 then infers the working language. That is, when your program stops in a
7511 frame (usually by encountering a breakpoint), @value{GDBN} sets the
7512 working language to the language recorded for the function in that
7513 frame. If the language for a frame is unknown (that is, if the function
7514 or block corresponding to the frame was defined in a source file that
7515 does not have a recognized extension), the current working language is
7516 not changed, and @value{GDBN} issues a warning.
7518 This may not seem necessary for most programs, which are written
7519 entirely in one source language. However, program modules and libraries
7520 written in one source language can be used by a main program written in
7521 a different source language. Using @samp{set language auto} in this
7522 case frees you from having to set the working language manually.
7525 @section Displaying the language
7527 The following commands help you find out which language is the
7528 working language, and also what language source files were written in.
7530 @kindex show language
7531 @kindex info frame@r{, show the source language}
7532 @kindex info source@r{, show the source language}
7535 Display the current working language. This is the
7536 language you can use with commands such as @code{print} to
7537 build and compute expressions that may involve variables in your program.
7540 Display the source language for this frame. This language becomes the
7541 working language if you use an identifier from this frame.
7542 @xref{Frame Info, ,Information about a frame}, to identify the other
7543 information listed here.
7546 Display the source language of this source file.
7547 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
7548 information listed here.
7551 In unusual circumstances, you may have source files with extensions
7552 not in the standard list. You can then set the extension associated
7553 with a language explicitly:
7555 @kindex set extension-language
7556 @kindex info extensions
7558 @item set extension-language @var{.ext} @var{language}
7559 Set source files with extension @var{.ext} to be assumed to be in
7560 the source language @var{language}.
7562 @item info extensions
7563 List all the filename extensions and the associated languages.
7567 @section Type and range checking
7570 @emph{Warning:} In this release, the @value{GDBN} commands for type and range
7571 checking are included, but they do not yet have any effect. This
7572 section documents the intended facilities.
7574 @c FIXME remove warning when type/range code added
7576 Some languages are designed to guard you against making seemingly common
7577 errors through a series of compile- and run-time checks. These include
7578 checking the type of arguments to functions and operators, and making
7579 sure mathematical overflows are caught at run time. Checks such as
7580 these help to ensure a program's correctness once it has been compiled
7581 by eliminating type mismatches, and providing active checks for range
7582 errors when your program is running.
7584 @value{GDBN} can check for conditions like the above if you wish.
7585 Although @value{GDBN} does not check the statements in your program, it
7586 can check expressions entered directly into @value{GDBN} for evaluation via
7587 the @code{print} command, for example. As with the working language,
7588 @value{GDBN} can also decide whether or not to check automatically based on
7589 your program's source language. @xref{Support, ,Supported languages},
7590 for the default settings of supported languages.
7593 * Type Checking:: An overview of type checking
7594 * Range Checking:: An overview of range checking
7597 @cindex type checking
7598 @cindex checks, type
7600 @subsection An overview of type checking
7602 Some languages, such as Modula-2, are strongly typed, meaning that the
7603 arguments to operators and functions have to be of the correct type,
7604 otherwise an error occurs. These checks prevent type mismatch
7605 errors from ever causing any run-time problems. For example,
7613 The second example fails because the @code{CARDINAL} 1 is not
7614 type-compatible with the @code{REAL} 2.3.
7616 For the expressions you use in @value{GDBN} commands, you can tell the
7617 @value{GDBN} type checker to skip checking;
7618 to treat any mismatches as errors and abandon the expression;
7619 or to only issue warnings when type mismatches occur,
7620 but evaluate the expression anyway. When you choose the last of
7621 these, @value{GDBN} evaluates expressions like the second example above, but
7622 also issues a warning.
7624 Even if you turn type checking off, there may be other reasons
7625 related to type that prevent @value{GDBN} from evaluating an expression.
7626 For instance, @value{GDBN} does not know how to add an @code{int} and
7627 a @code{struct foo}. These particular type errors have nothing to do
7628 with the language in use, and usually arise from expressions, such as
7629 the one described above, which make little sense to evaluate anyway.
7631 Each language defines to what degree it is strict about type. For
7632 instance, both Modula-2 and C require the arguments to arithmetical
7633 operators to be numbers. In C, enumerated types and pointers can be
7634 represented as numbers, so that they are valid arguments to mathematical
7635 operators. @xref{Support, ,Supported languages}, for further
7636 details on specific languages.
7638 @value{GDBN} provides some additional commands for controlling the type checker:
7640 @kindex set check@r{, type}
7641 @kindex set check type
7642 @kindex show check type
7644 @item set check type auto
7645 Set type checking on or off based on the current working language.
7646 @xref{Support, ,Supported languages}, for the default settings for
7649 @item set check type on
7650 @itemx set check type off
7651 Set type checking on or off, overriding the default setting for the
7652 current working language. Issue a warning if the setting does not
7653 match the language default. If any type mismatches occur in
7654 evaluating an expression while type checking is on, @value{GDBN} prints a
7655 message and aborts evaluation of the expression.
7657 @item set check type warn
7658 Cause the type checker to issue warnings, but to always attempt to
7659 evaluate the expression. Evaluating the expression may still
7660 be impossible for other reasons. For example, @value{GDBN} cannot add
7661 numbers and structures.
7664 Show the current setting of the type checker, and whether or not @value{GDBN}
7665 is setting it automatically.
7668 @cindex range checking
7669 @cindex checks, range
7670 @node Range Checking
7671 @subsection An overview of range checking
7673 In some languages (such as Modula-2), it is an error to exceed the
7674 bounds of a type; this is enforced with run-time checks. Such range
7675 checking is meant to ensure program correctness by making sure
7676 computations do not overflow, or indices on an array element access do
7677 not exceed the bounds of the array.
7679 For expressions you use in @value{GDBN} commands, you can tell
7680 @value{GDBN} to treat range errors in one of three ways: ignore them,
7681 always treat them as errors and abandon the expression, or issue
7682 warnings but evaluate the expression anyway.
7684 A range error can result from numerical overflow, from exceeding an
7685 array index bound, or when you type a constant that is not a member
7686 of any type. Some languages, however, do not treat overflows as an
7687 error. In many implementations of C, mathematical overflow causes the
7688 result to ``wrap around'' to lower values---for example, if @var{m} is
7689 the largest integer value, and @var{s} is the smallest, then
7692 @var{m} + 1 @result{} @var{s}
7695 This, too, is specific to individual languages, and in some cases
7696 specific to individual compilers or machines. @xref{Support, ,
7697 Supported languages}, for further details on specific languages.
7699 @value{GDBN} provides some additional commands for controlling the range checker:
7701 @kindex set check@r{, range}
7702 @kindex set check range
7703 @kindex show check range
7705 @item set check range auto
7706 Set range checking on or off based on the current working language.
7707 @xref{Support, ,Supported languages}, for the default settings for
7710 @item set check range on
7711 @itemx set check range off
7712 Set range checking on or off, overriding the default setting for the
7713 current working language. A warning is issued if the setting does not
7714 match the language default. If a range error occurs and range checking is on,
7715 then a message is printed and evaluation of the expression is aborted.
7717 @item set check range warn
7718 Output messages when the @value{GDBN} range checker detects a range error,
7719 but attempt to evaluate the expression anyway. Evaluating the
7720 expression may still be impossible for other reasons, such as accessing
7721 memory that the process does not own (a typical example from many Unix
7725 Show the current setting of the range checker, and whether or not it is
7726 being set automatically by @value{GDBN}.
7730 @section Supported languages
7732 @value{GDBN} supports C, C@t{++}, Fortran, Java,
7734 assembly, and Modula-2.
7735 @c This is false ...
7736 Some @value{GDBN} features may be used in expressions regardless of the
7737 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
7738 and the @samp{@{type@}addr} construct (@pxref{Expressions,
7739 ,Expressions}) can be used with the constructs of any supported
7742 The following sections detail to what degree each source language is
7743 supported by @value{GDBN}. These sections are not meant to be language
7744 tutorials or references, but serve only as a reference guide to what the
7745 @value{GDBN} expression parser accepts, and what input and output
7746 formats should look like for different languages. There are many good
7747 books written on each of these languages; please look to these for a
7748 language reference or tutorial.
7752 * Modula-2:: Modula-2
7753 @c OBSOLETE * Chill:: Chill
7757 @subsection C and C@t{++}
7759 @cindex C and C@t{++}
7760 @cindex expressions in C or C@t{++}
7762 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
7763 to both languages. Whenever this is the case, we discuss those languages
7767 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
7768 @cindex @sc{gnu} C@t{++}
7769 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
7770 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
7771 effectively, you must compile your C@t{++} programs with a supported
7772 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
7773 compiler (@code{aCC}).
7775 For best results when using @sc{gnu} C@t{++}, use the stabs debugging
7776 format. You can select that format explicitly with the @code{g++}
7777 command-line options @samp{-gstabs} or @samp{-gstabs+}. See
7778 @ref{Debugging Options,,Options for Debugging Your Program or @sc{gnu}
7779 CC, gcc.info, Using @sc{gnu} CC}, for more information.
7782 * C Operators:: C and C@t{++} operators
7783 * C Constants:: C and C@t{++} constants
7784 * C plus plus expressions:: C@t{++} expressions
7785 * C Defaults:: Default settings for C and C@t{++}
7786 * C Checks:: C and C@t{++} type and range checks
7787 * Debugging C:: @value{GDBN} and C
7788 * Debugging C plus plus:: @value{GDBN} features for C@t{++}
7792 @subsubsection C and C@t{++} operators
7794 @cindex C and C@t{++} operators
7796 Operators must be defined on values of specific types. For instance,
7797 @code{+} is defined on numbers, but not on structures. Operators are
7798 often defined on groups of types.
7800 For the purposes of C and C@t{++}, the following definitions hold:
7805 @emph{Integral types} include @code{int} with any of its storage-class
7806 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
7809 @emph{Floating-point types} include @code{float}, @code{double}, and
7810 @code{long double} (if supported by the target platform).
7813 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
7816 @emph{Scalar types} include all of the above.
7821 The following operators are supported. They are listed here
7822 in order of increasing precedence:
7826 The comma or sequencing operator. Expressions in a comma-separated list
7827 are evaluated from left to right, with the result of the entire
7828 expression being the last expression evaluated.
7831 Assignment. The value of an assignment expression is the value
7832 assigned. Defined on scalar types.
7835 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
7836 and translated to @w{@code{@var{a} = @var{a op b}}}.
7837 @w{@code{@var{op}=}} and @code{=} have the same precedence.
7838 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
7839 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
7842 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
7843 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
7847 Logical @sc{or}. Defined on integral types.
7850 Logical @sc{and}. Defined on integral types.
7853 Bitwise @sc{or}. Defined on integral types.
7856 Bitwise exclusive-@sc{or}. Defined on integral types.
7859 Bitwise @sc{and}. Defined on integral types.
7862 Equality and inequality. Defined on scalar types. The value of these
7863 expressions is 0 for false and non-zero for true.
7865 @item <@r{, }>@r{, }<=@r{, }>=
7866 Less than, greater than, less than or equal, greater than or equal.
7867 Defined on scalar types. The value of these expressions is 0 for false
7868 and non-zero for true.
7871 left shift, and right shift. Defined on integral types.
7874 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
7877 Addition and subtraction. Defined on integral types, floating-point types and
7880 @item *@r{, }/@r{, }%
7881 Multiplication, division, and modulus. Multiplication and division are
7882 defined on integral and floating-point types. Modulus is defined on
7886 Increment and decrement. When appearing before a variable, the
7887 operation is performed before the variable is used in an expression;
7888 when appearing after it, the variable's value is used before the
7889 operation takes place.
7892 Pointer dereferencing. Defined on pointer types. Same precedence as
7896 Address operator. Defined on variables. Same precedence as @code{++}.
7898 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
7899 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
7900 (or, if you prefer, simply @samp{&&@var{ref}}) to examine the address
7901 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
7905 Negative. Defined on integral and floating-point types. Same
7906 precedence as @code{++}.
7909 Logical negation. Defined on integral types. Same precedence as
7913 Bitwise complement operator. Defined on integral types. Same precedence as
7918 Structure member, and pointer-to-structure member. For convenience,
7919 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
7920 pointer based on the stored type information.
7921 Defined on @code{struct} and @code{union} data.
7924 Dereferences of pointers to members.
7927 Array indexing. @code{@var{a}[@var{i}]} is defined as
7928 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
7931 Function parameter list. Same precedence as @code{->}.
7934 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
7935 and @code{class} types.
7938 Doubled colons also represent the @value{GDBN} scope operator
7939 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
7943 If an operator is redefined in the user code, @value{GDBN} usually
7944 attempts to invoke the redefined version instead of using the operator's
7952 @subsubsection C and C@t{++} constants
7954 @cindex C and C@t{++} constants
7956 @value{GDBN} allows you to express the constants of C and C@t{++} in the
7961 Integer constants are a sequence of digits. Octal constants are
7962 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
7963 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
7964 @samp{l}, specifying that the constant should be treated as a
7968 Floating point constants are a sequence of digits, followed by a decimal
7969 point, followed by a sequence of digits, and optionally followed by an
7970 exponent. An exponent is of the form:
7971 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
7972 sequence of digits. The @samp{+} is optional for positive exponents.
7973 A floating-point constant may also end with a letter @samp{f} or
7974 @samp{F}, specifying that the constant should be treated as being of
7975 the @code{float} (as opposed to the default @code{double}) type; or with
7976 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
7980 Enumerated constants consist of enumerated identifiers, or their
7981 integral equivalents.
7984 Character constants are a single character surrounded by single quotes
7985 (@code{'}), or a number---the ordinal value of the corresponding character
7986 (usually its @sc{ascii} value). Within quotes, the single character may
7987 be represented by a letter or by @dfn{escape sequences}, which are of
7988 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
7989 of the character's ordinal value; or of the form @samp{\@var{x}}, where
7990 @samp{@var{x}} is a predefined special character---for example,
7991 @samp{\n} for newline.
7994 String constants are a sequence of character constants surrounded by
7995 double quotes (@code{"}). Any valid character constant (as described
7996 above) may appear. Double quotes within the string must be preceded by
7997 a backslash, so for instance @samp{"a\"b'c"} is a string of five
8001 Pointer constants are an integral value. You can also write pointers
8002 to constants using the C operator @samp{&}.
8005 Array constants are comma-separated lists surrounded by braces @samp{@{}
8006 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
8007 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
8008 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
8012 * C plus plus expressions::
8019 @node C plus plus expressions
8020 @subsubsection C@t{++} expressions
8022 @cindex expressions in C@t{++}
8023 @value{GDBN} expression handling can interpret most C@t{++} expressions.
8025 @cindex C@t{++} support, not in @sc{coff}
8026 @cindex @sc{coff} versus C@t{++}
8027 @cindex C@t{++} and object formats
8028 @cindex object formats and C@t{++}
8029 @cindex a.out and C@t{++}
8030 @cindex @sc{ecoff} and C@t{++}
8031 @cindex @sc{xcoff} and C@t{++}
8032 @cindex @sc{elf}/stabs and C@t{++}
8033 @cindex @sc{elf}/@sc{dwarf} and C@t{++}
8034 @c FIXME!! GDB may eventually be able to debug C++ using DWARF; check
8035 @c periodically whether this has happened...
8037 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use the
8038 proper compiler. Typically, C@t{++} debugging depends on the use of
8039 additional debugging information in the symbol table, and thus requires
8040 special support. In particular, if your compiler generates a.out, MIPS
8041 @sc{ecoff}, RS/6000 @sc{xcoff}, or @sc{elf} with stabs extensions to the
8042 symbol table, these facilities are all available. (With @sc{gnu} CC,
8043 you can use the @samp{-gstabs} option to request stabs debugging
8044 extensions explicitly.) Where the object code format is standard
8045 @sc{coff} or @sc{dwarf} in @sc{elf}, on the other hand, most of the C@t{++}
8046 support in @value{GDBN} does @emph{not} work.
8051 @cindex member functions
8053 Member function calls are allowed; you can use expressions like
8056 count = aml->GetOriginal(x, y)
8059 @vindex this@r{, inside C@t{++} member functions}
8060 @cindex namespace in C@t{++}
8062 While a member function is active (in the selected stack frame), your
8063 expressions have the same namespace available as the member function;
8064 that is, @value{GDBN} allows implicit references to the class instance
8065 pointer @code{this} following the same rules as C@t{++}.
8067 @cindex call overloaded functions
8068 @cindex overloaded functions, calling
8069 @cindex type conversions in C@t{++}
8071 You can call overloaded functions; @value{GDBN} resolves the function
8072 call to the right definition, with some restrictions. @value{GDBN} does not
8073 perform overload resolution involving user-defined type conversions,
8074 calls to constructors, or instantiations of templates that do not exist
8075 in the program. It also cannot handle ellipsis argument lists or
8078 It does perform integral conversions and promotions, floating-point
8079 promotions, arithmetic conversions, pointer conversions, conversions of
8080 class objects to base classes, and standard conversions such as those of
8081 functions or arrays to pointers; it requires an exact match on the
8082 number of function arguments.
8084 Overload resolution is always performed, unless you have specified
8085 @code{set overload-resolution off}. @xref{Debugging C plus plus,
8086 ,@value{GDBN} features for C@t{++}}.
8088 You must specify @code{set overload-resolution off} in order to use an
8089 explicit function signature to call an overloaded function, as in
8091 p 'foo(char,int)'('x', 13)
8094 The @value{GDBN} command-completion facility can simplify this;
8095 see @ref{Completion, ,Command completion}.
8097 @cindex reference declarations
8099 @value{GDBN} understands variables declared as C@t{++} references; you can use
8100 them in expressions just as you do in C@t{++} source---they are automatically
8103 In the parameter list shown when @value{GDBN} displays a frame, the values of
8104 reference variables are not displayed (unlike other variables); this
8105 avoids clutter, since references are often used for large structures.
8106 The @emph{address} of a reference variable is always shown, unless
8107 you have specified @samp{set print address off}.
8110 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
8111 expressions can use it just as expressions in your program do. Since
8112 one scope may be defined in another, you can use @code{::} repeatedly if
8113 necessary, for example in an expression like
8114 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
8115 resolving name scope by reference to source files, in both C and C@t{++}
8116 debugging (@pxref{Variables, ,Program variables}).
8119 In addition, when used with HP's C@t{++} compiler, @value{GDBN} supports
8120 calling virtual functions correctly, printing out virtual bases of
8121 objects, calling functions in a base subobject, casting objects, and
8122 invoking user-defined operators.
8125 @subsubsection C and C@t{++} defaults
8127 @cindex C and C@t{++} defaults
8129 If you allow @value{GDBN} to set type and range checking automatically, they
8130 both default to @code{off} whenever the working language changes to
8131 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
8132 selects the working language.
8134 If you allow @value{GDBN} to set the language automatically, it
8135 recognizes source files whose names end with @file{.c}, @file{.C}, or
8136 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
8137 these files, it sets the working language to C or C@t{++}.
8138 @xref{Automatically, ,Having @value{GDBN} infer the source language},
8139 for further details.
8141 @c Type checking is (a) primarily motivated by Modula-2, and (b)
8142 @c unimplemented. If (b) changes, it might make sense to let this node
8143 @c appear even if Mod-2 does not, but meanwhile ignore it. roland 16jul93.
8146 @subsubsection C and C@t{++} type and range checks
8148 @cindex C and C@t{++} checks
8150 By default, when @value{GDBN} parses C or C@t{++} expressions, type checking
8151 is not used. However, if you turn type checking on, @value{GDBN}
8152 considers two variables type equivalent if:
8156 The two variables are structured and have the same structure, union, or
8160 The two variables have the same type name, or types that have been
8161 declared equivalent through @code{typedef}.
8164 @c leaving this out because neither J Gilmore nor R Pesch understand it.
8167 The two @code{struct}, @code{union}, or @code{enum} variables are
8168 declared in the same declaration. (Note: this may not be true for all C
8173 Range checking, if turned on, is done on mathematical operations. Array
8174 indices are not checked, since they are often used to index a pointer
8175 that is not itself an array.
8178 @subsubsection @value{GDBN} and C
8180 The @code{set print union} and @code{show print union} commands apply to
8181 the @code{union} type. When set to @samp{on}, any @code{union} that is
8182 inside a @code{struct} or @code{class} is also printed. Otherwise, it
8183 appears as @samp{@{...@}}.
8185 The @code{@@} operator aids in the debugging of dynamic arrays, formed
8186 with pointers and a memory allocation function. @xref{Expressions,
8190 * Debugging C plus plus::
8193 @node Debugging C plus plus
8194 @subsubsection @value{GDBN} features for C@t{++}
8196 @cindex commands for C@t{++}
8198 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
8199 designed specifically for use with C@t{++}. Here is a summary:
8202 @cindex break in overloaded functions
8203 @item @r{breakpoint menus}
8204 When you want a breakpoint in a function whose name is overloaded,
8205 @value{GDBN} breakpoint menus help you specify which function definition
8206 you want. @xref{Breakpoint Menus,,Breakpoint menus}.
8208 @cindex overloading in C@t{++}
8209 @item rbreak @var{regex}
8210 Setting breakpoints using regular expressions is helpful for setting
8211 breakpoints on overloaded functions that are not members of any special
8213 @xref{Set Breaks, ,Setting breakpoints}.
8215 @cindex C@t{++} exception handling
8218 Debug C@t{++} exception handling using these commands. @xref{Set
8219 Catchpoints, , Setting catchpoints}.
8222 @item ptype @var{typename}
8223 Print inheritance relationships as well as other information for type
8225 @xref{Symbols, ,Examining the Symbol Table}.
8227 @cindex C@t{++} symbol display
8228 @item set print demangle
8229 @itemx show print demangle
8230 @itemx set print asm-demangle
8231 @itemx show print asm-demangle
8232 Control whether C@t{++} symbols display in their source form, both when
8233 displaying code as C@t{++} source and when displaying disassemblies.
8234 @xref{Print Settings, ,Print settings}.
8236 @item set print object
8237 @itemx show print object
8238 Choose whether to print derived (actual) or declared types of objects.
8239 @xref{Print Settings, ,Print settings}.
8241 @item set print vtbl
8242 @itemx show print vtbl
8243 Control the format for printing virtual function tables.
8244 @xref{Print Settings, ,Print settings}.
8245 (The @code{vtbl} commands do not work on programs compiled with the HP
8246 ANSI C@t{++} compiler (@code{aCC}).)
8248 @kindex set overload-resolution
8249 @cindex overloaded functions, overload resolution
8250 @item set overload-resolution on
8251 Enable overload resolution for C@t{++} expression evaluation. The default
8252 is on. For overloaded functions, @value{GDBN} evaluates the arguments
8253 and searches for a function whose signature matches the argument types,
8254 using the standard C@t{++} conversion rules (see @ref{C plus plus expressions, ,C@t{++}
8255 expressions}, for details). If it cannot find a match, it emits a
8258 @item set overload-resolution off
8259 Disable overload resolution for C@t{++} expression evaluation. For
8260 overloaded functions that are not class member functions, @value{GDBN}
8261 chooses the first function of the specified name that it finds in the
8262 symbol table, whether or not its arguments are of the correct type. For
8263 overloaded functions that are class member functions, @value{GDBN}
8264 searches for a function whose signature @emph{exactly} matches the
8267 @item @r{Overloaded symbol names}
8268 You can specify a particular definition of an overloaded symbol, using
8269 the same notation that is used to declare such symbols in C@t{++}: type
8270 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
8271 also use the @value{GDBN} command-line word completion facilities to list the
8272 available choices, or to finish the type list for you.
8273 @xref{Completion,, Command completion}, for details on how to do this.
8277 @subsection Modula-2
8279 @cindex Modula-2, @value{GDBN} support
8281 The extensions made to @value{GDBN} to support Modula-2 only support
8282 output from the @sc{gnu} Modula-2 compiler (which is currently being
8283 developed). Other Modula-2 compilers are not currently supported, and
8284 attempting to debug executables produced by them is most likely
8285 to give an error as @value{GDBN} reads in the executable's symbol
8288 @cindex expressions in Modula-2
8290 * M2 Operators:: Built-in operators
8291 * Built-In Func/Proc:: Built-in functions and procedures
8292 * M2 Constants:: Modula-2 constants
8293 * M2 Defaults:: Default settings for Modula-2
8294 * Deviations:: Deviations from standard Modula-2
8295 * M2 Checks:: Modula-2 type and range checks
8296 * M2 Scope:: The scope operators @code{::} and @code{.}
8297 * GDB/M2:: @value{GDBN} and Modula-2
8301 @subsubsection Operators
8302 @cindex Modula-2 operators
8304 Operators must be defined on values of specific types. For instance,
8305 @code{+} is defined on numbers, but not on structures. Operators are
8306 often defined on groups of types. For the purposes of Modula-2, the
8307 following definitions hold:
8312 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
8316 @emph{Character types} consist of @code{CHAR} and its subranges.
8319 @emph{Floating-point types} consist of @code{REAL}.
8322 @emph{Pointer types} consist of anything declared as @code{POINTER TO
8326 @emph{Scalar types} consist of all of the above.
8329 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
8332 @emph{Boolean types} consist of @code{BOOLEAN}.
8336 The following operators are supported, and appear in order of
8337 increasing precedence:
8341 Function argument or array index separator.
8344 Assignment. The value of @var{var} @code{:=} @var{value} is
8348 Less than, greater than on integral, floating-point, or enumerated
8352 Less than or equal to, greater than or equal to
8353 on integral, floating-point and enumerated types, or set inclusion on
8354 set types. Same precedence as @code{<}.
8356 @item =@r{, }<>@r{, }#
8357 Equality and two ways of expressing inequality, valid on scalar types.
8358 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
8359 available for inequality, since @code{#} conflicts with the script
8363 Set membership. Defined on set types and the types of their members.
8364 Same precedence as @code{<}.
8367 Boolean disjunction. Defined on boolean types.
8370 Boolean conjunction. Defined on boolean types.
8373 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
8376 Addition and subtraction on integral and floating-point types, or union
8377 and difference on set types.
8380 Multiplication on integral and floating-point types, or set intersection
8384 Division on floating-point types, or symmetric set difference on set
8385 types. Same precedence as @code{*}.
8388 Integer division and remainder. Defined on integral types. Same
8389 precedence as @code{*}.
8392 Negative. Defined on @code{INTEGER} and @code{REAL} data.
8395 Pointer dereferencing. Defined on pointer types.
8398 Boolean negation. Defined on boolean types. Same precedence as
8402 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
8403 precedence as @code{^}.
8406 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
8409 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
8413 @value{GDBN} and Modula-2 scope operators.
8417 @emph{Warning:} Sets and their operations are not yet supported, so @value{GDBN}
8418 treats the use of the operator @code{IN}, or the use of operators
8419 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
8420 @code{<=}, and @code{>=} on sets as an error.
8424 @node Built-In Func/Proc
8425 @subsubsection Built-in functions and procedures
8426 @cindex Modula-2 built-ins
8428 Modula-2 also makes available several built-in procedures and functions.
8429 In describing these, the following metavariables are used:
8434 represents an @code{ARRAY} variable.
8437 represents a @code{CHAR} constant or variable.
8440 represents a variable or constant of integral type.
8443 represents an identifier that belongs to a set. Generally used in the
8444 same function with the metavariable @var{s}. The type of @var{s} should
8445 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
8448 represents a variable or constant of integral or floating-point type.
8451 represents a variable or constant of floating-point type.
8457 represents a variable.
8460 represents a variable or constant of one of many types. See the
8461 explanation of the function for details.
8464 All Modula-2 built-in procedures also return a result, described below.
8468 Returns the absolute value of @var{n}.
8471 If @var{c} is a lower case letter, it returns its upper case
8472 equivalent, otherwise it returns its argument.
8475 Returns the character whose ordinal value is @var{i}.
8478 Decrements the value in the variable @var{v} by one. Returns the new value.
8480 @item DEC(@var{v},@var{i})
8481 Decrements the value in the variable @var{v} by @var{i}. Returns the
8484 @item EXCL(@var{m},@var{s})
8485 Removes the element @var{m} from the set @var{s}. Returns the new
8488 @item FLOAT(@var{i})
8489 Returns the floating point equivalent of the integer @var{i}.
8492 Returns the index of the last member of @var{a}.
8495 Increments the value in the variable @var{v} by one. Returns the new value.
8497 @item INC(@var{v},@var{i})
8498 Increments the value in the variable @var{v} by @var{i}. Returns the
8501 @item INCL(@var{m},@var{s})
8502 Adds the element @var{m} to the set @var{s} if it is not already
8503 there. Returns the new set.
8506 Returns the maximum value of the type @var{t}.
8509 Returns the minimum value of the type @var{t}.
8512 Returns boolean TRUE if @var{i} is an odd number.
8515 Returns the ordinal value of its argument. For example, the ordinal
8516 value of a character is its @sc{ascii} value (on machines supporting the
8517 @sc{ascii} character set). @var{x} must be of an ordered type, which include
8518 integral, character and enumerated types.
8521 Returns the size of its argument. @var{x} can be a variable or a type.
8523 @item TRUNC(@var{r})
8524 Returns the integral part of @var{r}.
8526 @item VAL(@var{t},@var{i})
8527 Returns the member of the type @var{t} whose ordinal value is @var{i}.
8531 @emph{Warning:} Sets and their operations are not yet supported, so
8532 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
8536 @cindex Modula-2 constants
8538 @subsubsection Constants
8540 @value{GDBN} allows you to express the constants of Modula-2 in the following
8546 Integer constants are simply a sequence of digits. When used in an
8547 expression, a constant is interpreted to be type-compatible with the
8548 rest of the expression. Hexadecimal integers are specified by a
8549 trailing @samp{H}, and octal integers by a trailing @samp{B}.
8552 Floating point constants appear as a sequence of digits, followed by a
8553 decimal point and another sequence of digits. An optional exponent can
8554 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
8555 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
8556 digits of the floating point constant must be valid decimal (base 10)
8560 Character constants consist of a single character enclosed by a pair of
8561 like quotes, either single (@code{'}) or double (@code{"}). They may
8562 also be expressed by their ordinal value (their @sc{ascii} value, usually)
8563 followed by a @samp{C}.
8566 String constants consist of a sequence of characters enclosed by a
8567 pair of like quotes, either single (@code{'}) or double (@code{"}).
8568 Escape sequences in the style of C are also allowed. @xref{C
8569 Constants, ,C and C@t{++} constants}, for a brief explanation of escape
8573 Enumerated constants consist of an enumerated identifier.
8576 Boolean constants consist of the identifiers @code{TRUE} and
8580 Pointer constants consist of integral values only.
8583 Set constants are not yet supported.
8587 @subsubsection Modula-2 defaults
8588 @cindex Modula-2 defaults
8590 If type and range checking are set automatically by @value{GDBN}, they
8591 both default to @code{on} whenever the working language changes to
8592 Modula-2. This happens regardless of whether you or @value{GDBN}
8593 selected the working language.
8595 If you allow @value{GDBN} to set the language automatically, then entering
8596 code compiled from a file whose name ends with @file{.mod} sets the
8597 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN} set
8598 the language automatically}, for further details.
8601 @subsubsection Deviations from standard Modula-2
8602 @cindex Modula-2, deviations from
8604 A few changes have been made to make Modula-2 programs easier to debug.
8605 This is done primarily via loosening its type strictness:
8609 Unlike in standard Modula-2, pointer constants can be formed by
8610 integers. This allows you to modify pointer variables during
8611 debugging. (In standard Modula-2, the actual address contained in a
8612 pointer variable is hidden from you; it can only be modified
8613 through direct assignment to another pointer variable or expression that
8614 returned a pointer.)
8617 C escape sequences can be used in strings and characters to represent
8618 non-printable characters. @value{GDBN} prints out strings with these
8619 escape sequences embedded. Single non-printable characters are
8620 printed using the @samp{CHR(@var{nnn})} format.
8623 The assignment operator (@code{:=}) returns the value of its right-hand
8627 All built-in procedures both modify @emph{and} return their argument.
8631 @subsubsection Modula-2 type and range checks
8632 @cindex Modula-2 checks
8635 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
8638 @c FIXME remove warning when type/range checks added
8640 @value{GDBN} considers two Modula-2 variables type equivalent if:
8644 They are of types that have been declared equivalent via a @code{TYPE
8645 @var{t1} = @var{t2}} statement
8648 They have been declared on the same line. (Note: This is true of the
8649 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
8652 As long as type checking is enabled, any attempt to combine variables
8653 whose types are not equivalent is an error.
8655 Range checking is done on all mathematical operations, assignment, array
8656 index bounds, and all built-in functions and procedures.
8659 @subsubsection The scope operators @code{::} and @code{.}
8661 @cindex @code{.}, Modula-2 scope operator
8662 @cindex colon, doubled as scope operator
8664 @vindex colon-colon@r{, in Modula-2}
8665 @c Info cannot handle :: but TeX can.
8668 @vindex ::@r{, in Modula-2}
8671 There are a few subtle differences between the Modula-2 scope operator
8672 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
8677 @var{module} . @var{id}
8678 @var{scope} :: @var{id}
8682 where @var{scope} is the name of a module or a procedure,
8683 @var{module} the name of a module, and @var{id} is any declared
8684 identifier within your program, except another module.
8686 Using the @code{::} operator makes @value{GDBN} search the scope
8687 specified by @var{scope} for the identifier @var{id}. If it is not
8688 found in the specified scope, then @value{GDBN} searches all scopes
8689 enclosing the one specified by @var{scope}.
8691 Using the @code{.} operator makes @value{GDBN} search the current scope for
8692 the identifier specified by @var{id} that was imported from the
8693 definition module specified by @var{module}. With this operator, it is
8694 an error if the identifier @var{id} was not imported from definition
8695 module @var{module}, or if @var{id} is not an identifier in
8699 @subsubsection @value{GDBN} and Modula-2
8701 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
8702 Five subcommands of @code{set print} and @code{show print} apply
8703 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
8704 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
8705 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
8706 analogue in Modula-2.
8708 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
8709 with any language, is not useful with Modula-2. Its
8710 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
8711 created in Modula-2 as they can in C or C@t{++}. However, because an
8712 address can be specified by an integral constant, the construct
8713 @samp{@{@var{type}@}@var{adrexp}} is still useful.
8715 @cindex @code{#} in Modula-2
8716 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
8717 interpreted as the beginning of a comment. Use @code{<>} instead.
8719 @c OBSOLETE @node Chill
8720 @c OBSOLETE @subsection Chill
8722 @c OBSOLETE The extensions made to @value{GDBN} to support Chill only support output
8723 @c OBSOLETE from the @sc{gnu} Chill compiler. Other Chill compilers are not currently
8724 @c OBSOLETE supported, and attempting to debug executables produced by them is most
8725 @c OBSOLETE likely to give an error as @value{GDBN} reads in the executable's symbol
8728 @c OBSOLETE @c This used to say "... following Chill related topics ...", but since
8729 @c OBSOLETE @c menus are not shown in the printed manual, it would look awkward.
8730 @c OBSOLETE This section covers the Chill related topics and the features
8731 @c OBSOLETE of @value{GDBN} which support these topics.
8734 @c OBSOLETE * How modes are displayed:: How modes are displayed
8735 @c OBSOLETE * Locations:: Locations and their accesses
8736 @c OBSOLETE * Values and their Operations:: Values and their Operations
8737 @c OBSOLETE * Chill type and range checks::
8738 @c OBSOLETE * Chill defaults::
8739 @c OBSOLETE @end menu
8741 @c OBSOLETE @node How modes are displayed
8742 @c OBSOLETE @subsubsection How modes are displayed
8744 @c OBSOLETE The Chill Datatype- (Mode) support of @value{GDBN} is directly related
8745 @c OBSOLETE with the functionality of the @sc{gnu} Chill compiler, and therefore deviates
8746 @c OBSOLETE slightly from the standard specification of the Chill language. The
8747 @c OBSOLETE provided modes are:
8749 @c OBSOLETE @c FIXME: this @table's contents effectively disable @code by using @r
8750 @c OBSOLETE @c on every @item. So why does it need @code?
8751 @c OBSOLETE @table @code
8752 @c OBSOLETE @item @r{@emph{Discrete modes:}}
8753 @c OBSOLETE @itemize @bullet
8755 @c OBSOLETE @emph{Integer Modes} which are predefined by @code{BYTE, UBYTE, INT,
8756 @c OBSOLETE UINT, LONG, ULONG},
8758 @c OBSOLETE @emph{Boolean Mode} which is predefined by @code{BOOL},
8760 @c OBSOLETE @emph{Character Mode} which is predefined by @code{CHAR},
8762 @c OBSOLETE @emph{Set Mode} which is displayed by the keyword @code{SET}.
8763 @c OBSOLETE @smallexample
8764 @c OBSOLETE (@value{GDBP}) ptype x
8765 @c OBSOLETE type = SET (karli = 10, susi = 20, fritzi = 100)
8766 @c OBSOLETE @end smallexample
8767 @c OBSOLETE If the type is an unnumbered set the set element values are omitted.
8769 @c OBSOLETE @emph{Range Mode} which is displayed by
8770 @c OBSOLETE @smallexample
8771 @c OBSOLETE @code{type = <basemode>(<lower bound> : <upper bound>)}
8772 @c OBSOLETE @end smallexample
8773 @c OBSOLETE where @code{<lower bound>, <upper bound>} can be of any discrete literal
8774 @c OBSOLETE expression (e.g. set element names).
8775 @c OBSOLETE @end itemize
8777 @c OBSOLETE @item @r{@emph{Powerset Mode:}}
8778 @c OBSOLETE A Powerset Mode is displayed by the keyword @code{POWERSET} followed by
8779 @c OBSOLETE the member mode of the powerset. The member mode can be any discrete mode.
8780 @c OBSOLETE @smallexample
8781 @c OBSOLETE (@value{GDBP}) ptype x
8782 @c OBSOLETE type = POWERSET SET (egon, hugo, otto)
8783 @c OBSOLETE @end smallexample
8785 @c OBSOLETE @item @r{@emph{Reference Modes:}}
8786 @c OBSOLETE @itemize @bullet
8788 @c OBSOLETE @emph{Bound Reference Mode} which is displayed by the keyword @code{REF}
8789 @c OBSOLETE followed by the mode name to which the reference is bound.
8791 @c OBSOLETE @emph{Free Reference Mode} which is displayed by the keyword @code{PTR}.
8792 @c OBSOLETE @end itemize
8794 @c OBSOLETE @item @r{@emph{Procedure mode}}
8795 @c OBSOLETE The procedure mode is displayed by @code{type = PROC(<parameter list>)
8796 @c OBSOLETE <return mode> EXCEPTIONS (<exception list>)}. The @code{<parameter
8797 @c OBSOLETE list>} is a list of the parameter modes. @code{<return mode>} indicates
8798 @c OBSOLETE the mode of the result of the procedure if any. The exceptionlist lists
8799 @c OBSOLETE all possible exceptions which can be raised by the procedure.
8802 @c OBSOLETE @item @r{@emph{Instance mode}}
8803 @c OBSOLETE The instance mode is represented by a structure, which has a static
8804 @c OBSOLETE type, and is therefore not really of interest.
8805 @c OBSOLETE @end ignore
8807 @c OBSOLETE @item @r{@emph{Synchronization Modes:}}
8808 @c OBSOLETE @itemize @bullet
8810 @c OBSOLETE @emph{Event Mode} which is displayed by
8811 @c OBSOLETE @smallexample
8812 @c OBSOLETE @code{EVENT (<event length>)}
8813 @c OBSOLETE @end smallexample
8814 @c OBSOLETE where @code{(<event length>)} is optional.
8816 @c OBSOLETE @emph{Buffer Mode} which is displayed by
8817 @c OBSOLETE @smallexample
8818 @c OBSOLETE @code{BUFFER (<buffer length>)<buffer element mode>}
8819 @c OBSOLETE @end smallexample
8820 @c OBSOLETE where @code{(<buffer length>)} is optional.
8821 @c OBSOLETE @end itemize
8823 @c OBSOLETE @item @r{@emph{Timing Modes:}}
8824 @c OBSOLETE @itemize @bullet
8826 @c OBSOLETE @emph{Duration Mode} which is predefined by @code{DURATION}
8828 @c OBSOLETE @emph{Absolute Time Mode} which is predefined by @code{TIME}
8829 @c OBSOLETE @end itemize
8831 @c OBSOLETE @item @r{@emph{Real Modes:}}
8832 @c OBSOLETE Real Modes are predefined with @code{REAL} and @code{LONG_REAL}.
8834 @c OBSOLETE @item @r{@emph{String Modes:}}
8835 @c OBSOLETE @itemize @bullet
8837 @c OBSOLETE @emph{Character String Mode} which is displayed by
8838 @c OBSOLETE @smallexample
8839 @c OBSOLETE @code{CHARS(<string length>)}
8840 @c OBSOLETE @end smallexample
8841 @c OBSOLETE followed by the keyword @code{VARYING} if the String Mode is a varying
8844 @c OBSOLETE @emph{Bit String Mode} which is displayed by
8845 @c OBSOLETE @smallexample
8846 @c OBSOLETE @code{BOOLS(<string
8847 @c OBSOLETE length>)}
8848 @c OBSOLETE @end smallexample
8849 @c OBSOLETE @end itemize
8851 @c OBSOLETE @item @r{@emph{Array Mode:}}
8852 @c OBSOLETE The Array Mode is displayed by the keyword @code{ARRAY(<range>)}
8853 @c OBSOLETE followed by the element mode (which may in turn be an array mode).
8854 @c OBSOLETE @smallexample
8855 @c OBSOLETE (@value{GDBP}) ptype x
8856 @c OBSOLETE type = ARRAY (1:42)
8857 @c OBSOLETE ARRAY (1:20)
8858 @c OBSOLETE SET (karli = 10, susi = 20, fritzi = 100)
8859 @c OBSOLETE @end smallexample
8861 @c OBSOLETE @item @r{@emph{Structure Mode}}
8862 @c OBSOLETE The Structure mode is displayed by the keyword @code{STRUCT(<field
8863 @c OBSOLETE list>)}. The @code{<field list>} consists of names and modes of fields
8864 @c OBSOLETE of the structure. Variant structures have the keyword @code{CASE <field>
8865 @c OBSOLETE OF <variant fields> ESAC} in their field list. Since the current version
8866 @c OBSOLETE of the GNU Chill compiler doesn't implement tag processing (no runtime
8867 @c OBSOLETE checks of variant fields, and therefore no debugging info), the output
8868 @c OBSOLETE always displays all variant fields.
8869 @c OBSOLETE @smallexample
8870 @c OBSOLETE (@value{GDBP}) ptype str
8871 @c OBSOLETE type = STRUCT (
8874 @c OBSOLETE CASE bs OF
8875 @c OBSOLETE (karli):
8881 @c OBSOLETE @end smallexample
8882 @c OBSOLETE @end table
8884 @c OBSOLETE @node Locations
8885 @c OBSOLETE @subsubsection Locations and their accesses
8887 @c OBSOLETE A location in Chill is an object which can contain values.
8889 @c OBSOLETE A value of a location is generally accessed by the (declared) name of
8890 @c OBSOLETE the location. The output conforms to the specification of values in
8891 @c OBSOLETE Chill programs. How values are specified
8892 @c OBSOLETE is the topic of the next section, @ref{Values and their Operations}.
8894 @c OBSOLETE The pseudo-location @code{RESULT} (or @code{result}) can be used to
8895 @c OBSOLETE display or change the result of a currently-active procedure:
8897 @c OBSOLETE @smallexample
8898 @c OBSOLETE set result := EXPR
8899 @c OBSOLETE @end smallexample
8901 @c OBSOLETE @noindent
8902 @c OBSOLETE This does the same as the Chill action @code{RESULT EXPR} (which
8903 @c OBSOLETE is not available in @value{GDBN}).
8905 @c OBSOLETE Values of reference mode locations are printed by @code{PTR(<hex
8906 @c OBSOLETE value>)} in case of a free reference mode, and by @code{(REF <reference
8907 @c OBSOLETE mode>) (<hex-value>)} in case of a bound reference. @code{<hex value>}
8908 @c OBSOLETE represents the address where the reference points to. To access the
8909 @c OBSOLETE value of the location referenced by the pointer, use the dereference
8910 @c OBSOLETE operator @samp{->}.
8912 @c OBSOLETE Values of procedure mode locations are displayed by
8913 @c OBSOLETE @smallexample
8914 @c OBSOLETE @code{@{ PROC
8915 @c OBSOLETE (<argument modes> ) <return mode> @} <address> <name of procedure
8916 @c OBSOLETE location>}
8917 @c OBSOLETE @end smallexample
8918 @c OBSOLETE @code{<argument modes>} is a list of modes according to the parameter
8919 @c OBSOLETE specification of the procedure and @code{<address>} shows the address of
8920 @c OBSOLETE the entry point.
8923 @c OBSOLETE Locations of instance modes are displayed just like a structure with two
8924 @c OBSOLETE fields specifying the @emph{process type} and the @emph{copy number} of
8925 @c OBSOLETE the investigated instance location@footnote{This comes from the current
8926 @c OBSOLETE implementation of instances. They are implemented as a structure (no
8927 @c OBSOLETE na). The output should be something like @code{[<name of the process>;
8928 @c OBSOLETE <instance number>]}.}. The field names are @code{__proc_type} and
8929 @c OBSOLETE @code{__proc_copy}.
8931 @c OBSOLETE Locations of synchronization modes are displayed like a structure with
8932 @c OBSOLETE the field name @code{__event_data} in case of a event mode location, and
8933 @c OBSOLETE like a structure with the field @code{__buffer_data} in case of a buffer
8934 @c OBSOLETE mode location (refer to previous paragraph).
8936 @c OBSOLETE Structure Mode locations are printed by @code{[.<field name>: <value>,
8937 @c OBSOLETE ...]}. The @code{<field name>} corresponds to the structure mode
8938 @c OBSOLETE definition and the layout of @code{<value>} varies depending of the mode
8939 @c OBSOLETE of the field. If the investigated structure mode location is of variant
8940 @c OBSOLETE structure mode, the variant parts of the structure are enclosed in curled
8941 @c OBSOLETE braces (@samp{@{@}}). Fields enclosed by @samp{@{,@}} are residing
8942 @c OBSOLETE on the same memory location and represent the current values of the
8943 @c OBSOLETE memory location in their specific modes. Since no tag processing is done
8944 @c OBSOLETE all variants are displayed. A variant field is printed by
8945 @c OBSOLETE @code{(<variant name>) = .<field name>: <value>}. (who implements the
8946 @c OBSOLETE stuff ???)
8947 @c OBSOLETE @smallexample
8948 @c OBSOLETE (@value{GDBP}) print str1 $4 = [.as: 0, .bs: karli, .<TAG>: { (karli) =
8949 @c OBSOLETE [.cs: []], (susi) = [.ds: susi]}]
8950 @c OBSOLETE @end smallexample
8951 @c OBSOLETE @end ignore
8953 @c OBSOLETE Substructures of string mode-, array mode- or structure mode-values
8954 @c OBSOLETE (e.g. array slices, fields of structure locations) are accessed using
8955 @c OBSOLETE certain operations which are described in the next section, @ref{Values
8956 @c OBSOLETE and their Operations}.
8958 @c OBSOLETE A location value may be interpreted as having a different mode using the
8959 @c OBSOLETE location conversion. This mode conversion is written as @code{<mode
8960 @c OBSOLETE name>(<location>)}. The user has to consider that the sizes of the modes
8961 @c OBSOLETE have to be equal otherwise an error occurs. Furthermore, no range
8962 @c OBSOLETE checking of the location against the destination mode is performed, and
8963 @c OBSOLETE therefore the result can be quite confusing.
8965 @c OBSOLETE @smallexample
8966 @c OBSOLETE (@value{GDBP}) print int (s(3 up 4)) XXX TO be filled in !! XXX
8967 @c OBSOLETE @end smallexample
8969 @c OBSOLETE @node Values and their Operations
8970 @c OBSOLETE @subsubsection Values and their Operations
8972 @c OBSOLETE Values are used to alter locations, to investigate complex structures in
8973 @c OBSOLETE more detail or to filter relevant information out of a large amount of
8974 @c OBSOLETE data. There are several (mode dependent) operations defined which enable
8975 @c OBSOLETE such investigations. These operations are not only applicable to
8976 @c OBSOLETE constant values but also to locations, which can become quite useful
8977 @c OBSOLETE when debugging complex structures. During parsing the command line
8978 @c OBSOLETE (e.g. evaluating an expression) @value{GDBN} treats location names as
8979 @c OBSOLETE the values behind these locations.
8981 @c OBSOLETE This section describes how values have to be specified and which
8982 @c OBSOLETE operations are legal to be used with such values.
8984 @c OBSOLETE @table @code
8985 @c OBSOLETE @item Literal Values
8986 @c OBSOLETE Literal values are specified in the same manner as in @sc{gnu} Chill programs.
8987 @c OBSOLETE For detailed specification refer to the @sc{gnu} Chill implementation Manual
8988 @c OBSOLETE chapter 1.5.
8989 @c OBSOLETE @c FIXME: if the Chill Manual is a Texinfo documents, the above should
8990 @c OBSOLETE @c be converted to a @ref.
8993 @c OBSOLETE @itemize @bullet
8995 @c OBSOLETE @emph{Integer Literals} are specified in the same manner as in Chill
8996 @c OBSOLETE programs (refer to the Chill Standard z200/88 chpt 5.2.4.2)
8998 @c OBSOLETE @emph{Boolean Literals} are defined by @code{TRUE} and @code{FALSE}.
9000 @c OBSOLETE @emph{Character Literals} are defined by @code{'<character>'}. (e.g.
9001 @c OBSOLETE @code{'M'})
9003 @c OBSOLETE @emph{Set Literals} are defined by a name which was specified in a set
9004 @c OBSOLETE mode. The value delivered by a Set Literal is the set value. This is
9005 @c OBSOLETE comparable to an enumeration in C/C@t{++} language.
9007 @c OBSOLETE @emph{Emptiness Literal} is predefined by @code{NULL}. The value of the
9008 @c OBSOLETE emptiness literal delivers either the empty reference value, the empty
9009 @c OBSOLETE procedure value or the empty instance value.
9012 @c OBSOLETE @emph{Character String Literals} are defined by a sequence of characters
9013 @c OBSOLETE enclosed in single- or double quotes. If a single- or double quote has
9014 @c OBSOLETE to be part of the string literal it has to be stuffed (specified twice).
9016 @c OBSOLETE @emph{Bitstring Literals} are specified in the same manner as in Chill
9017 @c OBSOLETE programs (refer z200/88 chpt 5.2.4.8).
9019 @c OBSOLETE @emph{Floating point literals} are specified in the same manner as in
9020 @c OBSOLETE (gnu-)Chill programs (refer @sc{gnu} Chill implementation Manual chapter 1.5).
9021 @c OBSOLETE @end itemize
9022 @c OBSOLETE @end ignore
9024 @c OBSOLETE @item Tuple Values
9025 @c OBSOLETE A tuple is specified by @code{<mode name>[<tuple>]}, where @code{<mode
9026 @c OBSOLETE name>} can be omitted if the mode of the tuple is unambiguous. This
9027 @c OBSOLETE unambiguity is derived from the context of a evaluated expression.
9028 @c OBSOLETE @code{<tuple>} can be one of the following:
9030 @c OBSOLETE @itemize @bullet
9031 @c OBSOLETE @item @emph{Powerset Tuple}
9032 @c OBSOLETE @item @emph{Array Tuple}
9033 @c OBSOLETE @item @emph{Structure Tuple}
9034 @c OBSOLETE Powerset tuples, array tuples and structure tuples are specified in the
9035 @c OBSOLETE same manner as in Chill programs refer to z200/88 chpt 5.2.5.
9036 @c OBSOLETE @end itemize
9038 @c OBSOLETE @item String Element Value
9039 @c OBSOLETE A string element value is specified by
9040 @c OBSOLETE @smallexample
9041 @c OBSOLETE @code{<string value>(<index>)}
9042 @c OBSOLETE @end smallexample
9043 @c OBSOLETE where @code{<index>} is a integer expression. It delivers a character
9044 @c OBSOLETE value which is equivalent to the character indexed by @code{<index>} in
9045 @c OBSOLETE the string.
9047 @c OBSOLETE @item String Slice Value
9048 @c OBSOLETE A string slice value is specified by @code{<string value>(<slice
9049 @c OBSOLETE spec>)}, where @code{<slice spec>} can be either a range of integer
9050 @c OBSOLETE expressions or specified by @code{<start expr> up <size>}.
9051 @c OBSOLETE @code{<size>} denotes the number of elements which the slice contains.
9052 @c OBSOLETE The delivered value is a string value, which is part of the specified
9055 @c OBSOLETE @item Array Element Values
9056 @c OBSOLETE An array element value is specified by @code{<array value>(<expr>)} and
9057 @c OBSOLETE delivers a array element value of the mode of the specified array.
9059 @c OBSOLETE @item Array Slice Values
9060 @c OBSOLETE An array slice is specified by @code{<array value>(<slice spec>)}, where
9061 @c OBSOLETE @code{<slice spec>} can be either a range specified by expressions or by
9062 @c OBSOLETE @code{<start expr> up <size>}. @code{<size>} denotes the number of
9063 @c OBSOLETE arrayelements the slice contains. The delivered value is an array value
9064 @c OBSOLETE which is part of the specified array.
9066 @c OBSOLETE @item Structure Field Values
9067 @c OBSOLETE A structure field value is derived by @code{<structure value>.<field
9068 @c OBSOLETE name>}, where @code{<field name>} indicates the name of a field specified
9069 @c OBSOLETE in the mode definition of the structure. The mode of the delivered value
9070 @c OBSOLETE corresponds to this mode definition in the structure definition.
9072 @c OBSOLETE @item Procedure Call Value
9073 @c OBSOLETE The procedure call value is derived from the return value of the
9074 @c OBSOLETE procedure@footnote{If a procedure call is used for instance in an
9075 @c OBSOLETE expression, then this procedure is called with all its side
9076 @c OBSOLETE effects. This can lead to confusing results if used carelessly.}.
9078 @c OBSOLETE Values of duration mode locations are represented by @code{ULONG} literals.
9080 @c OBSOLETE Values of time mode locations appear as
9081 @c OBSOLETE @smallexample
9082 @c OBSOLETE @code{TIME(<secs>:<nsecs>)}
9083 @c OBSOLETE @end smallexample
9087 @c OBSOLETE This is not implemented yet:
9088 @c OBSOLETE @item Built-in Value
9089 @c OBSOLETE @noindent
9090 @c OBSOLETE The following built in functions are provided:
9092 @c OBSOLETE @table @code
9093 @c OBSOLETE @item @code{ADDR()}
9094 @c OBSOLETE @item @code{NUM()}
9095 @c OBSOLETE @item @code{PRED()}
9096 @c OBSOLETE @item @code{SUCC()}
9097 @c OBSOLETE @item @code{ABS()}
9098 @c OBSOLETE @item @code{CARD()}
9099 @c OBSOLETE @item @code{MAX()}
9100 @c OBSOLETE @item @code{MIN()}
9101 @c OBSOLETE @item @code{SIZE()}
9102 @c OBSOLETE @item @code{UPPER()}
9103 @c OBSOLETE @item @code{LOWER()}
9104 @c OBSOLETE @item @code{LENGTH()}
9105 @c OBSOLETE @item @code{SIN()}
9106 @c OBSOLETE @item @code{COS()}
9107 @c OBSOLETE @item @code{TAN()}
9108 @c OBSOLETE @item @code{ARCSIN()}
9109 @c OBSOLETE @item @code{ARCCOS()}
9110 @c OBSOLETE @item @code{ARCTAN()}
9111 @c OBSOLETE @item @code{EXP()}
9112 @c OBSOLETE @item @code{LN()}
9113 @c OBSOLETE @item @code{LOG()}
9114 @c OBSOLETE @item @code{SQRT()}
9115 @c OBSOLETE @end table
9117 @c OBSOLETE For a detailed description refer to the GNU Chill implementation manual
9118 @c OBSOLETE chapter 1.6.
9119 @c OBSOLETE @end ignore
9121 @c OBSOLETE @item Zero-adic Operator Value
9122 @c OBSOLETE The zero-adic operator value is derived from the instance value for the
9123 @c OBSOLETE current active process.
9125 @c OBSOLETE @item Expression Values
9126 @c OBSOLETE The value delivered by an expression is the result of the evaluation of
9127 @c OBSOLETE the specified expression. If there are error conditions (mode
9128 @c OBSOLETE incompatibility, etc.) the evaluation of expressions is aborted with a
9129 @c OBSOLETE corresponding error message. Expressions may be parenthesised which
9130 @c OBSOLETE causes the evaluation of this expression before any other expression
9131 @c OBSOLETE which uses the result of the parenthesised expression. The following
9132 @c OBSOLETE operators are supported by @value{GDBN}:
9134 @c OBSOLETE @table @code
9135 @c OBSOLETE @item @code{OR, ORIF, XOR}
9136 @c OBSOLETE @itemx @code{AND, ANDIF}
9137 @c OBSOLETE @itemx @code{NOT}
9138 @c OBSOLETE Logical operators defined over operands of boolean mode.
9140 @c OBSOLETE @item @code{=, /=}
9141 @c OBSOLETE Equality and inequality operators defined over all modes.
9143 @c OBSOLETE @item @code{>, >=}
9144 @c OBSOLETE @itemx @code{<, <=}
9145 @c OBSOLETE Relational operators defined over predefined modes.
9147 @c OBSOLETE @item @code{+, -}
9148 @c OBSOLETE @itemx @code{*, /, MOD, REM}
9149 @c OBSOLETE Arithmetic operators defined over predefined modes.
9151 @c OBSOLETE @item @code{-}
9152 @c OBSOLETE Change sign operator.
9154 @c OBSOLETE @item @code{//}
9155 @c OBSOLETE String concatenation operator.
9157 @c OBSOLETE @item @code{()}
9158 @c OBSOLETE String repetition operator.
9160 @c OBSOLETE @item @code{->}
9161 @c OBSOLETE Referenced location operator which can be used either to take the
9162 @c OBSOLETE address of a location (@code{->loc}), or to dereference a reference
9163 @c OBSOLETE location (@code{loc->}).
9165 @c OBSOLETE @item @code{OR, XOR}
9166 @c OBSOLETE @itemx @code{AND}
9167 @c OBSOLETE @itemx @code{NOT}
9168 @c OBSOLETE Powerset and bitstring operators.
9170 @c OBSOLETE @item @code{>, >=}
9171 @c OBSOLETE @itemx @code{<, <=}
9172 @c OBSOLETE Powerset inclusion operators.
9174 @c OBSOLETE @item @code{IN}
9175 @c OBSOLETE Membership operator.
9176 @c OBSOLETE @end table
9177 @c OBSOLETE @end table
9179 @c OBSOLETE @node Chill type and range checks
9180 @c OBSOLETE @subsubsection Chill type and range checks
9182 @c OBSOLETE @value{GDBN} considers two Chill variables mode equivalent if the sizes
9183 @c OBSOLETE of the two modes are equal. This rule applies recursively to more
9184 @c OBSOLETE complex datatypes which means that complex modes are treated
9185 @c OBSOLETE equivalent if all element modes (which also can be complex modes like
9186 @c OBSOLETE structures, arrays, etc.) have the same size.
9188 @c OBSOLETE Range checking is done on all mathematical operations, assignment, array
9189 @c OBSOLETE index bounds and all built in procedures.
9191 @c OBSOLETE Strong type checks are forced using the @value{GDBN} command @code{set
9192 @c OBSOLETE check strong}. This enforces strong type and range checks on all
9193 @c OBSOLETE operations where Chill constructs are used (expressions, built in
9194 @c OBSOLETE functions, etc.) in respect to the semantics as defined in the z.200
9195 @c OBSOLETE language specification.
9197 @c OBSOLETE All checks can be disabled by the @value{GDBN} command @code{set check
9201 @c OBSOLETE @c Deviations from the Chill Standard Z200/88
9202 @c OBSOLETE see last paragraph ?
9203 @c OBSOLETE @end ignore
9205 @c OBSOLETE @node Chill defaults
9206 @c OBSOLETE @subsubsection Chill defaults
9208 @c OBSOLETE If type and range checking are set automatically by @value{GDBN}, they
9209 @c OBSOLETE both default to @code{on} whenever the working language changes to
9210 @c OBSOLETE Chill. This happens regardless of whether you or @value{GDBN}
9211 @c OBSOLETE selected the working language.
9213 @c OBSOLETE If you allow @value{GDBN} to set the language automatically, then entering
9214 @c OBSOLETE code compiled from a file whose name ends with @file{.ch} sets the
9215 @c OBSOLETE working language to Chill. @xref{Automatically, ,Having @value{GDBN} set
9216 @c OBSOLETE the language automatically}, for further details.
9219 @chapter Examining the Symbol Table
9221 The commands described in this chapter allow you to inquire about the
9222 symbols (names of variables, functions and types) defined in your
9223 program. This information is inherent in the text of your program and
9224 does not change as your program executes. @value{GDBN} finds it in your
9225 program's symbol table, in the file indicated when you started @value{GDBN}
9226 (@pxref{File Options, ,Choosing files}), or by one of the
9227 file-management commands (@pxref{Files, ,Commands to specify files}).
9229 @cindex symbol names
9230 @cindex names of symbols
9231 @cindex quoting names
9232 Occasionally, you may need to refer to symbols that contain unusual
9233 characters, which @value{GDBN} ordinarily treats as word delimiters. The
9234 most frequent case is in referring to static variables in other
9235 source files (@pxref{Variables,,Program variables}). File names
9236 are recorded in object files as debugging symbols, but @value{GDBN} would
9237 ordinarily parse a typical file name, like @file{foo.c}, as the three words
9238 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
9239 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
9246 looks up the value of @code{x} in the scope of the file @file{foo.c}.
9249 @kindex info address
9250 @cindex address of a symbol
9251 @item info address @var{symbol}
9252 Describe where the data for @var{symbol} is stored. For a register
9253 variable, this says which register it is kept in. For a non-register
9254 local variable, this prints the stack-frame offset at which the variable
9257 Note the contrast with @samp{print &@var{symbol}}, which does not work
9258 at all for a register variable, and for a stack local variable prints
9259 the exact address of the current instantiation of the variable.
9262 @cindex symbol from address
9263 @item info symbol @var{addr}
9264 Print the name of a symbol which is stored at the address @var{addr}.
9265 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
9266 nearest symbol and an offset from it:
9269 (@value{GDBP}) info symbol 0x54320
9270 _initialize_vx + 396 in section .text
9274 This is the opposite of the @code{info address} command. You can use
9275 it to find out the name of a variable or a function given its address.
9278 @item whatis @var{expr}
9279 Print the data type of expression @var{expr}. @var{expr} is not
9280 actually evaluated, and any side-effecting operations (such as
9281 assignments or function calls) inside it do not take place.
9282 @xref{Expressions, ,Expressions}.
9285 Print the data type of @code{$}, the last value in the value history.
9288 @item ptype @var{typename}
9289 Print a description of data type @var{typename}. @var{typename} may be
9290 the name of a type, or for C code it may have the form @samp{class
9291 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
9292 @var{union-tag}} or @samp{enum @var{enum-tag}}.
9294 @item ptype @var{expr}
9296 Print a description of the type of expression @var{expr}. @code{ptype}
9297 differs from @code{whatis} by printing a detailed description, instead
9298 of just the name of the type.
9300 For example, for this variable declaration:
9303 struct complex @{double real; double imag;@} v;
9307 the two commands give this output:
9311 (@value{GDBP}) whatis v
9312 type = struct complex
9313 (@value{GDBP}) ptype v
9314 type = struct complex @{
9322 As with @code{whatis}, using @code{ptype} without an argument refers to
9323 the type of @code{$}, the last value in the value history.
9326 @item info types @var{regexp}
9328 Print a brief description of all types whose names match @var{regexp}
9329 (or all types in your program, if you supply no argument). Each
9330 complete typename is matched as though it were a complete line; thus,
9331 @samp{i type value} gives information on all types in your program whose
9332 names include the string @code{value}, but @samp{i type ^value$} gives
9333 information only on types whose complete name is @code{value}.
9335 This command differs from @code{ptype} in two ways: first, like
9336 @code{whatis}, it does not print a detailed description; second, it
9337 lists all source files where a type is defined.
9340 @cindex local variables
9341 @item info scope @var{addr}
9342 List all the variables local to a particular scope. This command
9343 accepts a location---a function name, a source line, or an address
9344 preceded by a @samp{*}, and prints all the variables local to the
9345 scope defined by that location. For example:
9348 (@value{GDBP}) @b{info scope command_line_handler}
9349 Scope for command_line_handler:
9350 Symbol rl is an argument at stack/frame offset 8, length 4.
9351 Symbol linebuffer is in static storage at address 0x150a18, length 4.
9352 Symbol linelength is in static storage at address 0x150a1c, length 4.
9353 Symbol p is a local variable in register $esi, length 4.
9354 Symbol p1 is a local variable in register $ebx, length 4.
9355 Symbol nline is a local variable in register $edx, length 4.
9356 Symbol repeat is a local variable at frame offset -8, length 4.
9360 This command is especially useful for determining what data to collect
9361 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
9366 Show information about the current source file---that is, the source file for
9367 the function containing the current point of execution:
9370 the name of the source file, and the directory containing it,
9372 the directory it was compiled in,
9374 its length, in lines,
9376 which programming language it is written in,
9378 whether the executable includes debugging information for that file, and
9379 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
9381 whether the debugging information includes information about
9382 preprocessor macros.
9386 @kindex info sources
9388 Print the names of all source files in your program for which there is
9389 debugging information, organized into two lists: files whose symbols
9390 have already been read, and files whose symbols will be read when needed.
9392 @kindex info functions
9393 @item info functions
9394 Print the names and data types of all defined functions.
9396 @item info functions @var{regexp}
9397 Print the names and data types of all defined functions
9398 whose names contain a match for regular expression @var{regexp}.
9399 Thus, @samp{info fun step} finds all functions whose names
9400 include @code{step}; @samp{info fun ^step} finds those whose names
9401 start with @code{step}. If a function name contains characters
9402 that conflict with the regular expression language (eg.
9403 @samp{operator*()}), they may be quoted with a backslash.
9405 @kindex info variables
9406 @item info variables
9407 Print the names and data types of all variables that are declared
9408 outside of functions (i.e.@: excluding local variables).
9410 @item info variables @var{regexp}
9411 Print the names and data types of all variables (except for local
9412 variables) whose names contain a match for regular expression
9416 This was never implemented.
9417 @kindex info methods
9419 @itemx info methods @var{regexp}
9420 The @code{info methods} command permits the user to examine all defined
9421 methods within C@t{++} program, or (with the @var{regexp} argument) a
9422 specific set of methods found in the various C@t{++} classes. Many
9423 C@t{++} classes provide a large number of methods. Thus, the output
9424 from the @code{ptype} command can be overwhelming and hard to use. The
9425 @code{info-methods} command filters the methods, printing only those
9426 which match the regular-expression @var{regexp}.
9429 @cindex reloading symbols
9430 Some systems allow individual object files that make up your program to
9431 be replaced without stopping and restarting your program. For example,
9432 in VxWorks you can simply recompile a defective object file and keep on
9433 running. If you are running on one of these systems, you can allow
9434 @value{GDBN} to reload the symbols for automatically relinked modules:
9437 @kindex set symbol-reloading
9438 @item set symbol-reloading on
9439 Replace symbol definitions for the corresponding source file when an
9440 object file with a particular name is seen again.
9442 @item set symbol-reloading off
9443 Do not replace symbol definitions when encountering object files of the
9444 same name more than once. This is the default state; if you are not
9445 running on a system that permits automatic relinking of modules, you
9446 should leave @code{symbol-reloading} off, since otherwise @value{GDBN}
9447 may discard symbols when linking large programs, that may contain
9448 several modules (from different directories or libraries) with the same
9451 @kindex show symbol-reloading
9452 @item show symbol-reloading
9453 Show the current @code{on} or @code{off} setting.
9456 @kindex set opaque-type-resolution
9457 @item set opaque-type-resolution on
9458 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
9459 declared as a pointer to a @code{struct}, @code{class}, or
9460 @code{union}---for example, @code{struct MyType *}---that is used in one
9461 source file although the full declaration of @code{struct MyType} is in
9462 another source file. The default is on.
9464 A change in the setting of this subcommand will not take effect until
9465 the next time symbols for a file are loaded.
9467 @item set opaque-type-resolution off
9468 Tell @value{GDBN} not to resolve opaque types. In this case, the type
9469 is printed as follows:
9471 @{<no data fields>@}
9474 @kindex show opaque-type-resolution
9475 @item show opaque-type-resolution
9476 Show whether opaque types are resolved or not.
9478 @kindex maint print symbols
9480 @kindex maint print psymbols
9481 @cindex partial symbol dump
9482 @item maint print symbols @var{filename}
9483 @itemx maint print psymbols @var{filename}
9484 @itemx maint print msymbols @var{filename}
9485 Write a dump of debugging symbol data into the file @var{filename}.
9486 These commands are used to debug the @value{GDBN} symbol-reading code. Only
9487 symbols with debugging data are included. If you use @samp{maint print
9488 symbols}, @value{GDBN} includes all the symbols for which it has already
9489 collected full details: that is, @var{filename} reflects symbols for
9490 only those files whose symbols @value{GDBN} has read. You can use the
9491 command @code{info sources} to find out which files these are. If you
9492 use @samp{maint print psymbols} instead, the dump shows information about
9493 symbols that @value{GDBN} only knows partially---that is, symbols defined in
9494 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
9495 @samp{maint print msymbols} dumps just the minimal symbol information
9496 required for each object file from which @value{GDBN} has read some symbols.
9497 @xref{Files, ,Commands to specify files}, for a discussion of how
9498 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
9502 @chapter Altering Execution
9504 Once you think you have found an error in your program, you might want to
9505 find out for certain whether correcting the apparent error would lead to
9506 correct results in the rest of the run. You can find the answer by
9507 experiment, using the @value{GDBN} features for altering execution of the
9510 For example, you can store new values into variables or memory
9511 locations, give your program a signal, restart it at a different
9512 address, or even return prematurely from a function.
9515 * Assignment:: Assignment to variables
9516 * Jumping:: Continuing at a different address
9517 * Signaling:: Giving your program a signal
9518 * Returning:: Returning from a function
9519 * Calling:: Calling your program's functions
9520 * Patching:: Patching your program
9524 @section Assignment to variables
9527 @cindex setting variables
9528 To alter the value of a variable, evaluate an assignment expression.
9529 @xref{Expressions, ,Expressions}. For example,
9536 stores the value 4 into the variable @code{x}, and then prints the
9537 value of the assignment expression (which is 4).
9538 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
9539 information on operators in supported languages.
9541 @kindex set variable
9542 @cindex variables, setting
9543 If you are not interested in seeing the value of the assignment, use the
9544 @code{set} command instead of the @code{print} command. @code{set} is
9545 really the same as @code{print} except that the expression's value is
9546 not printed and is not put in the value history (@pxref{Value History,
9547 ,Value history}). The expression is evaluated only for its effects.
9549 If the beginning of the argument string of the @code{set} command
9550 appears identical to a @code{set} subcommand, use the @code{set
9551 variable} command instead of just @code{set}. This command is identical
9552 to @code{set} except for its lack of subcommands. For example, if your
9553 program has a variable @code{width}, you get an error if you try to set
9554 a new value with just @samp{set width=13}, because @value{GDBN} has the
9555 command @code{set width}:
9558 (@value{GDBP}) whatis width
9560 (@value{GDBP}) p width
9562 (@value{GDBP}) set width=47
9563 Invalid syntax in expression.
9567 The invalid expression, of course, is @samp{=47}. In
9568 order to actually set the program's variable @code{width}, use
9571 (@value{GDBP}) set var width=47
9574 Because the @code{set} command has many subcommands that can conflict
9575 with the names of program variables, it is a good idea to use the
9576 @code{set variable} command instead of just @code{set}. For example, if
9577 your program has a variable @code{g}, you run into problems if you try
9578 to set a new value with just @samp{set g=4}, because @value{GDBN} has
9579 the command @code{set gnutarget}, abbreviated @code{set g}:
9583 (@value{GDBP}) whatis g
9587 (@value{GDBP}) set g=4
9591 The program being debugged has been started already.
9592 Start it from the beginning? (y or n) y
9593 Starting program: /home/smith/cc_progs/a.out
9594 "/home/smith/cc_progs/a.out": can't open to read symbols:
9596 (@value{GDBP}) show g
9597 The current BFD target is "=4".
9602 The program variable @code{g} did not change, and you silently set the
9603 @code{gnutarget} to an invalid value. In order to set the variable
9607 (@value{GDBP}) set var g=4
9610 @value{GDBN} allows more implicit conversions in assignments than C; you can
9611 freely store an integer value into a pointer variable or vice versa,
9612 and you can convert any structure to any other structure that is the
9613 same length or shorter.
9614 @comment FIXME: how do structs align/pad in these conversions?
9615 @comment /doc@cygnus.com 18dec1990
9617 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
9618 construct to generate a value of specified type at a specified address
9619 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
9620 to memory location @code{0x83040} as an integer (which implies a certain size
9621 and representation in memory), and
9624 set @{int@}0x83040 = 4
9628 stores the value 4 into that memory location.
9631 @section Continuing at a different address
9633 Ordinarily, when you continue your program, you do so at the place where
9634 it stopped, with the @code{continue} command. You can instead continue at
9635 an address of your own choosing, with the following commands:
9639 @item jump @var{linespec}
9640 Resume execution at line @var{linespec}. Execution stops again
9641 immediately if there is a breakpoint there. @xref{List, ,Printing
9642 source lines}, for a description of the different forms of
9643 @var{linespec}. It is common practice to use the @code{tbreak} command
9644 in conjunction with @code{jump}. @xref{Set Breaks, ,Setting
9647 The @code{jump} command does not change the current stack frame, or
9648 the stack pointer, or the contents of any memory location or any
9649 register other than the program counter. If line @var{linespec} is in
9650 a different function from the one currently executing, the results may
9651 be bizarre if the two functions expect different patterns of arguments or
9652 of local variables. For this reason, the @code{jump} command requests
9653 confirmation if the specified line is not in the function currently
9654 executing. However, even bizarre results are predictable if you are
9655 well acquainted with the machine-language code of your program.
9657 @item jump *@var{address}
9658 Resume execution at the instruction at address @var{address}.
9661 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
9662 On many systems, you can get much the same effect as the @code{jump}
9663 command by storing a new value into the register @code{$pc}. The
9664 difference is that this does not start your program running; it only
9665 changes the address of where it @emph{will} run when you continue. For
9673 makes the next @code{continue} command or stepping command execute at
9674 address @code{0x485}, rather than at the address where your program stopped.
9675 @xref{Continuing and Stepping, ,Continuing and stepping}.
9677 The most common occasion to use the @code{jump} command is to back
9678 up---perhaps with more breakpoints set---over a portion of a program
9679 that has already executed, in order to examine its execution in more
9684 @section Giving your program a signal
9688 @item signal @var{signal}
9689 Resume execution where your program stopped, but immediately give it the
9690 signal @var{signal}. @var{signal} can be the name or the number of a
9691 signal. For example, on many systems @code{signal 2} and @code{signal
9692 SIGINT} are both ways of sending an interrupt signal.
9694 Alternatively, if @var{signal} is zero, continue execution without
9695 giving a signal. This is useful when your program stopped on account of
9696 a signal and would ordinary see the signal when resumed with the
9697 @code{continue} command; @samp{signal 0} causes it to resume without a
9700 @code{signal} does not repeat when you press @key{RET} a second time
9701 after executing the command.
9705 Invoking the @code{signal} command is not the same as invoking the
9706 @code{kill} utility from the shell. Sending a signal with @code{kill}
9707 causes @value{GDBN} to decide what to do with the signal depending on
9708 the signal handling tables (@pxref{Signals}). The @code{signal} command
9709 passes the signal directly to your program.
9713 @section Returning from a function
9716 @cindex returning from a function
9719 @itemx return @var{expression}
9720 You can cancel execution of a function call with the @code{return}
9721 command. If you give an
9722 @var{expression} argument, its value is used as the function's return
9726 When you use @code{return}, @value{GDBN} discards the selected stack frame
9727 (and all frames within it). You can think of this as making the
9728 discarded frame return prematurely. If you wish to specify a value to
9729 be returned, give that value as the argument to @code{return}.
9731 This pops the selected stack frame (@pxref{Selection, ,Selecting a
9732 frame}), and any other frames inside of it, leaving its caller as the
9733 innermost remaining frame. That frame becomes selected. The
9734 specified value is stored in the registers used for returning values
9737 The @code{return} command does not resume execution; it leaves the
9738 program stopped in the state that would exist if the function had just
9739 returned. In contrast, the @code{finish} command (@pxref{Continuing
9740 and Stepping, ,Continuing and stepping}) resumes execution until the
9741 selected stack frame returns naturally.
9744 @section Calling program functions
9746 @cindex calling functions
9749 @item call @var{expr}
9750 Evaluate the expression @var{expr} without displaying @code{void}
9754 You can use this variant of the @code{print} command if you want to
9755 execute a function from your program, but without cluttering the output
9756 with @code{void} returned values. If the result is not void, it
9757 is printed and saved in the value history.
9760 @section Patching programs
9762 @cindex patching binaries
9763 @cindex writing into executables
9764 @cindex writing into corefiles
9766 By default, @value{GDBN} opens the file containing your program's
9767 executable code (or the corefile) read-only. This prevents accidental
9768 alterations to machine code; but it also prevents you from intentionally
9769 patching your program's binary.
9771 If you'd like to be able to patch the binary, you can specify that
9772 explicitly with the @code{set write} command. For example, you might
9773 want to turn on internal debugging flags, or even to make emergency
9779 @itemx set write off
9780 If you specify @samp{set write on}, @value{GDBN} opens executable and
9781 core files for both reading and writing; if you specify @samp{set write
9782 off} (the default), @value{GDBN} opens them read-only.
9784 If you have already loaded a file, you must load it again (using the
9785 @code{exec-file} or @code{core-file} command) after changing @code{set
9786 write}, for your new setting to take effect.
9790 Display whether executable files and core files are opened for writing
9795 @chapter @value{GDBN} Files
9797 @value{GDBN} needs to know the file name of the program to be debugged,
9798 both in order to read its symbol table and in order to start your
9799 program. To debug a core dump of a previous run, you must also tell
9800 @value{GDBN} the name of the core dump file.
9803 * Files:: Commands to specify files
9804 * Symbol Errors:: Errors reading symbol files
9808 @section Commands to specify files
9810 @cindex symbol table
9811 @cindex core dump file
9813 You may want to specify executable and core dump file names. The usual
9814 way to do this is at start-up time, using the arguments to
9815 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
9816 Out of @value{GDBN}}).
9818 Occasionally it is necessary to change to a different file during a
9819 @value{GDBN} session. Or you may run @value{GDBN} and forget to specify
9820 a file you want to use. In these situations the @value{GDBN} commands
9821 to specify new files are useful.
9824 @cindex executable file
9826 @item file @var{filename}
9827 Use @var{filename} as the program to be debugged. It is read for its
9828 symbols and for the contents of pure memory. It is also the program
9829 executed when you use the @code{run} command. If you do not specify a
9830 directory and the file is not found in the @value{GDBN} working directory,
9831 @value{GDBN} uses the environment variable @code{PATH} as a list of
9832 directories to search, just as the shell does when looking for a program
9833 to run. You can change the value of this variable, for both @value{GDBN}
9834 and your program, using the @code{path} command.
9836 On systems with memory-mapped files, an auxiliary file named
9837 @file{@var{filename}.syms} may hold symbol table information for
9838 @var{filename}. If so, @value{GDBN} maps in the symbol table from
9839 @file{@var{filename}.syms}, starting up more quickly. See the
9840 descriptions of the file options @samp{-mapped} and @samp{-readnow}
9841 (available on the command line, and with the commands @code{file},
9842 @code{symbol-file}, or @code{add-symbol-file}, described below),
9843 for more information.
9846 @code{file} with no argument makes @value{GDBN} discard any information it
9847 has on both executable file and the symbol table.
9850 @item exec-file @r{[} @var{filename} @r{]}
9851 Specify that the program to be run (but not the symbol table) is found
9852 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
9853 if necessary to locate your program. Omitting @var{filename} means to
9854 discard information on the executable file.
9857 @item symbol-file @r{[} @var{filename} @r{]}
9858 Read symbol table information from file @var{filename}. @code{PATH} is
9859 searched when necessary. Use the @code{file} command to get both symbol
9860 table and program to run from the same file.
9862 @code{symbol-file} with no argument clears out @value{GDBN} information on your
9863 program's symbol table.
9865 The @code{symbol-file} command causes @value{GDBN} to forget the contents
9866 of its convenience variables, the value history, and all breakpoints and
9867 auto-display expressions. This is because they may contain pointers to
9868 the internal data recording symbols and data types, which are part of
9869 the old symbol table data being discarded inside @value{GDBN}.
9871 @code{symbol-file} does not repeat if you press @key{RET} again after
9874 When @value{GDBN} is configured for a particular environment, it
9875 understands debugging information in whatever format is the standard
9876 generated for that environment; you may use either a @sc{gnu} compiler, or
9877 other compilers that adhere to the local conventions.
9878 Best results are usually obtained from @sc{gnu} compilers; for example,
9879 using @code{@value{GCC}} you can generate debugging information for
9882 For most kinds of object files, with the exception of old SVR3 systems
9883 using COFF, the @code{symbol-file} command does not normally read the
9884 symbol table in full right away. Instead, it scans the symbol table
9885 quickly to find which source files and which symbols are present. The
9886 details are read later, one source file at a time, as they are needed.
9888 The purpose of this two-stage reading strategy is to make @value{GDBN}
9889 start up faster. For the most part, it is invisible except for
9890 occasional pauses while the symbol table details for a particular source
9891 file are being read. (The @code{set verbose} command can turn these
9892 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
9893 warnings and messages}.)
9895 We have not implemented the two-stage strategy for COFF yet. When the
9896 symbol table is stored in COFF format, @code{symbol-file} reads the
9897 symbol table data in full right away. Note that ``stabs-in-COFF''
9898 still does the two-stage strategy, since the debug info is actually
9902 @cindex reading symbols immediately
9903 @cindex symbols, reading immediately
9905 @cindex memory-mapped symbol file
9906 @cindex saving symbol table
9907 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9908 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9909 You can override the @value{GDBN} two-stage strategy for reading symbol
9910 tables by using the @samp{-readnow} option with any of the commands that
9911 load symbol table information, if you want to be sure @value{GDBN} has the
9912 entire symbol table available.
9914 If memory-mapped files are available on your system through the
9915 @code{mmap} system call, you can use another option, @samp{-mapped}, to
9916 cause @value{GDBN} to write the symbols for your program into a reusable
9917 file. Future @value{GDBN} debugging sessions map in symbol information
9918 from this auxiliary symbol file (if the program has not changed), rather
9919 than spending time reading the symbol table from the executable
9920 program. Using the @samp{-mapped} option has the same effect as
9921 starting @value{GDBN} with the @samp{-mapped} command-line option.
9923 You can use both options together, to make sure the auxiliary symbol
9924 file has all the symbol information for your program.
9926 The auxiliary symbol file for a program called @var{myprog} is called
9927 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
9928 than the corresponding executable), @value{GDBN} always attempts to use
9929 it when you debug @var{myprog}; no special options or commands are
9932 The @file{.syms} file is specific to the host machine where you run
9933 @value{GDBN}. It holds an exact image of the internal @value{GDBN}
9934 symbol table. It cannot be shared across multiple host platforms.
9936 @c FIXME: for now no mention of directories, since this seems to be in
9937 @c flux. 13mar1992 status is that in theory GDB would look either in
9938 @c current dir or in same dir as myprog; but issues like competing
9939 @c GDB's, or clutter in system dirs, mean that in practice right now
9940 @c only current dir is used. FFish says maybe a special GDB hierarchy
9941 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
9946 @item core-file @r{[} @var{filename} @r{]}
9947 Specify the whereabouts of a core dump file to be used as the ``contents
9948 of memory''. Traditionally, core files contain only some parts of the
9949 address space of the process that generated them; @value{GDBN} can access the
9950 executable file itself for other parts.
9952 @code{core-file} with no argument specifies that no core file is
9955 Note that the core file is ignored when your program is actually running
9956 under @value{GDBN}. So, if you have been running your program and you
9957 wish to debug a core file instead, you must kill the subprocess in which
9958 the program is running. To do this, use the @code{kill} command
9959 (@pxref{Kill Process, ,Killing the child process}).
9961 @kindex add-symbol-file
9962 @cindex dynamic linking
9963 @item add-symbol-file @var{filename} @var{address}
9964 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
9965 @itemx add-symbol-file @var{filename} @r{-s}@var{section} @var{address} @dots{}
9966 The @code{add-symbol-file} command reads additional symbol table
9967 information from the file @var{filename}. You would use this command
9968 when @var{filename} has been dynamically loaded (by some other means)
9969 into the program that is running. @var{address} should be the memory
9970 address at which the file has been loaded; @value{GDBN} cannot figure
9971 this out for itself. You can additionally specify an arbitrary number
9972 of @samp{@r{-s}@var{section} @var{address}} pairs, to give an explicit
9973 section name and base address for that section. You can specify any
9974 @var{address} as an expression.
9976 The symbol table of the file @var{filename} is added to the symbol table
9977 originally read with the @code{symbol-file} command. You can use the
9978 @code{add-symbol-file} command any number of times; the new symbol data
9979 thus read keeps adding to the old. To discard all old symbol data
9980 instead, use the @code{symbol-file} command without any arguments.
9982 @cindex relocatable object files, reading symbols from
9983 @cindex object files, relocatable, reading symbols from
9984 @cindex reading symbols from relocatable object files
9985 @cindex symbols, reading from relocatable object files
9986 @cindex @file{.o} files, reading symbols from
9987 Although @var{filename} is typically a shared library file, an
9988 executable file, or some other object file which has been fully
9989 relocated for loading into a process, you can also load symbolic
9990 information from relocatable @file{.o} files, as long as:
9994 the file's symbolic information refers only to linker symbols defined in
9995 that file, not to symbols defined by other object files,
9997 every section the file's symbolic information refers to has actually
9998 been loaded into the inferior, as it appears in the file, and
10000 you can determine the address at which every section was loaded, and
10001 provide these to the @code{add-symbol-file} command.
10005 Some embedded operating systems, like Sun Chorus and VxWorks, can load
10006 relocatable files into an already running program; such systems
10007 typically make the requirements above easy to meet. However, it's
10008 important to recognize that many native systems use complex link
10009 procedures (@code{.linkonce} section factoring and C++ constructor table
10010 assembly, for example) that make the requirements difficult to meet. In
10011 general, one cannot assume that using @code{add-symbol-file} to read a
10012 relocatable object file's symbolic information will have the same effect
10013 as linking the relocatable object file into the program in the normal
10016 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
10018 You can use the @samp{-mapped} and @samp{-readnow} options just as with
10019 the @code{symbol-file} command, to change how @value{GDBN} manages the symbol
10020 table information for @var{filename}.
10022 @kindex add-shared-symbol-file
10023 @item add-shared-symbol-file
10024 The @code{add-shared-symbol-file} command can be used only under Harris' CXUX
10025 operating system for the Motorola 88k. @value{GDBN} automatically looks for
10026 shared libraries, however if @value{GDBN} does not find yours, you can run
10027 @code{add-shared-symbol-file}. It takes no arguments.
10031 The @code{section} command changes the base address of section SECTION of
10032 the exec file to ADDR. This can be used if the exec file does not contain
10033 section addresses, (such as in the a.out format), or when the addresses
10034 specified in the file itself are wrong. Each section must be changed
10035 separately. The @code{info files} command, described below, lists all
10036 the sections and their addresses.
10039 @kindex info target
10042 @code{info files} and @code{info target} are synonymous; both print the
10043 current target (@pxref{Targets, ,Specifying a Debugging Target}),
10044 including the names of the executable and core dump files currently in
10045 use by @value{GDBN}, and the files from which symbols were loaded. The
10046 command @code{help target} lists all possible targets rather than
10049 @kindex maint info sections
10050 @item maint info sections
10051 Another command that can give you extra information about program sections
10052 is @code{maint info sections}. In addition to the section information
10053 displayed by @code{info files}, this command displays the flags and file
10054 offset of each section in the executable and core dump files. In addition,
10055 @code{maint info sections} provides the following command options (which
10056 may be arbitrarily combined):
10060 Display sections for all loaded object files, including shared libraries.
10061 @item @var{sections}
10062 Display info only for named @var{sections}.
10063 @item @var{section-flags}
10064 Display info only for sections for which @var{section-flags} are true.
10065 The section flags that @value{GDBN} currently knows about are:
10068 Section will have space allocated in the process when loaded.
10069 Set for all sections except those containing debug information.
10071 Section will be loaded from the file into the child process memory.
10072 Set for pre-initialized code and data, clear for @code{.bss} sections.
10074 Section needs to be relocated before loading.
10076 Section cannot be modified by the child process.
10078 Section contains executable code only.
10080 Section contains data only (no executable code).
10082 Section will reside in ROM.
10084 Section contains data for constructor/destructor lists.
10086 Section is not empty.
10088 An instruction to the linker to not output the section.
10089 @item COFF_SHARED_LIBRARY
10090 A notification to the linker that the section contains
10091 COFF shared library information.
10093 Section contains common symbols.
10096 @kindex set trust-readonly-sections
10097 @item set trust-readonly-sections on
10098 Tell @value{GDBN} that readonly sections in your object file
10099 really are read-only (i.e.@: that their contents will not change).
10100 In that case, @value{GDBN} can fetch values from these sections
10101 out of the object file, rather than from the target program.
10102 For some targets (notably embedded ones), this can be a significant
10103 enhancement to debugging performance.
10105 The default is off.
10107 @item set trust-readonly-sections off
10108 Tell @value{GDBN} not to trust readonly sections. This means that
10109 the contents of the section might change while the program is running,
10110 and must therefore be fetched from the target when needed.
10113 All file-specifying commands allow both absolute and relative file names
10114 as arguments. @value{GDBN} always converts the file name to an absolute file
10115 name and remembers it that way.
10117 @cindex shared libraries
10118 @value{GDBN} supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared
10121 @value{GDBN} automatically loads symbol definitions from shared libraries
10122 when you use the @code{run} command, or when you examine a core file.
10123 (Before you issue the @code{run} command, @value{GDBN} does not understand
10124 references to a function in a shared library, however---unless you are
10125 debugging a core file).
10127 On HP-UX, if the program loads a library explicitly, @value{GDBN}
10128 automatically loads the symbols at the time of the @code{shl_load} call.
10130 @c FIXME: some @value{GDBN} release may permit some refs to undef
10131 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
10132 @c FIXME...lib; check this from time to time when updating manual
10134 There are times, however, when you may wish to not automatically load
10135 symbol definitions from shared libraries, such as when they are
10136 particularly large or there are many of them.
10138 To control the automatic loading of shared library symbols, use the
10142 @kindex set auto-solib-add
10143 @item set auto-solib-add @var{mode}
10144 If @var{mode} is @code{on}, symbols from all shared object libraries
10145 will be loaded automatically when the inferior begins execution, you
10146 attach to an independently started inferior, or when the dynamic linker
10147 informs @value{GDBN} that a new library has been loaded. If @var{mode}
10148 is @code{off}, symbols must be loaded manually, using the
10149 @code{sharedlibrary} command. The default value is @code{on}.
10151 @kindex show auto-solib-add
10152 @item show auto-solib-add
10153 Display the current autoloading mode.
10156 To explicitly load shared library symbols, use the @code{sharedlibrary}
10160 @kindex info sharedlibrary
10163 @itemx info sharedlibrary
10164 Print the names of the shared libraries which are currently loaded.
10166 @kindex sharedlibrary
10168 @item sharedlibrary @var{regex}
10169 @itemx share @var{regex}
10170 Load shared object library symbols for files matching a
10171 Unix regular expression.
10172 As with files loaded automatically, it only loads shared libraries
10173 required by your program for a core file or after typing @code{run}. If
10174 @var{regex} is omitted all shared libraries required by your program are
10178 On some systems, such as HP-UX systems, @value{GDBN} supports
10179 autoloading shared library symbols until a limiting threshold size is
10180 reached. This provides the benefit of allowing autoloading to remain on
10181 by default, but avoids autoloading excessively large shared libraries,
10182 up to a threshold that is initially set, but which you can modify if you
10185 Beyond that threshold, symbols from shared libraries must be explicitly
10186 loaded. To load these symbols, use the command @code{sharedlibrary
10187 @var{filename}}. The base address of the shared library is determined
10188 automatically by @value{GDBN} and need not be specified.
10190 To display or set the threshold, use the commands:
10193 @kindex set auto-solib-limit
10194 @item set auto-solib-limit @var{threshold}
10195 Set the autoloading size threshold, in an integral number of megabytes.
10196 If @var{threshold} is nonzero and shared library autoloading is enabled,
10197 symbols from all shared object libraries will be loaded until the total
10198 size of the loaded shared library symbols exceeds this threshold.
10199 Otherwise, symbols must be loaded manually, using the
10200 @code{sharedlibrary} command. The default threshold is 100 (i.e.@: 100
10203 @kindex show auto-solib-limit
10204 @item show auto-solib-limit
10205 Display the current autoloading size threshold, in megabytes.
10208 @node Symbol Errors
10209 @section Errors reading symbol files
10211 While reading a symbol file, @value{GDBN} occasionally encounters problems,
10212 such as symbol types it does not recognize, or known bugs in compiler
10213 output. By default, @value{GDBN} does not notify you of such problems, since
10214 they are relatively common and primarily of interest to people
10215 debugging compilers. If you are interested in seeing information
10216 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
10217 only one message about each such type of problem, no matter how many
10218 times the problem occurs; or you can ask @value{GDBN} to print more messages,
10219 to see how many times the problems occur, with the @code{set
10220 complaints} command (@pxref{Messages/Warnings, ,Optional warnings and
10223 The messages currently printed, and their meanings, include:
10226 @item inner block not inside outer block in @var{symbol}
10228 The symbol information shows where symbol scopes begin and end
10229 (such as at the start of a function or a block of statements). This
10230 error indicates that an inner scope block is not fully contained
10231 in its outer scope blocks.
10233 @value{GDBN} circumvents the problem by treating the inner block as if it had
10234 the same scope as the outer block. In the error message, @var{symbol}
10235 may be shown as ``@code{(don't know)}'' if the outer block is not a
10238 @item block at @var{address} out of order
10240 The symbol information for symbol scope blocks should occur in
10241 order of increasing addresses. This error indicates that it does not
10244 @value{GDBN} does not circumvent this problem, and has trouble
10245 locating symbols in the source file whose symbols it is reading. (You
10246 can often determine what source file is affected by specifying
10247 @code{set verbose on}. @xref{Messages/Warnings, ,Optional warnings and
10250 @item bad block start address patched
10252 The symbol information for a symbol scope block has a start address
10253 smaller than the address of the preceding source line. This is known
10254 to occur in the SunOS 4.1.1 (and earlier) C compiler.
10256 @value{GDBN} circumvents the problem by treating the symbol scope block as
10257 starting on the previous source line.
10259 @item bad string table offset in symbol @var{n}
10262 Symbol number @var{n} contains a pointer into the string table which is
10263 larger than the size of the string table.
10265 @value{GDBN} circumvents the problem by considering the symbol to have the
10266 name @code{foo}, which may cause other problems if many symbols end up
10269 @item unknown symbol type @code{0x@var{nn}}
10271 The symbol information contains new data types that @value{GDBN} does
10272 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
10273 uncomprehended information, in hexadecimal.
10275 @value{GDBN} circumvents the error by ignoring this symbol information.
10276 This usually allows you to debug your program, though certain symbols
10277 are not accessible. If you encounter such a problem and feel like
10278 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
10279 on @code{complain}, then go up to the function @code{read_dbx_symtab}
10280 and examine @code{*bufp} to see the symbol.
10282 @item stub type has NULL name
10284 @value{GDBN} could not find the full definition for a struct or class.
10286 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
10287 The symbol information for a C@t{++} member function is missing some
10288 information that recent versions of the compiler should have output for
10291 @item info mismatch between compiler and debugger
10293 @value{GDBN} could not parse a type specification output by the compiler.
10298 @chapter Specifying a Debugging Target
10300 @cindex debugging target
10303 A @dfn{target} is the execution environment occupied by your program.
10305 Often, @value{GDBN} runs in the same host environment as your program;
10306 in that case, the debugging target is specified as a side effect when
10307 you use the @code{file} or @code{core} commands. When you need more
10308 flexibility---for example, running @value{GDBN} on a physically separate
10309 host, or controlling a standalone system over a serial port or a
10310 realtime system over a TCP/IP connection---you can use the @code{target}
10311 command to specify one of the target types configured for @value{GDBN}
10312 (@pxref{Target Commands, ,Commands for managing targets}).
10315 * Active Targets:: Active targets
10316 * Target Commands:: Commands for managing targets
10317 * Byte Order:: Choosing target byte order
10318 * Remote:: Remote debugging
10319 * KOD:: Kernel Object Display
10323 @node Active Targets
10324 @section Active targets
10326 @cindex stacking targets
10327 @cindex active targets
10328 @cindex multiple targets
10330 There are three classes of targets: processes, core files, and
10331 executable files. @value{GDBN} can work concurrently on up to three
10332 active targets, one in each class. This allows you to (for example)
10333 start a process and inspect its activity without abandoning your work on
10336 For example, if you execute @samp{gdb a.out}, then the executable file
10337 @code{a.out} is the only active target. If you designate a core file as
10338 well---presumably from a prior run that crashed and coredumped---then
10339 @value{GDBN} has two active targets and uses them in tandem, looking
10340 first in the corefile target, then in the executable file, to satisfy
10341 requests for memory addresses. (Typically, these two classes of target
10342 are complementary, since core files contain only a program's
10343 read-write memory---variables and so on---plus machine status, while
10344 executable files contain only the program text and initialized data.)
10346 When you type @code{run}, your executable file becomes an active process
10347 target as well. When a process target is active, all @value{GDBN}
10348 commands requesting memory addresses refer to that target; addresses in
10349 an active core file or executable file target are obscured while the
10350 process target is active.
10352 Use the @code{core-file} and @code{exec-file} commands to select a new
10353 core file or executable target (@pxref{Files, ,Commands to specify
10354 files}). To specify as a target a process that is already running, use
10355 the @code{attach} command (@pxref{Attach, ,Debugging an already-running
10358 @node Target Commands
10359 @section Commands for managing targets
10362 @item target @var{type} @var{parameters}
10363 Connects the @value{GDBN} host environment to a target machine or
10364 process. A target is typically a protocol for talking to debugging
10365 facilities. You use the argument @var{type} to specify the type or
10366 protocol of the target machine.
10368 Further @var{parameters} are interpreted by the target protocol, but
10369 typically include things like device names or host names to connect
10370 with, process numbers, and baud rates.
10372 The @code{target} command does not repeat if you press @key{RET} again
10373 after executing the command.
10375 @kindex help target
10377 Displays the names of all targets available. To display targets
10378 currently selected, use either @code{info target} or @code{info files}
10379 (@pxref{Files, ,Commands to specify files}).
10381 @item help target @var{name}
10382 Describe a particular target, including any parameters necessary to
10385 @kindex set gnutarget
10386 @item set gnutarget @var{args}
10387 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
10388 knows whether it is reading an @dfn{executable},
10389 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
10390 with the @code{set gnutarget} command. Unlike most @code{target} commands,
10391 with @code{gnutarget} the @code{target} refers to a program, not a machine.
10394 @emph{Warning:} To specify a file format with @code{set gnutarget},
10395 you must know the actual BFD name.
10399 @xref{Files, , Commands to specify files}.
10401 @kindex show gnutarget
10402 @item show gnutarget
10403 Use the @code{show gnutarget} command to display what file format
10404 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
10405 @value{GDBN} will determine the file format for each file automatically,
10406 and @code{show gnutarget} displays @samp{The current BDF target is "auto"}.
10409 Here are some common targets (available, or not, depending on the GDB
10413 @kindex target exec
10414 @item target exec @var{program}
10415 An executable file. @samp{target exec @var{program}} is the same as
10416 @samp{exec-file @var{program}}.
10418 @kindex target core
10419 @item target core @var{filename}
10420 A core dump file. @samp{target core @var{filename}} is the same as
10421 @samp{core-file @var{filename}}.
10423 @kindex target remote
10424 @item target remote @var{dev}
10425 Remote serial target in GDB-specific protocol. The argument @var{dev}
10426 specifies what serial device to use for the connection (e.g.
10427 @file{/dev/ttya}). @xref{Remote, ,Remote debugging}. @code{target remote}
10428 supports the @code{load} command. This is only useful if you have
10429 some other way of getting the stub to the target system, and you can put
10430 it somewhere in memory where it won't get clobbered by the download.
10434 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
10442 works; however, you cannot assume that a specific memory map, device
10443 drivers, or even basic I/O is available, although some simulators do
10444 provide these. For info about any processor-specific simulator details,
10445 see the appropriate section in @ref{Embedded Processors, ,Embedded
10450 Some configurations may include these targets as well:
10454 @kindex target nrom
10455 @item target nrom @var{dev}
10456 NetROM ROM emulator. This target only supports downloading.
10460 Different targets are available on different configurations of @value{GDBN};
10461 your configuration may have more or fewer targets.
10463 Many remote targets require you to download the executable's code
10464 once you've successfully established a connection.
10468 @kindex load @var{filename}
10469 @item load @var{filename}
10470 Depending on what remote debugging facilities are configured into
10471 @value{GDBN}, the @code{load} command may be available. Where it exists, it
10472 is meant to make @var{filename} (an executable) available for debugging
10473 on the remote system---by downloading, or dynamic linking, for example.
10474 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
10475 the @code{add-symbol-file} command.
10477 If your @value{GDBN} does not have a @code{load} command, attempting to
10478 execute it gets the error message ``@code{You can't do that when your
10479 target is @dots{}}''
10481 The file is loaded at whatever address is specified in the executable.
10482 For some object file formats, you can specify the load address when you
10483 link the program; for other formats, like a.out, the object file format
10484 specifies a fixed address.
10485 @c FIXME! This would be a good place for an xref to the GNU linker doc.
10487 @code{load} does not repeat if you press @key{RET} again after using it.
10491 @section Choosing target byte order
10493 @cindex choosing target byte order
10494 @cindex target byte order
10496 Some types of processors, such as the MIPS, PowerPC, and Hitachi SH,
10497 offer the ability to run either big-endian or little-endian byte
10498 orders. Usually the executable or symbol will include a bit to
10499 designate the endian-ness, and you will not need to worry about
10500 which to use. However, you may still find it useful to adjust
10501 @value{GDBN}'s idea of processor endian-ness manually.
10504 @kindex set endian big
10505 @item set endian big
10506 Instruct @value{GDBN} to assume the target is big-endian.
10508 @kindex set endian little
10509 @item set endian little
10510 Instruct @value{GDBN} to assume the target is little-endian.
10512 @kindex set endian auto
10513 @item set endian auto
10514 Instruct @value{GDBN} to use the byte order associated with the
10518 Display @value{GDBN}'s current idea of the target byte order.
10522 Note that these commands merely adjust interpretation of symbolic
10523 data on the host, and that they have absolutely no effect on the
10527 @section Remote debugging
10528 @cindex remote debugging
10530 If you are trying to debug a program running on a machine that cannot run
10531 @value{GDBN} in the usual way, it is often useful to use remote debugging.
10532 For example, you might use remote debugging on an operating system kernel,
10533 or on a small system which does not have a general purpose operating system
10534 powerful enough to run a full-featured debugger.
10536 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
10537 to make this work with particular debugging targets. In addition,
10538 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
10539 but not specific to any particular target system) which you can use if you
10540 write the remote stubs---the code that runs on the remote system to
10541 communicate with @value{GDBN}.
10543 Other remote targets may be available in your
10544 configuration of @value{GDBN}; use @code{help target} to list them.
10547 @section Kernel Object Display
10549 @cindex kernel object display
10550 @cindex kernel object
10553 Some targets support kernel object display. Using this facility,
10554 @value{GDBN} communicates specially with the underlying operating system
10555 and can display information about operating system-level objects such as
10556 mutexes and other synchronization objects. Exactly which objects can be
10557 displayed is determined on a per-OS basis.
10559 Use the @code{set os} command to set the operating system. This tells
10560 @value{GDBN} which kernel object display module to initialize:
10563 (@value{GDBP}) set os cisco
10566 If @code{set os} succeeds, @value{GDBN} will display some information
10567 about the operating system, and will create a new @code{info} command
10568 which can be used to query the target. The @code{info} command is named
10569 after the operating system:
10572 (@value{GDBP}) info cisco
10573 List of Cisco Kernel Objects
10575 any Any and all objects
10578 Further subcommands can be used to query about particular objects known
10581 There is currently no way to determine whether a given operating system
10582 is supported other than to try it.
10585 @node Remote Debugging
10586 @chapter Debugging remote programs
10589 * Server:: Using the gdbserver program
10590 * NetWare:: Using the gdbserve.nlm program
10591 * remote stub:: Implementing a remote stub
10595 @section Using the @code{gdbserver} program
10598 @cindex remote connection without stubs
10599 @code{gdbserver} is a control program for Unix-like systems, which
10600 allows you to connect your program with a remote @value{GDBN} via
10601 @code{target remote}---but without linking in the usual debugging stub.
10603 @code{gdbserver} is not a complete replacement for the debugging stubs,
10604 because it requires essentially the same operating-system facilities
10605 that @value{GDBN} itself does. In fact, a system that can run
10606 @code{gdbserver} to connect to a remote @value{GDBN} could also run
10607 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
10608 because it is a much smaller program than @value{GDBN} itself. It is
10609 also easier to port than all of @value{GDBN}, so you may be able to get
10610 started more quickly on a new system by using @code{gdbserver}.
10611 Finally, if you develop code for real-time systems, you may find that
10612 the tradeoffs involved in real-time operation make it more convenient to
10613 do as much development work as possible on another system, for example
10614 by cross-compiling. You can use @code{gdbserver} to make a similar
10615 choice for debugging.
10617 @value{GDBN} and @code{gdbserver} communicate via either a serial line
10618 or a TCP connection, using the standard @value{GDBN} remote serial
10622 @item On the target machine,
10623 you need to have a copy of the program you want to debug.
10624 @code{gdbserver} does not need your program's symbol table, so you can
10625 strip the program if necessary to save space. @value{GDBN} on the host
10626 system does all the symbol handling.
10628 To use the server, you must tell it how to communicate with @value{GDBN};
10629 the name of your program; and the arguments for your program. The usual
10633 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
10636 @var{comm} is either a device name (to use a serial line) or a TCP
10637 hostname and portnumber. For example, to debug Emacs with the argument
10638 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
10642 target> gdbserver /dev/com1 emacs foo.txt
10645 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
10648 To use a TCP connection instead of a serial line:
10651 target> gdbserver host:2345 emacs foo.txt
10654 The only difference from the previous example is the first argument,
10655 specifying that you are communicating with the host @value{GDBN} via
10656 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
10657 expect a TCP connection from machine @samp{host} to local TCP port 2345.
10658 (Currently, the @samp{host} part is ignored.) You can choose any number
10659 you want for the port number as long as it does not conflict with any
10660 TCP ports already in use on the target system (for example, @code{23} is
10661 reserved for @code{telnet}).@footnote{If you choose a port number that
10662 conflicts with another service, @code{gdbserver} prints an error message
10663 and exits.} You must use the same port number with the host @value{GDBN}
10664 @code{target remote} command.
10666 On some targets, @code{gdbserver} can also attach to running programs.
10667 This is accomplished via the @code{--attach} argument. The syntax is:
10670 target> gdbserver @var{comm} --attach @var{pid}
10673 @var{pid} is the process ID of a currently running process. It isn't necessary
10674 to point @code{gdbserver} at a binary for the running process.
10676 @item On the @value{GDBN} host machine,
10677 you need an unstripped copy of your program, since @value{GDBN} needs
10678 symbols and debugging information. Start up @value{GDBN} as usual,
10679 using the name of the local copy of your program as the first argument.
10680 (You may also need the @w{@samp{--baud}} option if the serial line is
10681 running at anything other than 9600@dmn{bps}.) After that, use @code{target
10682 remote} to establish communications with @code{gdbserver}. Its argument
10683 is either a device name (usually a serial device, like
10684 @file{/dev/ttyb}), or a TCP port descriptor in the form
10685 @code{@var{host}:@var{PORT}}. For example:
10688 (@value{GDBP}) target remote /dev/ttyb
10692 communicates with the server via serial line @file{/dev/ttyb}, and
10695 (@value{GDBP}) target remote the-target:2345
10699 communicates via a TCP connection to port 2345 on host @w{@file{the-target}}.
10700 For TCP connections, you must start up @code{gdbserver} prior to using
10701 the @code{target remote} command. Otherwise you may get an error whose
10702 text depends on the host system, but which usually looks something like
10703 @samp{Connection refused}.
10707 @section Using the @code{gdbserve.nlm} program
10709 @kindex gdbserve.nlm
10710 @code{gdbserve.nlm} is a control program for NetWare systems, which
10711 allows you to connect your program with a remote @value{GDBN} via
10712 @code{target remote}.
10714 @value{GDBN} and @code{gdbserve.nlm} communicate via a serial line,
10715 using the standard @value{GDBN} remote serial protocol.
10718 @item On the target machine,
10719 you need to have a copy of the program you want to debug.
10720 @code{gdbserve.nlm} does not need your program's symbol table, so you
10721 can strip the program if necessary to save space. @value{GDBN} on the
10722 host system does all the symbol handling.
10724 To use the server, you must tell it how to communicate with
10725 @value{GDBN}; the name of your program; and the arguments for your
10726 program. The syntax is:
10729 load gdbserve [ BOARD=@var{board} ] [ PORT=@var{port} ]
10730 [ BAUD=@var{baud} ] @var{program} [ @var{args} @dots{} ]
10733 @var{board} and @var{port} specify the serial line; @var{baud} specifies
10734 the baud rate used by the connection. @var{port} and @var{node} default
10735 to 0, @var{baud} defaults to 9600@dmn{bps}.
10737 For example, to debug Emacs with the argument @samp{foo.txt}and
10738 communicate with @value{GDBN} over serial port number 2 or board 1
10739 using a 19200@dmn{bps} connection:
10742 load gdbserve BOARD=1 PORT=2 BAUD=19200 emacs foo.txt
10745 @item On the @value{GDBN} host machine,
10746 you need an unstripped copy of your program, since @value{GDBN} needs
10747 symbols and debugging information. Start up @value{GDBN} as usual,
10748 using the name of the local copy of your program as the first argument.
10749 (You may also need the @w{@samp{--baud}} option if the serial line is
10750 running at anything other than 9600@dmn{bps}. After that, use @code{target
10751 remote} to establish communications with @code{gdbserve.nlm}. Its
10752 argument is a device name (usually a serial device, like
10753 @file{/dev/ttyb}). For example:
10756 (@value{GDBP}) target remote /dev/ttyb
10760 communications with the server via serial line @file{/dev/ttyb}.
10764 @section Implementing a remote stub
10766 @cindex debugging stub, example
10767 @cindex remote stub, example
10768 @cindex stub example, remote debugging
10769 The stub files provided with @value{GDBN} implement the target side of the
10770 communication protocol, and the @value{GDBN} side is implemented in the
10771 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
10772 these subroutines to communicate, and ignore the details. (If you're
10773 implementing your own stub file, you can still ignore the details: start
10774 with one of the existing stub files. @file{sparc-stub.c} is the best
10775 organized, and therefore the easiest to read.)
10777 @cindex remote serial debugging, overview
10778 To debug a program running on another machine (the debugging
10779 @dfn{target} machine), you must first arrange for all the usual
10780 prerequisites for the program to run by itself. For example, for a C
10785 A startup routine to set up the C runtime environment; these usually
10786 have a name like @file{crt0}. The startup routine may be supplied by
10787 your hardware supplier, or you may have to write your own.
10790 A C subroutine library to support your program's
10791 subroutine calls, notably managing input and output.
10794 A way of getting your program to the other machine---for example, a
10795 download program. These are often supplied by the hardware
10796 manufacturer, but you may have to write your own from hardware
10800 The next step is to arrange for your program to use a serial port to
10801 communicate with the machine where @value{GDBN} is running (the @dfn{host}
10802 machine). In general terms, the scheme looks like this:
10806 @value{GDBN} already understands how to use this protocol; when everything
10807 else is set up, you can simply use the @samp{target remote} command
10808 (@pxref{Targets,,Specifying a Debugging Target}).
10810 @item On the target,
10811 you must link with your program a few special-purpose subroutines that
10812 implement the @value{GDBN} remote serial protocol. The file containing these
10813 subroutines is called a @dfn{debugging stub}.
10815 On certain remote targets, you can use an auxiliary program
10816 @code{gdbserver} instead of linking a stub into your program.
10817 @xref{Server,,Using the @code{gdbserver} program}, for details.
10820 The debugging stub is specific to the architecture of the remote
10821 machine; for example, use @file{sparc-stub.c} to debug programs on
10824 @cindex remote serial stub list
10825 These working remote stubs are distributed with @value{GDBN}:
10830 @cindex @file{i386-stub.c}
10833 For Intel 386 and compatible architectures.
10836 @cindex @file{m68k-stub.c}
10837 @cindex Motorola 680x0
10839 For Motorola 680x0 architectures.
10842 @cindex @file{sh-stub.c}
10845 For Hitachi SH architectures.
10848 @cindex @file{sparc-stub.c}
10850 For @sc{sparc} architectures.
10852 @item sparcl-stub.c
10853 @cindex @file{sparcl-stub.c}
10856 For Fujitsu @sc{sparclite} architectures.
10860 The @file{README} file in the @value{GDBN} distribution may list other
10861 recently added stubs.
10864 * Stub Contents:: What the stub can do for you
10865 * Bootstrapping:: What you must do for the stub
10866 * Debug Session:: Putting it all together
10869 @node Stub Contents
10870 @subsection What the stub can do for you
10872 @cindex remote serial stub
10873 The debugging stub for your architecture supplies these three
10877 @item set_debug_traps
10878 @kindex set_debug_traps
10879 @cindex remote serial stub, initialization
10880 This routine arranges for @code{handle_exception} to run when your
10881 program stops. You must call this subroutine explicitly near the
10882 beginning of your program.
10884 @item handle_exception
10885 @kindex handle_exception
10886 @cindex remote serial stub, main routine
10887 This is the central workhorse, but your program never calls it
10888 explicitly---the setup code arranges for @code{handle_exception} to
10889 run when a trap is triggered.
10891 @code{handle_exception} takes control when your program stops during
10892 execution (for example, on a breakpoint), and mediates communications
10893 with @value{GDBN} on the host machine. This is where the communications
10894 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
10895 representative on the target machine. It begins by sending summary
10896 information on the state of your program, then continues to execute,
10897 retrieving and transmitting any information @value{GDBN} needs, until you
10898 execute a @value{GDBN} command that makes your program resume; at that point,
10899 @code{handle_exception} returns control to your own code on the target
10903 @cindex @code{breakpoint} subroutine, remote
10904 Use this auxiliary subroutine to make your program contain a
10905 breakpoint. Depending on the particular situation, this may be the only
10906 way for @value{GDBN} to get control. For instance, if your target
10907 machine has some sort of interrupt button, you won't need to call this;
10908 pressing the interrupt button transfers control to
10909 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
10910 simply receiving characters on the serial port may also trigger a trap;
10911 again, in that situation, you don't need to call @code{breakpoint} from
10912 your own program---simply running @samp{target remote} from the host
10913 @value{GDBN} session gets control.
10915 Call @code{breakpoint} if none of these is true, or if you simply want
10916 to make certain your program stops at a predetermined point for the
10917 start of your debugging session.
10920 @node Bootstrapping
10921 @subsection What you must do for the stub
10923 @cindex remote stub, support routines
10924 The debugging stubs that come with @value{GDBN} are set up for a particular
10925 chip architecture, but they have no information about the rest of your
10926 debugging target machine.
10928 First of all you need to tell the stub how to communicate with the
10932 @item int getDebugChar()
10933 @kindex getDebugChar
10934 Write this subroutine to read a single character from the serial port.
10935 It may be identical to @code{getchar} for your target system; a
10936 different name is used to allow you to distinguish the two if you wish.
10938 @item void putDebugChar(int)
10939 @kindex putDebugChar
10940 Write this subroutine to write a single character to the serial port.
10941 It may be identical to @code{putchar} for your target system; a
10942 different name is used to allow you to distinguish the two if you wish.
10945 @cindex control C, and remote debugging
10946 @cindex interrupting remote targets
10947 If you want @value{GDBN} to be able to stop your program while it is
10948 running, you need to use an interrupt-driven serial driver, and arrange
10949 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
10950 character). That is the character which @value{GDBN} uses to tell the
10951 remote system to stop.
10953 Getting the debugging target to return the proper status to @value{GDBN}
10954 probably requires changes to the standard stub; one quick and dirty way
10955 is to just execute a breakpoint instruction (the ``dirty'' part is that
10956 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
10958 Other routines you need to supply are:
10961 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
10962 @kindex exceptionHandler
10963 Write this function to install @var{exception_address} in the exception
10964 handling tables. You need to do this because the stub does not have any
10965 way of knowing what the exception handling tables on your target system
10966 are like (for example, the processor's table might be in @sc{rom},
10967 containing entries which point to a table in @sc{ram}).
10968 @var{exception_number} is the exception number which should be changed;
10969 its meaning is architecture-dependent (for example, different numbers
10970 might represent divide by zero, misaligned access, etc). When this
10971 exception occurs, control should be transferred directly to
10972 @var{exception_address}, and the processor state (stack, registers,
10973 and so on) should be just as it is when a processor exception occurs. So if
10974 you want to use a jump instruction to reach @var{exception_address}, it
10975 should be a simple jump, not a jump to subroutine.
10977 For the 386, @var{exception_address} should be installed as an interrupt
10978 gate so that interrupts are masked while the handler runs. The gate
10979 should be at privilege level 0 (the most privileged level). The
10980 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
10981 help from @code{exceptionHandler}.
10983 @item void flush_i_cache()
10984 @kindex flush_i_cache
10985 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
10986 instruction cache, if any, on your target machine. If there is no
10987 instruction cache, this subroutine may be a no-op.
10989 On target machines that have instruction caches, @value{GDBN} requires this
10990 function to make certain that the state of your program is stable.
10994 You must also make sure this library routine is available:
10997 @item void *memset(void *, int, int)
10999 This is the standard library function @code{memset} that sets an area of
11000 memory to a known value. If you have one of the free versions of
11001 @code{libc.a}, @code{memset} can be found there; otherwise, you must
11002 either obtain it from your hardware manufacturer, or write your own.
11005 If you do not use the GNU C compiler, you may need other standard
11006 library subroutines as well; this varies from one stub to another,
11007 but in general the stubs are likely to use any of the common library
11008 subroutines which @code{@value{GCC}} generates as inline code.
11011 @node Debug Session
11012 @subsection Putting it all together
11014 @cindex remote serial debugging summary
11015 In summary, when your program is ready to debug, you must follow these
11020 Make sure you have defined the supporting low-level routines
11021 (@pxref{Bootstrapping,,What you must do for the stub}):
11023 @code{getDebugChar}, @code{putDebugChar},
11024 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
11028 Insert these lines near the top of your program:
11036 For the 680x0 stub only, you need to provide a variable called
11037 @code{exceptionHook}. Normally you just use:
11040 void (*exceptionHook)() = 0;
11044 but if before calling @code{set_debug_traps}, you set it to point to a
11045 function in your program, that function is called when
11046 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
11047 error). The function indicated by @code{exceptionHook} is called with
11048 one parameter: an @code{int} which is the exception number.
11051 Compile and link together: your program, the @value{GDBN} debugging stub for
11052 your target architecture, and the supporting subroutines.
11055 Make sure you have a serial connection between your target machine and
11056 the @value{GDBN} host, and identify the serial port on the host.
11059 @c The "remote" target now provides a `load' command, so we should
11060 @c document that. FIXME.
11061 Download your program to your target machine (or get it there by
11062 whatever means the manufacturer provides), and start it.
11065 To start remote debugging, run @value{GDBN} on the host machine, and specify
11066 as an executable file the program that is running in the remote machine.
11067 This tells @value{GDBN} how to find your program's symbols and the contents
11071 @cindex serial line, @code{target remote}
11072 Establish communication using the @code{target remote} command.
11073 Its argument specifies how to communicate with the target
11074 machine---either via a devicename attached to a direct serial line, or a
11075 TCP or UDP port (usually to a terminal server which in turn has a serial line
11076 to the target). For example, to use a serial line connected to the
11077 device named @file{/dev/ttyb}:
11080 target remote /dev/ttyb
11083 @cindex TCP port, @code{target remote}
11084 To use a TCP connection, use an argument of the form
11085 @code{@var{host}:@var{port}} or @code{tcp:@var{host}:@var{port}}.
11086 For example, to connect to port 2828 on a
11087 terminal server named @code{manyfarms}:
11090 target remote manyfarms:2828
11093 If your remote target is actually running on the same machine as
11094 your debugger session (e.g.@: a simulator of your target running on
11095 the same host), you can omit the hostname. For example, to connect
11096 to port 1234 on your local machine:
11099 target remote :1234
11103 Note that the colon is still required here.
11105 @cindex UDP port, @code{target remote}
11106 To use a UDP connection, use an argument of the form
11107 @code{udp:@var{host}:@var{port}}. For example, to connect to UDP port 2828
11108 on a terminal server named @code{manyfarms}:
11111 target remote udp:manyfarms:2828
11114 When using a UDP connection for remote debugging, you should keep in mind
11115 that the `U' stands for ``Unreliable''. UDP can silently drop packets on
11116 busy or unreliable networks, which will cause havoc with your debugging
11121 Now you can use all the usual commands to examine and change data and to
11122 step and continue the remote program.
11124 To resume the remote program and stop debugging it, use the @code{detach}
11127 @cindex interrupting remote programs
11128 @cindex remote programs, interrupting
11129 Whenever @value{GDBN} is waiting for the remote program, if you type the
11130 interrupt character (often @key{C-C}), @value{GDBN} attempts to stop the
11131 program. This may or may not succeed, depending in part on the hardware
11132 and the serial drivers the remote system uses. If you type the
11133 interrupt character once again, @value{GDBN} displays this prompt:
11136 Interrupted while waiting for the program.
11137 Give up (and stop debugging it)? (y or n)
11140 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
11141 (If you decide you want to try again later, you can use @samp{target
11142 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
11143 goes back to waiting.
11146 @node Configurations
11147 @chapter Configuration-Specific Information
11149 While nearly all @value{GDBN} commands are available for all native and
11150 cross versions of the debugger, there are some exceptions. This chapter
11151 describes things that are only available in certain configurations.
11153 There are three major categories of configurations: native
11154 configurations, where the host and target are the same, embedded
11155 operating system configurations, which are usually the same for several
11156 different processor architectures, and bare embedded processors, which
11157 are quite different from each other.
11162 * Embedded Processors::
11169 This section describes details specific to particular native
11174 * SVR4 Process Information:: SVR4 process information
11175 * DJGPP Native:: Features specific to the DJGPP port
11176 * Cygwin Native:: Features specific to the Cygwin port
11182 On HP-UX systems, if you refer to a function or variable name that
11183 begins with a dollar sign, @value{GDBN} searches for a user or system
11184 name first, before it searches for a convenience variable.
11186 @node SVR4 Process Information
11187 @subsection SVR4 process information
11190 @cindex process image
11192 Many versions of SVR4 provide a facility called @samp{/proc} that can be
11193 used to examine the image of a running process using file-system
11194 subroutines. If @value{GDBN} is configured for an operating system with
11195 this facility, the command @code{info proc} is available to report on
11196 several kinds of information about the process running your program.
11197 @code{info proc} works only on SVR4 systems that include the
11198 @code{procfs} code. This includes OSF/1 (Digital Unix), Solaris, Irix,
11199 and Unixware, but not HP-UX or @sc{gnu}/Linux, for example.
11204 Summarize available information about the process.
11206 @kindex info proc mappings
11207 @item info proc mappings
11208 Report on the address ranges accessible in the program, with information
11209 on whether your program may read, write, or execute each range.
11211 @comment These sub-options of 'info proc' were not included when
11212 @comment procfs.c was re-written. Keep their descriptions around
11213 @comment against the day when someone finds the time to put them back in.
11214 @kindex info proc times
11215 @item info proc times
11216 Starting time, user CPU time, and system CPU time for your program and
11219 @kindex info proc id
11221 Report on the process IDs related to your program: its own process ID,
11222 the ID of its parent, the process group ID, and the session ID.
11224 @kindex info proc status
11225 @item info proc status
11226 General information on the state of the process. If the process is
11227 stopped, this report includes the reason for stopping, and any signal
11230 @item info proc all
11231 Show all the above information about the process.
11236 @subsection Features for Debugging @sc{djgpp} Programs
11237 @cindex @sc{djgpp} debugging
11238 @cindex native @sc{djgpp} debugging
11239 @cindex MS-DOS-specific commands
11241 @sc{djgpp} is the port of @sc{gnu} development tools to MS-DOS and
11242 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
11243 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
11244 top of real-mode DOS systems and their emulations.
11246 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
11247 defines a few commands specific to the @sc{djgpp} port. This
11248 subsection describes those commands.
11253 This is a prefix of @sc{djgpp}-specific commands which print
11254 information about the target system and important OS structures.
11257 @cindex MS-DOS system info
11258 @cindex free memory information (MS-DOS)
11259 @item info dos sysinfo
11260 This command displays assorted information about the underlying
11261 platform: the CPU type and features, the OS version and flavor, the
11262 DPMI version, and the available conventional and DPMI memory.
11267 @cindex segment descriptor tables
11268 @cindex descriptor tables display
11270 @itemx info dos ldt
11271 @itemx info dos idt
11272 These 3 commands display entries from, respectively, Global, Local,
11273 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
11274 tables are data structures which store a descriptor for each segment
11275 that is currently in use. The segment's selector is an index into a
11276 descriptor table; the table entry for that index holds the
11277 descriptor's base address and limit, and its attributes and access
11280 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
11281 segment (used for both data and the stack), and a DOS segment (which
11282 allows access to DOS/BIOS data structures and absolute addresses in
11283 conventional memory). However, the DPMI host will usually define
11284 additional segments in order to support the DPMI environment.
11286 @cindex garbled pointers
11287 These commands allow to display entries from the descriptor tables.
11288 Without an argument, all entries from the specified table are
11289 displayed. An argument, which should be an integer expression, means
11290 display a single entry whose index is given by the argument. For
11291 example, here's a convenient way to display information about the
11292 debugged program's data segment:
11295 @exdent @code{(@value{GDBP}) info dos ldt $ds}
11296 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
11300 This comes in handy when you want to see whether a pointer is outside
11301 the data segment's limit (i.e.@: @dfn{garbled}).
11303 @cindex page tables display (MS-DOS)
11305 @itemx info dos pte
11306 These two commands display entries from, respectively, the Page
11307 Directory and the Page Tables. Page Directories and Page Tables are
11308 data structures which control how virtual memory addresses are mapped
11309 into physical addresses. A Page Table includes an entry for every
11310 page of memory that is mapped into the program's address space; there
11311 may be several Page Tables, each one holding up to 4096 entries. A
11312 Page Directory has up to 4096 entries, one each for every Page Table
11313 that is currently in use.
11315 Without an argument, @kbd{info dos pde} displays the entire Page
11316 Directory, and @kbd{info dos pte} displays all the entries in all of
11317 the Page Tables. An argument, an integer expression, given to the
11318 @kbd{info dos pde} command means display only that entry from the Page
11319 Directory table. An argument given to the @kbd{info dos pte} command
11320 means display entries from a single Page Table, the one pointed to by
11321 the specified entry in the Page Directory.
11323 @cindex direct memory access (DMA) on MS-DOS
11324 These commands are useful when your program uses @dfn{DMA} (Direct
11325 Memory Access), which needs physical addresses to program the DMA
11328 These commands are supported only with some DPMI servers.
11330 @cindex physical address from linear address
11331 @item info dos address-pte @var{addr}
11332 This command displays the Page Table entry for a specified linear
11333 address. The argument linear address @var{addr} should already have the
11334 appropriate segment's base address added to it, because this command
11335 accepts addresses which may belong to @emph{any} segment. For
11336 example, here's how to display the Page Table entry for the page where
11337 the variable @code{i} is stored:
11340 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
11341 @exdent @code{Page Table entry for address 0x11a00d30:}
11342 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
11346 This says that @code{i} is stored at offset @code{0xd30} from the page
11347 whose physical base address is @code{0x02698000}, and prints all the
11348 attributes of that page.
11350 Note that you must cast the addresses of variables to a @code{char *},
11351 since otherwise the value of @code{__djgpp_base_address}, the base
11352 address of all variables and functions in a @sc{djgpp} program, will
11353 be added using the rules of C pointer arithmetics: if @code{i} is
11354 declared an @code{int}, @value{GDBN} will add 4 times the value of
11355 @code{__djgpp_base_address} to the address of @code{i}.
11357 Here's another example, it displays the Page Table entry for the
11361 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
11362 @exdent @code{Page Table entry for address 0x29110:}
11363 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
11367 (The @code{+ 3} offset is because the transfer buffer's address is the
11368 3rd member of the @code{_go32_info_block} structure.) The output of
11369 this command clearly shows that addresses in conventional memory are
11370 mapped 1:1, i.e.@: the physical and linear addresses are identical.
11372 This command is supported only with some DPMI servers.
11375 @node Cygwin Native
11376 @subsection Features for Debugging MS Windows PE executables
11377 @cindex MS Windows debugging
11378 @cindex native Cygwin debugging
11379 @cindex Cygwin-specific commands
11381 @value{GDBN} supports native debugging of MS Windows programs, and
11382 defines a few commands specific to the Cygwin port. This
11383 subsection describes those commands.
11388 This is a prefix of MS Windows specific commands which print
11389 information about the target system and important OS structures.
11391 @item info w32 selector
11392 This command displays information returned by
11393 the Win32 API @code{GetThreadSelectorEntry} function.
11394 It takes an optional argument that is evaluated to
11395 a long value to give the information about this given selector.
11396 Without argument, this command displays information
11397 about the the six segment registers.
11401 This is a Cygwin specific alias of info shared.
11403 @kindex dll-symbols
11405 This command loads symbols from a dll similarly to
11406 add-sym command but without the need to specify a base address.
11408 @kindex set new-console
11409 @item set new-console @var{mode}
11410 If @var{mode} is @code{on} the debuggee will
11411 be started in a new console on next start.
11412 If @var{mode} is @code{off}i, the debuggee will
11413 be started in the same console as the debugger.
11415 @kindex show new-console
11416 @item show new-console
11417 Displays whether a new console is used
11418 when the debuggee is started.
11420 @kindex set new-group
11421 @item set new-group @var{mode}
11422 This boolean value controls whether the debuggee should
11423 start a new group or stay in the same group as the debugger.
11424 This affects the way the Windows OS handles
11427 @kindex show new-group
11428 @item show new-group
11429 Displays current value of new-group boolean.
11431 @kindex set debugevents
11432 @item set debugevents
11433 This boolean value adds debug output concerning events seen by the debugger.
11435 @kindex set debugexec
11436 @item set debugexec
11437 This boolean value adds debug output concerning execute events
11438 seen by the debugger.
11440 @kindex set debugexceptions
11441 @item set debugexceptions
11442 This boolean value adds debug ouptut concerning exception events
11443 seen by the debugger.
11445 @kindex set debugmemory
11446 @item set debugmemory
11447 This boolean value adds debug ouptut concerning memory events
11448 seen by the debugger.
11452 This boolean values specifies whether the debuggee is called
11453 via a shell or directly (default value is on).
11457 Displays if the debuggee will be started with a shell.
11462 @section Embedded Operating Systems
11464 This section describes configurations involving the debugging of
11465 embedded operating systems that are available for several different
11469 * VxWorks:: Using @value{GDBN} with VxWorks
11472 @value{GDBN} includes the ability to debug programs running on
11473 various real-time operating systems.
11476 @subsection Using @value{GDBN} with VxWorks
11482 @kindex target vxworks
11483 @item target vxworks @var{machinename}
11484 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
11485 is the target system's machine name or IP address.
11489 On VxWorks, @code{load} links @var{filename} dynamically on the
11490 current target system as well as adding its symbols in @value{GDBN}.
11492 @value{GDBN} enables developers to spawn and debug tasks running on networked
11493 VxWorks targets from a Unix host. Already-running tasks spawned from
11494 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
11495 both the Unix host and on the VxWorks target. The program
11496 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
11497 installed with the name @code{vxgdb}, to distinguish it from a
11498 @value{GDBN} for debugging programs on the host itself.)
11501 @item VxWorks-timeout @var{args}
11502 @kindex vxworks-timeout
11503 All VxWorks-based targets now support the option @code{vxworks-timeout}.
11504 This option is set by the user, and @var{args} represents the number of
11505 seconds @value{GDBN} waits for responses to rpc's. You might use this if
11506 your VxWorks target is a slow software simulator or is on the far side
11507 of a thin network line.
11510 The following information on connecting to VxWorks was current when
11511 this manual was produced; newer releases of VxWorks may use revised
11514 @kindex INCLUDE_RDB
11515 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
11516 to include the remote debugging interface routines in the VxWorks
11517 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
11518 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
11519 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
11520 source debugging task @code{tRdbTask} when VxWorks is booted. For more
11521 information on configuring and remaking VxWorks, see the manufacturer's
11523 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
11525 Once you have included @file{rdb.a} in your VxWorks system image and set
11526 your Unix execution search path to find @value{GDBN}, you are ready to
11527 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
11528 @code{vxgdb}, depending on your installation).
11530 @value{GDBN} comes up showing the prompt:
11537 * VxWorks Connection:: Connecting to VxWorks
11538 * VxWorks Download:: VxWorks download
11539 * VxWorks Attach:: Running tasks
11542 @node VxWorks Connection
11543 @subsubsection Connecting to VxWorks
11545 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
11546 network. To connect to a target whose host name is ``@code{tt}'', type:
11549 (vxgdb) target vxworks tt
11553 @value{GDBN} displays messages like these:
11556 Attaching remote machine across net...
11561 @value{GDBN} then attempts to read the symbol tables of any object modules
11562 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
11563 these files by searching the directories listed in the command search
11564 path (@pxref{Environment, ,Your program's environment}); if it fails
11565 to find an object file, it displays a message such as:
11568 prog.o: No such file or directory.
11571 When this happens, add the appropriate directory to the search path with
11572 the @value{GDBN} command @code{path}, and execute the @code{target}
11575 @node VxWorks Download
11576 @subsubsection VxWorks download
11578 @cindex download to VxWorks
11579 If you have connected to the VxWorks target and you want to debug an
11580 object that has not yet been loaded, you can use the @value{GDBN}
11581 @code{load} command to download a file from Unix to VxWorks
11582 incrementally. The object file given as an argument to the @code{load}
11583 command is actually opened twice: first by the VxWorks target in order
11584 to download the code, then by @value{GDBN} in order to read the symbol
11585 table. This can lead to problems if the current working directories on
11586 the two systems differ. If both systems have NFS mounted the same
11587 filesystems, you can avoid these problems by using absolute paths.
11588 Otherwise, it is simplest to set the working directory on both systems
11589 to the directory in which the object file resides, and then to reference
11590 the file by its name, without any path. For instance, a program
11591 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
11592 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
11593 program, type this on VxWorks:
11596 -> cd "@var{vxpath}/vw/demo/rdb"
11600 Then, in @value{GDBN}, type:
11603 (vxgdb) cd @var{hostpath}/vw/demo/rdb
11604 (vxgdb) load prog.o
11607 @value{GDBN} displays a response similar to this:
11610 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
11613 You can also use the @code{load} command to reload an object module
11614 after editing and recompiling the corresponding source file. Note that
11615 this makes @value{GDBN} delete all currently-defined breakpoints,
11616 auto-displays, and convenience variables, and to clear the value
11617 history. (This is necessary in order to preserve the integrity of
11618 debugger's data structures that reference the target system's symbol
11621 @node VxWorks Attach
11622 @subsubsection Running tasks
11624 @cindex running VxWorks tasks
11625 You can also attach to an existing task using the @code{attach} command as
11629 (vxgdb) attach @var{task}
11633 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
11634 or suspended when you attach to it. Running tasks are suspended at
11635 the time of attachment.
11637 @node Embedded Processors
11638 @section Embedded Processors
11640 This section goes into details specific to particular embedded
11646 * H8/300:: Hitachi H8/300
11647 * H8/500:: Hitachi H8/500
11648 * i960:: Intel i960
11649 * M32R/D:: Mitsubishi M32R/D
11650 * M68K:: Motorola M68K
11651 @c OBSOLETE * M88K:: Motorola M88K
11652 * MIPS Embedded:: MIPS Embedded
11653 * PA:: HP PA Embedded
11656 * Sparclet:: Tsqware Sparclet
11657 * Sparclite:: Fujitsu Sparclite
11658 * ST2000:: Tandem ST2000
11659 * Z8000:: Zilog Z8000
11668 @item target rdi @var{dev}
11669 ARM Angel monitor, via RDI library interface to ADP protocol. You may
11670 use this target to communicate with both boards running the Angel
11671 monitor, or with the EmbeddedICE JTAG debug device.
11674 @item target rdp @var{dev}
11680 @subsection Hitachi H8/300
11684 @kindex target hms@r{, with H8/300}
11685 @item target hms @var{dev}
11686 A Hitachi SH, H8/300, or H8/500 board, attached via serial line to your host.
11687 Use special commands @code{device} and @code{speed} to control the serial
11688 line and the communications speed used.
11690 @kindex target e7000@r{, with H8/300}
11691 @item target e7000 @var{dev}
11692 E7000 emulator for Hitachi H8 and SH.
11694 @kindex target sh3@r{, with H8/300}
11695 @kindex target sh3e@r{, with H8/300}
11696 @item target sh3 @var{dev}
11697 @itemx target sh3e @var{dev}
11698 Hitachi SH-3 and SH-3E target systems.
11702 @cindex download to H8/300 or H8/500
11703 @cindex H8/300 or H8/500 download
11704 @cindex download to Hitachi SH
11705 @cindex Hitachi SH download
11706 When you select remote debugging to a Hitachi SH, H8/300, or H8/500
11707 board, the @code{load} command downloads your program to the Hitachi
11708 board and also opens it as the current executable target for
11709 @value{GDBN} on your host (like the @code{file} command).
11711 @value{GDBN} needs to know these things to talk to your
11712 Hitachi SH, H8/300, or H8/500:
11716 that you want to use @samp{target hms}, the remote debugging interface
11717 for Hitachi microprocessors, or @samp{target e7000}, the in-circuit
11718 emulator for the Hitachi SH and the Hitachi 300H. (@samp{target hms} is
11719 the default when @value{GDBN} is configured specifically for the Hitachi SH,
11720 H8/300, or H8/500.)
11723 what serial device connects your host to your Hitachi board (the first
11724 serial device available on your host is the default).
11727 what speed to use over the serial device.
11731 * Hitachi Boards:: Connecting to Hitachi boards.
11732 * Hitachi ICE:: Using the E7000 In-Circuit Emulator.
11733 * Hitachi Special:: Special @value{GDBN} commands for Hitachi micros.
11736 @node Hitachi Boards
11737 @subsubsection Connecting to Hitachi boards
11739 @c only for Unix hosts
11741 @cindex serial device, Hitachi micros
11742 Use the special @code{@value{GDBN}} command @samp{device @var{port}} if you
11743 need to explicitly set the serial device. The default @var{port} is the
11744 first available port on your host. This is only necessary on Unix
11745 hosts, where it is typically something like @file{/dev/ttya}.
11748 @cindex serial line speed, Hitachi micros
11749 @code{@value{GDBN}} has another special command to set the communications
11750 speed: @samp{speed @var{bps}}. This command also is only used from Unix
11751 hosts; on DOS hosts, set the line speed as usual from outside @value{GDBN} with
11752 the DOS @code{mode} command (for instance,
11753 @w{@kbd{mode com2:9600,n,8,1,p}} for a 9600@dmn{bps} connection).
11755 The @samp{device} and @samp{speed} commands are available only when you
11756 use a Unix host to debug your Hitachi microprocessor programs. If you
11758 @value{GDBN} depends on an auxiliary terminate-and-stay-resident program
11759 called @code{asynctsr} to communicate with the development board
11760 through a PC serial port. You must also use the DOS @code{mode} command
11761 to set up the serial port on the DOS side.
11763 The following sample session illustrates the steps needed to start a
11764 program under @value{GDBN} control on an H8/300. The example uses a
11765 sample H8/300 program called @file{t.x}. The procedure is the same for
11766 the Hitachi SH and the H8/500.
11768 First hook up your development board. In this example, we use a
11769 board attached to serial port @code{COM2}; if you use a different serial
11770 port, substitute its name in the argument of the @code{mode} command.
11771 When you call @code{asynctsr}, the auxiliary comms program used by the
11772 debugger, you give it just the numeric part of the serial port's name;
11773 for example, @samp{asyncstr 2} below runs @code{asyncstr} on
11777 C:\H8300\TEST> asynctsr 2
11778 C:\H8300\TEST> mode com2:9600,n,8,1,p
11780 Resident portion of MODE loaded
11782 COM2: 9600, n, 8, 1, p
11787 @emph{Warning:} We have noticed a bug in PC-NFS that conflicts with
11788 @code{asynctsr}. If you also run PC-NFS on your DOS host, you may need to
11789 disable it, or even boot without it, to use @code{asynctsr} to control
11790 your development board.
11793 @kindex target hms@r{, and serial protocol}
11794 Now that serial communications are set up, and the development board is
11795 connected, you can start up @value{GDBN}. Call @code{@value{GDBP}} with
11796 the name of your program as the argument. @code{@value{GDBN}} prompts
11797 you, as usual, with the prompt @samp{(@value{GDBP})}. Use two special
11798 commands to begin your debugging session: @samp{target hms} to specify
11799 cross-debugging to the Hitachi board, and the @code{load} command to
11800 download your program to the board. @code{load} displays the names of
11801 the program's sections, and a @samp{*} for each 2K of data downloaded.
11802 (If you want to refresh @value{GDBN} data on symbols or on the
11803 executable file without downloading, use the @value{GDBN} commands
11804 @code{file} or @code{symbol-file}. These commands, and @code{load}
11805 itself, are described in @ref{Files,,Commands to specify files}.)
11808 (eg-C:\H8300\TEST) @value{GDBP} t.x
11809 @value{GDBN} is free software and you are welcome to distribute copies
11810 of it under certain conditions; type "show copying" to see
11812 There is absolutely no warranty for @value{GDBN}; type "show warranty"
11814 @value{GDBN} @value{GDBVN}, Copyright 1992 Free Software Foundation, Inc...
11815 (@value{GDBP}) target hms
11816 Connected to remote H8/300 HMS system.
11817 (@value{GDBP}) load t.x
11818 .text : 0x8000 .. 0xabde ***********
11819 .data : 0xabde .. 0xad30 *
11820 .stack : 0xf000 .. 0xf014 *
11823 At this point, you're ready to run or debug your program. From here on,
11824 you can use all the usual @value{GDBN} commands. The @code{break} command
11825 sets breakpoints; the @code{run} command starts your program;
11826 @code{print} or @code{x} display data; the @code{continue} command
11827 resumes execution after stopping at a breakpoint. You can use the
11828 @code{help} command at any time to find out more about @value{GDBN} commands.
11830 Remember, however, that @emph{operating system} facilities aren't
11831 available on your development board; for example, if your program hangs,
11832 you can't send an interrupt---but you can press the @sc{reset} switch!
11834 Use the @sc{reset} button on the development board
11837 to interrupt your program (don't use @kbd{ctl-C} on the DOS host---it has
11838 no way to pass an interrupt signal to the development board); and
11841 to return to the @value{GDBN} command prompt after your program finishes
11842 normally. The communications protocol provides no other way for @value{GDBN}
11843 to detect program completion.
11846 In either case, @value{GDBN} sees the effect of a @sc{reset} on the
11847 development board as a ``normal exit'' of your program.
11850 @subsubsection Using the E7000 in-circuit emulator
11852 @kindex target e7000@r{, with Hitachi ICE}
11853 You can use the E7000 in-circuit emulator to develop code for either the
11854 Hitachi SH or the H8/300H. Use one of these forms of the @samp{target
11855 e7000} command to connect @value{GDBN} to your E7000:
11858 @item target e7000 @var{port} @var{speed}
11859 Use this form if your E7000 is connected to a serial port. The
11860 @var{port} argument identifies what serial port to use (for example,
11861 @samp{com2}). The third argument is the line speed in bits per second
11862 (for example, @samp{9600}).
11864 @item target e7000 @var{hostname}
11865 If your E7000 is installed as a host on a TCP/IP network, you can just
11866 specify its hostname; @value{GDBN} uses @code{telnet} to connect.
11869 @node Hitachi Special
11870 @subsubsection Special @value{GDBN} commands for Hitachi micros
11872 Some @value{GDBN} commands are available only for the H8/300:
11876 @kindex set machine
11877 @kindex show machine
11878 @item set machine h8300
11879 @itemx set machine h8300h
11880 Condition @value{GDBN} for one of the two variants of the H8/300
11881 architecture with @samp{set machine}. You can use @samp{show machine}
11882 to check which variant is currently in effect.
11891 @kindex set memory @var{mod}
11892 @cindex memory models, H8/500
11893 @item set memory @var{mod}
11895 Specify which H8/500 memory model (@var{mod}) you are using with
11896 @samp{set memory}; check which memory model is in effect with @samp{show
11897 memory}. The accepted values for @var{mod} are @code{small},
11898 @code{big}, @code{medium}, and @code{compact}.
11903 @subsection Intel i960
11907 @kindex target mon960
11908 @item target mon960 @var{dev}
11909 MON960 monitor for Intel i960.
11911 @kindex target nindy
11912 @item target nindy @var{devicename}
11913 An Intel 960 board controlled by a Nindy Monitor. @var{devicename} is
11914 the name of the serial device to use for the connection, e.g.
11921 @dfn{Nindy} is a ROM Monitor program for Intel 960 target systems. When
11922 @value{GDBN} is configured to control a remote Intel 960 using Nindy, you can
11923 tell @value{GDBN} how to connect to the 960 in several ways:
11927 Through command line options specifying serial port, version of the
11928 Nindy protocol, and communications speed;
11931 By responding to a prompt on startup;
11934 By using the @code{target} command at any point during your @value{GDBN}
11935 session. @xref{Target Commands, ,Commands for managing targets}.
11939 @cindex download to Nindy-960
11940 With the Nindy interface to an Intel 960 board, @code{load}
11941 downloads @var{filename} to the 960 as well as adding its symbols in
11945 * Nindy Startup:: Startup with Nindy
11946 * Nindy Options:: Options for Nindy
11947 * Nindy Reset:: Nindy reset command
11950 @node Nindy Startup
11951 @subsubsection Startup with Nindy
11953 If you simply start @code{@value{GDBP}} without using any command-line
11954 options, you are prompted for what serial port to use, @emph{before} you
11955 reach the ordinary @value{GDBN} prompt:
11958 Attach /dev/ttyNN -- specify NN, or "quit" to quit:
11962 Respond to the prompt with whatever suffix (after @samp{/dev/tty})
11963 identifies the serial port you want to use. You can, if you choose,
11964 simply start up with no Nindy connection by responding to the prompt
11965 with an empty line. If you do this and later wish to attach to Nindy,
11966 use @code{target} (@pxref{Target Commands, ,Commands for managing targets}).
11968 @node Nindy Options
11969 @subsubsection Options for Nindy
11971 These are the startup options for beginning your @value{GDBN} session with a
11972 Nindy-960 board attached:
11975 @item -r @var{port}
11976 Specify the serial port name of a serial interface to be used to connect
11977 to the target system. This option is only available when @value{GDBN} is
11978 configured for the Intel 960 target architecture. You may specify
11979 @var{port} as any of: a full pathname (e.g. @samp{-r /dev/ttya}), a
11980 device name in @file{/dev} (e.g. @samp{-r ttya}), or simply the unique
11981 suffix for a specific @code{tty} (e.g. @samp{-r a}).
11984 (An uppercase letter ``O'', not a zero.) Specify that @value{GDBN} should use
11985 the ``old'' Nindy monitor protocol to connect to the target system.
11986 This option is only available when @value{GDBN} is configured for the Intel 960
11987 target architecture.
11990 @emph{Warning:} if you specify @samp{-O}, but are actually trying to
11991 connect to a target system that expects the newer protocol, the connection
11992 fails, appearing to be a speed mismatch. @value{GDBN} repeatedly
11993 attempts to reconnect at several different line speeds. You can abort
11994 this process with an interrupt.
11998 Specify that @value{GDBN} should first send a @code{BREAK} signal to the target
11999 system, in an attempt to reset it, before connecting to a Nindy target.
12002 @emph{Warning:} Many target systems do not have the hardware that this
12003 requires; it only works with a few boards.
12007 The standard @samp{-b} option controls the line speed used on the serial
12012 @subsubsection Nindy reset command
12017 For a Nindy target, this command sends a ``break'' to the remote target
12018 system; this is only useful if the target has been equipped with a
12019 circuit to perform a hard reset (or some other interesting action) when
12020 a break is detected.
12025 @subsection Mitsubishi M32R/D
12029 @kindex target m32r
12030 @item target m32r @var{dev}
12031 Mitsubishi M32R/D ROM monitor.
12038 The Motorola m68k configuration includes ColdFire support, and
12039 target command for the following ROM monitors.
12043 @kindex target abug
12044 @item target abug @var{dev}
12045 ABug ROM monitor for M68K.
12047 @kindex target cpu32bug
12048 @item target cpu32bug @var{dev}
12049 CPU32BUG monitor, running on a CPU32 (M68K) board.
12051 @kindex target dbug
12052 @item target dbug @var{dev}
12053 dBUG ROM monitor for Motorola ColdFire.
12056 @item target est @var{dev}
12057 EST-300 ICE monitor, running on a CPU32 (M68K) board.
12059 @kindex target rom68k
12060 @item target rom68k @var{dev}
12061 ROM 68K monitor, running on an M68K IDP board.
12065 If @value{GDBN} is configured with @code{m68*-ericsson-*}, it will
12066 instead have only a single special target command:
12070 @kindex target es1800
12071 @item target es1800 @var{dev}
12072 ES-1800 emulator for M68K.
12080 @kindex target rombug
12081 @item target rombug @var{dev}
12082 ROMBUG ROM monitor for OS/9000.
12086 @c OBSOLETE @node M88K
12087 @c OBSOLETE @subsection M88K
12089 @c OBSOLETE @table @code
12091 @c OBSOLETE @kindex target bug
12092 @c OBSOLETE @item target bug @var{dev}
12093 @c OBSOLETE BUG monitor, running on a MVME187 (m88k) board.
12095 @c OBSOLETE @end table
12097 @node MIPS Embedded
12098 @subsection MIPS Embedded
12100 @cindex MIPS boards
12101 @value{GDBN} can use the MIPS remote debugging protocol to talk to a
12102 MIPS board attached to a serial line. This is available when
12103 you configure @value{GDBN} with @samp{--target=mips-idt-ecoff}.
12106 Use these @value{GDBN} commands to specify the connection to your target board:
12109 @item target mips @var{port}
12110 @kindex target mips @var{port}
12111 To run a program on the board, start up @code{@value{GDBP}} with the
12112 name of your program as the argument. To connect to the board, use the
12113 command @samp{target mips @var{port}}, where @var{port} is the name of
12114 the serial port connected to the board. If the program has not already
12115 been downloaded to the board, you may use the @code{load} command to
12116 download it. You can then use all the usual @value{GDBN} commands.
12118 For example, this sequence connects to the target board through a serial
12119 port, and loads and runs a program called @var{prog} through the
12123 host$ @value{GDBP} @var{prog}
12124 @value{GDBN} is free software and @dots{}
12125 (@value{GDBP}) target mips /dev/ttyb
12126 (@value{GDBP}) load @var{prog}
12130 @item target mips @var{hostname}:@var{portnumber}
12131 On some @value{GDBN} host configurations, you can specify a TCP
12132 connection (for instance, to a serial line managed by a terminal
12133 concentrator) instead of a serial port, using the syntax
12134 @samp{@var{hostname}:@var{portnumber}}.
12136 @item target pmon @var{port}
12137 @kindex target pmon @var{port}
12140 @item target ddb @var{port}
12141 @kindex target ddb @var{port}
12142 NEC's DDB variant of PMON for Vr4300.
12144 @item target lsi @var{port}
12145 @kindex target lsi @var{port}
12146 LSI variant of PMON.
12148 @kindex target r3900
12149 @item target r3900 @var{dev}
12150 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
12152 @kindex target array
12153 @item target array @var{dev}
12154 Array Tech LSI33K RAID controller board.
12160 @value{GDBN} also supports these special commands for MIPS targets:
12163 @item set processor @var{args}
12164 @itemx show processor
12165 @kindex set processor @var{args}
12166 @kindex show processor
12167 Use the @code{set processor} command to set the type of MIPS
12168 processor when you want to access processor-type-specific registers.
12169 For example, @code{set processor @var{r3041}} tells @value{GDBN}
12170 to use the CPU registers appropriate for the 3041 chip.
12171 Use the @code{show processor} command to see what MIPS processor @value{GDBN}
12172 is using. Use the @code{info reg} command to see what registers
12173 @value{GDBN} is using.
12175 @item set mipsfpu double
12176 @itemx set mipsfpu single
12177 @itemx set mipsfpu none
12178 @itemx show mipsfpu
12179 @kindex set mipsfpu
12180 @kindex show mipsfpu
12181 @cindex MIPS remote floating point
12182 @cindex floating point, MIPS remote
12183 If your target board does not support the MIPS floating point
12184 coprocessor, you should use the command @samp{set mipsfpu none} (if you
12185 need this, you may wish to put the command in your @value{GDBN} init
12186 file). This tells @value{GDBN} how to find the return value of
12187 functions which return floating point values. It also allows
12188 @value{GDBN} to avoid saving the floating point registers when calling
12189 functions on the board. If you are using a floating point coprocessor
12190 with only single precision floating point support, as on the @sc{r4650}
12191 processor, use the command @samp{set mipsfpu single}. The default
12192 double precision floating point coprocessor may be selected using
12193 @samp{set mipsfpu double}.
12195 In previous versions the only choices were double precision or no
12196 floating point, so @samp{set mipsfpu on} will select double precision
12197 and @samp{set mipsfpu off} will select no floating point.
12199 As usual, you can inquire about the @code{mipsfpu} variable with
12200 @samp{show mipsfpu}.
12202 @item set remotedebug @var{n}
12203 @itemx show remotedebug
12204 @kindex set remotedebug@r{, MIPS protocol}
12205 @kindex show remotedebug@r{, MIPS protocol}
12206 @cindex @code{remotedebug}, MIPS protocol
12207 @cindex MIPS @code{remotedebug} protocol
12208 @c FIXME! For this to be useful, you must know something about the MIPS
12209 @c FIXME...protocol. Where is it described?
12210 You can see some debugging information about communications with the board
12211 by setting the @code{remotedebug} variable. If you set it to @code{1} using
12212 @samp{set remotedebug 1}, every packet is displayed. If you set it
12213 to @code{2}, every character is displayed. You can check the current value
12214 at any time with the command @samp{show remotedebug}.
12216 @item set timeout @var{seconds}
12217 @itemx set retransmit-timeout @var{seconds}
12218 @itemx show timeout
12219 @itemx show retransmit-timeout
12220 @cindex @code{timeout}, MIPS protocol
12221 @cindex @code{retransmit-timeout}, MIPS protocol
12222 @kindex set timeout
12223 @kindex show timeout
12224 @kindex set retransmit-timeout
12225 @kindex show retransmit-timeout
12226 You can control the timeout used while waiting for a packet, in the MIPS
12227 remote protocol, with the @code{set timeout @var{seconds}} command. The
12228 default is 5 seconds. Similarly, you can control the timeout used while
12229 waiting for an acknowledgement of a packet with the @code{set
12230 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
12231 You can inspect both values with @code{show timeout} and @code{show
12232 retransmit-timeout}. (These commands are @emph{only} available when
12233 @value{GDBN} is configured for @samp{--target=mips-idt-ecoff}.)
12235 The timeout set by @code{set timeout} does not apply when @value{GDBN}
12236 is waiting for your program to stop. In that case, @value{GDBN} waits
12237 forever because it has no way of knowing how long the program is going
12238 to run before stopping.
12242 @subsection PowerPC
12246 @kindex target dink32
12247 @item target dink32 @var{dev}
12248 DINK32 ROM monitor.
12250 @kindex target ppcbug
12251 @item target ppcbug @var{dev}
12252 @kindex target ppcbug1
12253 @item target ppcbug1 @var{dev}
12254 PPCBUG ROM monitor for PowerPC.
12257 @item target sds @var{dev}
12258 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
12263 @subsection HP PA Embedded
12267 @kindex target op50n
12268 @item target op50n @var{dev}
12269 OP50N monitor, running on an OKI HPPA board.
12271 @kindex target w89k
12272 @item target w89k @var{dev}
12273 W89K monitor, running on a Winbond HPPA board.
12278 @subsection Hitachi SH
12282 @kindex target hms@r{, with Hitachi SH}
12283 @item target hms @var{dev}
12284 A Hitachi SH board attached via serial line to your host. Use special
12285 commands @code{device} and @code{speed} to control the serial line and
12286 the communications speed used.
12288 @kindex target e7000@r{, with Hitachi SH}
12289 @item target e7000 @var{dev}
12290 E7000 emulator for Hitachi SH.
12292 @kindex target sh3@r{, with SH}
12293 @kindex target sh3e@r{, with SH}
12294 @item target sh3 @var{dev}
12295 @item target sh3e @var{dev}
12296 Hitachi SH-3 and SH-3E target systems.
12301 @subsection Tsqware Sparclet
12305 @value{GDBN} enables developers to debug tasks running on
12306 Sparclet targets from a Unix host.
12307 @value{GDBN} uses code that runs on
12308 both the Unix host and on the Sparclet target. The program
12309 @code{@value{GDBP}} is installed and executed on the Unix host.
12312 @item remotetimeout @var{args}
12313 @kindex remotetimeout
12314 @value{GDBN} supports the option @code{remotetimeout}.
12315 This option is set by the user, and @var{args} represents the number of
12316 seconds @value{GDBN} waits for responses.
12319 @cindex compiling, on Sparclet
12320 When compiling for debugging, include the options @samp{-g} to get debug
12321 information and @samp{-Ttext} to relocate the program to where you wish to
12322 load it on the target. You may also want to add the options @samp{-n} or
12323 @samp{-N} in order to reduce the size of the sections. Example:
12326 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
12329 You can use @code{objdump} to verify that the addresses are what you intended:
12332 sparclet-aout-objdump --headers --syms prog
12335 @cindex running, on Sparclet
12337 your Unix execution search path to find @value{GDBN}, you are ready to
12338 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
12339 (or @code{sparclet-aout-gdb}, depending on your installation).
12341 @value{GDBN} comes up showing the prompt:
12348 * Sparclet File:: Setting the file to debug
12349 * Sparclet Connection:: Connecting to Sparclet
12350 * Sparclet Download:: Sparclet download
12351 * Sparclet Execution:: Running and debugging
12354 @node Sparclet File
12355 @subsubsection Setting file to debug
12357 The @value{GDBN} command @code{file} lets you choose with program to debug.
12360 (gdbslet) file prog
12364 @value{GDBN} then attempts to read the symbol table of @file{prog}.
12365 @value{GDBN} locates
12366 the file by searching the directories listed in the command search
12368 If the file was compiled with debug information (option "-g"), source
12369 files will be searched as well.
12370 @value{GDBN} locates
12371 the source files by searching the directories listed in the directory search
12372 path (@pxref{Environment, ,Your program's environment}).
12374 to find a file, it displays a message such as:
12377 prog: No such file or directory.
12380 When this happens, add the appropriate directories to the search paths with
12381 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
12382 @code{target} command again.
12384 @node Sparclet Connection
12385 @subsubsection Connecting to Sparclet
12387 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
12388 To connect to a target on serial port ``@code{ttya}'', type:
12391 (gdbslet) target sparclet /dev/ttya
12392 Remote target sparclet connected to /dev/ttya
12393 main () at ../prog.c:3
12397 @value{GDBN} displays messages like these:
12403 @node Sparclet Download
12404 @subsubsection Sparclet download
12406 @cindex download to Sparclet
12407 Once connected to the Sparclet target,
12408 you can use the @value{GDBN}
12409 @code{load} command to download the file from the host to the target.
12410 The file name and load offset should be given as arguments to the @code{load}
12412 Since the file format is aout, the program must be loaded to the starting
12413 address. You can use @code{objdump} to find out what this value is. The load
12414 offset is an offset which is added to the VMA (virtual memory address)
12415 of each of the file's sections.
12416 For instance, if the program
12417 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
12418 and bss at 0x12010170, in @value{GDBN}, type:
12421 (gdbslet) load prog 0x12010000
12422 Loading section .text, size 0xdb0 vma 0x12010000
12425 If the code is loaded at a different address then what the program was linked
12426 to, you may need to use the @code{section} and @code{add-symbol-file} commands
12427 to tell @value{GDBN} where to map the symbol table.
12429 @node Sparclet Execution
12430 @subsubsection Running and debugging
12432 @cindex running and debugging Sparclet programs
12433 You can now begin debugging the task using @value{GDBN}'s execution control
12434 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
12435 manual for the list of commands.
12439 Breakpoint 1 at 0x12010000: file prog.c, line 3.
12441 Starting program: prog
12442 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
12443 3 char *symarg = 0;
12445 4 char *execarg = "hello!";
12450 @subsection Fujitsu Sparclite
12454 @kindex target sparclite
12455 @item target sparclite @var{dev}
12456 Fujitsu sparclite boards, used only for the purpose of loading.
12457 You must use an additional command to debug the program.
12458 For example: target remote @var{dev} using @value{GDBN} standard
12464 @subsection Tandem ST2000
12466 @value{GDBN} may be used with a Tandem ST2000 phone switch, running Tandem's
12469 To connect your ST2000 to the host system, see the manufacturer's
12470 manual. Once the ST2000 is physically attached, you can run:
12473 target st2000 @var{dev} @var{speed}
12477 to establish it as your debugging environment. @var{dev} is normally
12478 the name of a serial device, such as @file{/dev/ttya}, connected to the
12479 ST2000 via a serial line. You can instead specify @var{dev} as a TCP
12480 connection (for example, to a serial line attached via a terminal
12481 concentrator) using the syntax @code{@var{hostname}:@var{portnumber}}.
12483 The @code{load} and @code{attach} commands are @emph{not} defined for
12484 this target; you must load your program into the ST2000 as you normally
12485 would for standalone operation. @value{GDBN} reads debugging information
12486 (such as symbols) from a separate, debugging version of the program
12487 available on your host computer.
12488 @c FIXME!! This is terribly vague; what little content is here is
12489 @c basically hearsay.
12491 @cindex ST2000 auxiliary commands
12492 These auxiliary @value{GDBN} commands are available to help you with the ST2000
12496 @item st2000 @var{command}
12497 @kindex st2000 @var{cmd}
12498 @cindex STDBUG commands (ST2000)
12499 @cindex commands to STDBUG (ST2000)
12500 Send a @var{command} to the STDBUG monitor. See the manufacturer's
12501 manual for available commands.
12504 @cindex connect (to STDBUG)
12505 Connect the controlling terminal to the STDBUG command monitor. When
12506 you are done interacting with STDBUG, typing either of two character
12507 sequences gets you back to the @value{GDBN} command prompt:
12508 @kbd{@key{RET}~.} (Return, followed by tilde and period) or
12509 @kbd{@key{RET}~@key{C-d}} (Return, followed by tilde and control-D).
12513 @subsection Zilog Z8000
12516 @cindex simulator, Z8000
12517 @cindex Zilog Z8000 simulator
12519 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
12522 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
12523 unsegmented variant of the Z8000 architecture) or the Z8001 (the
12524 segmented variant). The simulator recognizes which architecture is
12525 appropriate by inspecting the object code.
12528 @item target sim @var{args}
12530 @kindex target sim@r{, with Z8000}
12531 Debug programs on a simulated CPU. If the simulator supports setup
12532 options, specify them via @var{args}.
12536 After specifying this target, you can debug programs for the simulated
12537 CPU in the same style as programs for your host computer; use the
12538 @code{file} command to load a new program image, the @code{run} command
12539 to run your program, and so on.
12541 As well as making available all the usual machine registers
12542 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
12543 additional items of information as specially named registers:
12548 Counts clock-ticks in the simulator.
12551 Counts instructions run in the simulator.
12554 Execution time in 60ths of a second.
12558 You can refer to these values in @value{GDBN} expressions with the usual
12559 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
12560 conditional breakpoint that suspends only after at least 5000
12561 simulated clock ticks.
12563 @node Architectures
12564 @section Architectures
12566 This section describes characteristics of architectures that affect
12567 all uses of @value{GDBN} with the architecture, both native and cross.
12580 @kindex set rstack_high_address
12581 @cindex AMD 29K register stack
12582 @cindex register stack, AMD29K
12583 @item set rstack_high_address @var{address}
12584 On AMD 29000 family processors, registers are saved in a separate
12585 @dfn{register stack}. There is no way for @value{GDBN} to determine the
12586 extent of this stack. Normally, @value{GDBN} just assumes that the
12587 stack is ``large enough''. This may result in @value{GDBN} referencing
12588 memory locations that do not exist. If necessary, you can get around
12589 this problem by specifying the ending address of the register stack with
12590 the @code{set rstack_high_address} command. The argument should be an
12591 address, which you probably want to precede with @samp{0x} to specify in
12594 @kindex show rstack_high_address
12595 @item show rstack_high_address
12596 Display the current limit of the register stack, on AMD 29000 family
12604 See the following section.
12609 @cindex stack on Alpha
12610 @cindex stack on MIPS
12611 @cindex Alpha stack
12613 Alpha- and MIPS-based computers use an unusual stack frame, which
12614 sometimes requires @value{GDBN} to search backward in the object code to
12615 find the beginning of a function.
12617 @cindex response time, MIPS debugging
12618 To improve response time (especially for embedded applications, where
12619 @value{GDBN} may be restricted to a slow serial line for this search)
12620 you may want to limit the size of this search, using one of these
12624 @cindex @code{heuristic-fence-post} (Alpha, MIPS)
12625 @item set heuristic-fence-post @var{limit}
12626 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
12627 search for the beginning of a function. A value of @var{0} (the
12628 default) means there is no limit. However, except for @var{0}, the
12629 larger the limit the more bytes @code{heuristic-fence-post} must search
12630 and therefore the longer it takes to run.
12632 @item show heuristic-fence-post
12633 Display the current limit.
12637 These commands are available @emph{only} when @value{GDBN} is configured
12638 for debugging programs on Alpha or MIPS processors.
12641 @node Controlling GDB
12642 @chapter Controlling @value{GDBN}
12644 You can alter the way @value{GDBN} interacts with you by using the
12645 @code{set} command. For commands controlling how @value{GDBN} displays
12646 data, see @ref{Print Settings, ,Print settings}. Other settings are
12651 * Editing:: Command editing
12652 * History:: Command history
12653 * Screen Size:: Screen size
12654 * Numbers:: Numbers
12655 * Messages/Warnings:: Optional warnings and messages
12656 * Debugging Output:: Optional messages about internal happenings
12664 @value{GDBN} indicates its readiness to read a command by printing a string
12665 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
12666 can change the prompt string with the @code{set prompt} command. For
12667 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
12668 the prompt in one of the @value{GDBN} sessions so that you can always tell
12669 which one you are talking to.
12671 @emph{Note:} @code{set prompt} does not add a space for you after the
12672 prompt you set. This allows you to set a prompt which ends in a space
12673 or a prompt that does not.
12677 @item set prompt @var{newprompt}
12678 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
12680 @kindex show prompt
12682 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
12686 @section Command editing
12688 @cindex command line editing
12690 @value{GDBN} reads its input commands via the @dfn{readline} interface. This
12691 @sc{gnu} library provides consistent behavior for programs which provide a
12692 command line interface to the user. Advantages are @sc{gnu} Emacs-style
12693 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
12694 substitution, and a storage and recall of command history across
12695 debugging sessions.
12697 You may control the behavior of command line editing in @value{GDBN} with the
12698 command @code{set}.
12701 @kindex set editing
12704 @itemx set editing on
12705 Enable command line editing (enabled by default).
12707 @item set editing off
12708 Disable command line editing.
12710 @kindex show editing
12712 Show whether command line editing is enabled.
12716 @section Command history
12718 @value{GDBN} can keep track of the commands you type during your
12719 debugging sessions, so that you can be certain of precisely what
12720 happened. Use these commands to manage the @value{GDBN} command
12724 @cindex history substitution
12725 @cindex history file
12726 @kindex set history filename
12727 @kindex GDBHISTFILE
12728 @item set history filename @var{fname}
12729 Set the name of the @value{GDBN} command history file to @var{fname}.
12730 This is the file where @value{GDBN} reads an initial command history
12731 list, and where it writes the command history from this session when it
12732 exits. You can access this list through history expansion or through
12733 the history command editing characters listed below. This file defaults
12734 to the value of the environment variable @code{GDBHISTFILE}, or to
12735 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
12738 @cindex history save
12739 @kindex set history save
12740 @item set history save
12741 @itemx set history save on
12742 Record command history in a file, whose name may be specified with the
12743 @code{set history filename} command. By default, this option is disabled.
12745 @item set history save off
12746 Stop recording command history in a file.
12748 @cindex history size
12749 @kindex set history size
12750 @item set history size @var{size}
12751 Set the number of commands which @value{GDBN} keeps in its history list.
12752 This defaults to the value of the environment variable
12753 @code{HISTSIZE}, or to 256 if this variable is not set.
12756 @cindex history expansion
12757 History expansion assigns special meaning to the character @kbd{!}.
12758 @ifset have-readline-appendices
12759 @xref{Event Designators}.
12762 Since @kbd{!} is also the logical not operator in C, history expansion
12763 is off by default. If you decide to enable history expansion with the
12764 @code{set history expansion on} command, you may sometimes need to
12765 follow @kbd{!} (when it is used as logical not, in an expression) with
12766 a space or a tab to prevent it from being expanded. The readline
12767 history facilities do not attempt substitution on the strings
12768 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
12770 The commands to control history expansion are:
12773 @kindex set history expansion
12774 @item set history expansion on
12775 @itemx set history expansion
12776 Enable history expansion. History expansion is off by default.
12778 @item set history expansion off
12779 Disable history expansion.
12781 The readline code comes with more complete documentation of
12782 editing and history expansion features. Users unfamiliar with @sc{gnu} Emacs
12783 or @code{vi} may wish to read it.
12784 @ifset have-readline-appendices
12785 @xref{Command Line Editing}.
12789 @kindex show history
12791 @itemx show history filename
12792 @itemx show history save
12793 @itemx show history size
12794 @itemx show history expansion
12795 These commands display the state of the @value{GDBN} history parameters.
12796 @code{show history} by itself displays all four states.
12802 @item show commands
12803 Display the last ten commands in the command history.
12805 @item show commands @var{n}
12806 Print ten commands centered on command number @var{n}.
12808 @item show commands +
12809 Print ten commands just after the commands last printed.
12813 @section Screen size
12814 @cindex size of screen
12815 @cindex pauses in output
12817 Certain commands to @value{GDBN} may produce large amounts of
12818 information output to the screen. To help you read all of it,
12819 @value{GDBN} pauses and asks you for input at the end of each page of
12820 output. Type @key{RET} when you want to continue the output, or @kbd{q}
12821 to discard the remaining output. Also, the screen width setting
12822 determines when to wrap lines of output. Depending on what is being
12823 printed, @value{GDBN} tries to break the line at a readable place,
12824 rather than simply letting it overflow onto the following line.
12826 Normally @value{GDBN} knows the size of the screen from the terminal
12827 driver software. For example, on Unix @value{GDBN} uses the termcap data base
12828 together with the value of the @code{TERM} environment variable and the
12829 @code{stty rows} and @code{stty cols} settings. If this is not correct,
12830 you can override it with the @code{set height} and @code{set
12837 @kindex show height
12838 @item set height @var{lpp}
12840 @itemx set width @var{cpl}
12842 These @code{set} commands specify a screen height of @var{lpp} lines and
12843 a screen width of @var{cpl} characters. The associated @code{show}
12844 commands display the current settings.
12846 If you specify a height of zero lines, @value{GDBN} does not pause during
12847 output no matter how long the output is. This is useful if output is to a
12848 file or to an editor buffer.
12850 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
12851 from wrapping its output.
12856 @cindex number representation
12857 @cindex entering numbers
12859 You can always enter numbers in octal, decimal, or hexadecimal in
12860 @value{GDBN} by the usual conventions: octal numbers begin with
12861 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
12862 begin with @samp{0x}. Numbers that begin with none of these are, by
12863 default, entered in base 10; likewise, the default display for
12864 numbers---when no particular format is specified---is base 10. You can
12865 change the default base for both input and output with the @code{set
12869 @kindex set input-radix
12870 @item set input-radix @var{base}
12871 Set the default base for numeric input. Supported choices
12872 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12873 specified either unambiguously or using the current default radix; for
12883 sets the base to decimal. On the other hand, @samp{set radix 10}
12884 leaves the radix unchanged no matter what it was.
12886 @kindex set output-radix
12887 @item set output-radix @var{base}
12888 Set the default base for numeric display. Supported choices
12889 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
12890 specified either unambiguously or using the current default radix.
12892 @kindex show input-radix
12893 @item show input-radix
12894 Display the current default base for numeric input.
12896 @kindex show output-radix
12897 @item show output-radix
12898 Display the current default base for numeric display.
12901 @node Messages/Warnings
12902 @section Optional warnings and messages
12904 By default, @value{GDBN} is silent about its inner workings. If you are
12905 running on a slow machine, you may want to use the @code{set verbose}
12906 command. This makes @value{GDBN} tell you when it does a lengthy
12907 internal operation, so you will not think it has crashed.
12909 Currently, the messages controlled by @code{set verbose} are those
12910 which announce that the symbol table for a source file is being read;
12911 see @code{symbol-file} in @ref{Files, ,Commands to specify files}.
12914 @kindex set verbose
12915 @item set verbose on
12916 Enables @value{GDBN} output of certain informational messages.
12918 @item set verbose off
12919 Disables @value{GDBN} output of certain informational messages.
12921 @kindex show verbose
12923 Displays whether @code{set verbose} is on or off.
12926 By default, if @value{GDBN} encounters bugs in the symbol table of an
12927 object file, it is silent; but if you are debugging a compiler, you may
12928 find this information useful (@pxref{Symbol Errors, ,Errors reading
12933 @kindex set complaints
12934 @item set complaints @var{limit}
12935 Permits @value{GDBN} to output @var{limit} complaints about each type of
12936 unusual symbols before becoming silent about the problem. Set
12937 @var{limit} to zero to suppress all complaints; set it to a large number
12938 to prevent complaints from being suppressed.
12940 @kindex show complaints
12941 @item show complaints
12942 Displays how many symbol complaints @value{GDBN} is permitted to produce.
12946 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
12947 lot of stupid questions to confirm certain commands. For example, if
12948 you try to run a program which is already running:
12952 The program being debugged has been started already.
12953 Start it from the beginning? (y or n)
12956 If you are willing to unflinchingly face the consequences of your own
12957 commands, you can disable this ``feature'':
12961 @kindex set confirm
12963 @cindex confirmation
12964 @cindex stupid questions
12965 @item set confirm off
12966 Disables confirmation requests.
12968 @item set confirm on
12969 Enables confirmation requests (the default).
12971 @kindex show confirm
12973 Displays state of confirmation requests.
12977 @node Debugging Output
12978 @section Optional messages about internal happenings
12980 @kindex set debug arch
12981 @item set debug arch
12982 Turns on or off display of gdbarch debugging info. The default is off
12983 @kindex show debug arch
12984 @item show debug arch
12985 Displays the current state of displaying gdbarch debugging info.
12986 @kindex set debug event
12987 @item set debug event
12988 Turns on or off display of @value{GDBN} event debugging info. The
12990 @kindex show debug event
12991 @item show debug event
12992 Displays the current state of displaying @value{GDBN} event debugging
12994 @kindex set debug expression
12995 @item set debug expression
12996 Turns on or off display of @value{GDBN} expression debugging info. The
12998 @kindex show debug expression
12999 @item show debug expression
13000 Displays the current state of displaying @value{GDBN} expression
13002 @kindex set debug overload
13003 @item set debug overload
13004 Turns on or off display of @value{GDBN} C@t{++} overload debugging
13005 info. This includes info such as ranking of functions, etc. The default
13007 @kindex show debug overload
13008 @item show debug overload
13009 Displays the current state of displaying @value{GDBN} C@t{++} overload
13011 @kindex set debug remote
13012 @cindex packets, reporting on stdout
13013 @cindex serial connections, debugging
13014 @item set debug remote
13015 Turns on or off display of reports on all packets sent back and forth across
13016 the serial line to the remote machine. The info is printed on the
13017 @value{GDBN} standard output stream. The default is off.
13018 @kindex show debug remote
13019 @item show debug remote
13020 Displays the state of display of remote packets.
13021 @kindex set debug serial
13022 @item set debug serial
13023 Turns on or off display of @value{GDBN} serial debugging info. The
13025 @kindex show debug serial
13026 @item show debug serial
13027 Displays the current state of displaying @value{GDBN} serial debugging
13029 @kindex set debug target
13030 @item set debug target
13031 Turns on or off display of @value{GDBN} target debugging info. This info
13032 includes what is going on at the target level of GDB, as it happens. The
13034 @kindex show debug target
13035 @item show debug target
13036 Displays the current state of displaying @value{GDBN} target debugging
13038 @kindex set debug varobj
13039 @item set debug varobj
13040 Turns on or off display of @value{GDBN} variable object debugging
13041 info. The default is off.
13042 @kindex show debug varobj
13043 @item show debug varobj
13044 Displays the current state of displaying @value{GDBN} variable object
13049 @chapter Canned Sequences of Commands
13051 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
13052 command lists}), @value{GDBN} provides two ways to store sequences of
13053 commands for execution as a unit: user-defined commands and command
13057 * Define:: User-defined commands
13058 * Hooks:: User-defined command hooks
13059 * Command Files:: Command files
13060 * Output:: Commands for controlled output
13064 @section User-defined commands
13066 @cindex user-defined command
13067 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
13068 which you assign a new name as a command. This is done with the
13069 @code{define} command. User commands may accept up to 10 arguments
13070 separated by whitespace. Arguments are accessed within the user command
13071 via @var{$arg0@dots{}$arg9}. A trivial example:
13075 print $arg0 + $arg1 + $arg2
13079 To execute the command use:
13086 This defines the command @code{adder}, which prints the sum of
13087 its three arguments. Note the arguments are text substitutions, so they may
13088 reference variables, use complex expressions, or even perform inferior
13094 @item define @var{commandname}
13095 Define a command named @var{commandname}. If there is already a command
13096 by that name, you are asked to confirm that you want to redefine it.
13098 The definition of the command is made up of other @value{GDBN} command lines,
13099 which are given following the @code{define} command. The end of these
13100 commands is marked by a line containing @code{end}.
13105 Takes a single argument, which is an expression to evaluate.
13106 It is followed by a series of commands that are executed
13107 only if the expression is true (nonzero).
13108 There can then optionally be a line @code{else}, followed
13109 by a series of commands that are only executed if the expression
13110 was false. The end of the list is marked by a line containing @code{end}.
13114 The syntax is similar to @code{if}: the command takes a single argument,
13115 which is an expression to evaluate, and must be followed by the commands to
13116 execute, one per line, terminated by an @code{end}.
13117 The commands are executed repeatedly as long as the expression
13121 @item document @var{commandname}
13122 Document the user-defined command @var{commandname}, so that it can be
13123 accessed by @code{help}. The command @var{commandname} must already be
13124 defined. This command reads lines of documentation just as @code{define}
13125 reads the lines of the command definition, ending with @code{end}.
13126 After the @code{document} command is finished, @code{help} on command
13127 @var{commandname} displays the documentation you have written.
13129 You may use the @code{document} command again to change the
13130 documentation of a command. Redefining the command with @code{define}
13131 does not change the documentation.
13133 @kindex help user-defined
13134 @item help user-defined
13135 List all user-defined commands, with the first line of the documentation
13140 @itemx show user @var{commandname}
13141 Display the @value{GDBN} commands used to define @var{commandname} (but
13142 not its documentation). If no @var{commandname} is given, display the
13143 definitions for all user-defined commands.
13145 @kindex show max-user-call-depth
13146 @kindex set max-user-call-depth
13147 @item show max-user-call-depth
13148 @itemx set max-user-call-depth
13149 The value of @code{max-user-call-depth} controls how many recursion
13150 levels are allowed in user-defined commands before GDB suspects an
13151 infinite recursion and aborts the command.
13155 When user-defined commands are executed, the
13156 commands of the definition are not printed. An error in any command
13157 stops execution of the user-defined command.
13159 If used interactively, commands that would ask for confirmation proceed
13160 without asking when used inside a user-defined command. Many @value{GDBN}
13161 commands that normally print messages to say what they are doing omit the
13162 messages when used in a user-defined command.
13165 @section User-defined command hooks
13166 @cindex command hooks
13167 @cindex hooks, for commands
13168 @cindex hooks, pre-command
13172 You may define @dfn{hooks}, which are a special kind of user-defined
13173 command. Whenever you run the command @samp{foo}, if the user-defined
13174 command @samp{hook-foo} exists, it is executed (with no arguments)
13175 before that command.
13177 @cindex hooks, post-command
13180 A hook may also be defined which is run after the command you executed.
13181 Whenever you run the command @samp{foo}, if the user-defined command
13182 @samp{hookpost-foo} exists, it is executed (with no arguments) after
13183 that command. Post-execution hooks may exist simultaneously with
13184 pre-execution hooks, for the same command.
13186 It is valid for a hook to call the command which it hooks. If this
13187 occurs, the hook is not re-executed, thereby avoiding infinte recursion.
13189 @c It would be nice if hookpost could be passed a parameter indicating
13190 @c if the command it hooks executed properly or not. FIXME!
13192 @kindex stop@r{, a pseudo-command}
13193 In addition, a pseudo-command, @samp{stop} exists. Defining
13194 (@samp{hook-stop}) makes the associated commands execute every time
13195 execution stops in your program: before breakpoint commands are run,
13196 displays are printed, or the stack frame is printed.
13198 For example, to ignore @code{SIGALRM} signals while
13199 single-stepping, but treat them normally during normal execution,
13204 handle SIGALRM nopass
13208 handle SIGALRM pass
13211 define hook-continue
13212 handle SIGLARM pass
13216 As a further example, to hook at the begining and end of the @code{echo}
13217 command, and to add extra text to the beginning and end of the message,
13225 define hookpost-echo
13229 (@value{GDBP}) echo Hello World
13230 <<<---Hello World--->>>
13235 You can define a hook for any single-word command in @value{GDBN}, but
13236 not for command aliases; you should define a hook for the basic command
13237 name, e.g. @code{backtrace} rather than @code{bt}.
13238 @c FIXME! So how does Joe User discover whether a command is an alias
13240 If an error occurs during the execution of your hook, execution of
13241 @value{GDBN} commands stops and @value{GDBN} issues a prompt
13242 (before the command that you actually typed had a chance to run).
13244 If you try to define a hook which does not match any known command, you
13245 get a warning from the @code{define} command.
13247 @node Command Files
13248 @section Command files
13250 @cindex command files
13251 A command file for @value{GDBN} is a file of lines that are @value{GDBN}
13252 commands. Comments (lines starting with @kbd{#}) may also be included.
13253 An empty line in a command file does nothing; it does not mean to repeat
13254 the last command, as it would from the terminal.
13257 @cindex @file{.gdbinit}
13258 @cindex @file{gdb.ini}
13259 When you start @value{GDBN}, it automatically executes commands from its
13260 @dfn{init files}, normally called @file{.gdbinit}@footnote{The DJGPP
13261 port of @value{GDBN} uses the name @file{gdb.ini} instead, due to the
13262 limitations of file names imposed by DOS filesystems.}.
13263 During startup, @value{GDBN} does the following:
13267 Reads the init file (if any) in your home directory@footnote{On
13268 DOS/Windows systems, the home directory is the one pointed to by the
13269 @code{HOME} environment variable.}.
13272 Processes command line options and operands.
13275 Reads the init file (if any) in the current working directory.
13278 Reads command files specified by the @samp{-x} option.
13281 The init file in your home directory can set options (such as @samp{set
13282 complaints}) that affect subsequent processing of command line options
13283 and operands. Init files are not executed if you use the @samp{-nx}
13284 option (@pxref{Mode Options, ,Choosing modes}).
13286 @cindex init file name
13287 On some configurations of @value{GDBN}, the init file is known by a
13288 different name (these are typically environments where a specialized
13289 form of @value{GDBN} may need to coexist with other forms, hence a
13290 different name for the specialized version's init file). These are the
13291 environments with special init file names:
13293 @cindex @file{.vxgdbinit}
13296 VxWorks (Wind River Systems real-time OS): @file{.vxgdbinit}
13298 @cindex @file{.os68gdbinit}
13300 OS68K (Enea Data Systems real-time OS): @file{.os68gdbinit}
13302 @cindex @file{.esgdbinit}
13304 ES-1800 (Ericsson Telecom AB M68000 emulator): @file{.esgdbinit}
13307 You can also request the execution of a command file with the
13308 @code{source} command:
13312 @item source @var{filename}
13313 Execute the command file @var{filename}.
13316 The lines in a command file are executed sequentially. They are not
13317 printed as they are executed. An error in any command terminates
13318 execution of the command file and control is returned to the console.
13320 Commands that would ask for confirmation if used interactively proceed
13321 without asking when used in a command file. Many @value{GDBN} commands that
13322 normally print messages to say what they are doing omit the messages
13323 when called from command files.
13325 @value{GDBN} also accepts command input from standard input. In this
13326 mode, normal output goes to standard output and error output goes to
13327 standard error. Errors in a command file supplied on standard input do
13328 not terminate execution of the command file --- execution continues with
13332 gdb < cmds > log 2>&1
13335 (The syntax above will vary depending on the shell used.) This example
13336 will execute commands from the file @file{cmds}. All output and errors
13337 would be directed to @file{log}.
13340 @section Commands for controlled output
13342 During the execution of a command file or a user-defined command, normal
13343 @value{GDBN} output is suppressed; the only output that appears is what is
13344 explicitly printed by the commands in the definition. This section
13345 describes three commands useful for generating exactly the output you
13350 @item echo @var{text}
13351 @c I do not consider backslash-space a standard C escape sequence
13352 @c because it is not in ANSI.
13353 Print @var{text}. Nonprinting characters can be included in
13354 @var{text} using C escape sequences, such as @samp{\n} to print a
13355 newline. @strong{No newline is printed unless you specify one.}
13356 In addition to the standard C escape sequences, a backslash followed
13357 by a space stands for a space. This is useful for displaying a
13358 string with spaces at the beginning or the end, since leading and
13359 trailing spaces are otherwise trimmed from all arguments.
13360 To print @samp{@w{ }and foo =@w{ }}, use the command
13361 @samp{echo \@w{ }and foo = \@w{ }}.
13363 A backslash at the end of @var{text} can be used, as in C, to continue
13364 the command onto subsequent lines. For example,
13367 echo This is some text\n\
13368 which is continued\n\
13369 onto several lines.\n
13372 produces the same output as
13375 echo This is some text\n
13376 echo which is continued\n
13377 echo onto several lines.\n
13381 @item output @var{expression}
13382 Print the value of @var{expression} and nothing but that value: no
13383 newlines, no @samp{$@var{nn} = }. The value is not entered in the
13384 value history either. @xref{Expressions, ,Expressions}, for more information
13387 @item output/@var{fmt} @var{expression}
13388 Print the value of @var{expression} in format @var{fmt}. You can use
13389 the same formats as for @code{print}. @xref{Output Formats,,Output
13390 formats}, for more information.
13393 @item printf @var{string}, @var{expressions}@dots{}
13394 Print the values of the @var{expressions} under the control of
13395 @var{string}. The @var{expressions} are separated by commas and may be
13396 either numbers or pointers. Their values are printed as specified by
13397 @var{string}, exactly as if your program were to execute the C
13399 @c FIXME: the above implies that at least all ANSI C formats are
13400 @c supported, but it isn't true: %E and %G don't work (or so it seems).
13401 @c Either this is a bug, or the manual should document what formats are
13405 printf (@var{string}, @var{expressions}@dots{});
13408 For example, you can print two values in hex like this:
13411 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
13414 The only backslash-escape sequences that you can use in the format
13415 string are the simple ones that consist of backslash followed by a
13420 @chapter @value{GDBN} Text User Interface
13424 * TUI Overview:: TUI overview
13425 * TUI Keys:: TUI key bindings
13426 * TUI Single Key Mode:: TUI single key mode
13427 * TUI Commands:: TUI specific commands
13428 * TUI Configuration:: TUI configuration variables
13431 The @value{GDBN} Text User Interface, TUI in short,
13432 is a terminal interface which uses the @code{curses} library
13433 to show the source file, the assembly output, the program registers
13434 and @value{GDBN} commands in separate text windows.
13435 The TUI is available only when @value{GDBN} is configured
13436 with the @code{--enable-tui} configure option (@pxref{Configure Options}).
13439 @section TUI overview
13441 The TUI has two display modes that can be switched while
13446 A curses (or TUI) mode in which it displays several text
13447 windows on the terminal.
13450 A standard mode which corresponds to the @value{GDBN} configured without
13454 In the TUI mode, @value{GDBN} can display several text window
13459 This window is the @value{GDBN} command window with the @value{GDBN}
13460 prompt and the @value{GDBN} outputs. The @value{GDBN} input is still
13461 managed using readline but through the TUI. The @emph{command}
13462 window is always visible.
13465 The source window shows the source file of the program. The current
13466 line as well as active breakpoints are displayed in this window.
13469 The assembly window shows the disassembly output of the program.
13472 This window shows the processor registers. It detects when
13473 a register is changed and when this is the case, registers that have
13474 changed are highlighted.
13478 The source and assembly windows show the current program position
13479 by highlighting the current line and marking them with the @samp{>} marker.
13480 Breakpoints are also indicated with two markers. A first one
13481 indicates the breakpoint type:
13485 Breakpoint which was hit at least once.
13488 Breakpoint which was never hit.
13491 Hardware breakpoint which was hit at least once.
13494 Hardware breakpoint which was never hit.
13498 The second marker indicates whether the breakpoint is enabled or not:
13502 Breakpoint is enabled.
13505 Breakpoint is disabled.
13509 The source, assembly and register windows are attached to the thread
13510 and the frame position. They are updated when the current thread
13511 changes, when the frame changes or when the program counter changes.
13512 These three windows are arranged by the TUI according to several
13513 layouts. The layout defines which of these three windows are visible.
13514 The following layouts are available:
13524 source and assembly
13527 source and registers
13530 assembly and registers
13534 On top of the command window a status line gives various information
13535 concerning the current process begin debugged. The status line is
13536 updated when the information it shows changes. The following fields
13541 Indicates the current gdb target
13542 (@pxref{Targets, ,Specifying a Debugging Target}).
13545 Gives information about the current process or thread number.
13546 When no process is being debugged, this field is set to @code{No process}.
13549 Gives the current function name for the selected frame.
13550 The name is demangled if demangling is turned on (@pxref{Print Settings}).
13551 When there is no symbol corresponding to the current program counter
13552 the string @code{??} is displayed.
13555 Indicates the current line number for the selected frame.
13556 When the current line number is not known the string @code{??} is displayed.
13559 Indicates the current program counter address.
13564 @section TUI Key Bindings
13565 @cindex TUI key bindings
13567 The TUI installs several key bindings in the readline keymaps
13568 (@pxref{Command Line Editing}).
13569 They allow to leave or enter in the TUI mode or they operate
13570 directly on the TUI layout and windows. The TUI also provides
13571 a @emph{SingleKey} keymap which binds several keys directly to
13572 @value{GDBN} commands. The following key bindings
13573 are installed for both TUI mode and the @value{GDBN} standard mode.
13582 Enter or leave the TUI mode. When the TUI mode is left,
13583 the curses window management is left and @value{GDBN} operates using
13584 its standard mode writing on the terminal directly. When the TUI
13585 mode is entered, the control is given back to the curses windows.
13586 The screen is then refreshed.
13590 Use a TUI layout with only one window. The layout will
13591 either be @samp{source} or @samp{assembly}. When the TUI mode
13592 is not active, it will switch to the TUI mode.
13594 Think of this key binding as the Emacs @kbd{C-x 1} binding.
13598 Use a TUI layout with at least two windows. When the current
13599 layout shows already two windows, a next layout with two windows is used.
13600 When a new layout is chosen, one window will always be common to the
13601 previous layout and the new one.
13603 Think of it as the Emacs @kbd{C-x 2} binding.
13607 Use the TUI @emph{SingleKey} keymap that binds single key to gdb commands
13608 (@pxref{TUI Single Key Mode}).
13612 The following key bindings are handled only by the TUI mode:
13617 Scroll the active window one page up.
13621 Scroll the active window one page down.
13625 Scroll the active window one line up.
13629 Scroll the active window one line down.
13633 Scroll the active window one column left.
13637 Scroll the active window one column right.
13641 Refresh the screen.
13645 In the TUI mode, the arrow keys are used by the active window
13646 for scrolling. This means they are not available for readline. It is
13647 necessary to use other readline key bindings such as @key{C-p}, @key{C-n},
13648 @key{C-b} and @key{C-f}.
13650 @node TUI Single Key Mode
13651 @section TUI Single Key Mode
13652 @cindex TUI single key mode
13654 The TUI provides a @emph{SingleKey} mode in which it installs a particular
13655 key binding in the readline keymaps to connect single keys to
13659 @kindex c @r{(SingleKey TUI key)}
13663 @kindex d @r{(SingleKey TUI key)}
13667 @kindex f @r{(SingleKey TUI key)}
13671 @kindex n @r{(SingleKey TUI key)}
13675 @kindex q @r{(SingleKey TUI key)}
13677 exit the @emph{SingleKey} mode.
13679 @kindex r @r{(SingleKey TUI key)}
13683 @kindex s @r{(SingleKey TUI key)}
13687 @kindex u @r{(SingleKey TUI key)}
13691 @kindex v @r{(SingleKey TUI key)}
13695 @kindex w @r{(SingleKey TUI key)}
13701 Other keys temporarily switch to the @value{GDBN} command prompt.
13702 The key that was pressed is inserted in the editing buffer so that
13703 it is possible to type most @value{GDBN} commands without interaction
13704 with the TUI @emph{SingleKey} mode. Once the command is entered the TUI
13705 @emph{SingleKey} mode is restored. The only way to permanently leave
13706 this mode is by hitting @key{q} or @samp{@key{C-x} @key{s}}.
13710 @section TUI specific commands
13711 @cindex TUI commands
13713 The TUI has specific commands to control the text windows.
13714 These commands are always available, that is they do not depend on
13715 the current terminal mode in which @value{GDBN} runs. When @value{GDBN}
13716 is in the standard mode, using these commands will automatically switch
13722 List and give the size of all displayed windows.
13725 @kindex layout next
13726 Display the next layout.
13729 @kindex layout prev
13730 Display the previous layout.
13734 Display the source window only.
13738 Display the assembly window only.
13741 @kindex layout split
13742 Display the source and assembly window.
13745 @kindex layout regs
13746 Display the register window together with the source or assembly window.
13748 @item focus next | prev | src | asm | regs | split
13750 Set the focus to the named window.
13751 This command allows to change the active window so that scrolling keys
13752 can be affected to another window.
13756 Refresh the screen. This is similar to using @key{C-L} key.
13760 Update the source window and the current execution point.
13762 @item winheight @var{name} +@var{count}
13763 @itemx winheight @var{name} -@var{count}
13765 Change the height of the window @var{name} by @var{count}
13766 lines. Positive counts increase the height, while negative counts
13771 @node TUI Configuration
13772 @section TUI configuration variables
13773 @cindex TUI configuration variables
13775 The TUI has several configuration variables that control the
13776 appearance of windows on the terminal.
13779 @item set tui border-kind @var{kind}
13780 @kindex set tui border-kind
13781 Select the border appearance for the source, assembly and register windows.
13782 The possible values are the following:
13785 Use a space character to draw the border.
13788 Use ascii characters + - and | to draw the border.
13791 Use the Alternate Character Set to draw the border. The border is
13792 drawn using character line graphics if the terminal supports them.
13796 @item set tui active-border-mode @var{mode}
13797 @kindex set tui active-border-mode
13798 Select the attributes to display the border of the active window.
13799 The possible values are @code{normal}, @code{standout}, @code{reverse},
13800 @code{half}, @code{half-standout}, @code{bold} and @code{bold-standout}.
13802 @item set tui border-mode @var{mode}
13803 @kindex set tui border-mode
13804 Select the attributes to display the border of other windows.
13805 The @var{mode} can be one of the following:
13808 Use normal attributes to display the border.
13814 Use reverse video mode.
13817 Use half bright mode.
13819 @item half-standout
13820 Use half bright and standout mode.
13823 Use extra bright or bold mode.
13825 @item bold-standout
13826 Use extra bright or bold and standout mode.
13833 @chapter Using @value{GDBN} under @sc{gnu} Emacs
13836 @cindex @sc{gnu} Emacs
13837 A special interface allows you to use @sc{gnu} Emacs to view (and
13838 edit) the source files for the program you are debugging with
13841 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
13842 executable file you want to debug as an argument. This command starts
13843 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
13844 created Emacs buffer.
13845 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
13847 Using @value{GDBN} under Emacs is just like using @value{GDBN} normally except for two
13852 All ``terminal'' input and output goes through the Emacs buffer.
13855 This applies both to @value{GDBN} commands and their output, and to the input
13856 and output done by the program you are debugging.
13858 This is useful because it means that you can copy the text of previous
13859 commands and input them again; you can even use parts of the output
13862 All the facilities of Emacs' Shell mode are available for interacting
13863 with your program. In particular, you can send signals the usual
13864 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
13869 @value{GDBN} displays source code through Emacs.
13872 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
13873 source file for that frame and puts an arrow (@samp{=>}) at the
13874 left margin of the current line. Emacs uses a separate buffer for
13875 source display, and splits the screen to show both your @value{GDBN} session
13878 Explicit @value{GDBN} @code{list} or search commands still produce output as
13879 usual, but you probably have no reason to use them from Emacs.
13882 @emph{Warning:} If the directory where your program resides is not your
13883 current directory, it can be easy to confuse Emacs about the location of
13884 the source files, in which case the auxiliary display buffer does not
13885 appear to show your source. @value{GDBN} can find programs by searching your
13886 environment's @code{PATH} variable, so the @value{GDBN} input and output
13887 session proceeds normally; but Emacs does not get enough information
13888 back from @value{GDBN} to locate the source files in this situation. To
13889 avoid this problem, either start @value{GDBN} mode from the directory where
13890 your program resides, or specify an absolute file name when prompted for the
13891 @kbd{M-x gdb} argument.
13893 A similar confusion can result if you use the @value{GDBN} @code{file} command to
13894 switch to debugging a program in some other location, from an existing
13895 @value{GDBN} buffer in Emacs.
13898 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
13899 you need to call @value{GDBN} by a different name (for example, if you keep
13900 several configurations around, with different names) you can set the
13901 Emacs variable @code{gdb-command-name}; for example,
13904 (setq gdb-command-name "mygdb")
13908 (preceded by @kbd{M-:} or @kbd{ESC :}, or typed in the @code{*scratch*} buffer, or
13909 in your @file{.emacs} file) makes Emacs call the program named
13910 ``@code{mygdb}'' instead.
13912 In the @value{GDBN} I/O buffer, you can use these special Emacs commands in
13913 addition to the standard Shell mode commands:
13917 Describe the features of Emacs' @value{GDBN} Mode.
13920 Execute to another source line, like the @value{GDBN} @code{step} command; also
13921 update the display window to show the current file and location.
13924 Execute to next source line in this function, skipping all function
13925 calls, like the @value{GDBN} @code{next} command. Then update the display window
13926 to show the current file and location.
13929 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
13930 display window accordingly.
13932 @item M-x gdb-nexti
13933 Execute to next instruction, using the @value{GDBN} @code{nexti} command; update
13934 display window accordingly.
13937 Execute until exit from the selected stack frame, like the @value{GDBN}
13938 @code{finish} command.
13941 Continue execution of your program, like the @value{GDBN} @code{continue}
13944 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
13947 Go up the number of frames indicated by the numeric argument
13948 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
13949 like the @value{GDBN} @code{up} command.
13951 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
13954 Go down the number of frames indicated by the numeric argument, like the
13955 @value{GDBN} @code{down} command.
13957 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
13960 Read the number where the cursor is positioned, and insert it at the end
13961 of the @value{GDBN} I/O buffer. For example, if you wish to disassemble code
13962 around an address that was displayed earlier, type @kbd{disassemble};
13963 then move the cursor to the address display, and pick up the
13964 argument for @code{disassemble} by typing @kbd{C-x &}.
13966 You can customize this further by defining elements of the list
13967 @code{gdb-print-command}; once it is defined, you can format or
13968 otherwise process numbers picked up by @kbd{C-x &} before they are
13969 inserted. A numeric argument to @kbd{C-x &} indicates that you
13970 wish special formatting, and also acts as an index to pick an element of the
13971 list. If the list element is a string, the number to be inserted is
13972 formatted using the Emacs function @code{format}; otherwise the number
13973 is passed as an argument to the corresponding list element.
13976 In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
13977 tells @value{GDBN} to set a breakpoint on the source line point is on.
13979 If you accidentally delete the source-display buffer, an easy way to get
13980 it back is to type the command @code{f} in the @value{GDBN} buffer, to
13981 request a frame display; when you run under Emacs, this recreates
13982 the source buffer if necessary to show you the context of the current
13985 The source files displayed in Emacs are in ordinary Emacs buffers
13986 which are visiting the source files in the usual way. You can edit
13987 the files with these buffers if you wish; but keep in mind that @value{GDBN}
13988 communicates with Emacs in terms of line numbers. If you add or
13989 delete lines from the text, the line numbers that @value{GDBN} knows cease
13990 to correspond properly with the code.
13992 @c The following dropped because Epoch is nonstandard. Reactivate
13993 @c if/when v19 does something similar. ---doc@cygnus.com 19dec1990
13995 @kindex Emacs Epoch environment
13999 Version 18 of @sc{gnu} Emacs has a built-in window system
14000 called the @code{epoch}
14001 environment. Users of this environment can use a new command,
14002 @code{inspect} which performs identically to @code{print} except that
14003 each value is printed in its own window.
14006 @include annotate.texi
14007 @include gdbmi.texinfo
14010 @chapter Reporting Bugs in @value{GDBN}
14011 @cindex bugs in @value{GDBN}
14012 @cindex reporting bugs in @value{GDBN}
14014 Your bug reports play an essential role in making @value{GDBN} reliable.
14016 Reporting a bug may help you by bringing a solution to your problem, or it
14017 may not. But in any case the principal function of a bug report is to help
14018 the entire community by making the next version of @value{GDBN} work better. Bug
14019 reports are your contribution to the maintenance of @value{GDBN}.
14021 In order for a bug report to serve its purpose, you must include the
14022 information that enables us to fix the bug.
14025 * Bug Criteria:: Have you found a bug?
14026 * Bug Reporting:: How to report bugs
14030 @section Have you found a bug?
14031 @cindex bug criteria
14033 If you are not sure whether you have found a bug, here are some guidelines:
14036 @cindex fatal signal
14037 @cindex debugger crash
14038 @cindex crash of debugger
14040 If the debugger gets a fatal signal, for any input whatever, that is a
14041 @value{GDBN} bug. Reliable debuggers never crash.
14043 @cindex error on valid input
14045 If @value{GDBN} produces an error message for valid input, that is a
14046 bug. (Note that if you're cross debugging, the problem may also be
14047 somewhere in the connection to the target.)
14049 @cindex invalid input
14051 If @value{GDBN} does not produce an error message for invalid input,
14052 that is a bug. However, you should note that your idea of
14053 ``invalid input'' might be our idea of ``an extension'' or ``support
14054 for traditional practice''.
14057 If you are an experienced user of debugging tools, your suggestions
14058 for improvement of @value{GDBN} are welcome in any case.
14061 @node Bug Reporting
14062 @section How to report bugs
14063 @cindex bug reports
14064 @cindex @value{GDBN} bugs, reporting
14066 A number of companies and individuals offer support for @sc{gnu} products.
14067 If you obtained @value{GDBN} from a support organization, we recommend you
14068 contact that organization first.
14070 You can find contact information for many support companies and
14071 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
14073 @c should add a web page ref...
14075 In any event, we also recommend that you submit bug reports for
14076 @value{GDBN}. The prefered method is to submit them directly using
14077 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
14078 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
14081 @strong{Do not send bug reports to @samp{info-gdb}, or to
14082 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
14083 not want to receive bug reports. Those that do have arranged to receive
14086 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
14087 serves as a repeater. The mailing list and the newsgroup carry exactly
14088 the same messages. Often people think of posting bug reports to the
14089 newsgroup instead of mailing them. This appears to work, but it has one
14090 problem which can be crucial: a newsgroup posting often lacks a mail
14091 path back to the sender. Thus, if we need to ask for more information,
14092 we may be unable to reach you. For this reason, it is better to send
14093 bug reports to the mailing list.
14095 The fundamental principle of reporting bugs usefully is this:
14096 @strong{report all the facts}. If you are not sure whether to state a
14097 fact or leave it out, state it!
14099 Often people omit facts because they think they know what causes the
14100 problem and assume that some details do not matter. Thus, you might
14101 assume that the name of the variable you use in an example does not matter.
14102 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
14103 stray memory reference which happens to fetch from the location where that
14104 name is stored in memory; perhaps, if the name were different, the contents
14105 of that location would fool the debugger into doing the right thing despite
14106 the bug. Play it safe and give a specific, complete example. That is the
14107 easiest thing for you to do, and the most helpful.
14109 Keep in mind that the purpose of a bug report is to enable us to fix the
14110 bug. It may be that the bug has been reported previously, but neither
14111 you nor we can know that unless your bug report is complete and
14114 Sometimes people give a few sketchy facts and ask, ``Does this ring a
14115 bell?'' Those bug reports are useless, and we urge everyone to
14116 @emph{refuse to respond to them} except to chide the sender to report
14119 To enable us to fix the bug, you should include all these things:
14123 The version of @value{GDBN}. @value{GDBN} announces it if you start
14124 with no arguments; you can also print it at any time using @code{show
14127 Without this, we will not know whether there is any point in looking for
14128 the bug in the current version of @value{GDBN}.
14131 The type of machine you are using, and the operating system name and
14135 What compiler (and its version) was used to compile @value{GDBN}---e.g.
14136 ``@value{GCC}--2.8.1''.
14139 What compiler (and its version) was used to compile the program you are
14140 debugging---e.g. ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
14141 C Compiler''. For GCC, you can say @code{gcc --version} to get this
14142 information; for other compilers, see the documentation for those
14146 The command arguments you gave the compiler to compile your example and
14147 observe the bug. For example, did you use @samp{-O}? To guarantee
14148 you will not omit something important, list them all. A copy of the
14149 Makefile (or the output from make) is sufficient.
14151 If we were to try to guess the arguments, we would probably guess wrong
14152 and then we might not encounter the bug.
14155 A complete input script, and all necessary source files, that will
14159 A description of what behavior you observe that you believe is
14160 incorrect. For example, ``It gets a fatal signal.''
14162 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
14163 will certainly notice it. But if the bug is incorrect output, we might
14164 not notice unless it is glaringly wrong. You might as well not give us
14165 a chance to make a mistake.
14167 Even if the problem you experience is a fatal signal, you should still
14168 say so explicitly. Suppose something strange is going on, such as, your
14169 copy of @value{GDBN} is out of synch, or you have encountered a bug in
14170 the C library on your system. (This has happened!) Your copy might
14171 crash and ours would not. If you told us to expect a crash, then when
14172 ours fails to crash, we would know that the bug was not happening for
14173 us. If you had not told us to expect a crash, then we would not be able
14174 to draw any conclusion from our observations.
14177 If you wish to suggest changes to the @value{GDBN} source, send us context
14178 diffs. If you even discuss something in the @value{GDBN} source, refer to
14179 it by context, not by line number.
14181 The line numbers in our development sources will not match those in your
14182 sources. Your line numbers would convey no useful information to us.
14186 Here are some things that are not necessary:
14190 A description of the envelope of the bug.
14192 Often people who encounter a bug spend a lot of time investigating
14193 which changes to the input file will make the bug go away and which
14194 changes will not affect it.
14196 This is often time consuming and not very useful, because the way we
14197 will find the bug is by running a single example under the debugger
14198 with breakpoints, not by pure deduction from a series of examples.
14199 We recommend that you save your time for something else.
14201 Of course, if you can find a simpler example to report @emph{instead}
14202 of the original one, that is a convenience for us. Errors in the
14203 output will be easier to spot, running under the debugger will take
14204 less time, and so on.
14206 However, simplification is not vital; if you do not want to do this,
14207 report the bug anyway and send us the entire test case you used.
14210 A patch for the bug.
14212 A patch for the bug does help us if it is a good one. But do not omit
14213 the necessary information, such as the test case, on the assumption that
14214 a patch is all we need. We might see problems with your patch and decide
14215 to fix the problem another way, or we might not understand it at all.
14217 Sometimes with a program as complicated as @value{GDBN} it is very hard to
14218 construct an example that will make the program follow a certain path
14219 through the code. If you do not send us the example, we will not be able
14220 to construct one, so we will not be able to verify that the bug is fixed.
14222 And if we cannot understand what bug you are trying to fix, or why your
14223 patch should be an improvement, we will not install it. A test case will
14224 help us to understand.
14227 A guess about what the bug is or what it depends on.
14229 Such guesses are usually wrong. Even we cannot guess right about such
14230 things without first using the debugger to find the facts.
14233 @c The readline documentation is distributed with the readline code
14234 @c and consists of the two following files:
14236 @c inc-hist.texinfo
14237 @c Use -I with makeinfo to point to the appropriate directory,
14238 @c environment var TEXINPUTS with TeX.
14239 @include rluser.texinfo
14240 @include inc-hist.texinfo
14243 @node Formatting Documentation
14244 @appendix Formatting Documentation
14246 @cindex @value{GDBN} reference card
14247 @cindex reference card
14248 The @value{GDBN} 4 release includes an already-formatted reference card, ready
14249 for printing with PostScript or Ghostscript, in the @file{gdb}
14250 subdirectory of the main source directory@footnote{In
14251 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
14252 release.}. If you can use PostScript or Ghostscript with your printer,
14253 you can print the reference card immediately with @file{refcard.ps}.
14255 The release also includes the source for the reference card. You
14256 can format it, using @TeX{}, by typing:
14262 The @value{GDBN} reference card is designed to print in @dfn{landscape}
14263 mode on US ``letter'' size paper;
14264 that is, on a sheet 11 inches wide by 8.5 inches
14265 high. You will need to specify this form of printing as an option to
14266 your @sc{dvi} output program.
14268 @cindex documentation
14270 All the documentation for @value{GDBN} comes as part of the machine-readable
14271 distribution. The documentation is written in Texinfo format, which is
14272 a documentation system that uses a single source file to produce both
14273 on-line information and a printed manual. You can use one of the Info
14274 formatting commands to create the on-line version of the documentation
14275 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
14277 @value{GDBN} includes an already formatted copy of the on-line Info
14278 version of this manual in the @file{gdb} subdirectory. The main Info
14279 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
14280 subordinate files matching @samp{gdb.info*} in the same directory. If
14281 necessary, you can print out these files, or read them with any editor;
14282 but they are easier to read using the @code{info} subsystem in @sc{gnu}
14283 Emacs or the standalone @code{info} program, available as part of the
14284 @sc{gnu} Texinfo distribution.
14286 If you want to format these Info files yourself, you need one of the
14287 Info formatting programs, such as @code{texinfo-format-buffer} or
14290 If you have @code{makeinfo} installed, and are in the top level
14291 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
14292 version @value{GDBVN}), you can make the Info file by typing:
14299 If you want to typeset and print copies of this manual, you need @TeX{},
14300 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
14301 Texinfo definitions file.
14303 @TeX{} is a typesetting program; it does not print files directly, but
14304 produces output files called @sc{dvi} files. To print a typeset
14305 document, you need a program to print @sc{dvi} files. If your system
14306 has @TeX{} installed, chances are it has such a program. The precise
14307 command to use depends on your system; @kbd{lpr -d} is common; another
14308 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
14309 require a file name without any extension or a @samp{.dvi} extension.
14311 @TeX{} also requires a macro definitions file called
14312 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
14313 written in Texinfo format. On its own, @TeX{} cannot either read or
14314 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
14315 and is located in the @file{gdb-@var{version-number}/texinfo}
14318 If you have @TeX{} and a @sc{dvi} printer program installed, you can
14319 typeset and print this manual. First switch to the the @file{gdb}
14320 subdirectory of the main source directory (for example, to
14321 @file{gdb-@value{GDBVN}/gdb}) and type:
14327 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
14329 @node Installing GDB
14330 @appendix Installing @value{GDBN}
14331 @cindex configuring @value{GDBN}
14332 @cindex installation
14334 @value{GDBN} comes with a @code{configure} script that automates the process
14335 of preparing @value{GDBN} for installation; you can then use @code{make} to
14336 build the @code{gdb} program.
14338 @c irrelevant in info file; it's as current as the code it lives with.
14339 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
14340 look at the @file{README} file in the sources; we may have improved the
14341 installation procedures since publishing this manual.}
14344 The @value{GDBN} distribution includes all the source code you need for
14345 @value{GDBN} in a single directory, whose name is usually composed by
14346 appending the version number to @samp{gdb}.
14348 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
14349 @file{gdb-@value{GDBVN}} directory. That directory contains:
14352 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
14353 script for configuring @value{GDBN} and all its supporting libraries
14355 @item gdb-@value{GDBVN}/gdb
14356 the source specific to @value{GDBN} itself
14358 @item gdb-@value{GDBVN}/bfd
14359 source for the Binary File Descriptor library
14361 @item gdb-@value{GDBVN}/include
14362 @sc{gnu} include files
14364 @item gdb-@value{GDBVN}/libiberty
14365 source for the @samp{-liberty} free software library
14367 @item gdb-@value{GDBVN}/opcodes
14368 source for the library of opcode tables and disassemblers
14370 @item gdb-@value{GDBVN}/readline
14371 source for the @sc{gnu} command-line interface
14373 @item gdb-@value{GDBVN}/glob
14374 source for the @sc{gnu} filename pattern-matching subroutine
14376 @item gdb-@value{GDBVN}/mmalloc
14377 source for the @sc{gnu} memory-mapped malloc package
14380 The simplest way to configure and build @value{GDBN} is to run @code{configure}
14381 from the @file{gdb-@var{version-number}} source directory, which in
14382 this example is the @file{gdb-@value{GDBVN}} directory.
14384 First switch to the @file{gdb-@var{version-number}} source directory
14385 if you are not already in it; then run @code{configure}. Pass the
14386 identifier for the platform on which @value{GDBN} will run as an
14392 cd gdb-@value{GDBVN}
14393 ./configure @var{host}
14398 where @var{host} is an identifier such as @samp{sun4} or
14399 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
14400 (You can often leave off @var{host}; @code{configure} tries to guess the
14401 correct value by examining your system.)
14403 Running @samp{configure @var{host}} and then running @code{make} builds the
14404 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
14405 libraries, then @code{gdb} itself. The configured source files, and the
14406 binaries, are left in the corresponding source directories.
14409 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
14410 system does not recognize this automatically when you run a different
14411 shell, you may need to run @code{sh} on it explicitly:
14414 sh configure @var{host}
14417 If you run @code{configure} from a directory that contains source
14418 directories for multiple libraries or programs, such as the
14419 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN}, @code{configure}
14420 creates configuration files for every directory level underneath (unless
14421 you tell it not to, with the @samp{--norecursion} option).
14423 You can run the @code{configure} script from any of the
14424 subordinate directories in the @value{GDBN} distribution if you only want to
14425 configure that subdirectory, but be sure to specify a path to it.
14427 For example, with version @value{GDBVN}, type the following to configure only
14428 the @code{bfd} subdirectory:
14432 cd gdb-@value{GDBVN}/bfd
14433 ../configure @var{host}
14437 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
14438 However, you should make sure that the shell on your path (named by
14439 the @samp{SHELL} environment variable) is publicly readable. Remember
14440 that @value{GDBN} uses the shell to start your program---some systems refuse to
14441 let @value{GDBN} debug child processes whose programs are not readable.
14444 * Separate Objdir:: Compiling @value{GDBN} in another directory
14445 * Config Names:: Specifying names for hosts and targets
14446 * Configure Options:: Summary of options for configure
14449 @node Separate Objdir
14450 @section Compiling @value{GDBN} in another directory
14452 If you want to run @value{GDBN} versions for several host or target machines,
14453 you need a different @code{gdb} compiled for each combination of
14454 host and target. @code{configure} is designed to make this easy by
14455 allowing you to generate each configuration in a separate subdirectory,
14456 rather than in the source directory. If your @code{make} program
14457 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
14458 @code{make} in each of these directories builds the @code{gdb}
14459 program specified there.
14461 To build @code{gdb} in a separate directory, run @code{configure}
14462 with the @samp{--srcdir} option to specify where to find the source.
14463 (You also need to specify a path to find @code{configure}
14464 itself from your working directory. If the path to @code{configure}
14465 would be the same as the argument to @samp{--srcdir}, you can leave out
14466 the @samp{--srcdir} option; it is assumed.)
14468 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
14469 separate directory for a Sun 4 like this:
14473 cd gdb-@value{GDBVN}
14476 ../gdb-@value{GDBVN}/configure sun4
14481 When @code{configure} builds a configuration using a remote source
14482 directory, it creates a tree for the binaries with the same structure
14483 (and using the same names) as the tree under the source directory. In
14484 the example, you'd find the Sun 4 library @file{libiberty.a} in the
14485 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
14486 @file{gdb-sun4/gdb}.
14488 One popular reason to build several @value{GDBN} configurations in separate
14489 directories is to configure @value{GDBN} for cross-compiling (where
14490 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
14491 programs that run on another machine---the @dfn{target}).
14492 You specify a cross-debugging target by
14493 giving the @samp{--target=@var{target}} option to @code{configure}.
14495 When you run @code{make} to build a program or library, you must run
14496 it in a configured directory---whatever directory you were in when you
14497 called @code{configure} (or one of its subdirectories).
14499 The @code{Makefile} that @code{configure} generates in each source
14500 directory also runs recursively. If you type @code{make} in a source
14501 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
14502 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
14503 will build all the required libraries, and then build GDB.
14505 When you have multiple hosts or targets configured in separate
14506 directories, you can run @code{make} on them in parallel (for example,
14507 if they are NFS-mounted on each of the hosts); they will not interfere
14511 @section Specifying names for hosts and targets
14513 The specifications used for hosts and targets in the @code{configure}
14514 script are based on a three-part naming scheme, but some short predefined
14515 aliases are also supported. The full naming scheme encodes three pieces
14516 of information in the following pattern:
14519 @var{architecture}-@var{vendor}-@var{os}
14522 For example, you can use the alias @code{sun4} as a @var{host} argument,
14523 or as the value for @var{target} in a @code{--target=@var{target}}
14524 option. The equivalent full name is @samp{sparc-sun-sunos4}.
14526 The @code{configure} script accompanying @value{GDBN} does not provide
14527 any query facility to list all supported host and target names or
14528 aliases. @code{configure} calls the Bourne shell script
14529 @code{config.sub} to map abbreviations to full names; you can read the
14530 script, if you wish, or you can use it to test your guesses on
14531 abbreviations---for example:
14534 % sh config.sub i386-linux
14536 % sh config.sub alpha-linux
14537 alpha-unknown-linux-gnu
14538 % sh config.sub hp9k700
14540 % sh config.sub sun4
14541 sparc-sun-sunos4.1.1
14542 % sh config.sub sun3
14543 m68k-sun-sunos4.1.1
14544 % sh config.sub i986v
14545 Invalid configuration `i986v': machine `i986v' not recognized
14549 @code{config.sub} is also distributed in the @value{GDBN} source
14550 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
14552 @node Configure Options
14553 @section @code{configure} options
14555 Here is a summary of the @code{configure} options and arguments that
14556 are most often useful for building @value{GDBN}. @code{configure} also has
14557 several other options not listed here. @inforef{What Configure
14558 Does,,configure.info}, for a full explanation of @code{configure}.
14561 configure @r{[}--help@r{]}
14562 @r{[}--prefix=@var{dir}@r{]}
14563 @r{[}--exec-prefix=@var{dir}@r{]}
14564 @r{[}--srcdir=@var{dirname}@r{]}
14565 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
14566 @r{[}--target=@var{target}@r{]}
14571 You may introduce options with a single @samp{-} rather than
14572 @samp{--} if you prefer; but you may abbreviate option names if you use
14577 Display a quick summary of how to invoke @code{configure}.
14579 @item --prefix=@var{dir}
14580 Configure the source to install programs and files under directory
14583 @item --exec-prefix=@var{dir}
14584 Configure the source to install programs under directory
14587 @c avoid splitting the warning from the explanation:
14589 @item --srcdir=@var{dirname}
14590 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
14591 @code{make} that implements the @code{VPATH} feature.}@*
14592 Use this option to make configurations in directories separate from the
14593 @value{GDBN} source directories. Among other things, you can use this to
14594 build (or maintain) several configurations simultaneously, in separate
14595 directories. @code{configure} writes configuration specific files in
14596 the current directory, but arranges for them to use the source in the
14597 directory @var{dirname}. @code{configure} creates directories under
14598 the working directory in parallel to the source directories below
14601 @item --norecursion
14602 Configure only the directory level where @code{configure} is executed; do not
14603 propagate configuration to subdirectories.
14605 @item --target=@var{target}
14606 Configure @value{GDBN} for cross-debugging programs running on the specified
14607 @var{target}. Without this option, @value{GDBN} is configured to debug
14608 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
14610 There is no convenient way to generate a list of all available targets.
14612 @item @var{host} @dots{}
14613 Configure @value{GDBN} to run on the specified @var{host}.
14615 There is no convenient way to generate a list of all available hosts.
14618 There are many other options available as well, but they are generally
14619 needed for special purposes only.
14621 @node Maintenance Commands
14622 @appendix Maintenance Commands
14623 @cindex maintenance commands
14624 @cindex internal commands
14626 In addition to commands intended for @value{GDBN} users, @value{GDBN}
14627 includes a number of commands intended for @value{GDBN} developers.
14628 These commands are provided here for reference.
14631 @kindex maint info breakpoints
14632 @item @anchor{maint info breakpoints}maint info breakpoints
14633 Using the same format as @samp{info breakpoints}, display both the
14634 breakpoints you've set explicitly, and those @value{GDBN} is using for
14635 internal purposes. Internal breakpoints are shown with negative
14636 breakpoint numbers. The type column identifies what kind of breakpoint
14641 Normal, explicitly set breakpoint.
14644 Normal, explicitly set watchpoint.
14647 Internal breakpoint, used to handle correctly stepping through
14648 @code{longjmp} calls.
14650 @item longjmp resume
14651 Internal breakpoint at the target of a @code{longjmp}.
14654 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
14657 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
14660 Shared library events.
14664 @kindex maint internal-error
14665 @kindex maint internal-warning
14666 @item maint internal-error
14667 @itemx maint internal-warning
14668 Cause @value{GDBN} to call the internal function @code{internal_error}
14669 or @code{internal_warning} and hence behave as though an internal error
14670 or internal warning has been detected. In addition to reporting the
14671 internal problem, these functions give the user the opportunity to
14672 either quit @value{GDBN} or create a core file of the current
14673 @value{GDBN} session.
14676 (gdb) @kbd{maint internal-error testing, 1, 2}
14677 @dots{}/maint.c:121: internal-error: testing, 1, 2
14678 A problem internal to GDB has been detected. Further
14679 debugging may prove unreliable.
14680 Quit this debugging session? (y or n) @kbd{n}
14681 Create a core file? (y or n) @kbd{n}
14685 Takes an optional parameter that is used as the text of the error or
14688 @kindex maint print registers
14689 @kindex maint print raw-registers
14690 @kindex maint print cooked-registers
14691 @item maint print registers
14692 @itemx maint print raw-registers
14693 @itemx maint print cooked-registers
14694 Print @value{GDBN}'s internal register data structures.
14696 The command @samp{maint print raw-registers} includes the contents of
14697 the raw register cache; and the command @samp{maint print
14698 cooked-registers} includes the (cooked) value of all registers.
14699 @xref{Registers,, Registers, gdbint, @value{GDBN} Internals}.
14701 Takes an optional file parameter.
14706 @node Remote Protocol
14707 @appendix @value{GDBN} Remote Serial Protocol
14712 * Stop Reply Packets::
14713 * General Query Packets::
14714 * Register Packet Format::
14721 There may be occasions when you need to know something about the
14722 protocol---for example, if there is only one serial port to your target
14723 machine, you might want your program to do something special if it
14724 recognizes a packet meant for @value{GDBN}.
14726 In the examples below, @samp{->} and @samp{<-} are used to indicate
14727 transmitted and received data respectfully.
14729 @cindex protocol, @value{GDBN} remote serial
14730 @cindex serial protocol, @value{GDBN} remote
14731 @cindex remote serial protocol
14732 All @value{GDBN} commands and responses (other than acknowledgments) are
14733 sent as a @var{packet}. A @var{packet} is introduced with the character
14734 @samp{$}, the actual @var{packet-data}, and the terminating character
14735 @samp{#} followed by a two-digit @var{checksum}:
14738 @code{$}@var{packet-data}@code{#}@var{checksum}
14742 @cindex checksum, for @value{GDBN} remote
14744 The two-digit @var{checksum} is computed as the modulo 256 sum of all
14745 characters between the leading @samp{$} and the trailing @samp{#} (an
14746 eight bit unsigned checksum).
14748 Implementors should note that prior to @value{GDBN} 5.0 the protocol
14749 specification also included an optional two-digit @var{sequence-id}:
14752 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
14755 @cindex sequence-id, for @value{GDBN} remote
14757 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
14758 has never output @var{sequence-id}s. Stubs that handle packets added
14759 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
14761 @cindex acknowledgment, for @value{GDBN} remote
14762 When either the host or the target machine receives a packet, the first
14763 response expected is an acknowledgment: either @samp{+} (to indicate
14764 the package was received correctly) or @samp{-} (to request
14768 -> @code{$}@var{packet-data}@code{#}@var{checksum}
14773 The host (@value{GDBN}) sends @var{command}s, and the target (the
14774 debugging stub incorporated in your program) sends a @var{response}. In
14775 the case of step and continue @var{command}s, the response is only sent
14776 when the operation has completed (the target has again stopped).
14778 @var{packet-data} consists of a sequence of characters with the
14779 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
14782 Fields within the packet should be separated using @samp{,} @samp{;} or
14783 @cindex remote protocol, field separator
14784 @samp{:}. Except where otherwise noted all numbers are represented in
14785 @sc{hex} with leading zeros suppressed.
14787 Implementors should note that prior to @value{GDBN} 5.0, the character
14788 @samp{:} could not appear as the third character in a packet (as it
14789 would potentially conflict with the @var{sequence-id}).
14791 Response @var{data} can be run-length encoded to save space. A @samp{*}
14792 means that the next character is an @sc{ascii} encoding giving a repeat count
14793 which stands for that many repetitions of the character preceding the
14794 @samp{*}. The encoding is @code{n+29}, yielding a printable character
14795 where @code{n >=3} (which is where rle starts to win). The printable
14796 characters @samp{$}, @samp{#}, @samp{+} and @samp{-} or with a numeric
14797 value greater than 126 should not be used.
14799 Some remote systems have used a different run-length encoding mechanism
14800 loosely refered to as the cisco encoding. Following the @samp{*}
14801 character are two hex digits that indicate the size of the packet.
14808 means the same as "0000".
14810 The error response returned for some packets includes a two character
14811 error number. That number is not well defined.
14813 For any @var{command} not supported by the stub, an empty response
14814 (@samp{$#00}) should be returned. That way it is possible to extend the
14815 protocol. A newer @value{GDBN} can tell if a packet is supported based
14818 A stub is required to support the @samp{g}, @samp{G}, @samp{m}, @samp{M},
14819 @samp{c}, and @samp{s} @var{command}s. All other @var{command}s are
14825 The following table provides a complete list of all currently defined
14826 @var{command}s and their corresponding response @var{data}.
14830 @item @code{!} --- extended mode
14831 @cindex @code{!} packet
14833 Enable extended mode. In extended mode, the remote server is made
14834 persistent. The @samp{R} packet is used to restart the program being
14840 The remote target both supports and has enabled extended mode.
14843 @item @code{?} --- last signal
14844 @cindex @code{?} packet
14846 Indicate the reason the target halted. The reply is the same as for
14850 @xref{Stop Reply Packets}, for the reply specifications.
14852 @item @code{a} --- reserved
14854 Reserved for future use.
14856 @item @code{A}@var{arglen}@code{,}@var{argnum}@code{,}@var{arg}@code{,@dots{}} --- set program arguments @strong{(reserved)}
14857 @cindex @code{A} packet
14859 Initialized @samp{argv[]} array passed into program. @var{arglen}
14860 specifies the number of bytes in the hex encoded byte stream @var{arg}.
14861 See @code{gdbserver} for more details.
14869 @item @code{b}@var{baud} --- set baud @strong{(deprecated)}
14870 @cindex @code{b} packet
14872 Change the serial line speed to @var{baud}.
14874 JTC: @emph{When does the transport layer state change? When it's
14875 received, or after the ACK is transmitted. In either case, there are
14876 problems if the command or the acknowledgment packet is dropped.}
14878 Stan: @emph{If people really wanted to add something like this, and get
14879 it working for the first time, they ought to modify ser-unix.c to send
14880 some kind of out-of-band message to a specially-setup stub and have the
14881 switch happen "in between" packets, so that from remote protocol's point
14882 of view, nothing actually happened.}
14884 @item @code{B}@var{addr},@var{mode} --- set breakpoint @strong{(deprecated)}
14885 @cindex @code{B} packet
14887 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
14888 breakpoint at @var{addr}.
14890 This packet has been replaced by the @samp{Z} and @samp{z} packets
14891 (@pxref{insert breakpoint or watchpoint packet}).
14893 @item @code{c}@var{addr} --- continue
14894 @cindex @code{c} packet
14896 @var{addr} is address to resume. If @var{addr} is omitted, resume at
14900 @xref{Stop Reply Packets}, for the reply specifications.
14902 @item @code{C}@var{sig}@code{;}@var{addr} --- continue with signal
14903 @cindex @code{C} packet
14905 Continue with signal @var{sig} (hex signal number). If
14906 @code{;}@var{addr} is omitted, resume at same address.
14909 @xref{Stop Reply Packets}, for the reply specifications.
14911 @item @code{d} --- toggle debug @strong{(deprecated)}
14912 @cindex @code{d} packet
14916 @item @code{D} --- detach
14917 @cindex @code{D} packet
14919 Detach @value{GDBN} from the remote system. Sent to the remote target
14920 before @value{GDBN} disconnects.
14924 @item @emph{no response}
14925 @value{GDBN} does not check for any response after sending this packet.
14928 @item @code{e} --- reserved
14930 Reserved for future use.
14932 @item @code{E} --- reserved
14934 Reserved for future use.
14936 @item @code{f} --- reserved
14938 Reserved for future use.
14940 @item @code{F} --- reserved
14942 Reserved for future use.
14944 @item @code{g} --- read registers
14945 @anchor{read registers packet}
14946 @cindex @code{g} packet
14948 Read general registers.
14952 @item @var{XX@dots{}}
14953 Each byte of register data is described by two hex digits. The bytes
14954 with the register are transmitted in target byte order. The size of
14955 each register and their position within the @samp{g} @var{packet} are
14956 determined by the @value{GDBN} internal macros @var{REGISTER_RAW_SIZE}
14957 and @var{REGISTER_NAME} macros. The specification of several standard
14958 @code{g} packets is specified below.
14963 @item @code{G}@var{XX@dots{}} --- write regs
14964 @cindex @code{G} packet
14966 @xref{read registers packet}, for a description of the @var{XX@dots{}}
14977 @item @code{h} --- reserved
14979 Reserved for future use.
14981 @item @code{H}@var{c}@var{t@dots{}} --- set thread
14982 @cindex @code{H} packet
14984 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
14985 @samp{G}, et.al.). @var{c} depends on the operation to be performed: it
14986 should be @samp{c} for step and continue operations, @samp{g} for other
14987 operations. The thread designator @var{t@dots{}} may be -1, meaning all
14988 the threads, a thread number, or zero which means pick any thread.
14999 @c 'H': How restrictive (or permissive) is the thread model. If a
15000 @c thread is selected and stopped, are other threads allowed
15001 @c to continue to execute? As I mentioned above, I think the
15002 @c semantics of each command when a thread is selected must be
15003 @c described. For example:
15005 @c 'g': If the stub supports threads and a specific thread is
15006 @c selected, returns the register block from that thread;
15007 @c otherwise returns current registers.
15009 @c 'G' If the stub supports threads and a specific thread is
15010 @c selected, sets the registers of the register block of
15011 @c that thread; otherwise sets current registers.
15013 @item @code{i}@var{addr}@code{,}@var{nnn} --- cycle step @strong{(draft)}
15014 @anchor{cycle step packet}
15015 @cindex @code{i} packet
15017 Step the remote target by a single clock cycle. If @code{,}@var{nnn} is
15018 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
15019 step starting at that address.
15021 @item @code{I} --- signal then cycle step @strong{(reserved)}
15022 @cindex @code{I} packet
15024 @xref{step with signal packet}. @xref{cycle step packet}.
15026 @item @code{j} --- reserved
15028 Reserved for future use.
15030 @item @code{J} --- reserved
15032 Reserved for future use.
15034 @item @code{k} --- kill request
15035 @cindex @code{k} packet
15037 FIXME: @emph{There is no description of how to operate when a specific
15038 thread context has been selected (i.e.@: does 'k' kill only that
15041 @item @code{K} --- reserved
15043 Reserved for future use.
15045 @item @code{l} --- reserved
15047 Reserved for future use.
15049 @item @code{L} --- reserved
15051 Reserved for future use.
15053 @item @code{m}@var{addr}@code{,}@var{length} --- read memory
15054 @cindex @code{m} packet
15056 Read @var{length} bytes of memory starting at address @var{addr}.
15057 Neither @value{GDBN} nor the stub assume that sized memory transfers are
15058 assumed using word aligned accesses. FIXME: @emph{A word aligned memory
15059 transfer mechanism is needed.}
15063 @item @var{XX@dots{}}
15064 @var{XX@dots{}} is mem contents. Can be fewer bytes than requested if able
15065 to read only part of the data. Neither @value{GDBN} nor the stub assume
15066 that sized memory transfers are assumed using word aligned
15067 accesses. FIXME: @emph{A word aligned memory transfer mechanism is
15073 @item @code{M}@var{addr},@var{length}@code{:}@var{XX@dots{}} --- write mem
15074 @cindex @code{M} packet
15076 Write @var{length} bytes of memory starting at address @var{addr}.
15077 @var{XX@dots{}} is the data.
15084 for an error (this includes the case where only part of the data was
15088 @item @code{n} --- reserved
15090 Reserved for future use.
15092 @item @code{N} --- reserved
15094 Reserved for future use.
15096 @item @code{o} --- reserved
15098 Reserved for future use.
15100 @item @code{O} --- reserved
15102 Reserved for future use.
15104 @item @code{p}@var{n@dots{}} --- read reg @strong{(reserved)}
15105 @cindex @code{p} packet
15107 @xref{write register packet}.
15111 @item @var{r@dots{}.}
15112 The hex encoded value of the register in target byte order.
15115 @item @code{P}@var{n@dots{}}@code{=}@var{r@dots{}} --- write register
15116 @anchor{write register packet}
15117 @cindex @code{P} packet
15119 Write register @var{n@dots{}} with value @var{r@dots{}}, which contains two hex
15120 digits for each byte in the register (target byte order).
15130 @item @code{q}@var{query} --- general query
15131 @anchor{general query packet}
15132 @cindex @code{q} packet
15134 Request info about @var{query}. In general @value{GDBN} queries have a
15135 leading upper case letter. Custom vendor queries should use a company
15136 prefix (in lower case) ex: @samp{qfsf.var}. @var{query} may optionally
15137 be followed by a @samp{,} or @samp{;} separated list. Stubs must ensure
15138 that they match the full @var{query} name.
15142 @item @var{XX@dots{}}
15143 Hex encoded data from query. The reply can not be empty.
15147 Indicating an unrecognized @var{query}.
15150 @item @code{Q}@var{var}@code{=}@var{val} --- general set
15151 @cindex @code{Q} packet
15153 Set value of @var{var} to @var{val}.
15155 @xref{general query packet}, for a discussion of naming conventions.
15157 @item @code{r} --- reset @strong{(deprecated)}
15158 @cindex @code{r} packet
15160 Reset the entire system.
15162 @item @code{R}@var{XX} --- remote restart
15163 @cindex @code{R} packet
15165 Restart the program being debugged. @var{XX}, while needed, is ignored.
15166 This packet is only available in extended mode.
15170 @item @emph{no reply}
15171 The @samp{R} packet has no reply.
15174 @item @code{s}@var{addr} --- step
15175 @cindex @code{s} packet
15177 @var{addr} is address to resume. If @var{addr} is omitted, resume at
15181 @xref{Stop Reply Packets}, for the reply specifications.
15183 @item @code{S}@var{sig}@code{;}@var{addr} --- step with signal
15184 @anchor{step with signal packet}
15185 @cindex @code{S} packet
15187 Like @samp{C} but step not continue.
15190 @xref{Stop Reply Packets}, for the reply specifications.
15192 @item @code{t}@var{addr}@code{:}@var{PP}@code{,}@var{MM} --- search
15193 @cindex @code{t} packet
15195 Search backwards starting at address @var{addr} for a match with pattern
15196 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
15197 @var{addr} must be at least 3 digits.
15199 @item @code{T}@var{XX} --- thread alive
15200 @cindex @code{T} packet
15202 Find out if the thread XX is alive.
15207 thread is still alive
15212 @item @code{u} --- reserved
15214 Reserved for future use.
15216 @item @code{U} --- reserved
15218 Reserved for future use.
15220 @item @code{v} --- reserved
15222 Reserved for future use.
15224 @item @code{V} --- reserved
15226 Reserved for future use.
15228 @item @code{w} --- reserved
15230 Reserved for future use.
15232 @item @code{W} --- reserved
15234 Reserved for future use.
15236 @item @code{x} --- reserved
15238 Reserved for future use.
15240 @item @code{X}@var{addr}@code{,}@var{length}@var{:}@var{XX@dots{}} --- write mem (binary)
15241 @cindex @code{X} packet
15243 @var{addr} is address, @var{length} is number of bytes, @var{XX@dots{}}
15244 is binary data. The characters @code{$}, @code{#}, and @code{0x7d} are
15245 escaped using @code{0x7d}.
15255 @item @code{y} --- reserved
15257 Reserved for future use.
15259 @item @code{Y} reserved
15261 Reserved for future use.
15263 @item @code{z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- remove breakpoint or watchpoint @strong{(draft)}
15264 @itemx @code{Z}@var{type}@code{,}@var{addr}@code{,}@var{length} --- insert breakpoint or watchpoint @strong{(draft)}
15265 @anchor{insert breakpoint or watchpoint packet}
15266 @cindex @code{z} packet
15267 @cindex @code{Z} packets
15269 Insert (@code{Z}) or remove (@code{z}) a @var{type} breakpoint or
15270 watchpoint starting at address @var{address} and covering the next
15271 @var{length} bytes.
15273 Each breakpoint and watchpoint packet @var{type} is documented
15276 @emph{Implementation notes: A remote target shall return an empty string
15277 for an unrecognized breakpoint or watchpoint packet @var{type}. A
15278 remote target shall support either both or neither of a given
15279 @code{Z}@var{type}@dots{} and @code{z}@var{type}@dots{} packet pair. To
15280 avoid potential problems with duplicate packets, the operations should
15281 be implemented in an idempotent way.}
15283 @item @code{z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- remove memory breakpoint @strong{(draft)}
15284 @item @code{Z}@code{0}@code{,}@var{addr}@code{,}@var{length} --- insert memory breakpoint @strong{(draft)}
15285 @cindex @code{z0} packet
15286 @cindex @code{Z0} packet
15288 Insert (@code{Z0}) or remove (@code{z0}) a memory breakpoint at address
15289 @code{addr} of size @code{length}.
15291 A memory breakpoint is implemented by replacing the instruction at
15292 @var{addr} with a software breakpoint or trap instruction. The
15293 @code{length} is used by targets that indicates the size of the
15294 breakpoint (in bytes) that should be inserted (e.g., the @sc{arm} and
15295 @sc{mips} can insert either a 2 or 4 byte breakpoint).
15297 @emph{Implementation note: It is possible for a target to copy or move
15298 code that contains memory breakpoints (e.g., when implementing
15299 overlays). The behavior of this packet, in the presence of such a
15300 target, is not defined.}
15312 @item @code{z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- remove hardware breakpoint @strong{(draft)}
15313 @item @code{Z}@code{1}@code{,}@var{addr}@code{,}@var{length} --- insert hardware breakpoint @strong{(draft)}
15314 @cindex @code{z1} packet
15315 @cindex @code{Z1} packet
15317 Insert (@code{Z1}) or remove (@code{z1}) a hardware breakpoint at
15318 address @code{addr} of size @code{length}.
15320 A hardware breakpoint is implemented using a mechanism that is not
15321 dependant on being able to modify the target's memory.
15323 @emph{Implementation note: A hardware breakpoint is not affected by code
15336 @item @code{z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- remove write watchpoint @strong{(draft)}
15337 @item @code{Z}@code{2}@code{,}@var{addr}@code{,}@var{length} --- insert write watchpoint @strong{(draft)}
15338 @cindex @code{z2} packet
15339 @cindex @code{Z2} packet
15341 Insert (@code{Z2}) or remove (@code{z2}) a write watchpoint.
15353 @item @code{z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- remove read watchpoint @strong{(draft)}
15354 @item @code{Z}@code{3}@code{,}@var{addr}@code{,}@var{length} --- insert read watchpoint @strong{(draft)}
15355 @cindex @code{z3} packet
15356 @cindex @code{Z3} packet
15358 Insert (@code{Z3}) or remove (@code{z3}) a read watchpoint.
15370 @item @code{z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- remove access watchpoint @strong{(draft)}
15371 @item @code{Z}@code{4}@code{,}@var{addr}@code{,}@var{length} --- insert access watchpoint @strong{(draft)}
15372 @cindex @code{z4} packet
15373 @cindex @code{Z4} packet
15375 Insert (@code{Z4}) or remove (@code{z4}) an access watchpoint.
15389 @node Stop Reply Packets
15390 @section Stop Reply Packets
15391 @cindex stop reply packets
15393 The @samp{C}, @samp{c}, @samp{S}, @samp{s} and @samp{?} packets can
15394 receive any of the below as a reply. In the case of the @samp{C},
15395 @samp{c}, @samp{S} and @samp{s} packets, that reply is only returned
15396 when the target halts. In the below the exact meaning of @samp{signal
15397 number} is poorly defined. In general one of the UNIX signal numbering
15398 conventions is used.
15403 @var{AA} is the signal number
15405 @item @code{T}@var{AA}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}@var{n...}@code{:}@var{r...}@code{;}
15406 @cindex @code{T} packet reply
15408 @var{AA} = two hex digit signal number; @var{n...} = register number
15409 (hex), @var{r...} = target byte ordered register contents, size defined
15410 by @code{REGISTER_RAW_SIZE}; @var{n...} = @samp{thread}, @var{r...} =
15411 thread process ID, this is a hex integer; @var{n...} = (@samp{watch} |
15412 @samp{rwatch} | @samp{awatch}, @var{r...} = data address, this is a hex
15413 integer; @var{n...} = other string not starting with valid hex digit.
15414 @value{GDBN} should ignore this @var{n...}, @var{r...} pair and go on
15415 to the next. This way we can extend the protocol.
15419 The process exited, and @var{AA} is the exit status. This is only
15420 applicable to certain targets.
15424 The process terminated with signal @var{AA}.
15426 @item N@var{AA};@var{t@dots{}};@var{d@dots{}};@var{b@dots{}} @strong{(obsolete)}
15428 @var{AA} = signal number; @var{t@dots{}} = address of symbol
15429 @code{_start}; @var{d@dots{}} = base of data section; @var{b@dots{}} =
15430 base of bss section. @emph{Note: only used by Cisco Systems targets.
15431 The difference between this reply and the @samp{qOffsets} query is that
15432 the @samp{N} packet may arrive spontaneously whereas the @samp{qOffsets}
15433 is a query initiated by the host debugger.}
15435 @item O@var{XX@dots{}}
15437 @var{XX@dots{}} is hex encoding of @sc{ascii} data. This can happen at
15438 any time while the program is running and the debugger should continue
15439 to wait for @samp{W}, @samp{T}, etc.
15443 @node General Query Packets
15444 @section General Query Packets
15446 The following set and query packets have already been defined.
15450 @item @code{q}@code{C} --- current thread
15452 Return the current thread id.
15456 @item @code{QC}@var{pid}
15457 Where @var{pid} is a HEX encoded 16 bit process id.
15459 Any other reply implies the old pid.
15462 @item @code{q}@code{fThreadInfo} -- all thread ids
15464 @code{q}@code{sThreadInfo}
15466 Obtain a list of active thread ids from the target (OS). Since there
15467 may be too many active threads to fit into one reply packet, this query
15468 works iteratively: it may require more than one query/reply sequence to
15469 obtain the entire list of threads. The first query of the sequence will
15470 be the @code{qf}@code{ThreadInfo} query; subsequent queries in the
15471 sequence will be the @code{qs}@code{ThreadInfo} query.
15473 NOTE: replaces the @code{qL} query (see below).
15477 @item @code{m}@var{id}
15479 @item @code{m}@var{id},@var{id}@dots{}
15480 a comma-separated list of thread ids
15482 (lower case 'el') denotes end of list.
15485 In response to each query, the target will reply with a list of one or
15486 more thread ids, in big-endian hex, separated by commas. @value{GDBN}
15487 will respond to each reply with a request for more thread ids (using the
15488 @code{qs} form of the query), until the target responds with @code{l}
15489 (lower-case el, for @code{'last'}).
15491 @item @code{q}@code{ThreadExtraInfo}@code{,}@var{id} --- extra thread info
15493 Where @var{id} is a thread-id in big-endian hex. Obtain a printable
15494 string description of a thread's attributes from the target OS. This
15495 string may contain anything that the target OS thinks is interesting for
15496 @value{GDBN} to tell the user about the thread. The string is displayed
15497 in @value{GDBN}'s @samp{info threads} display. Some examples of
15498 possible thread extra info strings are ``Runnable'', or ``Blocked on
15503 @item @var{XX@dots{}}
15504 Where @var{XX@dots{}} is a hex encoding of @sc{ascii} data, comprising
15505 the printable string containing the extra information about the thread's
15509 @item @code{q}@code{L}@var{startflag}@var{threadcount}@var{nextthread} --- query @var{LIST} or @var{threadLIST} @strong{(deprecated)}
15511 Obtain thread information from RTOS. Where: @var{startflag} (one hex
15512 digit) is one to indicate the first query and zero to indicate a
15513 subsequent query; @var{threadcount} (two hex digits) is the maximum
15514 number of threads the response packet can contain; and @var{nextthread}
15515 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
15516 returned in the response as @var{argthread}.
15518 NOTE: this query is replaced by the @code{q}@code{fThreadInfo} query
15523 @item @code{q}@code{M}@var{count}@var{done}@var{argthread}@var{thread@dots{}}
15524 Where: @var{count} (two hex digits) is the number of threads being
15525 returned; @var{done} (one hex digit) is zero to indicate more threads
15526 and one indicates no further threads; @var{argthreadid} (eight hex
15527 digits) is @var{nextthread} from the request packet; @var{thread@dots{}}
15528 is a sequence of thread IDs from the target. @var{threadid} (eight hex
15529 digits). See @code{remote.c:parse_threadlist_response()}.
15532 @item @code{q}@code{CRC:}@var{addr}@code{,}@var{length} --- compute CRC of memory block
15536 @item @code{E}@var{NN}
15537 An error (such as memory fault)
15538 @item @code{C}@var{CRC32}
15539 A 32 bit cyclic redundancy check of the specified memory region.
15542 @item @code{q}@code{Offsets} --- query sect offs
15544 Get section offsets that the target used when re-locating the downloaded
15545 image. @emph{Note: while a @code{Bss} offset is included in the
15546 response, @value{GDBN} ignores this and instead applies the @code{Data}
15547 offset to the @code{Bss} section.}
15551 @item @code{Text=}@var{xxx}@code{;Data=}@var{yyy}@code{;Bss=}@var{zzz}
15554 @item @code{q}@code{P}@var{mode}@var{threadid} --- thread info request
15556 Returns information on @var{threadid}. Where: @var{mode} is a hex
15557 encoded 32 bit mode; @var{threadid} is a hex encoded 64 bit thread ID.
15564 See @code{remote.c:remote_unpack_thread_info_response()}.
15566 @item @code{q}@code{Rcmd,}@var{command} --- remote command
15568 @var{command} (hex encoded) is passed to the local interpreter for
15569 execution. Invalid commands should be reported using the output string.
15570 Before the final result packet, the target may also respond with a
15571 number of intermediate @code{O}@var{output} console output packets.
15572 @emph{Implementors should note that providing access to a stubs's
15573 interpreter may have security implications}.
15578 A command response with no output.
15580 A command response with the hex encoded output string @var{OUTPUT}.
15581 @item @code{E}@var{NN}
15582 Indicate a badly formed request.
15584 When @samp{q}@samp{Rcmd} is not recognized.
15587 @item @code{qSymbol::} --- symbol lookup
15589 Notify the target that @value{GDBN} is prepared to serve symbol lookup
15590 requests. Accept requests from the target for the values of symbols.
15595 The target does not need to look up any (more) symbols.
15596 @item @code{qSymbol:}@var{sym_name}
15597 The target requests the value of symbol @var{sym_name} (hex encoded).
15598 @value{GDBN} may provide the value by using the
15599 @code{qSymbol:}@var{sym_value}:@var{sym_name} message, described below.
15602 @item @code{qSymbol:}@var{sym_value}:@var{sym_name} --- symbol value
15604 Set the value of @var{sym_name} to @var{sym_value}.
15606 @var{sym_name} (hex encoded) is the name of a symbol whose value the
15607 target has previously requested.
15609 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
15610 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
15616 The target does not need to look up any (more) symbols.
15617 @item @code{qSymbol:}@var{sym_name}
15618 The target requests the value of a new symbol @var{sym_name} (hex
15619 encoded). @value{GDBN} will continue to supply the values of symbols
15620 (if available), until the target ceases to request them.
15625 @node Register Packet Format
15626 @section Register Packet Format
15628 The following @samp{g}/@samp{G} packets have previously been defined.
15629 In the below, some thirty-two bit registers are transferred as
15630 sixty-four bits. Those registers should be zero/sign extended (which?)
15631 to fill the space allocated. Register bytes are transfered in target
15632 byte order. The two nibbles within a register byte are transfered
15633 most-significant - least-significant.
15639 All registers are transfered as thirty-two bit quantities in the order:
15640 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
15641 registers; fsr; fir; fp.
15645 All registers are transfered as sixty-four bit quantities (including
15646 thirty-two bit registers such as @code{sr}). The ordering is the same
15654 Example sequence of a target being re-started. Notice how the restart
15655 does not get any direct output:
15660 @emph{target restarts}
15663 <- @code{T001:1234123412341234}
15667 Example sequence of a target being stepped by a single instruction:
15670 -> @code{G1445@dots{}}
15675 <- @code{T001:1234123412341234}
15679 <- @code{1455@dots{}}
15693 % I think something like @colophon should be in texinfo. In the
15695 \long\def\colophon{\hbox to0pt{}\vfill
15696 \centerline{The body of this manual is set in}
15697 \centerline{\fontname\tenrm,}
15698 \centerline{with headings in {\bf\fontname\tenbf}}
15699 \centerline{and examples in {\tt\fontname\tentt}.}
15700 \centerline{{\it\fontname\tenit\/},}
15701 \centerline{{\bf\fontname\tenbf}, and}
15702 \centerline{{\sl\fontname\tensl\/}}
15703 \centerline{are used for emphasis.}\vfill}
15705 % Blame: doc@cygnus.com, 1991.