2 _dnl__ Copyright (c) 1988 1989 1990 1991 1992 Free Software Foundation, Inc.
4 \input texinfo @c -*-texinfo-*-
5 @c Copyright (c) 1988 1989 1990 1991 1992 Free Software Foundation, Inc.
7 @setfilename _GDBP__.info
9 @settitle Debugging with _GDBN__
12 @settitle Debugging with _GDBN__ (_HOST__)
14 @setchapternewpage odd
22 _0__@c ===> NOTE! <==_1__
23 @c Determine the edition number in *three* places by hand:
24 @c 1. First ifinfo section 2. title page 3. top node
25 @c To find the locations, search for !!set
27 @c The following is for Pesch for his RCS system.
28 @c This revision number *not* the same as the Edition number.
30 \def\$#1${{#1}} % Kluge: collect RCS revision info without $...$
31 \xdef\manvers{\$Revision$} % For use in headers, footers too
34 @c GDB CHANGELOG CONSULTED BETWEEN:
35 @c Fri Oct 11 23:27:06 1991 John Gilmore (gnu at cygnus.com)
36 @c Sat Dec 22 02:51:40 1990 John Gilmore (gnu at cygint)
38 @c THIS MANUAL REQUIRES TEXINFO-2 macros and info-makers to format properly.
43 * Gdb: (gdb). The GNU debugger.
49 NOTE: this manual is marked up for preprocessing with a collection
50 of m4 macros called "pretex.m4".
52 THIS IS THE SOURCE PRIOR TO PREPROCESSING. The full source needs to
53 be run through m4 before either tex- or info- formatting: for example,
55 m4 pretex.m4 none.m4 all.m4 gdb.texinfo >gdb-all.texinfo
56 will produce (assuming your path finds either GNU m4 >= 0.84, or SysV
57 m4; Berkeley will not do) a file suitable for formatting. See the text in
58 "pretex.m4" for a fuller explanation (and the macro definitions).
64 This file documents the GNU debugger _GDBN__.
66 @c !!set edition, date, version
67 This is Edition 4.06, July 1992,
68 of @cite{Debugging with _GDBN__: the GNU Source-Level Debugger}
69 for GDB Version _GDB_VN__.
71 Copyright (C) 1988, 1989, 1990, 1991, 1992 Free Software Foundation, Inc.
73 Permission is granted to make and distribute verbatim copies of
74 this manual provided the copyright notice and this permission notice
75 are preserved on all copies.
78 Permission is granted to process this file through TeX and print the
79 results, provided the printed document carries copying permission
80 notice identical to this one except for the removal of this paragraph
81 (this paragraph not being relevant to the printed manual).
84 Permission is granted to copy and distribute modified versions of this
85 manual under the conditions for verbatim copying, provided also that the
86 section entitled ``GNU General Public License'' is included exactly as
87 in the original, and provided that the entire resulting derived work is
88 distributed under the terms of a permission notice identical to this
91 Permission is granted to copy and distribute translations of this manual
92 into another language, under the above conditions for modified versions,
93 except that the section entitled ``GNU General Public License'' may be
94 included in a translation approved by the Free Software Foundation
95 instead of in the original English.
99 @title Debugging with _GDBN__
100 @subtitle The GNU Source-Level Debugger
102 @subtitle on _HOST__ Systems
105 @c !!set edition, date, version
106 @subtitle Edition 4.06, for _GDBN__ version _GDB_VN__
108 @author by Richard M. Stallman and Roland H. Pesch
112 \hfill pesch\@cygnus.com\par
113 \hfill {\it Debugging with _GDBN__}, \manvers\par
114 \hfill \TeX{}info \texinfoversion\par
118 @vskip 0pt plus 1filll
119 Copyright @copyright{} 1988, 1989, 1990, 1991, 1992 Free Software Foundation, Inc.
121 Permission is granted to make and distribute verbatim copies of
122 this manual provided the copyright notice and this permission notice
123 are preserved on all copies.
125 Permission is granted to copy and distribute modified versions of this
126 manual under the conditions for verbatim copying, provided also that the
127 section entitled ``GNU General Public License'' is included exactly as
128 in the original, and provided that the entire resulting derived work is
129 distributed under the terms of a permission notice identical to this
132 Permission is granted to copy and distribute translations of this manual
133 into another language, under the above conditions for modified versions,
134 except that the section entitled ``GNU General Public License'' may be
135 included in a translation approved by the Free Software Foundation
136 instead of in the original English.
142 @top Debugging with _GDBN__
144 This file describes _GDBN__, the GNU symbolic debugger.
146 @c !!set edition, date, version
147 This is Edition 4.06, July 1992, for GDB Version _GDB_VN__.
151 * Summary:: Summary of _GDBN__
152 _if__(_GENERIC__ || !_H8__)
153 * New Features:: New features since GDB version 3.5
154 _fi__(_GENERIC__ || !_H8__)
155 * Sample Session:: A sample _GDBN__ session
156 * Invocation:: Getting in and out of _GDBN__
157 * Commands:: _GDBN__ commands
158 * Running:: Running programs under _GDBN__
159 * Stopping:: Stopping and continuing
160 * Stack:: Examining the stack
161 * Source:: Examining source files
162 * Data:: Examining data
164 * Languages:: Using _GDBN__ with different languages
169 * Symbols:: Examining the symbol table
170 * Altering:: Altering execution
171 * _GDBN__ Files:: _GDBN__'s files
172 * Targets:: Specifying a debugging target
173 * Controlling _GDBN__:: Controlling _GDBN__
174 * Sequences:: Canned sequences of commands
176 * Emacs:: Using _GDBN__ under GNU Emacs
178 * _GDBN__ Bugs:: Reporting bugs in _GDBN__
182 * Formatting Documentation:: How to format and print GDB documentation
183 * Installing GDB:: Installing GDB
184 * Copying:: GNU GENERAL PUBLIC LICENSE
189 @unnumbered Summary of _GDBN__
191 The purpose of a debugger such as _GDBN__ is to allow you to see what is
192 going on ``inside'' another program while it executes---or what another
193 program was doing at the moment it crashed.
195 _GDBN__ can do four main kinds of things (plus other things in support of
196 these) to help you catch bugs in the act:
200 Start your program, specifying anything that might affect its behavior.
203 Make your program stop on specified conditions.
206 Examine what has happened, when your program has stopped.
209 Change things in your program, so you can experiment with correcting the
210 effects of one bug and go on to learn about another.
213 You can use _GDBN__ to debug programs written in C, C++, and Modula-2.
214 Fortran support will be added when a GNU Fortran compiler is ready.
217 * Free Software:: Free Software
218 * Contributors:: Contributors to GDB
222 @unnumberedsec Free Software
224 _GDBN__ is @dfn{free software}, protected by the GNU General Public License
225 (GPL). The GPL gives you the freedom to copy or adapt a licensed
226 program---but every person getting a copy also gets with it the
227 freedom to modify that copy (which means that they must get access to
228 the source code), and the freedom to distribute further copies.
229 Typical software companies use copyrights to limit your freedoms; the
230 Free Software Foundation uses the GPL to preserve these freedoms.
232 Fundamentally, the General Public License is a license which says that
233 you have these freedoms and that you cannot take these freedoms away
236 For full details, @pxref{Copying, ,GNU GENERAL PUBLIC LICENSE}.
239 @unnumberedsec Contributors to GDB
241 Richard Stallman was the original author of GDB, and of many other GNU
242 programs. Many others have contributed to its development. This
243 section attempts to credit major contributors. One of the virtues of
244 free software is that everyone is free to contribute to it; with
245 regret, we cannot actually acknowledge everyone here. The file
246 @file{ChangeLog} in the GDB distribution approximates a blow-by-blow
249 Changes much prior to version 2.0 are lost in the mists of time.
252 @emph{Plea:} Additions to this section are particularly welcome. If you
253 or your friends (or enemies; let's be evenhanded) have been unfairly
254 omitted from this list, we would like to add your names!
257 So that they may not regard their long labor as thankless, we
258 particularly thank those who shepherded GDB through major releases: Stu
259 Grossman and John Gilmore (releases 4.6, 4.5, 4.4), John Gilmore
260 (releases 4.3, 4.2, 4.1, 4.0, and 3.9); Jim Kingdon (releases 3.5, 3.4,
261 3.3); and Randy Smith (releases 3.2, 3.1, 3.0). As major maintainer of
262 GDB for some period, each contributed significantly to the structure,
263 stability, and capabilities of the entire debugger.
265 Richard Stallman, assisted at various times by Pete TerMaat, Chris
266 Hanson, and Richard Mlynarik, handled releases through 2.8.
268 Michael Tiemann is the author of most of the GNU C++ support in GDB,
269 with significant additional contributions from Per Bothner. James
270 Clark wrote the GNU C++ demangler. Early work on C++ was by Peter
271 TerMaat (who also did much general update work leading to release 3.0).
273 GDB 4 uses the BFD subroutine library to examine multiple
274 object-file formats; BFD was a joint project of David V.
275 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
277 David Johnson wrote the original COFF support; Pace Willison did
278 the original support for encapsulated COFF.
280 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
281 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
282 support. Jean-Daniel Fekete contributed Sun 386i support. Chris
283 Hanson improved the HP9000 support. Noboyuki Hikichi and Tomoyuki
284 Hasei contributed Sony/News OS 3 support. David Johnson contributed
285 Encore Umax support. Jyrki Kuoppala contributed Altos 3068 support.
286 Keith Packard contributed NS32K support. Doug Rabson contributed
287 Acorn Risc Machine support. Chris Smith contributed Convex support
288 (and Fortran debugging). Jonathan Stone contributed Pyramid support.
289 Michael Tiemann contributed SPARC support. Tim Tucker contributed
290 support for the Gould NP1 and Gould Powernode. Pace Willison
291 contributed Intel 386 support. Jay Vosburgh contributed Symmetry
294 Rich Schaefer and Peter Schauer helped with support of SunOS shared
297 Jay Fenlason and Roland McGrath ensured that GDB and GAS agree about
298 several machine instruction sets.
300 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped
301 develop remote debugging. Intel Corporation and Wind River Systems
302 contributed remote debugging modules for their products.
304 Brian Fox is the author of the readline libraries providing
305 command-line editing and command history.
307 Andrew Beers of SUNY Buffalo wrote the language-switching code and
308 the Modula-2 support, and contributed the Languages chapter of this
311 Fred Fish wrote most of the support for Unix System Vr4, and enhanced
312 the command-completion support to cover C++ overloaded symbols.
314 _if__(_GENERIC__ || !_H8__)
316 @unnumbered New Features since GDB version 3.5
320 Using the new command @code{target}, you can select at runtime whether
321 you are debugging local files, local processes, standalone systems over
322 a serial port, realtime systems over a TCP/IP connection, etc. The
323 command @code{load} can download programs into a remote system. Serial
324 stubs are available for Motorola 680x0 and Intel 80386 remote systems;
325 GDB also supports debugging realtime processes running under
326 VxWorks, using SunRPC Remote Procedure Calls over TCP/IP to talk to a
327 debugger stub on the target system. Internally, GDB now uses a
328 function vector to mediate access to different targets; if you need to
329 add your own support for a remote protocol, this makes it much easier.
332 GDB now sports watchpoints as well as breakpoints. You can use a
333 watchpoint to stop execution whenever the value of an expression
334 changes, without having to predict a particular place in your program
335 where this may happen.
338 Commands that issue wide output now insert newlines at places designed
339 to make the output more readable.
341 @item Object Code Formats
342 GDB uses a new library called the Binary File Descriptor (BFD)
343 Library to permit it to switch dynamically, without reconfiguration or
344 recompilation, between different object-file formats. Formats currently
345 supported are COFF, a.out, and the Intel 960 b.out; files may be read as
346 .o's, archive libraries, or core dumps. BFD is available as a
347 subroutine library so that other programs may take advantage of it, and
348 the other GNU binary utilities are being converted to use it.
350 @item Configuration and Ports
351 Compile-time configuration (to select a particular architecture and
352 operating system) is much easier. The script @code{configure} now
353 allows you to configure GDB as either a native debugger or a
354 cross-debugger. @xref{Installing GDB}, for details on how to
358 The user interface to GDB's control variables has been simplified
359 and consolidated in two commands, @code{set} and @code{show}. Output
360 lines are now broken at readable places, rather than overflowing onto
361 the next line. You can suppress output of machine-level addresses,
362 displaying only source language information.
365 GDB now supports C++ multiple inheritance (if used with a GCC
366 version 2 compiler), and also has limited support for C++ exception
367 handling, with the commands @code{catch} and @code{info catch}: GDB
368 can break when an exception is raised, before the stack is peeled back
369 to the exception handler's context.
372 GDB now has preliminary support for the GNU Modula-2 compiler,
373 currently under development at the State University of New York at
374 Buffalo. Coordinated development of both GDB and the GNU Modula-2
375 compiler will continue into 1992. Other Modula-2 compilers are
376 currently not supported, and attempting to debug programs compiled with
377 them will likely result in an error as the symbol table of the
378 executable is read in.
380 @item Command Rationalization
381 Many GDB commands have been renamed to make them easier to remember
382 and use. In particular, the subcommands of @code{info} and
383 @code{show}/@code{set} are grouped to make the former refer to the state
384 of your program, and the latter refer to the state of GDB itself.
385 @xref{Renamed Commands}, for details on what commands were renamed.
387 @item Shared Libraries
388 GDB 4 can debug programs and core files that use SunOS, SVR4, or IBM RS/6000
392 GDB 4 has a reference card. @xref{Formatting Documentation,,Formatting
393 the Documentation}, for instructions to print it.
395 @item Work in Progress
396 Kernel debugging for BSD and Mach systems; Tahoe and HPPA architecture
399 _fi__(_GENERIC__ || !_H8__)
402 @chapter A Sample _GDBN__ Session
404 You can use this manual at your leisure to read all about _GDBN__.
405 However, a handful of commands are enough to get started using the
406 debugger. This chapter illustrates these commands.
409 In this sample session, we emphasize user input like this: @b{input},
410 to make it easier to pick out from the surrounding output.
413 @c FIXME: this example may not be appropriate for some configs, where
414 @c FIXME...primary interest is in remote use.
416 One of the preliminary versions of GNU @code{m4} (a generic macro
417 processor) exhibits the following bug: sometimes, when we change its
418 quote strings from the default, the commands used to capture one macro's
419 definition in another stop working. In the following short @code{m4}
420 session, we define a macro @code{foo} which expands to @code{0000}; we
421 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
422 same thing. However, when we change the open quote string to
423 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
424 procedure fails to define a new synonym @code{baz}:
433 @b{define(bar,defn(`foo'))}
437 @b{changequote(<QUOTE>,<UNQUOTE>)}
439 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
442 m4: End of input: 0: fatal error: EOF in string
446 Let's use _GDBN__ to try to see what's going on.
450 @c FIXME: this falsifies the exact text played out, to permit smallbook
451 @c FIXME... format to come out better.
452 GDB is free software and you are welcome to distribute copies
453 of it under certain conditions; type "show copying" to see
455 There is absolutely no warranty for GDB; type "show warranty"
457 GDB _GDB_VN__, Copyright 1992 Free Software Foundation, Inc...
462 _GDBN__ reads only enough symbol data to know where to find the rest when
463 needed; as a result, the first prompt comes up very quickly. We now
464 tell _GDBN__ to use a narrower display width than usual, so that examples
465 will fit in this manual.
468 (_GDBP__) @b{set width 70}
472 Let's see how the @code{m4} built-in @code{changequote} works.
473 Having looked at the source, we know the relevant subroutine is
474 @code{m4_changequote}, so we set a breakpoint there with _GDBN__'s
475 @code{break} command.
478 (_GDBP__) @b{break m4_changequote}
479 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
483 Using the @code{run} command, we start @code{m4} running under _GDBN__
484 control; as long as control does not reach the @code{m4_changequote}
485 subroutine, the program runs as usual:
489 Starting program: /work/Editorial/gdb/gnu/m4/m4
497 To trigger the breakpoint, we call @code{changequote}. _GDBN__
498 suspends execution of @code{m4}, displaying information about the
499 context where it stops.
502 @b{changequote(<QUOTE>,<UNQUOTE>)}
504 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
506 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
510 Now we use the command @code{n} (@code{next}) to advance execution to
511 the next line of the current function.
515 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
520 @code{set_quotes} looks like a promising subroutine. We can go into it
521 by using the command @code{s} (@code{step}) instead of @code{next}.
522 @code{step} goes to the next line to be executed in @emph{any}
523 subroutine, so it steps into @code{set_quotes}.
527 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
529 530 if (lquote != def_lquote)
533 The display that shows the subroutine where @code{m4} is now
534 suspended (and its arguments) is called a stack frame display. It
535 shows a summary of the stack. We can use the @code{backtrace}
536 command (which can also be spelled @code{bt}), to see where we are
537 in the stack as a whole: the @code{backtrace} command displays a
538 stack frame for each active subroutine.
542 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
544 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
546 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
547 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
549 #4 0x79dc in expand_input () at macro.c:40
550 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
554 Let's step through a few more lines to see what happens. The first two
555 times, we can use @samp{s}; the next two times we use @code{n} to avoid
556 falling into the @code{xstrdup} subroutine.
560 0x3b5c 532 if (rquote != def_rquote)
562 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
563 def_lquote : xstrdup(lq);
565 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
568 538 len_lquote = strlen(rquote);
572 The last line displayed looks a little odd; let's examine the variables
573 @code{lquote} and @code{rquote} to see if they are in fact the new left
574 and right quotes we specified. We can use the command @code{p}
575 (@code{print}) to see their values.
578 (_GDBP__) @b{p lquote}
579 $1 = 0x35d40 "<QUOTE>"
580 (_GDBP__) @b{p rquote}
581 $2 = 0x35d50 "<UNQUOTE>"
585 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
586 Let's look at some context; we can display ten lines of source
587 surrounding the current line, with the @code{l} (@code{list}) command.
593 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
595 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
598 538 len_lquote = strlen(rquote);
599 539 len_rquote = strlen(lquote);
606 Let's step past the two lines that set @code{len_lquote} and
607 @code{len_rquote}, and then examine the values of those variables.
611 539 len_rquote = strlen(lquote);
614 (_GDBP__) @b{p len_lquote}
616 (_GDBP__) @b{p len_rquote}
621 That certainly looks wrong, assuming @code{len_lquote} and
622 @code{len_rquote} are meant to be the lengths of @code{lquote} and
623 @code{rquote} respectively. Let's try setting them to better values.
624 We can use the @code{p} command for this, since it'll print the value of
625 any expression---and that expression can include subroutine calls and
629 (_GDBP__) @b{p len_lquote=strlen(lquote)}
631 (_GDBP__) @b{p len_rquote=strlen(rquote)}
636 Let's see if that fixes the problem of using the new quotes with the
637 @code{m4} built-in @code{defn}. We can allow @code{m4} to continue
638 executing with the @code{c} (@code{continue}) command, and then try the
639 example that caused trouble initially:
645 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
652 Success! The new quotes now work just as well as the default ones. The
653 problem seems to have been just the two typos defining the wrong
654 lengths. We'll let @code{m4} exit by giving it an EOF as input.
658 Program exited normally.
662 The message @samp{Program exited normally.} is from _GDBN__; it
663 indicates @code{m4} has finished executing. We can end our _GDBN__
664 session with the _GDBN__ @code{quit} command.
668 _1__@end smallexample
671 @chapter Getting In and Out of _GDBN__
673 This chapter discusses how to start _GDBN__, and how to get out of it.
674 (The essentials: type @samp{_GDBP__} to start GDB, and type @kbd{quit}
675 or @kbd{C-d} to exit.)
678 * Invoking _GDBN__:: Starting _GDBN__
679 * Leaving _GDBN__:: Leaving _GDBN__
681 * Shell Commands:: Shell Commands
685 @node Invoking _GDBN__
686 @section Starting _GDBN__
689 For details on starting up _GDBP__ as a
690 remote debugger attached to a Hitachi H8/300 board, see @ref{Hitachi
691 H8/300 Remote,,_GDBN__ and the Hitachi H8/300}.
694 Start _GDBN__ by running the program @code{_GDBP__}. Once it's running,
695 _GDBN__ reads commands from the terminal until you tell it to exit.
697 You can also run @code{_GDBP__} with a variety of arguments and options,
698 to specify more of your debugging environment at the outset.
700 The command-line options described here are designed
701 to cover a variety of situations; in some environments, some of these
702 options may effectively be unavailable.
704 The most usual way to start _GDBN__ is with one argument,
705 specifying an executable program:
708 _GDBP__ @var{program}
713 You can also start with both an executable program and a core file
717 _GDBP__ @var{program} @var{core}
720 You can, instead, specify a process ID as a second argument, if you want
721 to debug a running process:
724 _GDBP__ @var{program} 1234
728 would attach _GDBN__ to process @code{1234} (unless you also have a file
729 named @file{1234}; _GDBN__ does check for a core file first).
731 Taking advantage of the second command-line argument requires a fairly
732 complete operating system; when you use _GDBN__ as a remote debugger
733 attached to a bare board, there may not be any notion of ``process'',
734 and there is often no way to get a core dump.
738 You can further control how _GDBN__ starts up by using command-line
739 options. _GDBN__ itself can remind you of the options available.
749 to display all available options and briefly describe their use
750 (@samp{_GDBP__ -h} is a shorter equivalent).
752 All options and command line arguments you give are processed
753 in sequential order. The order makes a difference when the
754 @samp{-x} option is used.
758 _include__(gdbinv-m.m4)_dnl__
760 * File Options:: Choosing Files
761 * Mode Options:: Choosing Modes
765 _include__(gdbinv-s.m4)
769 @subsection Choosing Files
772 When _GDBN__ starts, it reads any arguments other than options as
773 specifying an executable file and core file (or process ID). This is
774 the same as if the arguments were specified by the @samp{-se} and
775 @samp{-c} options respectively. (_GDBN__ reads the first argument
776 that does not have an associated option flag as equivalent to the
777 @samp{-se} option followed by that argument; and the second argument
778 that does not have an associated option flag, if any, as equivalent to
779 the @samp{-c} option followed by that argument.)
782 When _GDBN__ starts, it reads any argument other than options as
783 specifying an executable file. This is the same as if the argument was
784 specified by the @samp{-se} option.
787 Many options have both long and short forms; both are shown in the
788 following list. _GDBN__ also recognizes the long forms if you truncate
789 them, so long as enough of the option is present to be unambiguous.
790 (If you prefer, you can flag option arguments with @samp{--} rather
791 than @samp{-}, though we illustrate the more usual convention.)
794 @item -symbols=@var{file}
796 Read symbol table from file @var{file}.
798 @item -exec=@var{file}
800 Use file @var{file} as the executable file to execute when
801 appropriate, and for examining pure data in conjunction with a core
805 Read symbol table from file @var{file} and use it as the executable
809 @item -core=@var{file}
811 Use file @var{file} as a core dump to examine.
814 @item -command=@var{file}
816 Execute _GDBN__ commands from file @var{file}. @xref{Command Files}.
818 @item -directory=@var{directory}
819 @itemx -d @var{directory}
820 Add @var{directory} to the path to search for source files.
825 @emph{Warning: this option depends on operating system facilities that are not
826 supported on all systems.}@*
827 If memory-mapped files are available on your system through the @code{mmap}
828 system call, you can use this option
829 to have _GDBN__ write the symbols from your
830 program into a reusable file in the current directory. If the program you are debugging is
831 called @file{/tmp/fred}, the mapped symbol file will be @file{./fred.syms}.
832 Future _GDBN__ debugging sessions will notice the presence of this file,
833 and will quickly map in symbol information from it, rather than reading
834 the symbol table from the executable program.
836 The @file{.syms} file is specific to the host machine on which _GDBN__ is run.
837 It holds an exact image of _GDBN__'s internal symbol table. It cannot be
838 shared across multiple host platforms.
843 Read each symbol file's entire symbol table immediately, rather than
844 the default, which is to read it incrementally as it is needed.
845 This makes startup slower, but makes future operations faster.
849 The @code{-mapped} and @code{-readnow} options are typically combined in order to
850 build a @file{.syms} file that contains complete symbol information.
851 A simple GDB invocation to do nothing but build a @file{.syms} file for future
855 gdb -batch -nx -mapped -readnow programname
860 @subsection Choosing Modes
862 You can run _GDBN__ in various alternative modes---for example, in
863 batch mode or quiet mode.
868 Do not execute commands from any @file{_GDBINIT__} initialization files.
869 Normally, the commands in these files are executed after all the
870 command options and arguments have been processed.
871 @xref{Command Files}.
875 ``Quiet''. Do not print the introductory and copyright messages. These
876 messages are also suppressed in batch mode.
879 Run in batch mode. Exit with status @code{0} after processing all the command
880 files specified with @samp{-x} (and @file{_GDBINIT__}, if not inhibited).
881 Exit with nonzero status if an error occurs in executing the _GDBN__
882 commands in the command files.
884 Batch mode may be useful for running _GDBN__ as a filter, for example to
885 download and run a program on another computer; in order to make this
886 more useful, the message
889 Program exited normally.
893 (which is ordinarily issued whenever a program running under _GDBN__ control
894 terminates) is not issued when running in batch mode.
896 @item -cd=@var{directory}
897 Run _GDBN__ using @var{directory} as its working directory,
898 instead of the current directory.
901 @item -context @var{authentication}
902 When the Energize programming system starts up _GDBN__, it uses this
903 option to trigger an alternate mode of interaction.
904 @var{authentication} is a pair of numeric codes that identify _GDBN__
905 as a client in the Energize environment. Avoid this option when you run
906 _GDBN__ directly from the command line. See @ref{Energize,,Using
907 _GDBN__ with Energize} for more discussion of using _GDBN__ with Energize.
912 Emacs sets this option when it runs _GDBN__ as a subprocess. It tells _GDBN__
913 to output the full file name and line number in a standard,
914 recognizable fashion each time a stack frame is displayed (which
915 includes each time your program stops). This recognizable format looks
916 like two @samp{\032} characters, followed by the file name, line number
917 and character position separated by colons, and a newline. The
918 Emacs-to-_GDBN__ interface program uses the two @samp{\032} characters as
919 a signal to display the source code for the frame.
921 _if__(_GENERIC__ || !_H8__)
923 Set the line speed (baud rate or bits per second) of any serial
924 interface used by _GDBN__ for remote debugging.
926 @item -tty=@var{device}
927 Run using @var{device} for your program's standard input and output.
928 @c FIXME: kingdon thinks there is more to -tty. Investigate.
929 _fi__(_GENERIC__ || !_H8__)
932 @node Leaving _GDBN__
933 @section Leaving _GDBN__
934 @cindex exiting _GDBN__
940 To exit _GDBN__, use the @code{quit} command (abbreviated @code{q}), or type
941 an end-of-file character (usually @kbd{C-d}).
945 An interrupt (often @kbd{C-c}) will not exit from _GDBN__, but rather
946 will terminate the action of any _GDBN__ command that is in progress and
947 return to _GDBN__ command level. It is safe to type the interrupt
948 character at any time because _GDBN__ does not allow it to take effect
949 until a time when it is safe.
952 If you have been using _GDBN__ to control an attached process or device, you
953 can release it with the @code{detach} command; @pxref{Attach,
954 ,Debugging an Already-Running Process}..
959 @section Shell Commands
961 If you need to execute occasional shell commands during your
962 debugging session, there is no need to leave or suspend _GDBN__; you can
963 just use the @code{shell} command.
966 @item shell @var{command string}
969 Directs _GDBN__ to invoke an inferior shell to execute @var{command
970 string}. If it exists, the environment variable @code{SHELL} is used
971 for the name of the shell to run. Otherwise _GDBN__ uses
975 The utility @code{make} is often needed in development environments.
976 You do not have to use the @code{shell} command for this purpose in _GDBN__:
979 @item make @var{make-args}
982 Causes _GDBN__ to execute an inferior @code{make} program with the specified
983 arguments. This is equivalent to @samp{shell make @var{make-args}}.
988 @chapter _GDBN__ Commands
990 You can abbreviate a _GDBN__ command to the first few letters of the command
991 name, if that abbreviation is unambiguous; and you can repeat certain
992 _GDBN__ commands by typing just @key{RET}. You can also use the @key{TAB}
993 key to get _GDBN__ to fill out the rest of a word in a command (or to
994 show you the alternatives available, if there's more than one possibility).
997 * Command Syntax:: Command Syntax
998 * Completion:: Command Completion
999 * Help:: Getting Help
1002 @node Command Syntax
1003 @section Command Syntax
1005 A _GDBN__ command is a single line of input. There is no limit on how long
1006 it can be. It starts with a command name, which is followed by arguments
1007 whose meaning depends on the command name. For example, the command
1008 @code{step} accepts an argument which is the number of times to step,
1009 as in @samp{step 5}. You can also use the @code{step} command with
1010 no arguments. Some command names do not allow any arguments.
1012 @cindex abbreviation
1013 _GDBN__ command names may always be truncated if that abbreviation is
1014 unambiguous. Other possible command abbreviations are listed in the
1015 documentation for individual commands. In some cases, even ambiguous
1016 abbreviations are allowed; for example, @code{s} is specially defined as
1017 equivalent to @code{step} even though there are other commands whose
1018 names start with @code{s}. You can test abbreviations by using them as
1019 arguments to the @code{help} command.
1021 @cindex repeating commands
1023 A blank line as input to _GDBN__ (typing just @key{RET}) means to
1024 repeat the previous command. Certain commands (for example, @code{run})
1025 will not repeat this way; these are commands for which unintentional
1026 repetition might cause trouble and which you are unlikely to want to
1029 The @code{list} and @code{x} commands, when you repeat them with
1030 @key{RET}, construct new arguments rather than repeating
1031 exactly as typed. This permits easy scanning of source or memory.
1033 _GDBN__ can also use @key{RET} in another way: to partition lengthy
1034 output, in a way similar to the common utility @code{more}
1035 (@pxref{Screen Size}). Since it is easy to press one @key{RET} too many
1036 in this situation, _GDBN__ disables command repetition after any command
1037 that generates this sort of display.
1041 A line of input starting with @kbd{#} is a comment; it does nothing.
1042 This is useful mainly in command files (@pxref{Command Files}).
1045 @section Command Completion
1048 @cindex word completion
1049 _GDBN__ can fill in the rest of a word in a command for you, if there's
1050 only one possibility; it can also show you what the valid possibilities
1051 are for the next word in a command, at any time. This works for _GDBN__
1052 commands, _GDBN__ subcommands, and the names of symbols in your program.
1054 Press the @key{TAB} key whenever you want _GDBN__ to fill out the rest
1055 of a word. If there's only one possibility, _GDBN__ will fill in the
1056 word, and wait for you to finish the command (or press @key{RET} to
1057 enter it). For example, if you type
1059 @c FIXME "@key" doesn't distinguish its argument sufficiently to permit
1060 @c complete accuracy in these examples; space introduced for clarity.
1061 @c If texinfo enhancements make it unnecessary, it would be nice to
1062 @c replace " @key" by "@key" in the following...
1064 (_GDBP__) info bre @key{TAB}
1068 _GDBN__ fills in the rest of the word @samp{breakpoints}, since that's
1069 the only @code{info} subcommand beginning with @samp{bre}:
1072 (_GDBP__) info breakpoints
1076 You can either press @key{RET} at this point, to run the @code{info
1077 breakpoints} command, or backspace and enter something else, if
1078 @samp{breakpoints} doesn't look like the command you expected. (If you
1079 were sure you wanted @code{info breakpoints} in the first place, you
1080 might as well just type @key{RET} immediately after @samp{info bre},
1081 to exploit command abbreviations rather than command completion).
1083 If there is more than one possibility for the next word when you press
1084 @key{TAB}, _GDBN__ will sound a bell. You can either supply more
1085 characters and try again, or just press @key{TAB} a second time, and
1086 _GDBN__ will display all the possible completions for that word. For
1087 example, you might want to set a breakpoint on a subroutine whose name
1088 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} _GDBN__
1089 just sounds the bell. Typing @key{TAB} again will display all the
1090 function names in your program that begin with those characters, for
1094 (_GDBP__) b make_ @key{TAB}
1095 @exdent _GDBN__ sounds bell; press @key{TAB} again, to see:
1096 make_a_section_from_file make_environ
1097 make_abs_section make_function_type
1098 make_blockvector make_pointer_type
1099 make_cleanup make_reference_type
1100 make_command make_symbol_completion_list
1105 After displaying the available possibilities, _GDBN__ copies your
1106 partial input (@samp{b make_} in the example) so you can finish the
1109 If you just want to see the list of alternatives in the first place, you
1110 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1111 means @kbd{@key{META} ?}. You can type this either by holding down a
1112 key designated as the @key{META} shift on your keyboard (if there is
1113 one) while typing @kbd{?}, or by typing @key{ESC} followed by @kbd{?}.
1115 @cindex quotes in commands
1116 @cindex completion of quoted strings
1117 Sometimes the string you need, while logically a ``word'', may contain
1118 parentheses or other characters that _GDBN__ normally excludes from its
1119 notion of a word. To permit word completion to work in this situation,
1120 you may enclose words in @code{'} (single quote marks) in _GDBN__ commands.
1122 The most likely situation where you might need this is in typing the
1123 name of a C++ function. This is because C++ allows function overloading
1124 (multiple definitions of the same function, distinguished by argument
1125 type). For example, when you want to set a breakpoint you may need to
1126 distinguish whether you mean the version of @code{name} that takes an
1127 @code{int} parameter, @code{name(int)}, or the version that takes a
1128 @code{float} parameter, @code{name(float)}. To use the word-completion
1129 facilities in this situation, type a single quote @code{'} at the
1130 beginning of the function name. This alerts _GDBN__ that it may need to
1131 consider more information than usual when you press @key{TAB} or
1132 @kbd{M-?} to request word completion:
1135 (_GDBP__) b 'bubble( @key{M-?}
1136 bubble(double,double) bubble(int,int)
1137 (_GDBP__) b 'bubble(
1140 In some cases, _GDBN__ can tell that completing a name will require
1141 quotes. When this happens, _GDBN__ will insert the quote for you (while
1142 completing as much as it can) if you do not type the quote in the first
1146 (_GDBP__) b bub @key{TAB}
1147 @exdent _GDBN__ alters your input line to the following, and rings a bell:
1148 (_GDBP__) b 'bubble(
1152 In general, _GDBN__ can tell that a quote is needed (and inserts it) if
1153 you have not yet started typing the argument list when you ask for
1154 completion on an overloaded symbol.
1158 @section Getting Help
1159 @cindex online documentation
1162 You can always ask _GDBN__ itself for information on its commands, using the
1163 command @code{help}.
1169 You can use @code{help} (abbreviated @code{h}) with no arguments to
1170 display a short list of named classes of commands:
1174 List of classes of commands:
1176 running -- Running the program
1177 stack -- Examining the stack
1178 data -- Examining data
1179 breakpoints -- Making program stop at certain points
1180 files -- Specifying and examining files
1181 status -- Status inquiries
1182 support -- Support facilities
1183 user-defined -- User-defined commands
1184 aliases -- Aliases of other commands
1185 obscure -- Obscure features
1187 Type "help" followed by a class name for a list of
1188 commands in that class.
1189 Type "help" followed by command name for full
1191 Command name abbreviations are allowed if unambiguous.
1195 @item help @var{class}
1196 Using one of the general help classes as an argument, you can get a
1197 list of the individual commands in that class. For example, here is the
1198 help display for the class @code{status}:
1201 (_GDBP__) help status
1206 show -- Generic command for showing things set with "set"
1207 info -- Generic command for printing status
1209 Type "help" followed by command name for full
1211 Command name abbreviations are allowed if unambiguous.
1215 @item help @var{command}
1216 With a command name as @code{help} argument, _GDBN__ will display a
1217 short paragraph on how to use that command.
1220 In addition to @code{help}, you can use the _GDBN__ commands @code{info}
1221 and @code{show} to inquire about the state of your program, or the state
1222 of _GDBN__ itself. Each command supports many topics of inquiry; this
1223 manual introduces each of them in the appropriate context. The listings
1224 under @code{info} and under @code{show} in the Index point to
1225 all the sub-commands. @xref{Index}.
1232 This command (abbreviated @code{i}) is for describing the state of your
1233 program; for example, it can list the arguments given to your program
1234 (@code{info args}), the registers currently in use (@code{info
1235 registers}), or the breakpoints you have set (@code{info breakpoints}).
1236 You can get a complete list of the @code{info} sub-commands with
1237 @w{@code{help info}}.
1241 In contrast, @code{show} is for describing the state of _GDBN__ itself.
1242 You can change most of the things you can @code{show}, by using the
1243 related command @code{set}; for example, you can control what number
1244 system is used for displays with @code{set radix}, or simply inquire
1245 which is currently in use with @code{show radix}.
1248 To display all the settable parameters and their current
1249 values, you can use @code{show} with no arguments; you may also use
1250 @code{info set}. Both commands produce the same display.
1251 @c FIXME: "info set" violates the rule that "info" is for state of
1252 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1253 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1257 Here are three miscellaneous @code{show} subcommands, all of which are
1258 exceptional in lacking corresponding @code{set} commands:
1261 @kindex show version
1262 @cindex version number
1264 Show what version of _GDBN__ is running. You should include this
1265 information in _GDBN__ bug-reports. If multiple versions of _GDBN__ are in
1266 use at your site, you may occasionally want to make sure what version
1267 of _GDBN__ you are running; as _GDBN__ evolves, new commands are introduced,
1268 and old ones may wither away. The version number is also announced
1269 when you start _GDBN__ with no arguments.
1271 @kindex show copying
1273 Display information about permission for copying _GDBN__.
1275 @kindex show warranty
1277 Display the GNU ``NO WARRANTY'' statement.
1281 @chapter Running Programs Under _GDBN__
1283 To debug a program, you must run it under _GDBN__.
1286 * Compilation:: Compiling for Debugging
1287 * Starting:: Starting your Program
1289 * Arguments:: Your Program's Arguments
1290 * Environment:: Your Program's Environment
1291 * Working Directory:: Your Program's Working Directory
1292 * Input/Output:: Your Program's Input and Output
1293 * Attach:: Debugging an Already-Running Process
1294 * Kill Process:: Killing the Child Process
1295 * Process Information:: Additional Process Information
1300 @section Compiling for Debugging
1302 In order to debug a program effectively, you need to generate
1303 debugging information when you compile it. This debugging information
1304 is stored in the object file; it describes the data type of each
1305 variable or function and the correspondence between source line numbers
1306 and addresses in the executable code.
1308 To request debugging information, specify the @samp{-g} option when you run
1311 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1312 options together. Using those compilers, you cannot generate optimized
1313 executables containing debugging information.
1315 _GCC__, the GNU C compiler, supports @samp{-g} with or without
1316 @samp{-O}, making it possible to debug optimized code. We recommend
1317 that you @emph{always} use @samp{-g} whenever you compile a program.
1318 You may think your program is correct, but there is no sense in pushing
1321 @cindex optimized code, debugging
1322 @cindex debugging optimized code
1323 When you debug a program compiled with @samp{-g -O}, remember that the
1324 optimizer is rearranging your code; the debugger will show you what's
1325 really there. Don't be too surprised when the execution path doesn't
1326 exactly match your source file! An extreme example: if you define a
1327 variable, but never use it, _GDBN__ will never see that
1328 variable---because the compiler optimizes it out of existence.
1330 Some things do not work as well with @samp{-g -O} as with just
1331 @samp{-g}, particularly on machines with instruction scheduling. If in
1332 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1333 please report it as a bug (including a test case!).
1335 Older versions of the GNU C compiler permitted a variant option
1336 @w{@samp{-gg}} for debugging information. _GDBN__ no longer supports this
1337 format; if your GNU C compiler has this option, do not use it.
1340 @comment As far as I know, there are no cases in which _GDBN__ will
1341 @comment produce strange output in this case. (but no promises).
1342 If your program includes archives made with the @code{ar} program, and
1343 if the object files used as input to @code{ar} were compiled without the
1344 @samp{-g} option and have names longer than 15 characters, _GDBN__ will get
1345 confused reading your program's symbol table. No error message will be
1346 given, but _GDBN__ may behave strangely. The reason for this problem is a
1347 deficiency in the Unix archive file format, which cannot represent file
1348 names longer than 15 characters.
1350 To avoid this problem, compile the archive members with the @samp{-g}
1351 option or use shorter file names. Alternatively, use a version of GNU
1352 @code{ar} dated more recently than August 1989.
1356 @section Starting your Program
1364 Use the @code{run} command to start your program under _GDBN__. You must
1365 first specify the program name
1370 _GDBN__ (@pxref{Invocation, ,Getting In and Out of _GDBN__}), or by using the
1371 @code{file} or @code{exec-file} command (@pxref{Files, ,Commands to
1377 If you are running your program in an execution environment that
1378 supports processes, @code{run} creates an inferior process and makes
1379 that process run your program. (In environments without processes,
1380 @code{run} jumps to the start of your program.)
1382 The execution of a program is affected by certain information it
1383 receives from its superior. _GDBN__ provides ways to specify this
1384 information, which you must do @emph{before} starting your program. (You
1385 can change it after starting your program, but such changes will only affect
1386 your program the next time you start it.) This information may be
1387 divided into four categories:
1390 @item The @emph{arguments.}
1391 Specify the arguments to give your program as the arguments of the
1392 @code{run} command. If a shell is available on your target, the shell
1393 is used to pass the arguments, so that you may use normal conventions
1394 (such as wildcard expansion or variable substitution) in describing
1395 the arguments. In Unix systems, you can control which shell is used
1396 with the @code{SHELL} environment variable. @xref{Arguments, ,Your
1397 Program's Arguments}.
1399 @item The @emph{environment.}
1400 Your program normally inherits its environment from _GDBN__, but you can
1401 use the _GDBN__ commands @code{set environment} and @code{unset
1402 environment} to change parts of the environment that will be given to
1403 your program. @xref{Environment, ,Your Program's Environment}.
1405 @item The @emph{working directory.}
1406 Your program inherits its working directory from _GDBN__. You can set
1407 _GDBN__'s working directory with the @code{cd} command in _GDBN__.
1408 @xref{Working Directory, ,Your Program's Working Directory}.
1410 @item The @emph{standard input and output.}
1411 Your program normally uses the same device for standard input and
1412 standard output as _GDBN__ is using. You can redirect input and output
1413 in the @code{run} command line, or you can use the @code{tty} command to
1414 set a different device for your program.
1415 @xref{Input/Output, ,Your Program's Input and Output}.
1418 @emph{Warning:} While input and output redirection work, you cannot use
1419 pipes to pass the output of the program you are debugging to another
1420 program; if you attempt this, _GDBN__ is likely to wind up debugging the
1425 When you issue the @code{run} command, your program begins to execute
1426 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1427 of how to arrange for your program to stop. Once your program has
1428 stopped, you may calls functions in your program, using the @code{print}
1429 or @code{call} commands. @xref{Data, ,Examining Data}.
1431 If the modification time of your symbol file has changed since the
1432 last time _GDBN__ read its symbols, _GDBN__ will discard its symbol table and
1433 re-read it. When it does this, _GDBN__ tries to retain your current
1438 @section Your Program's Arguments
1440 @cindex arguments (to your program)
1441 The arguments to your program can be specified by the arguments of the
1442 @code{run} command. They are passed to a shell, which expands wildcard
1443 characters and performs redirection of I/O, and thence to your program.
1444 _GDBN__ uses the shell indicated by your environment variable
1445 @code{SHELL} if it exists; otherwise, _GDBN__ uses @code{/bin/sh}.
1447 @code{run} with no arguments uses the same arguments used by the previous
1448 @code{run}, or those set by the @code{set args} command.
1453 Specify the arguments to be used the next time your program is run. If
1454 @code{set args} has no arguments, @code{run} will execute your program
1455 with no arguments. Once you have run your program with arguments,
1456 using @code{set args} before the next @code{run} is the only way to run
1457 it again without arguments.
1461 Show the arguments to give your program when it is started.
1465 @section Your Program's Environment
1467 @cindex environment (of your program)
1468 The @dfn{environment} consists of a set of environment variables and
1469 their values. Environment variables conventionally record such things as
1470 your user name, your home directory, your terminal type, and your search
1471 path for programs to run. Usually you set up environment variables with
1472 the shell and they are inherited by all the other programs you run. When
1473 debugging, it can be useful to try running your program with a modified
1474 environment without having to start _GDBN__ over again.
1477 @item path @var{directory}
1479 Add @var{directory} to the front of the @code{PATH} environment variable
1480 (the search path for executables), for both _GDBN__ and your program.
1481 You may specify several directory names, separated by @samp{:} or
1482 whitespace. If @var{directory} is already in the path, it is moved to
1483 the front, so it will be searched sooner.
1485 You can use the string @samp{$cwd} to refer to whatever is the current
1486 working directory at the time _GDBN__ searches the path. If you use
1487 @samp{.} instead, it refers to the directory where you executed the
1488 @code{path} command. _GDBN__ fills in the current path where needed in
1489 the @var{directory} argument, before adding it to the search path.
1490 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1491 @c document that, since repeating it would be a no-op.
1495 Display the list of search paths for executables (the @code{PATH}
1496 environment variable).
1498 @item show environment @r{[}@var{varname}@r{]}
1499 @kindex show environment
1500 Print the value of environment variable @var{varname} to be given to
1501 your program when it starts. If you do not supply @var{varname},
1502 print the names and values of all environment variables to be given to
1503 your program. You can abbreviate @code{environment} as @code{env}.
1505 @item set environment @var{varname} @r{[}=@r{]} @var{value}
1506 @kindex set environment
1507 Sets environment variable @var{varname} to @var{value}. The value
1508 changes for your program only, not for _GDBN__ itself. @var{value} may
1509 be any string; the values of environment variables are just strings, and
1510 any interpretation is supplied by your program itself. The @var{value}
1511 parameter is optional; if it is eliminated, the variable is set to a
1513 @c "any string" here does not include leading, trailing
1514 @c blanks. Gnu asks: does anyone care?
1516 For example, this command:
1523 tells a Unix program, when subsequently run, that its user is named
1524 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1525 are not actually required.)
1527 @item unset environment @var{varname}
1528 @kindex unset environment
1529 Remove variable @var{varname} from the environment to be passed to your
1530 program. This is different from @samp{set env @var{varname} =};
1531 @code{unset environment} removes the variable from the environment,
1532 rather than assigning it an empty value.
1535 @node Working Directory
1536 @section Your Program's Working Directory
1538 @cindex working directory (of your program)
1539 Each time you start your program with @code{run}, it inherits its
1540 working directory from the current working directory of _GDBN__. _GDBN__'s
1541 working directory is initially whatever it inherited from its parent
1542 process (typically the shell), but you can specify a new working
1543 directory in _GDBN__ with the @code{cd} command.
1545 The _GDBN__ working directory also serves as a default for the commands
1546 that specify files for _GDBN__ to operate on. @xref{Files, ,Commands to
1550 @item cd @var{directory}
1552 Set _GDBN__'s working directory to @var{directory}.
1556 Print _GDBN__'s working directory.
1560 @section Your Program's Input and Output
1565 By default, the program you run under _GDBN__ does input and output to
1566 the same terminal that _GDBN__ uses. _GDBN__ switches the terminal to
1567 its own terminal modes to interact with you, but it records the terminal
1568 modes your program was using and switches back to them when you continue
1569 running your program.
1573 @kindex info terminal
1574 Displays _GDBN__'s recorded information about the terminal modes your
1578 You can redirect your program's input and/or output using shell
1579 redirection with the @code{run} command. For example,
1586 starts your program, diverting its output to the file @file{outfile}.
1589 @cindex controlling terminal
1590 Another way to specify where your program should do input and output is
1591 with the @code{tty} command. This command accepts a file name as
1592 argument, and causes this file to be the default for future @code{run}
1593 commands. It also resets the controlling terminal for the child
1594 process, for future @code{run} commands. For example,
1601 directs that processes started with subsequent @code{run} commands
1602 default to do input and output on the terminal @file{/dev/ttyb} and have
1603 that as their controlling terminal.
1605 An explicit redirection in @code{run} overrides the @code{tty} command's
1606 effect on the input/output device, but not its effect on the controlling
1609 When you use the @code{tty} command or redirect input in the @code{run}
1610 command, only the input @emph{for your program} is affected. The input
1611 for _GDBN__ still comes from your terminal.
1614 @section Debugging an Already-Running Process
1619 @item attach @var{process-id}
1621 attaches to a running process---one that was started outside _GDBN__.
1622 (@code{info files} will show your active targets.) The command takes as
1623 argument a process ID. The usual way to find out the process-id of
1624 a Unix process is with the @code{ps} utility, or with the @samp{jobs -l}
1627 @code{attach} will not repeat if you press @key{RET} a second time after
1628 executing the command.
1631 To use @code{attach}, you must be debugging in an environment which
1632 supports processes. You must also have permission to send the process a
1633 signal, and it must have the same effective user ID as the _GDBN__
1636 When using @code{attach}, you should first use the @code{file} command
1637 to specify the program running in the process and load its symbol table.
1638 @xref{Files, ,Commands to Specify Files}.
1640 The first thing _GDBN__ does after arranging to debug the specified
1641 process is to stop it. You can examine and modify an attached process
1642 with all the _GDBN__ commands that are ordinarily available when you start
1643 processes with @code{run}. You can insert breakpoints; you can step and
1644 continue; you can modify storage. If you would rather the process
1645 continue running, you may use the @code{continue} command after
1646 attaching _GDBN__ to the process.
1651 When you have finished debugging the attached process, you can use the
1652 @code{detach} command to release it from _GDBN__'s control. Detaching
1653 the process continues its execution. After the @code{detach} command,
1654 that process and _GDBN__ become completely independent once more, and you
1655 are ready to @code{attach} another process or start one with @code{run}.
1656 @code{detach} will not repeat if you press @key{RET} again after
1657 executing the command.
1660 If you exit _GDBN__ or use the @code{run} command while you have an attached
1661 process, you kill that process. By default, you will be asked for
1662 confirmation if you try to do either of these things; you can control
1663 whether or not you need to confirm by using the @code{set confirm} command
1664 (@pxref{Messages/Warnings, ,Optional Warnings and Messages}).
1668 @section Killing the Child Process
1673 Kill the child process in which your program is running under _GDBN__.
1676 This command is useful if you wish to debug a core dump instead of a
1677 running process. _GDBN__ ignores any core dump file while your program
1681 On some operating systems, a program cannot be executed outside _GDBN__
1682 while you have breakpoints set on it inside _GDBN__. You can use the
1683 @code{kill} command in this situation to permit running your program
1684 outside the debugger.
1686 The @code{kill} command is also useful if you wish to recompile and
1687 relink your program, since on many systems it is impossible to modify an
1688 executable file while it is running in a process. In this case, when you
1689 next type @code{run}, _GDBN__ will notice that the file has changed, and
1690 will re-read the symbol table (while trying to preserve your current
1691 breakpoint settings).
1693 @node Process Information
1694 @section Additional Process Information
1697 @cindex process image
1698 Some operating systems provide a facility called @samp{/proc} that can
1699 be used to examine the image of a running process using file-system
1700 subroutines. If _GDBN__ is configured for an operating system with this
1701 facility, the command @code{info proc} is available to report on several
1702 kinds of information about the process running your program.
1707 Summarize available information about the process.
1709 @item info proc mappings
1710 @kindex info proc mappings
1711 Report on the address ranges accessible in the program, with information
1712 on whether your program may read, write, or execute each range.
1714 @item info proc times
1715 @kindex info proc times
1716 Starting time, user CPU time, and system CPU time for your program and
1720 @kindex info proc id
1721 Report on the process ID's related to your program: its own process id,
1722 the id of its parent, the process group id, and the session id.
1724 @item info proc status
1725 @kindex info proc status
1726 General information on the state of the process. If the process is
1727 stopped, this report includes the reason for stopping, and any signal
1731 Show all the above information about the process.
1736 @chapter Stopping and Continuing
1738 The principal purpose of using a debugger is so that you can stop your
1739 program before it terminates; or so that, if your program runs into
1740 trouble, you can investigate and find out why.
1742 Inside _GDBN__, your program may stop for any of several reasons, such
1743 as a signal, a breakpoint, or reaching a new line after a _GDBN__
1744 command such as @code{step}. You may then examine and change
1745 variables, set new breakpoints or remove old ones, and then continue
1746 execution. Usually, the messages shown by _GDBN__ provide ample
1747 explanation of the status of your program---but you can also explicitly
1748 request this information at any time.
1752 @kindex info program
1753 Display information about the status of your program: whether it is
1754 running or not, what process it is, and why it stopped.
1758 * Breakpoints:: Breakpoints, Watchpoints, and Exceptions
1759 * Continuing and Stepping:: Resuming Execution
1760 _if__(_GENERIC__ || !_H8__)
1762 _fi__(_GENERIC__ || !_H8__)
1766 @section Breakpoints, Watchpoints, and Exceptions
1769 A @dfn{breakpoint} makes your program stop whenever a certain point in
1770 the program is reached. For each breakpoint, you can add various
1771 conditions to control in finer detail whether your program will stop.
1772 You can set breakpoints with the @code{break} command and its variants
1773 (@pxref{Set Breaks, ,Setting Breakpoints}), to specify the place where
1774 your program should stop by line number, function name or exact address
1775 in the program. In languages with exception handling (such as GNU
1776 C++), you can also set breakpoints where an exception is raised
1777 (@pxref{Exception Handling, ,Breakpoints and Exceptions}).
1780 @cindex memory tracing
1781 @cindex breakpoint on memory address
1782 @cindex breakpoint on variable modification
1783 A @dfn{watchpoint} is a special breakpoint that stops your program
1784 when the value of an expression changes. You must use a different
1785 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
1786 Watchpoints}), but aside from that, you can manage a watchpoint like
1787 any other breakpoint: you enable, disable, and delete both breakpoints
1788 and watchpoints using the same commands.
1790 @cindex breakpoint numbers
1791 @cindex numbers for breakpoints
1792 _GDBN__ assigns a number to each breakpoint or watchpoint when you
1793 create it; these numbers are successive integers starting with one. In
1794 many of the commands for controlling various features of breakpoints you
1795 use the breakpoint number to say which breakpoint you want to change.
1796 Each breakpoint may be @dfn{enabled} or @dfn{disabled}; if disabled, it has
1797 no effect on your program until you enable it again.
1800 * Set Breaks:: Setting Breakpoints
1801 * Set Watchpoints:: Setting Watchpoints
1802 * Exception Handling:: Breakpoints and Exceptions
1803 * Delete Breaks:: Deleting Breakpoints
1804 * Disabling:: Disabling Breakpoints
1805 * Conditions:: Break Conditions
1806 * Break Commands:: Breakpoint Command Lists
1807 * Breakpoint Menus:: Breakpoint Menus
1808 * Error in Breakpoints::
1812 @subsection Setting Breakpoints
1814 @c FIXME LMB what does GDB do if no code on line of breakpt?
1815 @c consider in particular declaration with/without initialization.
1817 @c FIXME 2 is there stuff on this already? break at fun start, already init?
1822 @cindex latest breakpoint
1823 Breakpoints are set with the @code{break} command (abbreviated
1824 @code{b}). The debugger convenience variable @samp{$bpnum} records the
1825 number of the beakpoint you've set most recently; see @ref{Convenience
1826 Vars,, Convenience Variables}, for a discussion of what you can do with
1827 convenience variables.
1829 You have several ways to say where the breakpoint should go.
1832 @item break @var{function}
1833 Set a breakpoint at entry to function @var{function}. When using source
1834 languages that permit overloading of symbols, such as C++,
1835 @var{function} may refer to more than one possible place to break.
1836 @xref{Breakpoint Menus}, for a discussion of that situation.
1838 @item break +@var{offset}
1839 @itemx break -@var{offset}
1840 Set a breakpoint some number of lines forward or back from the position
1841 at which execution stopped in the currently selected frame.
1843 @item break @var{linenum}
1844 Set a breakpoint at line @var{linenum} in the current source file.
1845 That file is the last file whose source text was printed. This
1846 breakpoint will stop your program just before it executes any of the
1849 @item break @var{filename}:@var{linenum}
1850 Set a breakpoint at line @var{linenum} in source file @var{filename}.
1852 @item break @var{filename}:@var{function}
1853 Set a breakpoint at entry to function @var{function} found in file
1854 @var{filename}. Specifying a file name as well as a function name is
1855 superfluous except when multiple files contain similarly named
1858 @item break *@var{address}
1859 Set a breakpoint at address @var{address}. You can use this to set
1860 breakpoints in parts of your program which do not have debugging
1861 information or source files.
1864 When called without any arguments, @code{break} sets a breakpoint at
1865 the next instruction to be executed in the selected stack frame
1866 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
1867 innermost, this will cause your program to stop as soon as control
1868 returns to that frame. This is similar to the effect of a
1869 @code{finish} command in the frame inside the selected frame---except
1870 that @code{finish} does not leave an active breakpoint. If you use
1871 @code{break} without an argument in the innermost frame, _GDBN__ will stop
1872 the next time it reaches the current location; this may be useful
1875 _GDBN__ normally ignores breakpoints when it resumes execution, until at
1876 least one instruction has been executed. If it did not do this, you
1877 would be unable to proceed past a breakpoint without first disabling the
1878 breakpoint. This rule applies whether or not the breakpoint already
1879 existed when your program stopped.
1881 @item break @dots{} if @var{cond}
1882 Set a breakpoint with condition @var{cond}; evaluate the expression
1883 @var{cond} each time the breakpoint is reached, and stop only if the
1884 value is nonzero---that is, if @var{cond} evaluates as true.
1885 @samp{@dots{}} stands for one of the possible arguments described
1886 above (or no argument) specifying where to break. @xref{Conditions,
1887 ,Break Conditions}, for more information on breakpoint conditions.
1889 @item tbreak @var{args}
1891 Set a breakpoint enabled only for one stop. @var{args} are the
1892 same as for the @code{break} command, and the breakpoint is set in the same
1893 way, but the breakpoint is automatically disabled after the first time your
1894 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
1896 @item rbreak @var{regex}
1898 @cindex regular expression
1899 @c FIXME what kind of regexp?
1900 Set breakpoints on all functions matching the regular expression
1901 @var{regex}. This command
1902 sets an unconditional breakpoint on all matches, printing a list of all
1903 breakpoints it set. Once these breakpoints are set, they are treated
1904 just like the breakpoints set with the @code{break} command. They can
1905 be deleted, disabled, made conditional, etc., in the standard ways.
1907 When debugging C++ programs, @code{rbreak} is useful for setting
1908 breakpoints on overloaded functions that are not members of any special
1911 @kindex info breakpoints
1912 @cindex @code{$_} and @code{info breakpoints}
1913 @item info breakpoints @r{[}@var{n}@r{]}
1914 @itemx info break @r{[}@var{n}@r{]}
1915 @itemx info watchpoints @r{[}@var{n}@r{]}
1916 Print a table of all breakpoints and watchpoints set and not
1917 deleted, with the following columns for each breakpoint:
1920 @item Breakpoint Numbers
1922 Breakpoint or watchpoint.
1924 Whether the breakpoint is marked to be disabled or deleted when hit.
1925 @item Enabled or Disabled
1926 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
1927 that are not enabled.
1929 Where the breakpoint is in your program, as a memory address
1931 Where the breakpoint is in the source for your program, as a file and
1936 Breakpoint commands, if any, are listed after the line for the
1937 corresponding breakpoint.
1940 @code{info break} with a breakpoint
1941 number @var{n} as argument lists only that breakpoint. The
1942 convenience variable @code{$_} and the default examining-address for
1943 the @code{x} command are set to the address of the last breakpoint
1944 listed (@pxref{Memory, ,Examining Memory}).
1947 _GDBN__ allows you to set any number of breakpoints at the same place in
1948 your program. There is nothing silly or meaningless about this. When
1949 the breakpoints are conditional, this is even useful
1950 (@pxref{Conditions, ,Break Conditions}).
1952 @cindex negative breakpoint numbers
1953 @cindex internal _GDBN__ breakpoints
1954 _GDBN__ itself sometimes sets breakpoints in your program for special
1955 purposes, such as proper handling of @code{longjmp} (in C programs).
1956 These internal breakpoints are assigned negative numbers, starting with
1957 @code{-1}; @samp{info breakpoints} does not display them.
1959 You can see these breakpoints with the _GDBN__ maintenance command
1960 @samp{maint info breakpoints}.
1963 @kindex maint info breakpoints
1964 @item maint info breakpoints
1965 Using the same format as @samp{info breakpoints}, display both the
1966 breakpoints you've set explicitly, and those _GDBN__ is using for
1967 internal purposes. Internal breakpoints are shown with negative
1968 breakpoint numbers. The type column identifies what kind of breakpoint
1973 Normal, explicitly set breakpoint.
1976 Normal, explicitly set watchpoint.
1979 Internal breakpoint, used to handle correctly stepping through
1980 @code{longjmp} calls.
1982 @item longjmp resume
1983 Internal breakpoint at the target of a @code{longjmp}.
1986 Temporary internal breakpoint used by the _GDBN__ @code{until} command.
1989 Temporary internal breakpoint used by the _GDBN__ @code{finish} command.
1995 @node Set Watchpoints
1996 @subsection Setting Watchpoints
1997 @cindex setting watchpoints
1999 You can use a watchpoint to stop execution whenever the value of an
2000 expression changes, without having to predict a particular place
2001 where this may happen.
2003 Watchpoints currently execute two orders of magnitude more slowly than
2004 other breakpoints, but this can well be worth it to catch errors where
2005 you have no clue what part of your program is the culprit. Some
2006 processors provide special hardware to support watchpoint evaluation; future
2007 releases of _GDBN__ will use such hardware if it is available.
2011 @item watch @var{expr}
2012 Set a watchpoint for an expression.
2014 @kindex info watchpoints
2015 @item info watchpoints
2016 This command prints a list of watchpoints and breakpoints; it is the
2017 same as @code{info break}.
2020 @node Exception Handling
2021 @subsection Breakpoints and Exceptions
2022 @cindex exception handlers
2024 Some languages, such as GNU C++, implement exception handling. You can
2025 use _GDBN__ to examine what caused your program to raise an exception,
2026 and to list the exceptions your program is prepared to handle at a
2027 given point in time.
2030 @item catch @var{exceptions}
2032 You can set breakpoints at active exception handlers by using the
2033 @code{catch} command. @var{exceptions} is a list of names of exceptions
2037 You can use @code{info catch} to list active exception handlers.
2038 @xref{Frame Info, ,Information About a Frame}.
2040 There are currently some limitations to exception handling in _GDBN__.
2041 These will be corrected in a future release.
2045 If you call a function interactively, _GDBN__ normally returns
2046 control to you when the function has finished executing. If the call
2047 raises an exception, however, the call may bypass the mechanism that
2048 returns control to you and cause your program to simply continue
2049 running until it hits a breakpoint, catches a signal that _GDBN__ is
2050 listening for, or exits.
2052 You cannot raise an exception interactively.
2054 You cannot interactively install an exception handler.
2057 @cindex raise exceptions
2058 Sometimes @code{catch} is not the best way to debug exception handling:
2059 if you need to know exactly where an exception is raised, it is better to
2060 stop @emph{before} the exception handler is called, since that way you
2061 can see the stack before any unwinding takes place. If you set a
2062 breakpoint in an exception handler instead, it may not be easy to find
2063 out where the exception was raised.
2065 To stop just before an exception handler is called, you need some
2066 knowledge of the implementation. In the case of GNU C++, exceptions are
2067 raised by calling a library function named @code{__raise_exception}
2068 which has the following ANSI C interface:
2071 /* @var{addr} is where the exception identifier is stored.
2072 ID is the exception identifier. */
2073 void __raise_exception (void **@var{addr}, void *@var{id});
2077 To make the debugger catch all exceptions before any stack
2078 unwinding takes place, set a breakpoint on @code{__raise_exception}
2079 (@pxref{Breakpoints, ,Breakpoints Watchpoints and Exceptions}).
2081 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
2082 that depends on the value of @var{id}, you can stop your program when
2083 a specific exception is raised. You can use multiple conditional
2084 breakpoints to stop your program when any of a number of exceptions are
2088 @subsection Deleting Breakpoints
2090 @cindex clearing breakpoints, watchpoints
2091 @cindex deleting breakpoints, watchpoints
2092 It is often necessary to eliminate a breakpoint or watchpoint once it
2093 has done its job and you no longer want your program to stop there. This
2094 is called @dfn{deleting} the breakpoint. A breakpoint that has been
2095 deleted no longer exists; it is forgotten.
2097 With the @code{clear} command you can delete breakpoints according to
2098 where they are in your program. With the @code{delete} command you can
2099 delete individual breakpoints or watchpoints by specifying their
2102 It is not necessary to delete a breakpoint to proceed past it. _GDBN__
2103 automatically ignores breakpoints on the first instruction to be executed
2104 when you continue execution without changing the execution address.
2109 Delete any breakpoints at the next instruction to be executed in the
2110 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
2111 the innermost frame is selected, this is a good way to delete a
2112 breakpoint where your program just stopped.
2114 @item clear @var{function}
2115 @itemx clear @var{filename}:@var{function}
2116 Delete any breakpoints set at entry to the function @var{function}.
2118 @item clear @var{linenum}
2119 @itemx clear @var{filename}:@var{linenum}
2120 Delete any breakpoints set at or within the code of the specified line.
2122 @item delete @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]}
2123 @cindex delete breakpoints
2126 Delete the breakpoints or watchpoints of the numbers specified as
2127 arguments. If no argument is specified, delete all breakpoints (_GDBN__
2128 asks confirmation, unless you have @code{set confirm off}). You
2129 can abbreviate this command as @code{d}.
2133 @subsection Disabling Breakpoints
2135 @cindex disabled breakpoints
2136 @cindex enabled breakpoints
2137 Rather than deleting a breakpoint or watchpoint, you might prefer to
2138 @dfn{disable} it. This makes the breakpoint inoperative as if it had
2139 been deleted, but remembers the information on the breakpoint so that
2140 you can @dfn{enable} it again later.
2142 You disable and enable breakpoints and watchpoints with the
2143 @code{enable} and @code{disable} commands, optionally specifying one or
2144 more breakpoint numbers as arguments. Use @code{info break} or
2145 @code{info watch} to print a list of breakpoints or watchpoints if you
2146 do not know which numbers to use.
2148 A breakpoint or watchpoint can have any of four different states of
2153 Enabled. The breakpoint will stop your program. A breakpoint set
2154 with the @code{break} command starts out in this state.
2156 Disabled. The breakpoint has no effect on your program.
2158 Enabled once. The breakpoint will stop your program, but
2159 when it does so it will become disabled. A breakpoint set
2160 with the @code{tbreak} command starts out in this state.
2162 Enabled for deletion. The breakpoint will stop your program, but
2163 immediately after it does so it will be deleted permanently.
2166 You can use the following commands to enable or disable breakpoints and
2170 @item disable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]}
2171 @kindex disable breakpoints
2174 Disable the specified breakpoints---or all breakpoints, if none are
2175 listed. A disabled breakpoint has no effect but is not forgotten. All
2176 options such as ignore-counts, conditions and commands are remembered in
2177 case the breakpoint is enabled again later. You may abbreviate
2178 @code{disable} as @code{dis}.
2180 @item enable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]}
2181 @kindex enable breakpoints
2183 Enable the specified breakpoints (or all defined breakpoints). They
2184 become effective once again in stopping your program.
2186 @item enable @r{[}breakpoints@r{]} once @var{bnums}@dots{}
2187 Enable the specified breakpoints temporarily. Each will be disabled
2188 again the next time it stops your program.
2190 @item enable @r{[}breakpoints@r{]} delete @var{bnums}@dots{}
2191 Enable the specified breakpoints to work once and then die. Each of
2192 the breakpoints will be deleted the next time it stops your program.
2195 Save for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
2196 ,Setting Breakpoints}), breakpoints that you set are initially
2197 enabled; subsequently, they become disabled or enabled only when you
2198 use one of the commands above. (The command @code{until} can set and
2199 delete a breakpoint of its own, but it will not change the state of
2200 your other breakpoints; see @ref{Continuing and Stepping, ,Continuing and Stepping}.)
2203 @subsection Break Conditions
2204 @cindex conditional breakpoints
2205 @cindex breakpoint conditions
2207 @c FIXME what is scope of break condition expr? Context where wanted?
2208 @c in particular for a watchpoint?
2209 The simplest sort of breakpoint breaks every time your program reaches a
2210 specified place. You can also specify a @dfn{condition} for a
2211 breakpoint. A condition is just a Boolean expression in your
2212 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
2213 a condition evaluates the expression each time your program reaches it,
2214 and your program stops only if the condition is @emph{true}.
2216 This is the converse of using assertions for program validation; in that
2217 situation, you want to stop when the assertion is violated---that is,
2218 when the condition is false. In C, if you want to test an assertion expressed
2219 by the condition @var{assert}, you should set the condition
2220 @samp{! @var{assert}} on the appropriate breakpoint.
2222 Conditions are also accepted for watchpoints; you may not need them,
2223 since a watchpoint is inspecting the value of an expression anyhow---but
2224 it might be simpler, say, to just set a watchpoint on a variable name,
2225 and specify a condition that tests whether the new value is an interesting
2228 Break conditions can have side effects, and may even call functions in
2229 your program. This can be useful, for example, to activate functions
2230 that log program progress, or to use your own print functions to
2231 format special data structures. The effects are completely predictable
2232 unless there is another enabled breakpoint at the same address. (In
2233 that case, _GDBN__ might see the other breakpoint first and stop your
2234 program without checking the condition of this one.) Note that
2235 breakpoint commands are usually more convenient and flexible for the
2236 purpose of performing side effects when a breakpoint is reached
2237 (@pxref{Break Commands, ,Breakpoint Command Lists}).
2239 Break conditions can be specified when a breakpoint is set, by using
2240 @samp{if} in the arguments to the @code{break} command. @xref{Set
2241 Breaks, ,Setting Breakpoints}. They can also be changed at any time
2242 with the @code{condition} command. The @code{watch} command does not
2243 recognize the @code{if} keyword; @code{condition} is the only way to
2244 impose a further condition on a watchpoint.
2247 @item condition @var{bnum} @var{expression}
2249 Specify @var{expression} as the break condition for breakpoint or
2250 watchpoint number @var{bnum}. From now on, this breakpoint will stop
2251 your program only if the value of @var{expression} is true (nonzero, in
2252 C). When you use @code{condition}, _GDBN__ checks @var{expression}
2253 immediately for syntactic correctness, and to determine whether symbols
2254 in it have referents in the context of your breakpoint.
2255 @c FIXME so what does GDB do if there is no referent? Moreover, what
2256 @c about watchpoints?
2258 not actually evaluate @var{expression} at the time the @code{condition}
2259 command is given, however. @xref{Expressions, ,Expressions}.
2261 @item condition @var{bnum}
2262 Remove the condition from breakpoint number @var{bnum}. It becomes
2263 an ordinary unconditional breakpoint.
2266 @cindex ignore count (of breakpoint)
2267 A special case of a breakpoint condition is to stop only when the
2268 breakpoint has been reached a certain number of times. This is so
2269 useful that there is a special way to do it, using the @dfn{ignore
2270 count} of the breakpoint. Every breakpoint has an ignore count, which
2271 is an integer. Most of the time, the ignore count is zero, and
2272 therefore has no effect. But if your program reaches a breakpoint whose
2273 ignore count is positive, then instead of stopping, it just decrements
2274 the ignore count by one and continues. As a result, if the ignore count
2275 value is @var{n}, the breakpoint will not stop the next @var{n} times it
2279 @item ignore @var{bnum} @var{count}
2281 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
2282 The next @var{count} times the breakpoint is reached, your program's
2283 execution will not stop; other than to decrement the ignore count, _GDBN__
2286 To make the breakpoint stop the next time it is reached, specify
2289 @item continue @var{count}
2290 @itemx c @var{count}
2291 @itemx fg @var{count}
2292 @kindex continue @var{count}
2293 Continue execution of your program, setting the ignore count of the
2294 breakpoint where your program stopped to @var{count} minus one.
2295 Thus, your program will not stop at this breakpoint until the
2296 @var{count}'th time it is reached.
2298 An argument to this command is meaningful only when your program stopped
2299 due to a breakpoint. At other times, the argument to @code{continue} is
2302 The synonym @code{fg} is provided purely for convenience, and has
2303 exactly the same behavior as other forms of the command.
2306 If a breakpoint has a positive ignore count and a condition, the condition
2307 is not checked. Once the ignore count reaches zero, the condition will
2310 You could achieve the effect of the ignore count with a condition such
2311 as _0__@w{@samp{$foo-- <= 0}}_1__ using a debugger convenience variable that
2312 is decremented each time. @xref{Convenience Vars, ,Convenience
2315 @node Break Commands
2316 @subsection Breakpoint Command Lists
2318 @cindex breakpoint commands
2319 You can give any breakpoint (or watchpoint) a series of commands to
2320 execute when your program stops due to that breakpoint. For example, you
2321 might want to print the values of certain expressions, or enable other
2325 @item commands @r{[}@var{bnum}@r{]}
2326 @itemx @dots{} @var{command-list} @dots{}
2330 Specify a list of commands for breakpoint number @var{bnum}. The commands
2331 themselves appear on the following lines. Type a line containing just
2332 @code{end} to terminate the commands.
2334 To remove all commands from a breakpoint, type @code{commands} and
2335 follow it immediately with @code{end}; that is, give no commands.
2337 With no @var{bnum} argument, @code{commands} refers to the last
2338 breakpoint or watchpoint set (not to the breakpoint most recently
2342 Pressing @key{RET} as a means of repeating the last _GDBN__ command is
2343 disabled within a @var{command-list}.
2345 You can use breakpoint commands to start your program up again. Simply
2346 use the @code{continue} command, or @code{step}, or any other command
2347 that resumes execution. Subsequent commands in the command list are
2351 If the first command specified is @code{silent}, the usual message about
2352 stopping at a breakpoint is not printed. This may be desirable for
2353 breakpoints that are to print a specific message and then continue.
2354 If the remaining commands too print nothing, you will see no sign that
2355 the breakpoint was reached at all. @code{silent} is meaningful only
2356 at the beginning of a breakpoint command list.
2358 The commands @code{echo} and @code{output} that allow you to print
2359 precisely controlled output are often useful in silent breakpoints.
2360 @xref{Output, ,Commands for Controlled Output}.
2362 For example, here is how you could use breakpoint commands to print the
2363 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
2376 One application for breakpoint commands is to compensate for one bug so
2377 you can test for another. Put a breakpoint just after the erroneous line
2378 of code, give it a condition to detect the case in which something
2379 erroneous has been done, and give it commands to assign correct values
2380 to any variables that need them. End with the @code{continue} command
2381 so that your program does not stop, and start with the @code{silent}
2382 command so that no output is produced. Here is an example:
2394 One deficiency in the operation of automatically continuing breakpoints
2395 under Unix appears when your program uses raw mode for the terminal.
2396 _GDBN__ switches back to its own terminal modes (not raw) before executing
2397 commands, and then must switch back to raw mode when your program is
2398 continued. This causes any pending terminal input to be lost.
2399 @c FIXME: revisit below when GNU sys avail.
2400 @c In the GNU system, this will be fixed by changing the behavior of
2403 Under Unix, you can get around this problem by writing actions into
2404 the breakpoint condition rather than in commands. For example
2407 condition 5 (x = y + 4), 0
2411 specifies a condition expression (@pxref{Expressions, ,Expressions}) that will
2412 change @code{x} as needed, then always have the value zero so your
2413 program will not stop. No input is lost here, because _GDBN__ evaluates
2414 break conditions without changing the terminal modes. When you want
2415 to have nontrivial conditions for performing the side effects, the
2416 operators @samp{&&}, @samp{||} and @samp{?@dots{}:} may be useful.
2418 @node Breakpoint Menus
2419 @subsection Breakpoint Menus
2421 @cindex symbol overloading
2423 Some programming languages (notably C++) permit a single function name
2424 to be defined several times, for application in different contexts.
2425 This is called @dfn{overloading}. When a function name is overloaded,
2426 @samp{break @var{function}} is not enough to tell _GDBN__ where you want
2427 a breakpoint. If you realize this will be a problem, you can use
2428 something like @samp{break @var{function}(@var{types})} to specify which
2429 particular version of the function you want. Otherwise, _GDBN__ offers
2430 you a menu of numbered choices for different possible breakpoints, and
2431 waits for your selection with the prompt @samp{>}. The first two
2432 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
2433 sets a breakpoint at each definition of @var{function}, and typing
2434 @kbd{0} aborts the @code{break} command without setting any new
2437 For example, the following session excerpt shows an attempt to set a
2438 breakpoint at the overloaded symbol @code{String::after}.
2439 We choose three particular definitions of that function name:
2441 @c FIXME! This is likely to change to show arg type lists, at least
2443 (_GDBP__) b String::after
2446 [2] file:String.cc; line number:867
2447 [3] file:String.cc; line number:860
2448 [4] file:String.cc; line number:875
2449 [5] file:String.cc; line number:853
2450 [6] file:String.cc; line number:846
2451 [7] file:String.cc; line number:735
2453 Breakpoint 1 at 0xb26c: file String.cc, line 867.
2454 Breakpoint 2 at 0xb344: file String.cc, line 875.
2455 Breakpoint 3 at 0xafcc: file String.cc, line 846.
2456 Multiple breakpoints were set.
2457 Use the "delete" command to delete unwanted breakpoints.
2461 @node Error in Breakpoints
2462 @subsection ``Cannot Insert Breakpoints''
2464 @c FIXME: "cannot insert breakpoints" error, v unclear.
2465 @c Q in pending mail to Gilmore. ---pesch@cygnus.com, 26mar91
2466 @c some light may be shed by looking at instances of
2467 @c ONE_PROCESS_WRITETEXT. But error message seems possible otherwise
2468 @c too. pesch, 20sep91
2469 Under some operating systems, breakpoints cannot be used in a program if
2470 any other process is running that program. In this situation,
2471 attempting to run or continue a program with a breakpoint causes _GDBN__
2472 to stop the other process.
2474 When this happens, you have three ways to proceed:
2478 Remove or disable the breakpoints, then continue.
2481 Suspend _GDBN__, and copy the file containing your program to a new name.
2482 Resume _GDBN__ and use the @code{exec-file} command to specify that _GDBN__
2483 should run your program under that name. Then start your program again.
2485 @c FIXME: RMS commented here "Show example". Maybe when someone
2486 @c explains the first FIXME: in this section...
2489 Relink your program so that the text segment is nonsharable, using the
2490 linker option @samp{-N}. The operating system limitation may not apply
2491 to nonsharable executables.
2494 @node Continuing and Stepping
2495 @section Continuing and Stepping
2499 @cindex resuming execution
2500 @dfn{Continuing} means resuming program execution until your program
2501 completes normally. In contrast, @dfn{stepping} means executing just
2502 one more ``step'' of your program, where ``step'' may mean either one
2503 line of source code, or one machine instruction (depending on what
2504 particular command you use). Either when continuing
2505 or when stepping, your program may stop even sooner, due to
2510 a breakpoint or to a signal. (If due to a signal, you may want to use
2511 @code{handle}, or use @samp{signal 0} to resume execution.
2512 @xref{Signals, ,Signals}.)
2516 @item continue @r{[}@var{ignore-count}@r{]}
2518 Resume program execution, at the address where your program last stopped;
2519 any breakpoints set at that address are bypassed. The optional argument
2520 @var{ignore-count} allows you to specify a further number of times to
2521 ignore a breakpoint at this location; its effect is like that of
2522 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
2524 To resume execution at a different place, you can use @code{return}
2525 (@pxref{Returning, ,Returning from a Function}) to go back to the
2526 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
2527 Different Address}) to go to an arbitrary location in your program.
2530 A typical technique for using stepping is to set a breakpoint
2531 (@pxref{Breakpoints, ,Breakpoints Watchpoints and Exceptions}) at the
2532 beginning of the function or the section of your program where a
2533 problem is believed to lie, run your program until it stops at that
2534 breakpoint, and then step through the suspect area, examining the
2535 variables that are interesting, until you see the problem happen.
2541 Continue running your program until control reaches a different source
2542 line, then stop it and return control to _GDBN__. This command is
2543 abbreviated @code{s}.
2546 @emph{Warning:} If you use the @code{step} command while control is
2547 within a function that was compiled without debugging information,
2548 execution will proceed until control reaches another function.
2551 @item step @var{count}
2552 Continue running as in @code{step}, but do so @var{count} times. If a
2553 breakpoint is reached or a signal not related to stepping occurs before
2554 @var{count} steps, stepping stops right away.
2556 @item next @r{[}@var{count}@r{]}
2559 Continue to the next source line in the current (innermost) stack frame.
2560 Similar to @code{step}, but any function calls appearing within the line
2561 of code are executed without stopping. Execution stops when control
2562 reaches a different line of code at the stack level which was executing
2563 when the @code{next} command was given. This command is abbreviated
2566 An argument @var{count} is a repeat count, as for @code{step}.
2568 @code{next} within a function that lacks debugging information acts like
2569 @code{step}, but any function calls appearing within the code of the
2570 function are executed without stopping.
2574 Continue running until just after function in the selected stack frame
2575 returns. Print the returned value (if any).
2577 Contrast this with the @code{return} command (@pxref{Returning,
2578 ,Returning from a Function}).
2584 Continue running until a source line past the current line, in the
2585 current stack frame, is reached. This command is used to avoid single
2586 stepping through a loop more than once. It is like the @code{next}
2587 command, except that when @code{until} encounters a jump, it
2588 automatically continues execution until the program counter is greater
2589 than the address of the jump.
2591 This means that when you reach the end of a loop after single stepping
2592 though it, @code{until} will cause your program to continue execution
2593 until the loop is exited. In contrast, a @code{next} command at the end
2594 of a loop will simply step back to the beginning of the loop, which
2595 would force you to step through the next iteration.
2597 @code{until} always stops your program if it attempts to exit the current
2600 @code{until} may produce somewhat counterintuitive results if the order
2601 of machine code does not match the order of the source lines. For
2602 example, in the following excerpt from a debugging session, the @code{f}
2603 (@code{frame}) command shows that execution is stopped at line
2604 @code{206}; yet when we use @code{until}, we get to line @code{195}:
2608 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
2611 195 for ( ; argc > 0; NEXTARG) @{
2614 This happened because, for execution efficiency, the compiler had
2615 generated code for the loop closure test at the end, rather than the
2616 start, of the loop---even though the test in a C @code{for}-loop is
2617 written before the body of the loop. The @code{until} command appeared
2618 to step back to the beginning of the loop when it advanced to this
2619 expression; however, it has not really gone to an earlier
2620 statement---not in terms of the actual machine code.
2622 @code{until} with no argument works by means of single
2623 instruction stepping, and hence is slower than @code{until} with an
2626 @item until @var{location}
2627 @item u @var{location}
2628 Continue running your program until either the specified location is
2629 reached, or the current stack frame returns. @var{location} is any of
2630 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
2631 ,Setting Breakpoints}). This form of the command uses breakpoints,
2632 and hence is quicker than @code{until} without an argument.
2638 Execute one machine instruction, then stop and return to the debugger.
2640 It is often useful to do @samp{display/i $pc} when stepping by machine
2641 instructions. This will cause the next instruction to be executed to
2642 be displayed automatically at each stop. @xref{Auto Display,
2643 ,Automatic Display}.
2645 An argument is a repeat count, as in @code{step}.
2651 Execute one machine instruction, but if it is a function call,
2652 proceed until the function returns.
2654 An argument is a repeat count, as in @code{next}.
2657 _if__(_GENERIC__ || !_H8__)
2662 A signal is an asynchronous event that can happen in a program. The
2663 operating system defines the possible kinds of signals, and gives each
2664 kind a name and a number. For example, in Unix @code{SIGINT} is the
2665 signal a program gets when you type an interrupt (often @kbd{C-c});
2666 @code{SIGSEGV} is the signal a program gets from referencing a place in
2667 memory far away from all the areas in use; @code{SIGALRM} occurs when
2668 the alarm clock timer goes off (which happens only if your program has
2669 requested an alarm).
2671 @cindex fatal signals
2672 Some signals, including @code{SIGALRM}, are a normal part of the
2673 functioning of your program. Others, such as @code{SIGSEGV}, indicate
2674 errors; these signals are @dfn{fatal} (kill your program immediately) if the
2675 program has not specified in advance some other way to handle the signal.
2676 @code{SIGINT} does not indicate an error in your program, but it is normally
2677 fatal so it can carry out the purpose of the interrupt: to kill the program.
2679 _GDBN__ has the ability to detect any occurrence of a signal in your
2680 program. You can tell _GDBN__ in advance what to do for each kind of
2683 @cindex handling signals
2684 Normally, _GDBN__ is set up to ignore non-erroneous signals like @code{SIGALRM}
2685 (so as not to interfere with their role in the functioning of your program)
2686 but to stop your program immediately whenever an error signal happens.
2687 You can change these settings with the @code{handle} command.
2691 @kindex info signals
2692 Print a table of all the kinds of signals and how _GDBN__ has been told to
2693 handle each one. You can use this to see the signal numbers of all
2694 the defined types of signals.
2696 @item handle @var{signal} @var{keywords}@dots{}
2698 Change the way _GDBN__ handles signal @var{signal}. @var{signal} can be the
2699 number of a signal or its name (with or without the @samp{SIG} at the
2700 beginning). The @var{keywords} say what change to make.
2704 The keywords allowed by the @code{handle} command can be abbreviated.
2705 Their full names are:
2709 _GDBN__ should not stop your program when this signal happens. It may
2710 still print a message telling you that the signal has come in.
2713 _GDBN__ should stop your program when this signal happens. This implies
2714 the @code{print} keyword as well.
2717 _GDBN__ should print a message when this signal happens.
2720 _GDBN__ should not mention the occurrence of the signal at all. This
2721 implies the @code{nostop} keyword as well.
2724 _GDBN__ should allow your program to see this signal; your program will be
2725 able to handle the signal, or may be terminated if the signal is fatal
2729 _GDBN__ should not allow your program to see this signal.
2733 When a signal has been set to stop your program, your program cannot see the
2734 signal until you continue. It will see the signal then, if @code{pass} is
2735 in effect for the signal in question @emph{at that time}. In other words,
2736 after _GDBN__ reports a signal, you can use the @code{handle} command with
2737 @code{pass} or @code{nopass} to control whether that signal will be seen by
2738 your program when you later continue it.
2740 You can also use the @code{signal} command to prevent your program from
2741 seeing a signal, or cause it to see a signal it normally would not see,
2742 or to give it any signal at any time. For example, if your program stopped
2743 due to some sort of memory reference error, you might store correct
2744 values into the erroneous variables and continue, hoping to see more
2745 execution; but your program would probably terminate immediately as
2746 a result of the fatal signal once it saw the signal. To prevent this,
2747 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
2749 _fi__(_GENERIC__ || !_H8__)
2752 @chapter Examining the Stack
2754 When your program has stopped, the first thing you need to know is where it
2755 stopped and how it got there.
2758 Each time your program performs a function call, the information about
2759 where in your program the call was made from is saved in a block of data
2760 called a @dfn{stack frame}. The frame also contains the arguments of the
2761 call and the local variables of the function that was called. All the
2762 stack frames are allocated in a region of memory called the @dfn{call
2765 When your program stops, the _GDBN__ commands for examining the stack allow you
2766 to see all of this information.
2768 @cindex selected frame
2769 One of the stack frames is @dfn{selected} by _GDBN__ and many _GDBN__ commands
2770 refer implicitly to the selected frame. In particular, whenever you ask
2771 _GDBN__ for the value of a variable in your program, the value is found in the
2772 selected frame. There are special _GDBN__ commands to select whichever frame
2773 you are interested in.
2775 When your program stops, _GDBN__ automatically selects the currently executing
2776 frame and describes it briefly as the @code{frame} command does
2777 (@pxref{Frame Info, ,Information About a Frame}).
2780 * Frames:: Stack Frames
2781 * Backtrace:: Backtraces
2782 * Selection:: Selecting a Frame
2783 * Frame Info:: Information on a Frame
2787 @section Stack Frames
2791 The call stack is divided up into contiguous pieces called @dfn{stack
2792 frames}, or @dfn{frames} for short; each frame is the data associated
2793 with one call to one function. The frame contains the arguments given
2794 to the function, the function's local variables, and the address at
2795 which the function is executing.
2797 @cindex initial frame
2798 @cindex outermost frame
2799 @cindex innermost frame
2800 When your program is started, the stack has only one frame, that of the
2801 function @code{main}. This is called the @dfn{initial} frame or the
2802 @dfn{outermost} frame. Each time a function is called, a new frame is
2803 made. Each time a function returns, the frame for that function invocation
2804 is eliminated. If a function is recursive, there can be many frames for
2805 the same function. The frame for the function in which execution is
2806 actually occurring is called the @dfn{innermost} frame. This is the most
2807 recently created of all the stack frames that still exist.
2809 @cindex frame pointer
2810 Inside your program, stack frames are identified by their addresses. A
2811 stack frame consists of many bytes, each of which has its own address; each
2812 kind of computer has a convention for choosing one of those bytes whose
2813 address serves as the address of the frame. Usually this address is kept
2814 in a register called the @dfn{frame pointer register} while execution is
2815 going on in that frame.
2817 @cindex frame number
2818 _GDBN__ assigns numbers to all existing stack frames, starting with
2819 zero for the innermost frame, one for the frame that called it,
2820 and so on upward. These numbers do not really exist in your program;
2821 they are assigned by _GDBN__ to give you a way of designating stack
2822 frames in _GDBN__ commands.
2824 @cindex frameless execution
2825 Some compilers allow functions to be compiled so that they operate
2826 without stack frames. (For example, the @code{_GCC__} option
2827 @samp{-fomit-frame-pointer} will generate functions without a frame.)
2828 This is occasionally done with heavily used library functions to save
2829 the frame setup time. _GDBN__ has limited facilities for dealing with
2830 these function invocations. If the innermost function invocation has no
2831 stack frame, _GDBN__ will nevertheless regard it as though it had a
2832 separate frame, which is numbered zero as usual, allowing correct
2833 tracing of the function call chain. However, _GDBN__ has no provision
2834 for frameless functions elsewhere in the stack.
2839 A backtrace is a summary of how your program got where it is. It shows one
2840 line per frame, for many frames, starting with the currently executing
2841 frame (frame zero), followed by its caller (frame one), and on up the
2849 Print a backtrace of the entire stack: one line per frame for all
2850 frames in the stack.
2852 You can stop the backtrace at any time by typing the system interrupt
2853 character, normally @kbd{C-c}.
2855 @item backtrace @var{n}
2857 Similar, but print only the innermost @var{n} frames.
2859 @item backtrace -@var{n}
2861 Similar, but print only the outermost @var{n} frames.
2867 The names @code{where} and @code{info stack} (abbreviated @code{info s})
2868 are additional aliases for @code{backtrace}.
2870 Each line in the backtrace shows the frame number and the function name.
2871 The program counter value is also shown---unless you use @code{set
2872 print address off}. The backtrace also shows the source file name and
2873 line number, as well as the arguments to the function. The program
2874 counter value is omitted if it is at the beginning of the code for that
2877 Here is an example of a backtrace. It was made with the command
2878 @samp{bt 3}, so it shows the innermost three frames.
2882 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
2884 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
2885 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
2887 (More stack frames follow...)
2892 The display for frame zero does not begin with a program counter
2893 value, indicating that your program has stopped at the beginning of the
2894 code for line @code{993} of @code{builtin.c}.
2897 @section Selecting a Frame
2899 Most commands for examining the stack and other data in your program work on
2900 whichever stack frame is selected at the moment. Here are the commands for
2901 selecting a stack frame; all of them finish by printing a brief description
2902 of the stack frame just selected.
2909 Select frame number @var{n}. Recall that frame zero is the innermost
2910 (currently executing) frame, frame one is the frame that called the
2911 innermost one, and so on. The highest-numbered frame is @code{main}'s
2914 @item frame @var{addr}
2916 Select the frame at address @var{addr}. This is useful mainly if the
2917 chaining of stack frames has been damaged by a bug, making it
2918 impossible for _GDBN__ to assign numbers properly to all frames. In
2919 addition, this can be useful when your program has multiple stacks and
2920 switches between them.
2923 On the SPARC architecture, @code{frame} needs two addresses to
2924 select an arbitrary frame: a frame pointer and a stack pointer.
2925 @c note to future updaters: this is conditioned on a flag
2926 @c FRAME_SPECIFICATION_DYADIC in the tm-*.h files, currently only used
2927 @c by SPARC, hence the specific attribution. Generalize or list all
2928 @c possibilities if more supported machines start doing this.
2933 Move @var{n} frames up the stack. For positive numbers @var{n}, this
2934 advances toward the outermost frame, to higher frame numbers, to frames
2935 that have existed longer. @var{n} defaults to one.
2940 Move @var{n} frames down the stack. For positive numbers @var{n}, this
2941 advances toward the innermost frame, to lower frame numbers, to frames
2942 that were created more recently. @var{n} defaults to one. You may
2943 abbreviate @code{down} as @code{do}.
2946 All of these commands end by printing two lines of output describing the
2947 frame. The first line shows the frame number, the function name, the
2948 arguments, and the source file and line number of execution in that
2949 frame. The second line shows the text of that source line. For
2955 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
2957 10 read_input_file (argv[i]);
2961 After such a printout, the @code{list} command with no arguments will
2962 print ten lines centered on the point of execution in the frame.
2963 @xref{List, ,Printing Source Lines}.
2966 @item up-silently @var{n}
2967 @itemx down-silently @var{n}
2968 @kindex down-silently
2970 These two commands are variants of @code{up} and @code{down},
2971 respectively; they differ in that they do their work silently, without
2972 causing display of the new frame. They are intended primarily for use
2973 in _GDBN__ command scripts, where the output might be unnecessary and
2978 @section Information About a Frame
2980 There are several other commands to print information about the selected
2986 When used without any argument, this command does not change which
2987 frame is selected, but prints a brief description of the currently
2988 selected stack frame. It can be abbreviated @code{f}. With an
2989 argument, this command is used to select a stack frame
2990 (@pxref{Selection, ,Selecting a Frame}).
2996 This command prints a verbose description of the selected stack frame,
2997 including the address of the frame, the addresses of the next frame down
2998 (called by this frame) and the next frame up (caller of this frame), the
2999 language that the source code corresponding to this frame was written in,
3000 the address of the frame's arguments, the program counter saved in it
3001 (the address of execution in the caller frame), and which registers
3002 were saved in the frame. The verbose description is useful when
3003 something has gone wrong that has made the stack format fail to fit
3004 the usual conventions.
3006 @item info frame @var{addr}
3007 @itemx info f @var{addr}
3008 Print a verbose description of the frame at address @var{addr},
3009 without selecting that frame. The selected frame remains unchanged by
3014 Print the arguments of the selected frame, each on a separate line.
3018 Print the local variables of the selected frame, each on a separate
3019 line. These are all variables declared static or automatic within all
3020 program blocks that execution in this frame is currently inside of.
3024 @cindex catch exceptions
3025 @cindex exception handlers
3026 Print a list of all the exception handlers that are active in the
3027 current stack frame at the current point of execution. To see other
3028 exception handlers, visit the associated frame (using the @code{up},
3029 @code{down}, or @code{frame} commands); then type @code{info catch}.
3030 @xref{Exception Handling, ,Breakpoints and Exceptions}.
3034 @chapter Examining Source Files
3036 _GDBN__ can print parts of your program's source, since the debugging
3037 information recorded in your program tells _GDBN__ what source files were
3038 used to build it. When your program stops, _GDBN__ spontaneously prints
3039 the line where it stopped. Likewise, when you select a stack frame
3040 (@pxref{Selection, ,Selecting a Frame}), _GDBN__ prints the line where
3041 execution in that frame has stopped. You can print other portions of
3042 source files by explicit command.
3045 If you use _GDBN__ through its GNU Emacs interface, you may prefer to use
3046 Emacs facilities to view source; @pxref{Emacs, ,Using _GDBN__ under GNU
3051 * List:: Printing Source Lines
3052 _if__(_GENERIC__ || !_H8__)
3053 * Search:: Searching Source Files
3054 _fi__(_GENERIC__ || !_H8__)
3055 * Source Path:: Specifying Source Directories
3056 * Machine Code:: Source and Machine Code
3060 @section Printing Source Lines
3064 To print lines from a source file, use the @code{list} command
3065 (abbreviated @code{l}). There are several ways to specify what part
3066 of the file you want to print.
3068 Here are the forms of the @code{list} command most commonly used:
3071 @item list @var{linenum}
3072 Print lines centered around line number @var{linenum} in the
3073 current source file.
3075 @item list @var{function}
3076 Print lines centered around the beginning of function
3080 Print more lines. If the last lines printed were printed with a
3081 @code{list} command, this prints lines following the last lines
3082 printed; however, if the last line printed was a solitary line printed
3083 as part of displaying a stack frame (@pxref{Stack, ,Examining the
3084 Stack}), this prints lines centered around that line.
3087 Print lines just before the lines last printed.
3090 By default, _GDBN__ prints ten source lines with any of these forms of
3091 the @code{list} command. You can change this using @code{set listsize}:
3094 @item set listsize @var{count}
3095 @kindex set listsize
3096 Make the @code{list} command display @var{count} source lines (unless
3097 the @code{list} argument explicitly specifies some other number).
3100 @kindex show listsize
3101 Display the number of lines that @code{list} will currently display by
3105 Repeating a @code{list} command with @key{RET} discards the argument,
3106 so it is equivalent to typing just @code{list}. This is more useful
3107 than listing the same lines again. An exception is made for an
3108 argument of @samp{-}; that argument is preserved in repetition so that
3109 each repetition moves up in the source file.
3112 In general, the @code{list} command expects you to supply zero, one or two
3113 @dfn{linespecs}. Linespecs specify source lines; there are several ways
3114 of writing them but the effect is always to specify some source line.
3115 Here is a complete description of the possible arguments for @code{list}:
3118 @item list @var{linespec}
3119 Print lines centered around the line specified by @var{linespec}.
3121 @item list @var{first},@var{last}
3122 Print lines from @var{first} to @var{last}. Both arguments are
3125 @item list ,@var{last}
3126 Print lines ending with @var{last}.
3128 @item list @var{first},
3129 Print lines starting with @var{first}.
3132 Print lines just after the lines last printed.
3135 Print lines just before the lines last printed.
3138 As described in the preceding table.
3141 Here are the ways of specifying a single source line---all the
3146 Specifies line @var{number} of the current source file.
3147 When a @code{list} command has two linespecs, this refers to
3148 the same source file as the first linespec.
3151 Specifies the line @var{offset} lines after the last line printed.
3152 When used as the second linespec in a @code{list} command that has
3153 two, this specifies the line @var{offset} lines down from the
3157 Specifies the line @var{offset} lines before the last line printed.
3159 @item @var{filename}:@var{number}
3160 Specifies line @var{number} in the source file @var{filename}.
3162 @item @var{function}
3163 @c FIXME: "of the open-brace" is C-centric. When we add other langs...
3164 Specifies the line of the open-brace that begins the body of the
3165 function @var{function}.
3167 @item @var{filename}:@var{function}
3168 Specifies the line of the open-brace that begins the body of the
3169 function @var{function} in the file @var{filename}. You only need the
3170 file name with a function name to avoid ambiguity when there are
3171 identically named functions in different source files.
3173 @item *@var{address}
3174 Specifies the line containing the program address @var{address}.
3175 @var{address} may be any expression.
3178 _if__(_GENERIC__ || !_H8__)
3180 @section Searching Source Files
3182 @kindex reverse-search
3184 There are two commands for searching through the current source file for a
3188 @item forward-search @var{regexp}
3189 @itemx search @var{regexp}
3191 @kindex forward-search
3192 The command @samp{forward-search @var{regexp}} checks each line,
3193 starting with the one following the last line listed, for a match for
3194 @var{regexp}. It lists the line that is found. You can use
3195 synonym @samp{search @var{regexp}} or abbreviate the command name as
3198 @item reverse-search @var{regexp}
3199 The command @samp{reverse-search @var{regexp}} checks each line, starting
3200 with the one before the last line listed and going backward, for a match
3201 for @var{regexp}. It lists the line that is found. You can abbreviate
3202 this command as @code{rev}.
3204 _fi__(_GENERIC__ || !_H8__)
3207 @section Specifying Source Directories
3210 @cindex directories for source files
3211 Executable programs sometimes do not record the directories of the source
3212 files from which they were compiled, just the names. Even when they do,
3213 the directories could be moved between the compilation and your debugging
3214 session. _GDBN__ has a list of directories to search for source files;
3215 this is called the @dfn{source path}. Each time _GDBN__ wants a source file,
3216 it tries all the directories in the list, in the order they are present
3217 in the list, until it finds a file with the desired name. Note that
3218 the executable search path is @emph{not} used for this purpose. Neither is
3219 the current working directory, unless it happens to be in the source
3222 If _GDBN__ cannot find a source file in the source path, and the object
3223 program records a directory, _GDBN__ tries that directory too. If the
3224 source path is empty, and there is no record of the compilation
3225 directory, _GDBN__ will, as a last resort, look in the current
3228 Whenever you reset or rearrange the source path, _GDBN__ will clear out
3229 any information it has cached about where source files are found, where
3230 each line is in the file, etc.
3233 When you start _GDBN__, its source path is empty.
3234 To add other directories, use the @code{directory} command.
3237 @item directory @var{dirname} @dots{}
3238 Add directory @var{dirname} to the front of the source path. Several
3239 directory names may be given to this command, separated by @samp{:} or
3240 whitespace. You may specify a directory that is already in the source
3241 path; this moves it forward, so it will be searched sooner.
3243 You can use the string @samp{$cdir} to refer to the compilation
3244 directory (if one is recorded), and @samp{$cwd} to refer to the current
3245 working directory. @samp{$cwd} is not the same as @samp{.}---the former
3246 tracks the current working directory as it changes during your _GDBN__
3247 session, while the latter is immediately expanded to the current
3248 directory at the time you add an entry to the source path.
3251 Reset the source path to empty again. This requires confirmation.
3253 @c RET-repeat for @code{directory} is explicitly disabled, but since
3254 @c repeating it would be a no-op we do not say that. (thanks to RMS)
3256 @item show directories
3257 @kindex show directories
3258 Print the source path: show which directories it contains.
3261 If your source path is cluttered with directories that are no longer of
3262 interest, _GDBN__ may sometimes cause confusion by finding the wrong
3263 versions of source. You can correct the situation as follows:
3267 Use @code{directory} with no argument to reset the source path to empty.
3270 Use @code{directory} with suitable arguments to reinstall the
3271 directories you want in the source path. You can add all the
3272 directories in one command.
3276 @section Source and Machine Code
3278 You can use the command @code{info line} to map source lines to program
3279 addresses (and viceversa), and the command @code{disassemble} to display
3280 a range of addresses as machine instructions.
3283 @item info line @var{linespec}
3285 Print the starting and ending addresses of the compiled code for
3286 source line @var{linespec}. You can specify source lines in any of
3287 the ways understood by the @code{list} command (@pxref{List, ,Printing
3291 For example, we can use @code{info line} to discover the location of
3292 the object code for the first line of function
3293 @code{m4_changequote}:
3296 (_GDBP__) info line m4_changecom
3297 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
3301 We can also inquire (using @code{*@var{addr}} as the form for
3302 @var{linespec}) what source line covers a particular address:
3304 (_GDBP__) info line *0x63ff
3305 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
3308 @cindex @code{$_} and @code{info line}
3309 After @code{info line}, the default address for the @code{x} command
3310 is changed to the starting address of the line, so that @samp{x/i} is
3311 sufficient to begin examining the machine code (@pxref{Memory,
3312 ,Examining Memory}). Also, this address is saved as the value of the
3313 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
3319 This specialized command dumps a range of memory as machine
3320 instructions. The default memory range is the function surrounding the
3321 program counter of the selected frame. A single argument to this
3322 command is a program counter value; the function surrounding this value
3323 will be dumped. Two arguments specify a range of addresses (first
3324 inclusive, second exclusive) to dump.
3327 _if__(_GENERIC__||!_H8__)
3328 We can use @code{disassemble} to inspect the object code
3329 range shown in the last @code{info line} example (the example
3330 shows SPARC machine instructions):
3334 (_GDBP__) disas 0x63e4 0x6404
3335 Dump of assembler code from 0x63e4 to 0x6404:
3336 0x63e4 <builtin_init+5340>: ble 0x63f8 <builtin_init+5360>
3337 0x63e8 <builtin_init+5344>: sethi %hi(0x4c00), %o0
3338 0x63ec <builtin_init+5348>: ld [%i1+4], %o0
3339 0x63f0 <builtin_init+5352>: b 0x63fc <builtin_init+5364>
3340 0x63f4 <builtin_init+5356>: ld [%o0+4], %o0
3341 0x63f8 <builtin_init+5360>: or %o0, 0x1a4, %o0
3342 0x63fc <builtin_init+5364>: call 0x9288 <path_search>
3343 0x6400 <builtin_init+5368>: nop
3344 End of assembler dump.
3347 _fi__(_GENERIC__||!_H8__)
3349 _if__(!_GENERIC__||_H8__)
3350 For example, here is the beginning of the output for the
3351 disassembly of a function @code{fact}:
3355 (_GDBP__) disas fact
3356 Dump of assembler code for function fact:
3358 0x802c <fact>: 6d f2 mov.w r2,@@-r7
3359 0x802e <fact+2>: 6d f3 mov.w r3,@@-r7
3360 0x8030 <fact+4>: 6d f6 mov.w r6,@@-r7
3361 0x8032 <fact+6>: 0d 76 mov.w r7,r6
3362 0x8034 <fact+8>: 6f 70 00 08 mov.w @@(0x8,r7),r0
3363 0x8038 <fact+12> 19 11 sub.w r1,r1
3369 _fi__(!_GENERIC__||_H8__)
3373 @chapter Examining Data
3375 @cindex printing data
3376 @cindex examining data
3379 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
3380 @c document because it is nonstandard... Under Epoch it displays in a
3381 @c different window or something like that.
3382 The usual way to examine data in your program is with the @code{print}
3383 command (abbreviated @code{p}), or its synonym @code{inspect}.
3385 It evaluates and prints the value of an expression of the language your
3386 program is written in (@pxref{Languages, ,Using _GDBN__ with Different
3391 @item print @var{exp}
3392 @itemx print /@var{f} @var{exp}
3393 @var{exp} is an expression (in the source language). By default
3394 the value of @var{exp} is printed in a format appropriate to its data
3395 type; you can choose a different format by specifying @samp{/@var{f}},
3396 where @var{f} is a letter specifying the format; @pxref{Output formats}.
3399 @itemx print /@var{f}
3400 If you omit @var{exp}, _GDBN__ displays the last value again (from the
3401 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
3402 conveniently inspect the same value in an alternative format.
3405 A more low-level way of examining data is with the @code{x} command.
3406 It examines data in memory at a specified address and prints it in a
3407 specified format. @xref{Memory, ,Examining Memory}.
3409 If you are interested in information about types, or about how the fields
3410 of a struct or class are declared, use the @code{ptype @var{exp}}
3411 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol Table}.
3414 * Expressions:: Expressions
3415 * Variables:: Program Variables
3416 * Arrays:: Artificial Arrays
3417 * Output formats:: Output formats
3418 * Memory:: Examining Memory
3419 * Auto Display:: Automatic Display
3420 * Print Settings:: Print Settings
3421 * Value History:: Value History
3422 * Convenience Vars:: Convenience Variables
3423 * Registers:: Registers
3424 _if__(_GENERIC__ || !_H8__)
3425 * Floating Point Hardware:: Floating Point Hardware
3426 _fi__(_GENERIC__ || !_H8__)
3430 @section Expressions
3433 @code{print} and many other _GDBN__ commands accept an expression and
3434 compute its value. Any kind of constant, variable or operator defined
3435 by the programming language you are using is legal in an expression in
3436 _GDBN__. This includes conditional expressions, function calls, casts
3437 and string constants. It unfortunately does not include symbols defined
3438 by preprocessor @code{#define} commands.
3441 Because C is so widespread, most of the expressions shown in examples in
3442 this manual are in C. @xref{Languages, , Using _GDBN__ with Different
3443 Languages}, for information on how to use expressions in other
3446 In this section, we discuss operators that you can use in _GDBN__
3447 expressions regardless of your programming language.
3449 Casts are supported in all languages, not just in C, because it is so
3450 useful to cast a number into a pointer so as to examine a structure
3451 at that address in memory.
3452 @c FIXME: casts supported---Mod2 true?
3455 _GDBN__ supports these operators in addition to those of programming
3460 @samp{@@} is a binary operator for treating parts of memory as arrays.
3461 @xref{Arrays, ,Artificial Arrays}, for more information.
3464 @samp{::} allows you to specify a variable in terms of the file or
3465 function where it is defined. @xref{Variables, ,Program Variables}.
3467 @item @{@var{type}@} @var{addr}
3468 Refers to an object of type @var{type} stored at address @var{addr} in
3469 memory. @var{addr} may be any expression whose value is an integer or
3470 pointer (but parentheses are required around binary operators, just as in
3471 a cast). This construct is allowed regardless of what kind of data is
3472 normally supposed to reside at @var{addr}.
3476 @section Program Variables
3478 The most common kind of expression to use is the name of a variable
3481 Variables in expressions are understood in the selected stack frame
3482 (@pxref{Selection, ,Selecting a Frame}); they must either be global
3483 (or static) or be visible according to the scope rules of the
3484 programming language from the point of execution in that frame. This
3485 means that in the function
3500 the variable @code{a} is usable whenever your program is executing
3501 within the function @code{foo}, but the variable @code{b} is visible
3502 only while your program is executing inside the block in which @code{b}
3505 @cindex variable name conflict
3506 There is an exception: you can refer to a variable or function whose
3507 scope is a single source file even if the current execution point is not
3508 in this file. But it is possible to have more than one such variable or
3509 function with the same name (in different source files). If that
3510 happens, referring to that name has unpredictable effects. If you wish,
3511 you can specify a static variable in a particular function or file,
3512 using the colon-colon notation:
3516 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
3520 @var{file}::@var{variable}
3521 @var{function}::@var{variable}
3525 Here @var{file} or @var{function} is the name of the context for the
3526 static @var{variable}. In the case of file names, you can use quotes to
3527 make sure _GDBN__ parses the file name as a single word---for example,
3528 to print a global value of @code{x} defined in @file{f2.c}:
3531 (_GDBP__) p 'f2.c'::x
3534 @cindex C++ scope resolution
3535 This use of @samp{::} is very rarely in conflict with the very similar
3536 use of the same notation in C++. _GDBN__ also supports use of the C++
3537 scope resolution operator in _GDBN__ expressions.
3539 @cindex wrong values
3540 @cindex variable values, wrong
3542 @emph{Warning:} Occasionally, a local variable may appear to have the
3543 wrong value at certain points in a function---just after entry to the
3544 function, and just before exit. You may see this problem when you are
3545 stepping by machine instructions. This is because on most machines, it
3546 takes more than one instruction to set up a stack frame (including local
3547 variable definitions); if you are stepping by machine instructions,
3548 variables may appear to have the wrong values until the stack frame is
3549 completely built. On function exit, it usually also takes more than one
3550 machine instruction to destroy a stack frame; after you begin stepping
3551 through that group of instructions, local variable definitions may be
3556 @section Artificial Arrays
3558 @cindex artificial array
3560 It is often useful to print out several successive objects of the
3561 same type in memory; a section of an array, or an array of
3562 dynamically determined size for which only a pointer exists in the
3565 This can be done by constructing an @dfn{artificial array} with the
3566 binary operator @samp{@@}. The left operand of @samp{@@} should be
3567 the first element of the desired array, as an individual object.
3568 The right operand should be the desired length of the array. The result is
3569 an array value whose elements are all of the type of the left argument.
3570 The first element is actually the left argument; the second element
3571 comes from bytes of memory immediately following those that hold the
3572 first element, and so on. Here is an example. If a program says
3575 int *array = (int *) malloc (len * sizeof (int));
3579 you can print the contents of @code{array} with
3585 The left operand of @samp{@@} must reside in memory. Array values made
3586 with @samp{@@} in this way behave just like other arrays in terms of
3587 subscripting, and are coerced to pointers when used in expressions.
3588 Artificial arrays most often appear in expressions via the value history
3589 (@pxref{Value History, ,Value History}), after printing one out.)
3591 Sometimes the artificial array mechanism is not quite enough; in
3592 moderately complex data structures, the elements of interest may not
3593 actually be adjacent---for example, if you are interested in the values
3594 of pointers in an array. One useful work-around in this situation is
3595 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
3596 Variables}) as a counter in an expression that prints the first
3597 interesting value, and then repeat that expression via @key{RET}. For
3598 instance, suppose you have an array @code{dtab} of pointers to
3599 structures, and you are interested in the values of a field @code{fv}
3600 in each structure. Here is an example of what you might type:
3610 @node Output formats
3611 @section Output formats
3613 @cindex formatted output
3614 @cindex output formats
3615 By default, _GDBN__ prints a value according to its data type. Sometimes
3616 this is not what you want. For example, you might want to print a number
3617 in hex, or a pointer in decimal. Or you might want to view data in memory
3618 at a certain address as a character string or as an instruction. To do
3619 these things, specify an @dfn{output format} when you print a value.
3621 The simplest use of output formats is to say how to print a value
3622 already computed. This is done by starting the arguments of the
3623 @code{print} command with a slash and a format letter. The format
3624 letters supported are:
3628 Regard the bits of the value as an integer, and print the integer in
3632 Print as integer in signed decimal.
3635 Print as integer in unsigned decimal.
3638 Print as integer in octal.
3641 Print as integer in binary. The letter @samp{t} stands for ``two''.
3644 Print as an address, both absolute in hex and as an offset from the
3645 nearest preceding symbol. This format can be used to discover where (in
3646 what function) an unknown address is located:
3649 (_GDBP__) p/a 0x54320
3650 _0__$3 = 0x54320 <_initialize_vx+396>_1__
3654 Regard as an integer and print it as a character constant.
3657 Regard the bits of the value as a floating point number and print
3658 using typical floating point syntax.
3661 For example, to print the program counter in hex (@pxref{Registers}), type
3668 Note that no space is required before the slash; this is because command
3669 names in _GDBN__ cannot contain a slash.
3671 To reprint the last value in the value history with a different format,
3672 you can use the @code{print} command with just a format and no
3673 expression. For example, @samp{p/x} reprints the last value in hex.
3676 @section Examining Memory
3678 You can use the command @code{x} (for ``examine'') to examine memory in
3679 any of several formats, independently of your program's data types.
3681 @cindex examining memory
3684 @item x/@var{nfu} @var{addr}
3687 Use the command @code{x} to examine memory.
3690 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
3691 much memory to display and how to format it; @var{addr} is an
3692 expression giving the address where you want to start displaying memory.
3693 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
3694 Several commands set convenient defaults for @var{addr}.
3697 @item @var{n}, the repeat count
3698 The repeat count is a decimal integer; the default is 1. It specifies
3699 how much memory (counting by units @var{u}) to display.
3700 @c This really is **decimal**; unaffected by 'set radix' as of GDB
3703 @item @var{f}, the display format
3704 The display format is one of the formats used by @code{print},
3705 or @samp{s} (null-terminated string) or @samp{i} (machine instruction).
3706 The default is @samp{x} (hexadecimal) initially, or the format from the
3707 last time you used either @code{x} or @code{print}.
3709 @item @var{u}, the unit size
3710 The unit size is any of
3715 Halfwords (two bytes).
3717 Words (four bytes). This is the initial default.
3719 Giant words (eight bytes).
3722 Each time you specify a unit size with @code{x}, that size becomes the
3723 default unit the next time you use @code{x}. (For the @samp{s} and
3724 @samp{i} formats, the unit size is ignored and is normally not written.)
3726 @item @var{addr}, starting display address
3727 @var{addr} is the address where you want _GDBN__ to begin displaying
3728 memory. The expression need not have a pointer value (though it may);
3729 it is always interpreted as an integer address of a byte of memory.
3730 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
3731 @var{addr} is usually just after the last address examined---but several
3732 other commands also set the default address: @code{info breakpoints} (to
3733 the address of the last breakpoint listed), @code{info line} (to the
3734 starting address of a line), and @code{print} (if you use it to display
3735 a value from memory).
3738 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
3739 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
3740 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
3741 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
3742 @pxref{Registers}) in hexadecimal (@samp{x}).
3744 Since the letters indicating unit sizes are all distinct from the
3745 letters specifying output formats, you do not have to remember whether
3746 unit size or format comes first; either order will work. The output
3747 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
3748 (However, the count @var{n} must come first; @samp{wx4} will not work.)
3750 Even though the unit size @var{u} is ignored for the formats @samp{s}
3751 and @samp{i}, you might still want to use a count @var{n}; for example,
3752 @samp{3i} specifies that you want to see three machine instructions,
3753 including any operands. The command @code{disassemble} gives an
3754 alternative way of inspecting machine instructions; @pxref{Machine
3757 All the defaults for the arguments to @code{x} are designed to make it
3758 easy to continue scanning memory with minimal specifications each time
3759 you use @code{x}. For example, after you have inspected three machine
3760 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
3761 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
3762 the repeat count @var{n} is used again; the other arguments default as
3763 for successive uses of @code{x}.
3765 @cindex @code{$_}, @code{$__}, and value history
3766 The addresses and contents printed by the @code{x} command are not saved
3767 in the value history because there is often too much of them and they
3768 would get in the way. Instead, _GDBN__ makes these values available for
3769 subsequent use in expressions as values of the convenience variables
3770 @code{$_} and @code{$__}. After an @code{x} command, the last address
3771 examined is available for use in expressions in the convenience variable
3772 @code{$_}. The contents of that address, as examined, are available in
3773 the convenience variable @code{$__}.
3775 If the @code{x} command has a repeat count, the address and contents saved
3776 are from the last memory unit printed; this is not the same as the last
3777 address printed if several units were printed on the last line of output.
3780 @section Automatic Display
3781 @cindex automatic display
3782 @cindex display of expressions
3784 If you find that you want to print the value of an expression frequently
3785 (to see how it changes), you might want to add it to the @dfn{automatic
3786 display list} so that _GDBN__ will print its value each time your program stops.
3787 Each expression added to the list is given a number to identify it;
3788 to remove an expression from the list, you specify that number.
3789 The automatic display looks like this:
3793 3: bar[5] = (struct hack *) 0x3804
3797 showing item numbers, expressions and their current values. As with
3798 displays you request manually using @code{x} or @code{print}, you can
3799 specify the output format you prefer; in fact, @code{display} decides
3800 whether to use @code{print} or @code{x} depending on how elaborate your
3801 format specification is---it uses @code{x} if you specify a unit size,
3802 or one of the two formats (@samp{i} and @samp{s}) that are only
3803 supported by @code{x}; otherwise it uses @code{print}.
3806 @item display @var{exp}
3808 Add the expression @var{exp} to the list of expressions to display
3809 each time your program stops. @xref{Expressions, ,Expressions}.
3811 @code{display} will not repeat if you press @key{RET} again after using it.
3813 @item display/@var{fmt} @var{exp}
3814 For @var{fmt} specifying only a display format and not a size or
3815 count, add the expression @var{exp} to the auto-display list but
3816 arranges to display it each time in the specified format @var{fmt}.
3817 @xref{Output formats}.
3819 @item display/@var{fmt} @var{addr}
3820 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
3821 number of units, add the expression @var{addr} as a memory address to
3822 be examined each time your program stops. Examining means in effect
3823 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
3826 For example, @samp{display/i $pc} can be helpful, to see the machine
3827 instruction about to be executed each time execution stops (@samp{$pc}
3828 is a common name for the program counter; @pxref{Registers}).
3831 @item undisplay @var{dnums}@dots{}
3832 @itemx delete display @var{dnums}@dots{}
3833 @kindex delete display
3835 Remove item numbers @var{dnums} from the list of expressions to display.
3837 @code{undisplay} will not repeat if you press @key{RET} after using it.
3838 (Otherwise you would just get the error @samp{No display number @dots{}}.)
3840 @item disable display @var{dnums}@dots{}
3841 @kindex disable display
3842 Disable the display of item numbers @var{dnums}. A disabled display
3843 item is not printed automatically, but is not forgotten. It may be
3844 enabled again later.
3846 @item enable display @var{dnums}@dots{}
3847 @kindex enable display
3848 Enable display of item numbers @var{dnums}. It becomes effective once
3849 again in auto display of its expression, until you specify otherwise.
3852 Display the current values of the expressions on the list, just as is
3853 done when your program stops.
3856 @kindex info display
3857 Print the list of expressions previously set up to display
3858 automatically, each one with its item number, but without showing the
3859 values. This includes disabled expressions, which are marked as such.
3860 It also includes expressions which would not be displayed right now
3861 because they refer to automatic variables not currently available.
3864 If a display expression refers to local variables, then it does not make
3865 sense outside the lexical context for which it was set up. Such an
3866 expression is disabled when execution enters a context where one of its
3867 variables is not defined. For example, if you give the command
3868 @code{display last_char} while inside a function with an argument
3869 @code{last_char}, then this argument will be displayed while your program
3870 continues to stop inside that function. When it stops elsewhere---where
3871 there is no variable @code{last_char}---display is disabled. The next time
3872 your program stops where @code{last_char} is meaningful, you can enable the
3873 display expression once again.
3875 @node Print Settings
3876 @section Print Settings
3878 @cindex format options
3879 @cindex print settings
3880 _GDBN__ provides the following ways to control how arrays, structures,
3881 and symbols are printed.
3884 These settings are useful for debugging programs in any language:
3887 @item set print address
3888 @item set print address on
3889 @kindex set print address
3890 _GDBN__ will print memory addresses showing the location of stack
3891 traces, structure values, pointer values, breakpoints, and so forth,
3892 even when it also displays the contents of those addresses. The default
3893 is on. For example, this is what a stack frame display looks like, with
3894 @code{set print address on}:
3899 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
3901 530 if (lquote != def_lquote)
3905 @item set print address off
3906 Do not print addresses when displaying their contents. For example,
3907 this is the same stack frame displayed with @code{set print address off}:
3911 (_GDBP__) set print addr off
3913 #0 set_quotes (lq="<<", rq=">>") at input.c:530
3914 530 if (lquote != def_lquote)
3918 @item show print address
3919 @kindex show print address
3920 Show whether or not addresses are to be printed.
3922 @item set print array
3923 @itemx set print array on
3924 @kindex set print array
3925 _GDBN__ will pretty print arrays. This format is more convenient to read,
3926 but uses more space. The default is off.
3928 @item set print array off.
3929 Return to compressed format for arrays.
3931 @item show print array
3932 @kindex show print array
3933 Show whether compressed or pretty format is selected for displaying
3936 @item set print elements @var{number-of-elements}
3937 @kindex set print elements
3938 If _GDBN__ is printing a large array, it will stop printing after it has
3939 printed the number of elements set by the @code{set print elements} command.
3940 This limit also applies to the display of strings.
3942 @item show print elements
3943 @kindex show print elements
3944 Display the number of elements of a large array that _GDBN__ will print
3945 before losing patience.
3947 @item set print pretty on
3948 @kindex set print pretty
3949 Cause _GDBN__ to print structures in an indented format with one member per
3965 @item set print pretty off
3966 Cause _GDBN__ to print structures in a compact format, like this:
3970 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
3971 meat = 0x54 "Pork"@}
3976 This is the default format.
3978 @item show print pretty
3979 @kindex show print pretty
3980 Show which format _GDBN__ will use to print structures.
3982 @item set print sevenbit-strings on
3983 @kindex set print sevenbit-strings
3984 Print using only seven-bit characters; if this option is set,
3985 _GDBN__ will display any eight-bit characters (in strings or character
3986 values) using the notation @code{\}@var{nnn}. For example, @kbd{M-a} is
3987 displayed as @code{\341}.
3989 @item set print sevenbit-strings off
3990 Print using either seven-bit or eight-bit characters, as required. This
3993 @item show print sevenbit-strings
3994 @kindex show print sevenbit-strings
3995 Show whether or not _GDBN__ will print only seven-bit characters.
3997 @item set print union on
3998 @kindex set print union
3999 Tell _GDBN__ to print unions which are contained in structures. This is the
4002 @item set print union off
4003 Tell _GDBN__ not to print unions which are contained in structures.
4005 @item show print union
4006 @kindex show print union
4007 Ask _GDBN__ whether or not it will print unions which are contained in
4010 For example, given the declarations
4013 typedef enum @{Tree, Bug@} Species;
4014 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
4015 typedef enum @{Caterpillar, Cocoon, Butterfly@}
4026 struct thing foo = @{Tree, @{Acorn@}@};
4030 with @code{set print union on} in effect @samp{p foo} would print
4033 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
4037 and with @code{set print union off} in effect it would print
4040 $1 = @{it = Tree, form = @{...@}@}
4045 These settings are of interest when debugging C++ programs:
4048 @item set print demangle
4049 @itemx set print demangle on
4050 @kindex set print demangle
4051 Print C++ names in their source form rather than in the mangled form
4052 in which they are passed to the assembler and linker for type-safe linkage.
4055 @item show print demangle
4056 @kindex show print demangle
4057 Show whether C++ names will be printed in mangled or demangled form.
4059 @item set print asm-demangle
4060 @itemx set print asm-demangle on
4061 @kindex set print asm-demangle
4062 Print C++ names in their source form rather than their mangled form, even
4063 in assembler code printouts such as instruction disassemblies.
4066 @item show print asm-demangle
4067 @kindex show print asm-demangle
4068 Show whether C++ names in assembly listings will be printed in mangled
4071 @item set print object
4072 @itemx set print object on
4073 @kindex set print object
4074 When displaying a pointer to an object, identify the @emph{actual}
4075 (derived) type of the object rather than the @emph{declared} type, using
4076 the virtual function table.
4078 @item set print object off
4079 Display only the declared type of objects, without reference to the
4080 virtual function table. This is the default setting.
4082 @item show print object
4083 @kindex show print object
4084 Show whether actual, or declared, object types will be displayed.
4086 @item set print vtbl
4087 @itemx set print vtbl on
4088 @kindex set print vtbl
4089 Pretty print C++ virtual function tables. The default is off.
4091 @item set print vtbl off
4092 Do not pretty print C++ virtual function tables.
4094 @item show print vtbl
4095 @kindex show print vtbl
4096 Show whether C++ virtual function tables are pretty printed, or not.
4100 @section Value History
4102 @cindex value history
4103 Values printed by the @code{print} command are saved in _GDBN__'s @dfn{value
4104 history} so that you can refer to them in other expressions. Values are
4105 kept until the symbol table is re-read or discarded (for example with
4106 the @code{file} or @code{symbol-file} commands). When the symbol table
4107 changes, the value history is discarded, since the values may contain
4108 pointers back to the types defined in the symbol table.
4112 @cindex history number
4113 The values printed are given @dfn{history numbers} for you to refer to them
4114 by. These are successive integers starting with one. @code{print} shows you
4115 the history number assigned to a value by printing @samp{$@var{num} = }
4116 before the value; here @var{num} is the history number.
4118 To refer to any previous value, use @samp{$} followed by the value's
4119 history number. The way @code{print} labels its output is designed to
4120 remind you of this. Just @code{$} refers to the most recent value in
4121 the history, and @code{$$} refers to the value before that.
4122 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
4123 is the value just prior to @code{$$}, @code{$$1} is equivalent to
4124 @code{$$}, and @code{$$0} is equivalent to @code{$}.
4126 For example, suppose you have just printed a pointer to a structure and
4127 want to see the contents of the structure. It suffices to type
4133 If you have a chain of structures where the component @code{next} points
4134 to the next one, you can print the contents of the next one with this:
4141 You can print successive links in the chain by repeating this
4142 command---which you can do by just typing @key{RET}.
4144 Note that the history records values, not expressions. If the value of
4145 @code{x} is 4 and you type these commands:
4153 then the value recorded in the value history by the @code{print} command
4154 remains 4 even though the value of @code{x} has changed.
4159 Print the last ten values in the value history, with their item numbers.
4160 This is like @samp{p@ $$9} repeated ten times, except that @code{show
4161 values} does not change the history.
4163 @item show values @var{n}
4164 Print ten history values centered on history item number @var{n}.
4167 Print ten history values just after the values last printed. If no more
4168 values are available, produces no display.
4171 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
4172 same effect as @samp{show values +}.
4174 @node Convenience Vars
4175 @section Convenience Variables
4177 @cindex convenience variables
4178 _GDBN__ provides @dfn{convenience variables} that you can use within
4179 _GDBN__ to hold on to a value and refer to it later. These variables
4180 exist entirely within _GDBN__; they are not part of your program, and
4181 setting a convenience variable has no direct effect on further execution
4182 of your program. That is why you can use them freely.
4184 Convenience variables are prefixed with @samp{$}. Any name preceded by
4185 @samp{$} can be used for a convenience variable, unless it is one of
4186 the predefined machine-specific register names (@pxref{Registers}).
4187 (Value history references, in contrast, are @emph{numbers} preceded
4188 by @samp{$}. @xref{Value History, ,Value History}.)
4190 You can save a value in a convenience variable with an assignment
4191 expression, just as you would set a variable in your program. Example:
4194 set $foo = *object_ptr
4198 would save in @code{$foo} the value contained in the object pointed to by
4201 Using a convenience variable for the first time creates it; but its value
4202 is @code{void} until you assign a new value. You can alter the value with
4203 another assignment at any time.
4205 Convenience variables have no fixed types. You can assign a convenience
4206 variable any type of value, including structures and arrays, even if
4207 that variable already has a value of a different type. The convenience
4208 variable, when used as an expression, has the type of its current value.
4211 @item show convenience
4212 @kindex show convenience
4213 Print a list of convenience variables used so far, and their values.
4214 Abbreviated @code{show con}.
4217 One of the ways to use a convenience variable is as a counter to be
4218 incremented or a pointer to be advanced. For example, to print
4219 a field from successive elements of an array of structures:
4223 print bar[$i++]->contents
4224 @i{@dots{} repeat that command by typing @key{RET}.}
4227 Some convenience variables are created automatically by _GDBN__ and given
4228 values likely to be useful.
4233 The variable @code{$_} is automatically set by the @code{x} command to
4234 the last address examined (@pxref{Memory, ,Examining Memory}). Other
4235 commands which provide a default address for @code{x} to examine also
4236 set @code{$_} to that address; these commands include @code{info line}
4237 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
4238 except when set by the @code{x} command, in which case it is a pointer
4239 to the type of @code{$__}.
4243 The variable @code{$__} is automatically set by the @code{x} command
4244 to the value found in the last address examined. Its type is chosen
4245 to match the format in which the data was printed.
4252 You can refer to machine register contents, in expressions, as variables
4253 with names starting with @samp{$}. The names of registers are different
4254 for each machine; use @code{info registers} to see the names used on
4258 @item info registers
4259 @kindex info registers
4260 Print the names and values of all registers except floating-point
4261 registers (in the selected stack frame).
4263 @item info all-registers
4264 @kindex info all-registers
4265 @cindex floating point registers
4266 Print the names and values of all registers, including floating-point
4269 @item info registers @var{regname} @dots{}
4270 Print the relativized value of each specified register @var{regname}.
4271 @var{regname} may be any register name valid on the machine you are using, with
4272 or without the initial @samp{$}.
4275 _GDBN__ has four ``standard'' register names that are available (in
4276 expressions) on most machines---whenever they do not conflict with an
4277 architecture's canonical mnemonics for registers. The register names
4278 @code{$pc} and @code{$sp} are used for the program counter register and
4279 the stack pointer. @code{$fp} is used for a register that contains a
4280 pointer to the current stack frame, and @code{$ps} is used for a
4281 register that contains the processor status. For example,
4282 you could print the program counter in hex with
4289 or print the instruction to be executed next with
4296 or add four to the stack pointer @footnote{This is a way of removing
4297 one word from the stack, on machines where stacks grow downward in
4298 memory (most machines, nowadays). This assumes that the innermost
4299 stack frame is selected; setting @code{$sp} is not allowed when other
4300 stack frames are selected. To pop entire frames off the stack,
4301 regardless of machine architecture, use @code{return};
4302 @pxref{Returning, ,Returning from a Function}.} with
4308 Whenever possible, these four standard register names are available on
4309 your machine even though the machine has different canonical mnemonics,
4310 so long as there is no conflict. The @code{info registers} command
4311 shows the canonical names. For example, on the SPARC, @code{info
4312 registers} displays the processor status register as @code{$psr} but you
4313 can also refer to it as @code{$ps}.
4315 _GDBN__ always considers the contents of an ordinary register as an
4316 integer when the register is examined in this way. Some machines have
4317 special registers which can hold nothing but floating point; these
4318 registers are considered to have floating point values. There is no way
4319 to refer to the contents of an ordinary register as floating point value
4320 (although you can @emph{print} it as a floating point value with
4321 @samp{print/f $@var{regname}}).
4323 Some registers have distinct ``raw'' and ``virtual'' data formats. This
4324 means that the data format in which the register contents are saved by
4325 the operating system is not the same one that your program normally
4326 sees. For example, the registers of the 68881 floating point
4327 coprocessor are always saved in ``extended'' (raw) format, but all C
4328 programs expect to work with ``double'' (virtual) format. In such
4329 cases, _GDBN__ normally works with the virtual format only (the format that
4330 makes sense for your program), but the @code{info registers} command
4331 prints the data in both formats.
4333 Normally, register values are relative to the selected stack frame
4334 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
4335 value that the register would contain if all stack frames farther in
4336 were exited and their saved registers restored. In order to see the
4337 true contents of hardware registers, you must select the innermost
4338 frame (with @samp{frame 0}).
4340 However, _GDBN__ must deduce where registers are saved, from the machine
4341 code generated by your compiler. If some registers are not saved, or if
4342 _GDBN__ is unable to locate the saved registers, the selected stack
4343 frame will make no difference.
4347 @item set rstack_high_address @var{address}
4348 @kindex set rstack_high_address
4349 @cindex AMD 29K register stack
4350 @cindex register stack, AMD29K
4351 On AMD 29000 family processors, registers are saved in a separate
4352 ``register stack''. There is no way for _GDBN__ to determine the extent
4353 of this stack. Normally, _GDBN__ just assumes that the stack is ``large
4354 enough''. This may result in _GDBN__ referencing memory locations that
4355 don't exist. If necessary, you can get around this problem by
4356 specifying the ending address of the register stack with the @code{set
4357 rstack_high_address} command. The argument should be an address, which
4358 you will probably want to precede with @samp{0x} to specify in
4361 @item show rstack_high_address
4362 @kindex show rstack_high_address
4363 Display the current limit of the register stack, on AMD 29000 family
4368 _if__(_GENERIC__ || !_H8__)
4369 @node Floating Point Hardware
4370 @section Floating Point Hardware
4371 @cindex floating point
4373 Depending on the host machine architecture, _GDBN__ may be able to give
4374 you more information about the status of the floating point hardware.
4379 If available, provides hardware-dependent information about the floating
4380 point unit. The exact contents and layout vary depending on the
4381 floating point chip.
4383 @c FIXME: this is a cop-out. Try to get examples, explanations. Only
4384 @c FIXME...supported currently on arm's and 386's. Mark properly with
4385 @c FIXME... m4 macros to isolate general statements from hardware-dep,
4386 @c FIXME... at that point.
4387 _fi__(_GENERIC__ || !_H8__)
4391 @chapter Using _GDBN__ with Different Languages
4394 Although programming languages generally have common aspects, they are
4395 rarely expressed in the same manner. For instance, in ANSI C,
4396 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
4397 Modula-2, it is accomplished by @code{p^}. Values can also be
4398 represented (and displayed) differently. Hex numbers in C are written
4399 like @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
4401 @cindex working language
4402 Language-specific information is built into _GDBN__ for some languages,
4403 allowing you to express operations like the above in your program's
4404 native language, and allowing _GDBN__ to output values in a manner
4405 consistent with the syntax of your program's native language. The
4406 language you use to build expressions, called the @dfn{working
4407 language}, can be selected manually, or _GDBN__ can set it
4411 * Setting:: Switching between source languages
4412 * Show:: Displaying the language
4413 * Checks:: Type and Range checks
4414 * Support:: Supported languages
4418 @section Switching between source languages
4420 There are two ways to control the working language---either have _GDBN__
4421 set it automatically, or select it manually yourself. You can use the
4422 @code{set language} command for either purpose. On startup, _GDBN__
4423 defaults to setting the language automatically.
4426 * Manually:: Setting the working language manually
4427 * Automatically:: Having _GDBN__ infer the source language
4431 @subsection Setting the working language
4433 @kindex set language
4434 To set the language, issue the command @samp{set language @var{lang}},
4435 where @var{lang} is the name of a language: @code{c} or @code{modula-2}.
4436 For a list of the supported languages, type @samp{set language}.
4438 Setting the language manually prevents _GDBN__ from updating the working
4439 language automatically. This can lead to confusion if you try
4440 to debug a program when the working language is not the same as the
4441 source language, when an expression is acceptable to both
4442 languages---but means different things. For instance, if the current
4443 source file were written in C, and _GDBN__ was parsing Modula-2, a
4451 might not have the effect you intended. In C, this means to add
4452 @code{b} and @code{c} and place the result in @code{a}. The result
4453 printed would be the value of @code{a}. In Modula-2, this means to compare
4454 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
4456 If you allow _GDBN__ to set the language automatically, then
4457 you can count on expressions evaluating the same way in your debugging
4458 session and in your program.
4461 @subsection Having _GDBN__ infer the source language
4463 To have _GDBN__ set the working language automatically, use @samp{set
4464 language local} or @samp{set language auto}. _GDBN__ then infers the
4465 language that a program was written in by looking at the name of its
4466 source files, and examining their extensions:
4470 Modula-2 source file
4480 This information is recorded for each function or procedure in a source
4481 file. When your program stops in a frame (usually by encountering a
4482 breakpoint), _GDBN__ sets the working language to the language recorded
4483 for the function in that frame. If the language for a frame is unknown
4484 (that is, if the function or block corresponding to the frame was
4485 defined in a source file that does not have a recognized extension), the
4486 current working language is not changed, and _GDBN__ issues a warning.
4488 This may not seem necessary for most programs, which are written
4489 entirely in one source language. However, program modules and libraries
4490 written in one source language can be used by a main program written in
4491 a different source language. Using @samp{set language auto} in this
4492 case frees you from having to set the working language manually.
4495 @section Displaying the language
4497 The following commands will help you find out which language is the
4498 working language, and also what language source files were written in.
4500 @kindex show language
4505 Display the current working language. This is the
4506 language you can use with commands such as @code{print} to
4507 build and compute expressions that may involve variables in your program.
4510 Among the other information listed here (@pxref{Frame Info, ,Information
4511 about a Frame}) is the source language for this frame. This is the
4512 language that will become the working language if you ever use an
4513 identifier that is in this frame.
4516 Among the other information listed here (@pxref{Symbols, ,Examining the
4517 Symbol Table}) is the source language of this source file.
4521 @section Type and range Checking
4524 @emph{Warning:} In this release, the _GDBN__ commands for type and range
4525 checking are included, but they do not yet have any effect. This
4526 section documents the intended facilities.
4528 @c FIXME remove warning when type/range code added
4530 Some languages are designed to guard you against making seemingly common
4531 errors through a series of compile- and run-time checks. These include
4532 checking the type of arguments to functions and operators, and making
4533 sure mathematical overflows are caught at run time. Checks such as
4534 these help to ensure a program's correctness once it has been compiled
4535 by eliminating type mismatches, and providing active checks for range
4536 errors when your program is running.
4538 _GDBN__ can check for conditions like the above if you wish.
4539 Although _GDBN__ will not check the statements in your program, it
4540 can check expressions entered directly into _GDBN__ for evaluation via
4541 the @code{print} command, for example. As with the working language,
4542 _GDBN__ can also decide whether or not to check automatically based on
4543 your program's source language. @xref{Support, ,Supported Languages},
4544 for the default settings of supported languages.
4547 * Type Checking:: An overview of type checking
4548 * Range Checking:: An overview of range checking
4551 @cindex type checking
4552 @cindex checks, type
4554 @subsection An overview of type checking
4556 Some languages, such as Modula-2, are strongly typed, meaning that the
4557 arguments to operators and functions have to be of the correct type,
4558 otherwise an error occurs. These checks prevent type mismatch
4559 errors from ever causing any run-time problems. For example,
4567 The second example fails because the @code{CARDINAL} 1 is not
4568 type-compatible with the @code{REAL} 2.3.
4570 For expressions you use in _GDBN__ commands, you can tell the _GDBN__
4571 type checker to skip checking; to treat any mismatches as errors and
4572 abandon the expression; or only issue warnings when type mismatches
4573 occur, but evaluate the expression anyway. When you choose the last of
4574 these, _GDBN__ evaluates expressions like the second example above, but
4575 also issues a warning.
4577 Even though you may turn type checking off, other type-based reasons may
4578 prevent _GDBN__ from evaluating an expression. For instance, _GDBN__ does not
4579 know how to add an @code{int} and a @code{struct foo}. These particular
4580 type errors have nothing to do with the language in use, and usually
4581 arise from expressions, such as the one described above, which make
4582 little sense to evaluate anyway.
4584 Each language defines to what degree it is strict about type. For
4585 instance, both Modula-2 and C require the arguments to arithmetical
4586 operators to be numbers. In C, enumerated types and pointers can be
4587 represented as numbers, so that they are valid arguments to mathematical
4588 operators. @xref{Support, ,Supported Languages}, for further
4589 details on specific languages.
4591 _GDBN__ provides some additional commands for controlling the type checker:
4594 @kindex set check type
4595 @kindex show check type
4597 @item set check type auto
4598 Set type checking on or off based on the current working language.
4599 @xref{Support, ,Supported Languages}, for the default settings for
4602 @item set check type on
4603 @itemx set check type off
4604 Set type checking on or off, overriding the default setting for the
4605 current working language. Issue a warning if the setting does not
4606 match the language's default. If any type mismatches occur in
4607 evaluating an expression while typechecking is on, _GDBN__ prints a
4608 message and aborts evaluation of the expression.
4610 @item set check type warn
4611 Cause the type checker to issue warnings, but to always attempt to
4612 evaluate the expression. Evaluating the expression may still
4613 be impossible for other reasons. For example, _GDBN__ cannot add
4614 numbers and structures.
4617 Show the current setting of the type checker, and whether or not _GDBN__ is
4618 setting it automatically.
4621 @cindex range checking
4622 @cindex checks, range
4623 @node Range Checking
4624 @subsection An overview of Range Checking
4626 In some languages (such as Modula-2), it is an error to exceed the
4627 bounds of a type; this is enforced with run-time checks. Such range
4628 checking is meant to ensure program correctness by making sure
4629 computations do not overflow, or indices on an array element access do
4630 not exceed the bounds of the array.
4632 For expressions you use in _GDBN__ commands, you can tell _GDBN__ to
4633 ignore range errors; to always treat them as errors and abandon the
4634 expression; or to issue warnings when a range error occurs but evaluate
4635 the expression anyway.
4637 A range error can result from numerical overflow, from exceeding an
4638 array index bound, or when you type in a constant that is not a member
4639 of any type. Some languages, however, do not treat overflows as an
4640 error. In many implementations of C, mathematical overflow causes the
4641 result to ``wrap around'' to lower values---for example, if @var{m} is
4642 the largest integer value, and @var{s} is the smallest, then
4645 @var{m} + 1 @result{} @var{s}
4648 This, too, is specific to individual languages, and in some cases
4649 specific to individual compilers or machines. @xref{Support, ,
4650 Supported Languages}, for further details on specific languages.
4652 _GDBN__ provides some additional commands for controlling the range checker:
4655 @kindex set check range
4656 @kindex show check range
4658 @item set check range auto
4659 Set range checking on or off based on the current working language.
4660 @xref{Support, ,Supported Languages}, for the default settings for
4663 @item set check range on
4664 @itemx set check range off
4665 Set range checking on or off, overriding the default setting for the
4666 current working language. A warning is issued if the setting does not
4667 match the language's default. If a range error occurs, then a message
4668 is printed and evaluation of the expression is aborted.
4670 @item set check range warn
4671 Output messages when the _GDBN__ range checker detects a range error,
4672 but attempt to evaluate the expression anyway. Evaluating the
4673 expression may still be impossible for other reasons, such as accessing
4674 memory that the process does not own (a typical example from many UNIX
4678 Show the current setting of the range checker, and whether or not it is
4679 being set automatically by _GDBN__.
4683 @section Supported Languages
4685 _GDBN__ 4 supports C, C++, and Modula-2. Some _GDBN__
4686 features may be used in expressions regardless of the language you
4687 use: the _GDBN__ @code{@@} and @code{::} operators, and the
4688 @samp{@{type@}addr} construct (@pxref{Expressions, ,Expressions}) can be
4689 used with the constructs of any of the supported languages.
4691 The following sections detail to what degree each of these
4692 source languages is supported by _GDBN__. These sections are
4693 not meant to be language tutorials or references, but serve only as a
4694 reference guide to what the _GDBN__ expression parser will accept, and
4695 what input and output formats should look like for different languages.
4696 There are many good books written on each of these languages; please
4697 look to these for a language reference or tutorial.
4701 * Modula-2:: Modula-2
4705 @subsection C and C++
4713 @cindex expressions in C or C++
4714 Since C and C++ are so closely related, many features of _GDBN__ apply
4715 to both languages. Whenever this is the case, we discuss both languages
4721 The C++ debugging facilities are jointly implemented by the GNU C++
4722 compiler and _GDBN__. Therefore, to debug your C++ code effectively,
4723 you must compile your C++ programs with the GNU C++ compiler,
4727 * C Operators:: C and C++ Operators
4728 * C Constants:: C and C++ Constants
4729 * Cplusplus expressions:: C++ Expressions
4731 * C Defaults:: Default settings for C and C++
4733 * C Checks:: C and C++ Type and Range Checks
4734 * Debugging C:: _GDBN__ and C
4735 * Debugging C plus plus:: Special features for C++
4738 @cindex C and C++ operators
4741 @subsubsection C and C++ Operators
4744 @section C and C++ Operators
4747 Operators must be defined on values of specific types. For instance,
4748 @code{+} is defined on numbers, but not on structures. Operators are
4749 often defined on groups of types. For the purposes of C and C++, the
4750 following definitions hold:
4754 @emph{Integral types} include @code{int} with any of its storage-class
4755 specifiers, @code{char}, and @code{enum}s.
4758 @emph{Floating-point types} include @code{float} and @code{double}.
4761 @emph{Pointer types} include all types defined as @code{(@var{type}
4765 @emph{Scalar types} include all of the above.
4769 The following operators are supported. They are listed here
4770 in order of increasing precedence:
4774 The comma or sequencing operator. Expressions in a comma-separated list
4775 are evaluated from left to right, with the result of the entire
4776 expression being the last expression evaluated.
4779 Assignment. The value of an assignment expression is the value
4780 assigned. Defined on scalar types.
4783 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
4784 and translated to @w{@code{@var{a} = @var{a op b}}}.
4785 @w{@code{@var{op}=}} and @code{=} have the same precendence.
4786 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
4787 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
4790 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
4791 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
4795 Logical @sc{or}. Defined on integral types.
4798 Logical @sc{and}. Defined on integral types.
4801 Bitwise @sc{or}. Defined on integral types.
4804 Bitwise exclusive-@sc{or}. Defined on integral types.
4807 Bitwise @sc{and}. Defined on integral types.
4810 Equality and inequality. Defined on scalar types. The value of these
4811 expressions is 0 for false and non-zero for true.
4813 @item <@r{, }>@r{, }<=@r{, }>=
4814 Less than, greater than, less than or equal, greater than or equal.
4815 Defined on scalar types. The value of these expressions is 0 for false
4816 and non-zero for true.
4819 left shift, and right shift. Defined on integral types.
4822 The _GDBN__ ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
4825 Addition and subtraction. Defined on integral types, floating-point types and
4828 @item *@r{, }/@r{, }%
4829 Multiplication, division, and modulus. Multiplication and division are
4830 defined on integral and floating-point types. Modulus is defined on
4834 Increment and decrement. When appearing before a variable, the
4835 operation is performed before the variable is used in an expression;
4836 when appearing after it, the variable's value is used before the
4837 operation takes place.
4840 Pointer dereferencing. Defined on pointer types. Same precedence as
4844 Address operator. Defined on variables. Same precedence as @code{++}.
4846 For debugging C++, _GDBN__ implements a use of @samp{&} beyond what's
4847 allowed in the C++ language itself: you can use @samp{&(&@var{ref})}
4848 (or, if you prefer, simply @samp{&&@var{ref}} to examine the address
4849 where a C++ reference variable (declared with @samp{&@var{ref}}) is
4853 Negative. Defined on integral and floating-point types. Same
4854 precedence as @code{++}.
4857 Logical negation. Defined on integral types. Same precedence as
4861 Bitwise complement operator. Defined on integral types. Same precedence as
4865 Structure member, and pointer-to-structure member. For convenience,
4866 _GDBN__ regards the two as equivalent, choosing whether to dereference a
4867 pointer based on the stored type information.
4868 Defined on @code{struct}s and @code{union}s.
4871 Array indexing. @code{@var{a}[@var{i}]} is defined as
4872 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
4875 Function parameter list. Same precedence as @code{->}.
4878 C++ scope resolution operator. Defined on
4879 @code{struct}, @code{union}, and @code{class} types.
4882 The _GDBN__ scope operator (@pxref{Expressions, ,Expressions}). Same precedence as
4883 @code{::}, above._1__
4886 @cindex C and C++ constants
4889 @subsubsection C and C++ Constants
4892 @section C and C++ Constants
4895 _GDBN__ allows you to express the constants of C and C++ in the
4900 Integer constants are a sequence of digits. Octal constants are
4901 specified by a leading @samp{0} (ie. zero), and hexadecimal constants by
4902 a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
4903 @samp{l}, specifying that the constant should be treated as a
4907 Floating point constants are a sequence of digits, followed by a decimal
4908 point, followed by a sequence of digits, and optionally followed by an
4909 exponent. An exponent is of the form:
4910 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
4911 sequence of digits. The @samp{+} is optional for positive exponents.
4914 Enumerated constants consist of enumerated identifiers, or their
4915 integral equivalents.
4918 Character constants are a single character surrounded by single quotes
4919 (@code{'}), or a number---the ordinal value of the corresponding character
4920 (usually its @sc{ASCII} value). Within quotes, the single character may
4921 be represented by a letter or by @dfn{escape sequences}, which are of
4922 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
4923 of the character's ordinal value; or of the form @samp{\@var{x}}, where
4924 @samp{@var{x}} is a predefined special character---for example,
4925 @samp{\n} for newline.
4928 String constants are a sequence of character constants surrounded
4929 by double quotes (@code{"}).
4932 Pointer constants are an integral value.
4935 @node Cplusplus expressions
4937 @subsubsection C++ Expressions
4940 @section C++ Expressions
4943 @cindex expressions in C++
4944 _GDBN__'s expression handling has a number of extensions to
4945 interpret a significant subset of C++ expressions.
4947 @cindex C++ support, not in @sc{coff}
4948 @cindex @sc{coff} versus C++
4949 @cindex C++ and object formats
4950 @cindex object formats and C++
4951 @cindex a.out and C++
4952 @cindex @sc{ecoff} and C++
4953 @cindex @sc{xcoff} and C++
4954 @cindex @sc{elf}/stabs and C++
4955 @cindex @sc{elf}/@sc{dwarf} and C++
4957 @emph{Warning:} Most of these extensions depend on the use of additional
4958 debugging information in the symbol table, and thus require a rich,
4959 extendable object code format. In particular, if your system uses
4960 a.out, MIPS @sc{ecoff}, RS/6000 @sc{xcoff}, or Sun @sc{elf} with stabs
4961 extensions to the symbol table, these facilities are all available.
4962 Where the object code format is standard @sc{coff}, on the other hand,
4963 most of the C++ support in _GDBN__ will @emph{not} work, nor can it.
4964 For the standard SVr4 debugging format, @sc{dwarf} in @sc{elf}, the
4965 standard is still evolving, so the C++ support in _GDBN__ is still
4966 fragile; when this debugging format stabilizes, however, C++ support
4967 will also be available on systems that use it.
4972 @cindex member functions
4974 Member function calls are allowed; you can use expressions like
4977 count = aml->GetOriginal(x, y)
4981 @cindex namespace in C++
4983 While a member function is active (in the selected stack frame), your
4984 expressions have the same namespace available as the member function;
4985 that is, _GDBN__ allows implicit references to the class instance
4986 pointer @code{this} following the same rules as C++.
4988 @cindex call overloaded functions
4989 @cindex type conversions in C++
4991 You can call overloaded functions; _GDBN__ will resolve the function
4992 call to the right definition, with one restriction---you must use
4993 arguments of the type required by the function that you want to call.
4994 _GDBN__ will not perform conversions requiring constructors or
4995 user-defined type operators.
4997 @cindex reference declarations
4999 _GDBN__ understands variables declared as C++ references; you can use them in
5000 expressions just as you do in C++ source---they are automatically
5003 In the parameter list shown when _GDBN__ displays a frame, the values of
5004 reference variables are not displayed (unlike other variables); this
5005 avoids clutter, since references are often used for large structures.
5006 The @emph{address} of a reference variable is always shown, unless
5007 you have specified @samp{set print address off}.
5010 _GDBN__ supports the C++ name resolution operator @code{::}---your
5011 expressions can use it just as expressions in your program do. Since
5012 one scope may be defined in another, you can use @code{::} repeatedly if
5013 necessary, for example in an expression like
5014 @samp{@var{scope1}::@var{scope2}::@var{name}}. _GDBN__ also allows
5015 resolving name scope by reference to source files, in both C and C++
5016 debugging (@pxref{Variables, ,Program Variables}).
5021 @subsubsection C and C++ Defaults
5022 @cindex C and C++ defaults
5024 If you allow _GDBN__ to set type and range checking automatically, they
5025 both default to @code{off} whenever the working language changes to
5026 C or C++. This happens regardless of whether you, or _GDBN__,
5027 selected the working language.
5029 If you allow _GDBN__ to set the language automatically, it sets the
5030 working language to C or C++ on entering code compiled from a source file
5031 whose name ends with @file{.c}, @file{.C}, or @file{.cc}.
5032 @xref{Automatically, ,Having _GDBN__ infer the source language}, for
5038 @subsubsection C and C++ Type and Range Checks
5041 @section C and C++ Type and Range Checks
5043 @cindex C and C++ checks
5046 @emph{Warning:} in this release, _GDBN__ does not yet perform type or
5049 @c FIXME remove warning when type/range checks added
5051 By default, when _GDBN__ parses C or C++ expressions, type checking
5052 is not used. However, if you turn type checking on, _GDBN__ will
5053 consider two variables type equivalent if:
5057 The two variables are structured and have the same structure, union, or
5061 Two two variables have the same type name, or types that have been
5062 declared equivalent through @code{typedef}.
5065 @c leaving this out because neither J Gilmore nor R Pesch understand it.
5068 The two @code{struct}, @code{union}, or @code{enum} variables are
5069 declared in the same declaration. (Note: this may not be true for all C
5074 Range checking, if turned on, is done on mathematical operations. Array
5075 indices are not checked, since they are often used to index a pointer
5076 that is not itself an array.
5080 @subsubsection _GDBN__ and C
5083 @section _GDBN__ and C
5086 The @code{set print union} and @code{show print union} commands apply to
5087 the @code{union} type. When set to @samp{on}, any @code{union} that is
5088 inside a @code{struct} or @code{class} will also be printed.
5089 Otherwise, it will appear as @samp{@{...@}}.
5091 The @code{@@} operator aids in the debugging of dynamic arrays, formed
5092 with pointers and a memory allocation function. (@pxref{Expressions, ,Expressions})
5094 @node Debugging C plus plus
5096 @subsubsection _GDBN__ Features for C++
5099 @section _GDBN__ Features for C++
5102 @cindex commands for C++
5103 Some _GDBN__ commands are particularly useful with C++, and some are
5104 designed specifically for use with C++. Here is a summary:
5107 @cindex break in overloaded functions
5108 @item @r{breakpoint menus}
5109 When you want a breakpoint in a function whose name is overloaded,
5110 _GDBN__'s breakpoint menus help you specify which function definition
5111 you want. @xref{Breakpoint Menus}.
5113 @cindex overloading in C++
5114 @item rbreak @var{regex}
5115 Setting breakpoints using regular expressions is helpful for setting
5116 breakpoints on overloaded functions that are not members of any special
5118 @xref{Set Breaks, ,Setting Breakpoints}.
5120 @cindex C++ exception handling
5121 @item catch @var{exceptions}
5123 Debug C++ exception handling using these commands. @xref{Exception
5124 Handling, ,Breakpoints and Exceptions}.
5127 @item ptype @var{typename}
5128 Print inheritance relationships as well as other information for type
5130 @xref{Symbols, ,Examining the Symbol Table}.
5132 @cindex C++ symbol display
5133 @item set print demangle
5134 @itemx show print demangle
5135 @itemx set print asm-demangle
5136 @itemx show print asm-demangle
5137 Control whether C++ symbols display in their source form, both when
5138 displaying code as C++ source and when displaying disassemblies.
5139 @xref{Print Settings, ,Print Settings}.
5141 @item set print object
5142 @itemx show print object
5143 Choose whether to print derived (actual) or declared types of objects.
5144 @xref{Print Settings, ,Print Settings}.
5146 @item set print vtbl
5147 @itemx show print vtbl
5148 Control the format for printing virtual function tables.
5149 @xref{Print Settings, ,Print Settings}.
5151 @item @r{Overloaded symbol names}
5152 You can specify a particular definition of an overloaded symbol, using
5153 the same notation that's used to declare such symbols in C++: type
5154 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
5155 also use _GDBN__'s command-line word completion facilities to list the
5156 available choices, or to finish the type list for you.
5157 @xref{Completion,, Command Completion}, for details on how to do this.
5162 @subsection Modula-2
5165 The extensions made to _GDBN__ to support Modula-2 support output
5166 from the GNU Modula-2 compiler (which is currently being developed).
5167 Other Modula-2 compilers are not currently supported, and attempting to
5168 debug executables produced by them will most likely result in an error
5169 as _GDBN__ reads in the executable's symbol table.
5171 @cindex expressions in Modula-2
5173 * M2 Operators:: Built-in operators
5174 * Built-In Func/Proc:: Built-in Functions and Procedures
5175 * M2 Constants:: Modula-2 Constants
5176 * M2 Defaults:: Default settings for Modula-2
5177 * Deviations:: Deviations from standard Modula-2
5178 * M2 Checks:: Modula-2 Type and Range Checks
5179 * M2 Scope:: The scope operators @code{::} and @code{.}
5180 * GDB/M2:: _GDBN__ and Modula-2
5184 @subsubsection Operators
5185 @cindex Modula-2 operators
5187 Operators must be defined on values of specific types. For instance,
5188 @code{+} is defined on numbers, but not on structures. Operators are
5189 often defined on groups of types. For the purposes of Modula-2, the
5190 following definitions hold:
5195 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
5199 @emph{Character types} consist of @code{CHAR} and its subranges.
5202 @emph{Floating-point types} consist of @code{REAL}.
5205 @emph{Pointer types} consist of anything declared as @code{POINTER TO
5209 @emph{Scalar types} consist of all of the above.
5212 @emph{Set types} consist of @code{SET}s and @code{BITSET}s.
5215 @emph{Boolean types} consist of @code{BOOLEAN}.
5219 The following operators are supported, and appear in order of
5220 increasing precedence:
5224 Function argument or array index separator.
5227 Assignment. The value of @var{var} @code{:=} @var{value} is
5231 Less than, greater than on integral, floating-point, or enumerated
5235 Less than, greater than, less than or equal to, greater than or equal to
5236 on integral, floating-point and enumerated types, or set inclusion on
5237 set types. Same precedence as @code{<}.
5239 @item =@r{, }<>@r{, }#
5240 Equality and two ways of expressing inequality, valid on scalar types.
5241 Same precedence as @code{<}. In _GDBN__ scripts, only @code{<>} is
5242 available for inequality, since @code{#} conflicts with the script
5246 Set membership. Defined on set types and the types of their members.
5247 Same precedence as @code{<}.
5250 Boolean disjunction. Defined on boolean types.
5253 Boolean conjuction. Defined on boolean types.
5256 The _GDBN__ ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
5259 Addition and subtraction on integral and floating-point types, or union
5260 and difference on set types.
5263 Multiplication on integral and floating-point types, or set intersection
5267 Division on floating-point types, or symmetric set difference on set
5268 types. Same precedence as @code{*}.
5271 Integer division and remainder. Defined on integral types. Same
5272 precedence as @code{*}.
5275 Negative. Defined on @code{INTEGER}s and @code{REAL}s.
5278 Pointer dereferencing. Defined on pointer types.
5281 Boolean negation. Defined on boolean types. Same precedence as
5285 @code{RECORD} field selector. Defined on @code{RECORD}s. Same
5286 precedence as @code{^}.
5289 Array indexing. Defined on @code{ARRAY}s. Same precedence as @code{^}.
5292 Procedure argument list. Defined on @code{PROCEDURE}s. Same precedence
5296 _GDBN__ and Modula-2 scope operators.
5300 @emph{Warning:} Sets and their operations are not yet supported, so _GDBN__
5301 will treat the use of the operator @code{IN}, or the use of operators
5302 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
5303 @code{<=}, and @code{>=} on sets as an error.
5306 @cindex Modula-2 built-ins
5307 @node Built-In Func/Proc
5308 @subsubsection Built-in Functions and Procedures
5310 Modula-2 also makes available several built-in procedures and functions.
5311 In describing these, the following metavariables are used:
5316 represents an @code{ARRAY} variable.
5319 represents a @code{CHAR} constant or variable.
5322 represents a variable or constant of integral type.
5325 represents an identifier that belongs to a set. Generally used in the
5326 same function with the metavariable @var{s}. The type of @var{s} should
5327 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}.
5330 represents a variable or constant of integral or floating-point type.
5333 represents a variable or constant of floating-point type.
5339 represents a variable.
5342 represents a variable or constant of one of many types. See the
5343 explanation of the function for details.
5346 All Modula-2 built-in procedures also return a result, described below.
5350 Returns the absolute value of @var{n}.
5353 If @var{c} is a lower case letter, it returns its upper case
5354 equivalent, otherwise it returns its argument
5357 Returns the character whose ordinal value is @var{i}.
5360 Decrements the value in the variable @var{v}. Returns the new value.
5362 @item DEC(@var{v},@var{i})
5363 Decrements the value in the variable @var{v} by @var{i}. Returns the
5366 @item EXCL(@var{m},@var{s})
5367 Removes the element @var{m} from the set @var{s}. Returns the new
5370 @item FLOAT(@var{i})
5371 Returns the floating point equivalent of the integer @var{i}.
5374 Returns the index of the last member of @var{a}.
5377 Increments the value in the variable @var{v}. Returns the new value.
5379 @item INC(@var{v},@var{i})
5380 Increments the value in the variable @var{v} by @var{i}. Returns the
5383 @item INCL(@var{m},@var{s})
5384 Adds the element @var{m} to the set @var{s} if it is not already
5385 there. Returns the new set.
5388 Returns the maximum value of the type @var{t}.
5391 Returns the minimum value of the type @var{t}.
5394 Returns boolean TRUE if @var{i} is an odd number.
5397 Returns the ordinal value of its argument. For example, the ordinal
5398 value of a character is its ASCII value (on machines supporting the
5399 ASCII character set). @var{x} must be of an ordered type, which include
5400 integral, character and enumerated types.
5403 Returns the size of its argument. @var{x} can be a variable or a type.
5405 @item TRUNC(@var{r})
5406 Returns the integral part of @var{r}.
5408 @item VAL(@var{t},@var{i})
5409 Returns the member of the type @var{t} whose ordinal value is @var{i}.
5413 @emph{Warning:} Sets and their operations are not yet supported, so
5414 _GDBN__ will treat the use of procedures @code{INCL} and @code{EXCL} as
5418 @cindex Modula-2 constants
5420 @subsubsection Constants
5422 _GDBN__ allows you to express the constants of Modula-2 in the following
5428 Integer constants are simply a sequence of digits. When used in an
5429 expression, a constant is interpreted to be type-compatible with the
5430 rest of the expression. Hexadecimal integers are specified by a
5431 trailing @samp{H}, and octal integers by a trailing @samp{B}.
5434 Floating point constants appear as a sequence of digits, followed by a
5435 decimal point and another sequence of digits. An optional exponent can
5436 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
5437 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
5438 digits of the floating point constant must be valid decimal (base 10)
5442 Character constants consist of a single character enclosed by a pair of
5443 like quotes, either single (@code{'}) or double (@code{"}). They may
5444 also be expressed by their ordinal value (their ASCII value, usually)
5445 followed by a @samp{C}.
5448 String constants consist of a sequence of characters enclosed by a
5449 pair of like quotes, either single (@code{'}) or double (@code{"}).
5450 Escape sequences in the style of C are also allowed. @xref{C
5451 Constants, ,C and C++ Constants}, for a brief explanation of escape
5455 Enumerated constants consist of an enumerated identifier.
5458 Boolean constants consist of the identifiers @code{TRUE} and
5462 Pointer constants consist of integral values only.
5465 Set constants are not yet supported.
5469 @subsubsection Modula-2 Defaults
5470 @cindex Modula-2 defaults
5472 If type and range checking are set automatically by _GDBN__, they
5473 both default to @code{on} whenever the working language changes to
5474 Modula-2. This happens regardless of whether you, or _GDBN__,
5475 selected the working language.
5477 If you allow _GDBN__ to set the language automatically, then entering
5478 code compiled from a file whose name ends with @file{.mod} will set the
5479 working language to Modula-2. @xref{Automatically, ,Having _GDBN__ set
5480 the language automatically}, for further details.
5483 @subsubsection Deviations from Standard Modula-2
5484 @cindex Modula-2, deviations from
5486 A few changes have been made to make Modula-2 programs easier to debug.
5487 This is done primarily via loosening its type strictness:
5491 Unlike in standard Modula-2, pointer constants can be formed by
5492 integers. This allows you to modify pointer variables during
5493 debugging. (In standard Modula-2, the actual address contained in a
5494 pointer variable is hidden from you; it can only be modified
5495 through direct assignment to another pointer variable or expression that
5496 returned a pointer.)
5499 C escape sequences can be used in strings and characters to represent
5500 non-printable characters. _GDBN__ will print out strings with these
5501 escape sequences embedded. Single non-printable characters are
5502 printed using the @samp{CHR(@var{nnn})} format.
5505 The assignment operator (@code{:=}) returns the value of its right-hand
5509 All built-in procedures both modify @emph{and} return their argument.
5513 @subsubsection Modula-2 Type and Range Checks
5514 @cindex Modula-2 checks
5517 @emph{Warning:} in this release, _GDBN__ does not yet perform type or
5520 @c FIXME remove warning when type/range checks added
5522 _GDBN__ considers two Modula-2 variables type equivalent if:
5526 They are of types that have been declared equivalent via a @code{TYPE
5527 @var{t1} = @var{t2}} statement
5530 They have been declared on the same line. (Note: This is true of the
5531 GNU Modula-2 compiler, but it may not be true of other compilers.)
5534 As long as type checking is enabled, any attempt to combine variables
5535 whose types are not equivalent is an error.
5537 Range checking is done on all mathematical operations, assignment, array
5538 index bounds, and all built-in functions and procedures.
5541 @subsubsection The scope operators @code{::} and @code{.}
5544 @cindex colon, doubled as scope operator
5547 @c Info cannot handoe :: but TeX can.
5553 There are a few subtle differences between the Modula-2 scope operator
5554 (@code{.}) and the _GDBN__ scope operator (@code{::}). The two have
5559 @var{module} . @var{id}
5560 @var{scope} :: @var{id}
5564 where @var{scope} is the name of a module or a procedure,
5565 @var{module} the name of a module, and @var{id} is any declared
5566 identifier within your program, except another module.
5568 Using the @code{::} operator makes _GDBN__ search the scope
5569 specified by @var{scope} for the identifier @var{id}. If it is not
5570 found in the specified scope, then _GDBN__ will search all scopes
5571 enclosing the one specified by @var{scope}.
5573 Using the @code{.} operator makes _GDBN__ search the current scope for
5574 the identifier specified by @var{id} that was imported from the
5575 definition module specified by @var{module}. With this operator, it is
5576 an error if the identifier @var{id} was not imported from definition
5577 module @var{module}, or if @var{id} is not an identifier in
5581 @subsubsection _GDBN__ and Modula-2
5583 Some _GDBN__ commands have little use when debugging Modula-2 programs.
5584 Five subcommands of @code{set print} and @code{show print} apply
5585 specifically to C and C++: @samp{vtbl}, @samp{demangle},
5586 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
5587 apply to C++, and the last to C's @code{union} type, which has no direct
5588 analogue in Modula-2.
5590 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
5591 while using any language, is not useful with Modula-2. Its
5592 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
5593 created in Modula-2 as they can in C or C++. However, because an
5594 address can be specified by an integral constant, the construct
5595 @samp{@{@var{type}@}@var{adrexp}} is still useful. (@pxref{Expressions, ,Expressions})
5597 @cindex @code{#} in Modula-2
5598 In _GDBN__ scripts, the Modula-2 inequality operator @code{#} is
5599 interpreted as the beginning of a comment. Use @code{<>} instead.
5604 @chapter Examining the Symbol Table
5606 The commands described in this section allow you to inquire about the
5607 symbols (names of variables, functions and types) defined in your
5608 program. This information is inherent in the text of your program and
5609 does not change as your program executes. _GDBN__ finds it in your
5610 program's symbol table, in the file indicated when you started _GDBN__
5611 (@pxref{File Options, ,Choosing Files}), or by one of the
5612 file-management commands (@pxref{Files, ,Commands to Specify Files}).
5614 @c FIXME! This might be intentionally specific to C and C++; if so, move
5615 @c to someplace in C section of lang chapter.
5616 @cindex symbol names
5617 @cindex names of symbols
5618 @cindex quoting names
5619 Occasionally, you may need to refer to symbols that contain unusual
5620 characters, which _GDBN__ ordinarily treats as word delimiters. The
5621 most frequent case is in referring to static variables in other
5622 source files (@pxref{Variables,,Program Variables}). File names
5623 are recorded in object files as debugging symbols, but _GDBN__ would
5624 ordinarily parse a typical file name, like @file{foo.c}, as the three words
5625 @samp{foo} @samp{.} @samp{c}. To allow _GDBN__ to recognize
5626 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
5633 looks up the value of @code{x} in the scope of the file @file{foo.c}.
5636 @item info address @var{symbol}
5637 @kindex info address
5638 Describe where the data for @var{symbol} is stored. For a register
5639 variable, this says which register it is kept in. For a non-register
5640 local variable, this prints the stack-frame offset at which the variable
5643 Note the contrast with @samp{print &@var{symbol}}, which does not work
5644 at all for a register variables, and for a stack local variable prints
5645 the exact address of the current instantiation of the variable.
5647 @item whatis @var{exp}
5649 Print the data type of expression @var{exp}. @var{exp} is not
5650 actually evaluated, and any side-effecting operations (such as
5651 assignments or function calls) inside it do not take place.
5652 @xref{Expressions, ,Expressions}.
5655 Print the data type of @code{$}, the last value in the value history.
5657 @item ptype @var{typename}
5659 Print a description of data type @var{typename}. @var{typename} may be
5660 the name of a type, or for C code it may have the form
5661 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
5662 @samp{enum @var{enum-tag}}.
5664 @item ptype @var{exp}
5666 Print a description of the type of expression @var{exp}. @code{ptype}
5667 differs from @code{whatis} by printing a detailed description, instead
5668 of just the name of the type. For example, if your program declares a
5672 struct complex @{double real; double imag;@} v;
5676 compare the output of the two commands:
5681 type = struct complex
5683 type = struct complex @{
5691 As with @code{whatis}, using @code{ptype} without an argument refers to
5692 the type of @code{$}, the last value in the value history.
5694 @item info types @var{regexp}
5697 Print a brief description of all types whose name matches @var{regexp}
5698 (or all types in your program, if you supply no argument). Each
5699 complete typename is matched as though it were a complete line; thus,
5700 @samp{i type value} gives information on all types in your program whose
5701 name includes the string @code{value}, but @samp{i type ^value$} gives
5702 information only on types whose complete name is @code{value}.
5704 This command differs from @code{ptype} in two ways: first, like
5705 @code{whatis}, it does not print a detailed description; second, it
5706 lists all source files where a type is defined.
5710 Show the name of the current source file---that is, the source file for
5711 the function containing the current point of execution---and the language
5715 @kindex info sources
5716 Print the names of all source files in your program for which there is
5717 debugging information, organized into two lists: files whose symbols
5718 have already been read, and files whose symbols will be read when needed.
5720 @item info functions
5721 @kindex info functions
5722 Print the names and data types of all defined functions.
5724 @item info functions @var{regexp}
5725 Print the names and data types of all defined functions
5726 whose names contain a match for regular expression @var{regexp}.
5727 Thus, @samp{info fun step} finds all functions whose names
5728 include @code{step}; @samp{info fun ^step} finds those whose names
5729 start with @code{step}.
5731 @item info variables
5732 @kindex info variables
5733 Print the names and data types of all variables that are declared
5734 outside of functions (i.e., excluding local variables).
5736 @item info variables @var{regexp}
5737 Print the names and data types of all variables (except for local
5738 variables) whose names contain a match for regular expression
5742 This was never implemented.
5744 @itemx info methods @var{regexp}
5745 @kindex info methods
5746 The @code{info methods} command permits the user to examine all defined
5747 methods within C++ program, or (with the @var{regexp} argument) a
5748 specific set of methods found in the various C++ classes. Many
5749 C++ classes provide a large number of methods. Thus, the output
5750 from the @code{ptype} command can be overwhelming and hard to use. The
5751 @code{info-methods} command filters the methods, printing only those
5752 which match the regular-expression @var{regexp}.
5755 @item maint print symbols @var{filename}
5756 @itemx maint print psymbols @var{filename}
5757 @itemx maint print msymbols @var{filename}
5758 @kindex maint print symbols
5760 @kindex maint print psymbols
5761 @cindex partial symbol dump
5762 Write a dump of debugging symbol data into the file @var{filename}.
5763 These commands are used to debug the _GDBN__ symbol-reading code. Only
5764 symbols with debugging data are included. If you use @samp{maint print
5765 symbols}, _GDBN__ includes all the symbols for which it has already
5766 collected full details: that is, @var{filename} reflects symbols for
5767 only those files whose symbols _GDBN__ has read. You can use the
5768 command @code{info sources} to find out which files these are. If you
5769 use @samp{maint print psymbols} instead, the dump shows information about
5770 symbols that _GDBN__ only knows partially---that is, symbols defined in
5771 files that _GDBN__ has skimmed, but not yet read completely. Finally,
5772 @samp{maint print msymbols} dumps just the minimal symbol information
5773 required for each object file from which _GDBN__ has read some symbols.
5774 The description of @code{symbol-file} explains how _GDBN__ reads
5775 symbols; both @code{info source} and @code{symbol-file} are described in
5776 @ref{Files, ,Commands to Specify Files}.
5780 @chapter Altering Execution
5782 Once you think you have found an error in your program, you might want to
5783 find out for certain whether correcting the apparent error would lead to
5784 correct results in the rest of the run. You can find the answer by
5785 experiment, using the _GDBN__ features for altering execution of the
5788 For example, you can store new values into variables or memory
5789 locations, give your program a signal, restart it at a different address,
5790 or even return prematurely from a function to its caller.
5793 * Assignment:: Assignment to Variables
5794 * Jumping:: Continuing at a Different Address
5796 * Signaling:: Giving your program a Signal
5798 * Returning:: Returning from a Function
5799 * Calling:: Calling your Program's Functions
5800 * Patching:: Patching your Program
5804 @section Assignment to Variables
5807 @cindex setting variables
5808 To alter the value of a variable, evaluate an assignment expression.
5809 @xref{Expressions, ,Expressions}. For example,
5816 stores the value 4 into the variable @code{x}, and then prints the
5817 value of the assignment expression (which is 4).
5819 @xref{Languages, ,Using _GDBN__ with Different Languages}, for more
5820 information on operators in supported languages.
5823 @kindex set variable
5824 @cindex variables, setting
5825 If you are not interested in seeing the value of the assignment, use the
5826 @code{set} command instead of the @code{print} command. @code{set} is
5827 really the same as @code{print} except that the expression's value is not
5828 printed and is not put in the value history (@pxref{Value History, ,Value History}). The
5829 expression is evaluated only for its effects.
5831 If the beginning of the argument string of the @code{set} command
5832 appears identical to a @code{set} subcommand, use the @code{set
5833 variable} command instead of just @code{set}. This command is identical
5834 to @code{set} except for its lack of subcommands. For example, a
5835 program might well have a variable @code{width}---which leads to
5836 an error if we try to set a new value with just @samp{set width=13}, as
5837 we might if @code{set width} did not happen to be a _GDBN__ command:
5840 (_GDBP__) whatis width
5844 (_GDBP__) set width=47
5845 Invalid syntax in expression.
5849 The invalid expression, of course, is @samp{=47}. What we can do in
5850 order to actually set our program's variable @code{width} is
5853 (_GDBP__) set var width=47
5856 _GDBN__ allows more implicit conversions in assignments than C; you can
5857 freely store an integer value into a pointer variable or vice versa,
5858 and any structure can be converted to any other structure that is the
5859 same length or shorter.
5860 @comment FIXME: how do structs align/pad in these conversions?
5861 @comment /pesch@cygnus.com 18dec1990
5863 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
5864 construct to generate a value of specified type at a specified address
5865 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
5866 to memory location @code{0x83040} as an integer (which implies a certain size
5867 and representation in memory), and
5870 set @{int@}0x83040 = 4
5874 stores the value 4 into that memory location.
5877 @section Continuing at a Different Address
5879 Ordinarily, when you continue your program, you do so at the place where
5880 it stopped, with the @code{continue} command. You can instead continue at
5881 an address of your own choosing, with the following commands:
5884 @item jump @var{linespec}
5886 Resume execution at line @var{linespec}. Execution will stop
5887 immediately if there is a breakpoint there. @xref{List, ,Printing
5888 Source Lines}, for a description of the different forms of
5891 The @code{jump} command does not change the current stack frame, or
5892 the stack pointer, or the contents of any memory location or any
5893 register other than the program counter. If line @var{linespec} is in
5894 a different function from the one currently executing, the results may
5895 be bizarre if the two functions expect different patterns of arguments or
5896 of local variables. For this reason, the @code{jump} command requests
5897 confirmation if the specified line is not in the function currently
5898 executing. However, even bizarre results are predictable if you are
5899 well acquainted with the machine-language code of your program.
5901 @item jump *@var{address}
5902 Resume execution at the instruction at address @var{address}.
5905 You can get much the same effect as the @code{jump} command by storing a
5906 new value into the register @code{$pc}. The difference is that this
5907 does not start your program running; it only changes the address where it
5908 @emph{will} run when it is continued. For example,
5915 causes the next @code{continue} command or stepping command to execute at
5916 address @code{0x485}, rather than at the address where your program stopped.
5917 @xref{Continuing and Stepping, ,Continuing and Stepping}.
5919 The most common occasion to use the @code{jump} command is to back up,
5920 perhaps with more breakpoints set, over a portion of a program that has
5921 already executed, in order to examine its execution in more detail.
5926 @section Giving your program a Signal
5929 @item signal @var{signalnum}
5931 Resume execution where your program stopped, but give it immediately the
5932 signal number @var{signalnum}.
5934 Alternatively, if @var{signalnum} is zero, continue execution without
5935 giving a signal. This is useful when your program stopped on account of
5936 a signal and would ordinary see the signal when resumed with the
5937 @code{continue} command; @samp{signal 0} causes it to resume without a
5940 @code{signal} does not repeat when you press @key{RET} a second time
5941 after executing the command.
5947 @section Returning from a Function
5951 @itemx return @var{expression}
5952 @cindex returning from a function
5954 You can cancel execution of a function call with the @code{return}
5955 command. If you give an
5956 @var{expression} argument, its value is used as the function's return
5960 When you use @code{return}, _GDBN__ discards the selected stack frame
5961 (and all frames within it). You can think of this as making the
5962 discarded frame return prematurely. If you wish to specify a value to
5963 be returned, give that value as the argument to @code{return}.
5965 This pops the selected stack frame (@pxref{Selection, ,Selecting a
5966 Frame}), and any other frames inside of it, leaving its caller as the
5967 innermost remaining frame. That frame becomes selected. The
5968 specified value is stored in the registers used for returning values
5971 The @code{return} command does not resume execution; it leaves the
5972 program stopped in the state that would exist if the function had just
5973 returned. In contrast, the @code{finish} command (@pxref{Continuing
5974 and Stepping, ,Continuing and Stepping}) resumes execution until the
5975 selected stack frame returns naturally.
5978 @section Calling your Program's Functions
5980 @cindex calling functions
5983 @item call @var{expr}
5984 Evaluate the expression @var{expr} without displaying @code{void}
5988 You can use this variant of the @code{print} command if you want to
5989 execute a function from your program, but without cluttering the output
5990 with @code{void} returned values. The result is printed and saved in
5991 the value history, if it is not void.
5994 @section Patching your Program
5995 @cindex patching binaries
5996 @cindex writing into executables
5997 @cindex writing into corefiles
5999 By default, _GDBN__ opens the file containing your program's executable
6000 code (or the corefile) read-only. This prevents accidental alterations
6001 to machine code; but it also prevents you from intentionally patching
6002 your program's binary.
6004 If you'd like to be able to patch the binary, you can specify that
6005 explicitly with the @code{set write} command. For example, you might
6006 want to turn on internal debugging flags, or even to make emergency
6011 @itemx set write off
6013 If you specify @samp{set write on}, _GDBN__ will open executable and
6014 core files for both reading and writing; if you specify @samp{set write
6015 off} (the default), _GDBN__ will open them read-only.
6017 If you have already loaded a file, you must load it
6018 again (using the @code{exec-file} or @code{core-file} command) after
6019 changing @code{set write}, for your new setting to take effect.
6023 Display whether executable files and core files will be opened for
6024 writing as well as reading.
6028 @chapter _GDBN__'s Files
6030 _GDBN__ needs to know the file name of the program to be debugged, both in
6031 order to read its symbol table and in order to start your program.
6033 To debug a core dump of a previous run, _GDBN__ must be told the file
6034 name of the core dump.
6038 * Files:: Commands to Specify Files
6039 * Symbol Errors:: Errors Reading Symbol Files
6043 @section Commands to Specify Files
6044 @cindex core dump file
6045 @cindex symbol table
6048 The usual way to specify executable and core dump file names is with
6049 the command arguments given when you start _GDBN__, (@pxref{Invocation,
6050 ,Getting In and Out of _GDBN__}.
6053 The usual way to specify an executable file name is with
6054 the command argument given when you start _GDBN__, (@pxref{Invocation,
6055 ,Getting In and Out of _GDBN__}.
6058 Occasionally it is necessary to change to a different file during a
6059 _GDBN__ session. Or you may run _GDBN__ and forget to specify a file you
6060 want to use. In these situations the _GDBN__ commands to specify new files
6064 @item file @var{filename}
6065 @cindex executable file
6067 Use @var{filename} as the program to be debugged. It is read for its
6068 symbols and for the contents of pure memory. It is also the program
6069 executed when you use the @code{run} command. If you do not specify a
6070 directory and the file is not found in _GDBN__'s working directory, _GDBN__
6071 uses the environment variable @code{PATH} as a list of directories to
6072 search, just as the shell does when looking for a program to run. You
6073 can change the value of this variable, for both _GDBN__ and your program,
6074 using the @code{path} command.
6076 On systems with memory-mapped files, an auxiliary symbol table file
6077 @file{@var{filename}.syms} may be available for @var{filename}. If it
6078 is, _GDBN__ will map in the symbol table from
6079 @file{@var{filename}.syms}, starting up more quickly. See the
6080 descriptions of the options @samp{-mapped} and @samp{-readnow} (available
6081 on the command line, and with the commands @code{file}, @code{symbol-file},
6082 or @code{add-symbol-file}), for more information.
6085 @code{file} with no argument makes _GDBN__ discard any information it
6086 has on both executable file and the symbol table.
6088 @item exec-file @r{[} @var{filename} @r{]}
6090 Specify that the program to be run (but not the symbol table) is found
6091 in @var{filename}. _GDBN__ will search the environment variable @code{PATH}
6092 if necessary to locate your program. Omitting @var{filename} means to
6093 discard information on the executable file.
6095 @item symbol-file @r{[} @var{filename} @r{]}
6097 Read symbol table information from file @var{filename}. @code{PATH} is
6098 searched when necessary. Use the @code{file} command to get both symbol
6099 table and program to run from the same file.
6101 @code{symbol-file} with no argument clears out _GDBN__'s information on your
6102 program's symbol table.
6104 The @code{symbol-file} command causes _GDBN__ to forget the contents of its
6105 convenience variables, the value history, and all breakpoints and
6106 auto-display expressions. This is because they may contain pointers to
6107 the internal data recording symbols and data types, which are part of
6108 the old symbol table data being discarded inside _GDBN__.
6110 @code{symbol-file} will not repeat if you press @key{RET} again after
6113 When _GDBN__ is configured for a particular environment, it will
6114 understand debugging information in whatever format is the standard
6115 generated for that environment; you may use either a GNU compiler, or
6116 other compilers that adhere to the local conventions. Best results are
6117 usually obtained from GNU compilers; for example, using @code{_GCC__}
6118 you can generate debugging information for optimized code.
6120 On some kinds of object files, the @code{symbol-file} command does not
6121 normally read the symbol table in full right away. Instead, it scans
6122 the symbol table quickly to find which source files and which symbols
6123 are present. The details are read later, one source file at a time,
6126 The purpose of this two-stage reading strategy is to make _GDBN__ start up
6127 faster. For the most part, it is invisible except for occasional
6128 pauses while the symbol table details for a particular source file are
6129 being read. (The @code{set verbose} command can turn these pauses
6130 into messages if desired. @xref{Messages/Warnings, ,Optional Warnings
6133 When the symbol table is stored in COFF format, @code{symbol-file} does
6134 read the symbol table data in full right away. We have not implemented
6135 the two-stage strategy for COFF yet.
6137 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
6138 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
6140 @cindex reading symbols immediately
6141 @cindex symbols, reading immediately
6143 @cindex memory-mapped symbol file
6144 @cindex saving symbol table
6145 You can override the _GDBN__ two-stage strategy for reading symbol
6146 tables by using the @samp{-readnow} option with any of the commands that
6147 load symbol table information, if you want to be sure _GDBN__ has the
6148 entire symbol table available.
6151 If memory-mapped files are available on your system through the
6152 @code{mmap} system call, you can use another option, @samp{-mapped}, to
6153 cause _GDBN__ to write the symbols for your program into a reusable
6154 file. Future _GDBN__ debugging sessions will map in symbol information
6155 from this auxiliary symbol file (if the program hasn't changed), rather
6156 than spending time reading the symbol table from the executable
6157 program. Using the @samp{-mapped} option has the same effect as
6158 starting _GDBN__ with the @samp{-mapped} command-line option.
6160 You can use both options together, to make sure the auxiliary symbol
6161 file has all the symbol information for your program.
6163 The @code{.syms} file is specific to the host machine on which GDB is run.
6164 It holds an exact image of GDB's internal symbol table. It cannot be
6165 shared across multiple host platforms.
6167 The auxiliary symbol file for a program called @var{myprog} is called
6168 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
6169 than the corresponding executable), _GDBN__ will always attempt to use
6170 it when you debug @var{myprog}; no special options or commands are
6172 @c FIXME: for now no mention of directories, since this seems to be in
6173 @c flux. 13mar1992 status is that in theory GDB would look either in
6174 @c current dir or in same dir as myprog; but issues like competing
6175 @c GDB's, or clutter in system dirs, mean that in practice right now
6176 @c only current dir is used. FFish says maybe a special GDB hierarchy
6177 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
6180 @item core-file @r{[} @var{filename} @r{]}
6183 Specify the whereabouts of a core dump file to be used as the ``contents
6184 of memory''. Traditionally, core files contain only some parts of the
6185 address space of the process that generated them; _GDBN__ can access the
6186 executable file itself for other parts.
6188 @code{core-file} with no argument specifies that no core file is
6191 Note that the core file is ignored when your program is actually running
6192 under _GDBN__. So, if you have been running your program and you wish to
6193 debug a core file instead, you must kill the subprocess in which the
6194 program is running. To do this, use the @code{kill} command
6195 (@pxref{Kill Process, ,Killing the Child Process}).
6198 @item load @var{filename}
6201 Depending on what remote debugging facilities are configured into
6202 _GDBN__, the @code{load} command may be available. Where it exists, it
6203 is meant to make @var{filename} (an executable) available for debugging
6204 on the remote system---by downloading, or dynamic linking, for example.
6205 @code{load} also records @var{filename}'s symbol table in _GDBN__, like
6206 the @code{add-symbol-file} command.
6208 If @code{load} is not available on your _GDBN__, attempting to execute
6209 it gets the error message ``@code{You can't do that when your target is
6214 On VxWorks, @code{load} will dynamically link @var{filename} on the
6215 current target system as well as adding its symbols in _GDBN__.
6219 @cindex download to Nindy-960
6220 With the Nindy interface to an Intel 960 board, @code{load} will
6221 download @var{filename} to the 960 as well as adding its symbols in
6226 @cindex download to H8/300
6227 @cindex H8/300 download
6228 When you select remote debugging to a Hitachi H8/300 board (@pxref{Hitachi
6229 H8/300 Remote,,_GDBN__ and the Hitachi H8/300}), the
6230 @code{load} command downloads your program to the H8/300 and also opens
6231 it as the current executable target for _GDBN__ on your host (like the
6232 @code{file} command).
6235 @code{load} will not repeat if you press @key{RET} again after using it.
6237 @item add-symbol-file @var{filename} @var{address}
6238 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
6239 @kindex add-symbol-file
6240 @cindex dynamic linking
6241 The @code{add-symbol-file} command reads additional symbol table information
6242 from the file @var{filename}. You would use this command when @var{filename}
6243 has been dynamically loaded (by some other means) into the program that
6244 is running. @var{address} should be the memory address at which the
6245 file has been loaded; _GDBN__ cannot figure this out for itself.
6247 The symbol table of the file @var{filename} is added to the symbol table
6248 originally read with the @code{symbol-file} command. You can use the
6249 @code{add-symbol-file} command any number of times; the new symbol data thus
6250 read keeps adding to the old. To discard all old symbol data instead,
6251 use the @code{symbol-file} command.
6253 @code{add-symbol-file} will not repeat if you press @key{RET} after using it.
6255 You can use the @samp{-mapped} and @samp{-readnow} options just as with
6256 the @code{symbol-file} command, to change how _GDBN__ manages the symbol
6257 tabl einformation for @var{filename}.
6263 @code{info files} and @code{info target} are synonymous; both print
6264 the current targets (@pxref{Targets, ,Specifying a Debugging Target}),
6265 including the names of the executable and core dump files currently in
6266 use by _GDBN__, and the files from which symbols were loaded. The command
6267 @code{help targets} lists all possible targets rather than current
6272 All file-specifying commands allow both absolute and relative file names
6273 as arguments. _GDBN__ always converts the file name to an absolute path
6274 name and remembers it that way.
6277 @cindex shared libraries
6278 _GDBN__ supports SunOS, SVR4, and IBM RS/6000 shared libraries.
6279 _GDBN__ automatically loads symbol definitions from shared libraries
6280 when you use the @code{run} command, or when you examine a core file.
6281 (Before you issue the @code{run} command, _GDBN__ will not understand
6282 references to a function in a shared library, however---unless you are
6283 debugging a core file).
6284 @c FIXME: next _GDBN__ release should permit some refs to undef
6285 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared lib
6289 @itemx info sharedlibrary
6290 @kindex info sharedlibrary
6292 Print the names of the shared libraries which are currently loaded.
6294 @item sharedlibrary @var{regex}
6295 @itemx share @var{regex}
6296 @kindex sharedlibrary
6298 This is an obsolescent command; you can use it to explicitly
6299 load shared object library symbols for files matching a UNIX regular
6300 expression, but as with files loaded automatically, it will only load
6301 shared libraries required by your program for a core file or after
6302 typing @code{run}. If @var{regex} is omitted all shared libraries
6303 required by your program are loaded.
6308 @section Errors Reading Symbol Files
6310 While reading a symbol file, _GDBN__ will occasionally encounter problems,
6311 such as symbol types it does not recognize, or known bugs in compiler
6312 output. By default, _GDBN__ does not notify you of such problems, since
6313 they are relatively common and primarily of interest to people
6314 debugging compilers. If you are interested in seeing information
6315 about ill-constructed symbol tables, you can either ask _GDBN__ to print
6316 only one message about each such type of problem, no matter how many
6317 times the problem occurs; or you can ask _GDBN__ to print more messages,
6318 to see how many times the problems occur, with the @code{set
6319 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
6322 The messages currently printed, and their meanings, are:
6325 @item inner block not inside outer block in @var{symbol}
6327 The symbol information shows where symbol scopes begin and end
6328 (such as at the start of a function or a block of statements). This
6329 error indicates that an inner scope block is not fully contained
6330 in its outer scope blocks.
6332 _GDBN__ circumvents the problem by treating the inner block as if it had
6333 the same scope as the outer block. In the error message, @var{symbol}
6334 may be shown as ``@code{(don't know)}'' if the outer block is not a
6337 @item block at @var{address} out of order
6339 The symbol information for symbol scope blocks should occur in
6340 order of increasing addresses. This error indicates that it does not
6343 _GDBN__ does not circumvent this problem, and will have trouble locating
6344 symbols in the source file whose symbols being read. (You can often
6345 determine what source file is affected by specifying @code{set verbose
6346 on}. @xref{Messages/Warnings, ,Optional Warnings and Messages}.)
6348 @item bad block start address patched
6350 The symbol information for a symbol scope block has a start address
6351 smaller than the address of the preceding source line. This is known
6352 to occur in the SunOS 4.1.1 (and earlier) C compiler.
6354 _GDBN__ circumvents the problem by treating the symbol scope block as
6355 starting on the previous source line.
6357 @item bad string table offset in symbol @var{n}
6360 Symbol number @var{n} contains a pointer into the string table which is
6361 larger than the size of the string table.
6363 _GDBN__ circumvents the problem by considering the symbol to have the
6364 name @code{foo}, which may cause other problems if many symbols end up
6367 @item unknown symbol type @code{0x@var{nn}}
6369 The symbol information contains new data types that _GDBN__ does not yet
6370 know how to read. @code{0x@var{nn}} is the symbol type of the misunderstood
6371 information, in hexadecimal.
6373 _GDBN__ circumvents the error by ignoring this symbol information. This
6374 will usually allow your program to be debugged, though certain symbols
6375 will not be accessible. If you encounter such a problem and feel like
6376 debugging it, you can debug @code{_GDBP__} with itself, breakpoint on
6377 @code{complain}, then go up to the function @code{read_dbx_symtab} and
6378 examine @code{*bufp} to see the symbol.
6380 @item stub type has NULL name
6381 _GDBN__ could not find the full definition for a struct or class.
6383 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
6385 The symbol information for a C++ member function is missing some
6386 information that recent versions of the compiler should have output
6389 @item info mismatch between compiler and debugger
6391 _GDBN__ could not parse a type specification output by the compiler.
6395 @chapter Specifying a Debugging Target
6396 @cindex debugging target
6399 A @dfn{target} is the execution environment occupied by your program.
6400 Often, _GDBN__ runs in the same host environment as your program; in
6401 that case, the debugging target is specified as a side effect when you
6402 use the @code{file} or @code{core} commands. When you need more
6403 flexibility---for example, running _GDBN__ on a physically separate
6404 host, or controlling a standalone system over a serial port or a
6405 realtime system over a TCP/IP connection---you can use the @code{target}
6406 command to specify one of the target types configured for _GDBN__
6407 (@pxref{Target Commands, ,Commands for Managing Targets}).
6410 * Active Targets:: Active Targets
6411 * Target Commands:: Commands for Managing Targets
6412 * Remote:: Remote Debugging
6415 @node Active Targets
6416 @section Active Targets
6417 @cindex stacking targets
6418 @cindex active targets
6419 @cindex multiple targets
6421 There are three classes of targets: processes, core files, and
6422 executable files. _GDBN__ can work concurrently on up to three active
6423 targets, one in each class. This allows you to (for example) start a
6424 process and inspect its activity without abandoning your work on a core
6427 If, for example, you execute @samp{gdb a.out}, then the executable file
6428 @code{a.out} is the only active target. If you designate a core file as
6429 well---presumably from a prior run that crashed and coredumped---then
6430 _GDBN__ has two active targets and will use them in tandem, looking
6431 first in the corefile target, then in the executable file, to satisfy
6432 requests for memory addresses. (Typically, these two classes of target
6433 are complementary, since core files contain only a program's
6434 read-write memory---variables and so on---plus machine status, while
6435 executable files contain only the program text and initialized data.)
6437 When you type @code{run}, your executable file becomes an active process
6438 target as well. When a process target is active, all _GDBN__ commands
6439 requesting memory addresses refer to that target; addresses in an active
6440 core file or executable file target are obscured while the process
6444 Use the @code{exec-file} command to select a
6445 new executable target (@pxref{Files, ,Commands to Specify
6449 Use the @code{core-file} and @code{exec-file} commands to select a
6450 new core file or executable target (@pxref{Files, ,Commands to Specify
6451 Files}). To specify as a target a process that is already running, use
6452 the @code{attach} command (@pxref{Attach, ,Debugging an
6453 Already-Running Process}.).
6456 @node Target Commands
6457 @section Commands for Managing Targets
6460 @item target @var{type} @var{parameters}
6461 Connects the _GDBN__ host environment to a target machine or process. A
6462 target is typically a protocol for talking to debugging facilities. You
6463 use the argument @var{type} to specify the type or protocol of the
6466 Further @var{parameters} are interpreted by the target protocol, but
6467 typically include things like device names or host names to connect
6468 with, process numbers, and baud rates.
6470 The @code{target} command will not repeat if you press @key{RET} again
6471 after executing the command.
6475 Displays the names of all targets available. To display targets
6476 currently selected, use either @code{info target} or @code{info files}
6477 (@pxref{Files, ,Commands to Specify Files}).
6479 @item help target @var{name}
6480 Describe a particular target, including any parameters necessary to
6484 Here are some common targets (available, or not, depending on the GDB
6488 @item target exec @var{prog}
6490 An executable file. @samp{target exec @var{prog}} is the same as
6491 @samp{exec-file @var{prog}}.
6493 @item target core @var{filename}
6495 A core dump file. @samp{target core @var{filename}} is the same as
6496 @samp{core-file @var{filename}}.
6498 @item target remote @var{dev}
6499 @kindex target remote
6500 Remote serial target in GDB-specific protocol. The argument @var{dev}
6501 specifies what serial device to use for the connection (e.g.
6502 @file{/dev/ttya}). @xref{Remote, ,Remote Debugging}.
6505 @item target amd-eb @var{dev} @var{speed} @var{PROG}
6506 @kindex target amd-eb
6508 Remote PC-resident AMD EB29K board, attached over serial lines.
6509 @var{dev} is the serial device, as for @code{target remote};
6510 @var{speed} allows you to specify the linespeed; and @var{PROG} is the
6511 name of the program to be debugged, as it appears to DOS on the PC.
6512 @xref{EB29K Remote, ,GDB with a Remote EB29K}.
6518 A Hitachi H8/300 board, attached via serial line to your host. Use
6519 special commands @code{device} and @code{speed} to control the serial
6520 line and the communications speed used. @xref{Hitachi H8/300
6521 Remote,,_GDBN__ and the Hitachi H8/300}.
6525 @item target nindy @var{devicename}
6526 @kindex target nindy
6527 An Intel 960 board controlled by a Nindy Monitor. @var{devicename} is
6528 the name of the serial device to use for the connection, e.g.
6529 @file{/dev/ttya}. @xref{i960-Nindy Remote, ,_GDBN__ with a Remote i960 (Nindy)}.
6533 @item target vxworks @var{machinename}
6534 @kindex target vxworks
6535 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
6536 is the target system's machine name or IP address.
6537 @xref{VxWorks Remote, ,_GDBN__ and VxWorks}.
6542 Different targets are available on different configurations of _GDBN__; your
6543 configuration may have more or fewer targets.
6547 @section Remote Debugging
6548 @cindex remote debugging
6550 If you are trying to debug a program running on a machine that cannot run
6551 GDB in the usual way, it is often useful to use remote debugging. For
6552 example, you might use remote debugging on an operating system kernel, or on
6553 a small system which does not have a general purpose operating system
6554 powerful enough to run a full-featured debugger.
6556 Some configurations of GDB have special serial or TCP/IP interfaces
6557 to make this work with particular debugging targets. In addition,
6558 GDB comes with a generic serial protocol (specific to GDB, but
6559 not specific to any particular target system) which you can use if you
6560 write the remote stubs---the code that will run on the remote system to
6561 communicate with GDB.
6563 To use the GDB remote serial protocol, the program to be debugged on
6564 the remote machine needs to contain a debugging stub which talks to
6565 GDB over the serial line. Several working remote stubs are
6566 distributed with GDB; see the @file{README} file in the GDB
6567 distribution for more information.
6569 For details of this communication protocol, see the comments in the
6570 GDB source file @file{remote.c}.
6572 To start remote debugging, first run GDB and specify as an executable file
6573 the program that is running in the remote machine. This tells GDB how
6574 to find your program's symbols and the contents of its pure text. Then
6575 establish communication using the @code{target remote} command with a device
6576 name as an argument. For example:
6579 target remote /dev/ttyb
6583 if the serial line is connected to the device named @file{/dev/ttyb}. This
6584 will stop the remote machine if it is not already stopped.
6586 Now you can use all the usual commands to examine and change data and to
6587 step and continue the remote program.
6589 To resume the remote program and stop debugging it, use the @code{detach}
6592 @kindex set remotedebug
6593 @kindex show remotedebug
6594 @cindex packets, reporting on stdout
6595 @cindex serial connections, debugging
6596 If you have trouble with the serial connection, you can use the command
6597 @code{set remotedebug}. This makes _GDBN__ report on all packets sent
6598 back and forth across the serial line to the remote machine. The
6599 packet-debugging information is printed on the _GDBN__ standard output
6600 stream. @code{set remotedebug off} turns it off, and @code{show
6601 remotedebug} will show you its current state.
6603 Other remote targets may be available in your
6604 configuration of GDB; use @code{help targets} to list them.
6607 _dnl__ Text on starting up GDB in various specific cases; it goes up front
6608 _dnl__ in manuals configured for any of those particular situations, here
6611 _include__(gdbinv-m.m4)<>_dnl__
6613 _include__(gdbinv-s.m4)
6616 @node Controlling _GDBN__
6617 @chapter Controlling _GDBN__
6619 You can alter many aspects of _GDBN__'s interaction with you by using
6620 the @code{set} command. For commands controlling how _GDBN__ displays
6621 data, @pxref{Print Settings, ,Print Settings}; other settings are described here.
6625 * Editing:: Command Editing
6626 * History:: Command History
6627 * Screen Size:: Screen Size
6629 * Messages/Warnings:: Optional Warnings and Messages
6636 _GDBN__ indicates its readiness to read a command by printing a string
6637 called the @dfn{prompt}. This string is normally @samp{(_GDBP__)}. You
6638 can change the prompt string with the @code{set prompt} command. For
6639 instance, when debugging _GDBN__ with _GDBN__, it is useful to change
6640 the prompt in one of the _GDBN__<>s so that you can always tell which
6641 one you are talking to.
6644 @item set prompt @var{newprompt}
6646 Directs _GDBN__ to use @var{newprompt} as its prompt string henceforth.
6649 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
6653 @section Command Editing
6655 @cindex command line editing
6657 _GDBN__ reads its input commands via the @dfn{readline} interface. This
6658 GNU library provides consistent behavior for programs which provide a
6659 command line interface to the user. Advantages are @code{emacs}-style
6660 or @code{vi}-style inline editing of commands, @code{csh}-like history
6661 substitution, and a storage and recall of command history across
6664 You may control the behavior of command line editing in _GDBN__ with the
6671 @itemx set editing on
6672 Enable command line editing (enabled by default).
6674 @item set editing off
6675 Disable command line editing.
6677 @kindex show editing
6679 Show whether command line editing is enabled.
6683 @section Command History
6686 @cindex history substitution
6687 @cindex history file
6688 @kindex set history filename
6689 @item set history filename @var{fname}
6690 Set the name of the _GDBN__ command history file to @var{fname}. This is
6691 the file from which _GDBN__ will read an initial command history
6692 list or to which it will write this list when it exits. This list is
6693 accessed through history expansion or through the history
6694 command editing characters listed below. This file defaults to the
6695 value of the environment variable @code{GDBHISTFILE}, or to
6696 @file{./.gdb_history} if this variable is not set.
6698 @cindex history save
6699 @kindex set history save
6700 @item set history save
6701 @itemx set history save on
6702 Record command history in a file, whose name may be specified with the
6703 @code{set history filename} command. By default, this option is disabled.
6705 @item set history save off
6706 Stop recording command history in a file.
6708 @cindex history size
6709 @kindex set history size
6710 @item set history size @var{size}
6711 Set the number of commands which _GDBN__ will keep in its history list.
6712 This defaults to the value of the environment variable
6713 @code{HISTSIZE}, or to 256 if this variable is not set.
6716 @cindex history expansion
6717 History expansion assigns special meaning to the character @kbd{!}.
6719 @xref{Event Designators}.
6721 Since @kbd{!} is also the logical not operator in C, history expansion
6722 is off by default. If you decide to enable history expansion with the
6723 @code{set history expansion on} command, you may sometimes need to
6724 follow @kbd{!} (when it is used as logical not, in an expression) with
6725 a space or a tab to prevent it from being expanded. The readline
6726 history facilities will not attempt substitution on the strings
6727 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
6729 The commands to control history expansion are:
6733 @kindex set history expansion
6734 @item set history expansion on
6735 @itemx set history expansion
6736 Enable history expansion. History expansion is off by default.
6738 @item set history expansion off
6739 Disable history expansion.
6741 The readline code comes with more complete documentation of
6742 editing and history expansion features. Users unfamiliar with @code{emacs}
6743 or @code{vi} may wish to read it.
6745 @xref{Command Line Editing}.
6749 @kindex show history
6751 @itemx show history filename
6752 @itemx show history save
6753 @itemx show history size
6754 @itemx show history expansion
6755 These commands display the state of the _GDBN__ history parameters.
6756 @code{show history} by itself displays all four states.
6761 @kindex show commands
6763 Display the last ten commands in the command history.
6765 @item show commands @var{n}
6766 Print ten commands centered on command number @var{n}.
6768 @item show commands +
6769 Print ten commands just after the commands last printed.
6773 @section Screen Size
6774 @cindex size of screen
6775 @cindex pauses in output
6777 Certain commands to _GDBN__ may produce large amounts of information
6778 output to the screen. To help you read all of it, _GDBN__ pauses and
6779 asks you for input at the end of each page of output. Type @key{RET}
6780 when you want to continue the output. _GDBN__ also uses the screen
6781 width setting to determine when to wrap lines of output. Depending on
6782 what is being printed, it tries to break the line at a readable place,
6783 rather than simply letting it overflow onto the following line.
6785 Normally _GDBN__ knows the size of the screen from the termcap data base
6786 together with the value of the @code{TERM} environment variable and the
6787 @code{stty rows} and @code{stty cols} settings. If this is not correct,
6788 you can override it with the @code{set height} and @code{set
6792 @item set height @var{lpp}
6794 @itemx set width @var{cpl}
6800 These @code{set} commands specify a screen height of @var{lpp} lines and
6801 a screen width of @var{cpl} characters. The associated @code{show}
6802 commands display the current settings.
6804 If you specify a height of zero lines, _GDBN__ will not pause during output
6805 no matter how long the output is. This is useful if output is to a file
6806 or to an editor buffer.
6811 @cindex number representation
6812 @cindex entering numbers
6814 You can always enter numbers in octal, decimal, or hexadecimal in _GDBN__ by
6815 the usual conventions: octal numbers begin with @samp{0}, decimal
6816 numbers end with @samp{.}, and hexadecimal numbers begin with @samp{0x}.
6817 Numbers that begin with none of these are, by default, entered in base
6818 10; likewise, the default display for numbers---when no particular
6819 format is specified---is base 10. You can change the default base for
6820 both input and output with the @code{set radix} command.
6824 @item set radix @var{base}
6825 Set the default base for numeric input and display. Supported choices
6826 for @var{base} are decimal 2, 8, 10, 16. @var{base} must itself be
6827 specified either unambiguously or using the current default radix; for
6838 will set the base to decimal. On the other hand, @samp{set radix 10}
6839 will leave the radix unchanged no matter what it was.
6843 Display the current default base for numeric input and display.
6846 @node Messages/Warnings
6847 @section Optional Warnings and Messages
6849 By default, _GDBN__ is silent about its inner workings. If you are running
6850 on a slow machine, you may want to use the @code{set verbose} command.
6851 It will make _GDBN__ tell you when it does a lengthy internal operation, so
6852 you will not think it has crashed.
6854 Currently, the messages controlled by @code{set verbose} are those
6855 which announce that the symbol table for a source file is being read;
6856 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
6860 @item set verbose on
6861 Enables _GDBN__'s output of certain informational messages.
6863 @item set verbose off
6864 Disables _GDBN__'s output of certain informational messages.
6866 @kindex show verbose
6868 Displays whether @code{set verbose} is on or off.
6871 By default, if _GDBN__ encounters bugs in the symbol table of an object
6872 file, it is silent; but if you are debugging a compiler, you may find
6873 this information useful (@pxref{Symbol Errors, ,Errors Reading Symbol Files}).
6876 @kindex set complaints
6877 @item set complaints @var{limit}
6878 Permits _GDBN__ to output @var{limit} complaints about each type of unusual
6879 symbols before becoming silent about the problem. Set @var{limit} to
6880 zero to suppress all complaints; set it to a large number to prevent
6881 complaints from being suppressed.
6883 @kindex show complaints
6884 @item show complaints
6885 Displays how many symbol complaints _GDBN__ is permitted to produce.
6888 By default, _GDBN__ is cautious, and asks what sometimes seem to be a
6889 lot of stupid questions to confirm certain commands. For example, if
6890 you try to run a program which is already running:
6894 The program being debugged has been started already.
6895 Start it from the beginning? (y or n)
6898 If you are willing to unflinchingly face the consequences of your own
6899 commands, you can disable this ``feature'':
6904 @cindex confirmation
6905 @cindex stupid questions
6906 @item set confirm off
6907 Disables confirmation requests.
6909 @item set confirm on
6910 Enables confirmation requests (the default).
6913 @kindex show confirm
6914 Displays state of confirmation requests.
6917 @c FIXME this does not really belong here. But where *does* it belong?
6918 @cindex reloading symbols
6919 Some systems allow individual object files that make up your program to
6920 be replaced without stopping and restarting your program.
6922 For example, in VxWorks you can simply recompile a defective object file
6923 and keep on running.
6925 If you are running on one of these systems, you can allow _GDBN__ to
6926 reload the symbols for automatically relinked modules:
6929 @kindex set symbol-reloading
6930 @item set symbol-reloading on
6931 Replace symbol definitions for the corresponding source file when an
6932 object file with a particular name is seen again.
6934 @item set symbol-reloading off
6935 Do not replace symbol definitions when re-encountering object files of
6936 the same name. This is the default state; if you are not running on a
6937 system that permits automatically relinking modules, you should leave
6938 @code{symbol-reloading} off, since otherwise _GDBN__ may discard symbols
6939 when linking large programs, that may contain several modules (from
6940 different directories or libraries) with the same name.
6942 @item show symbol-reloading
6943 Show the current @code{on} or @code{off} setting.
6947 @chapter Canned Sequences of Commands
6949 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
6950 Command Lists}), _GDBN__ provides two ways to store sequences of commands
6951 for execution as a unit: user-defined commands and command files.
6954 * Define:: User-Defined Commands
6955 * Command Files:: Command Files
6956 * Output:: Commands for Controlled Output
6960 @section User-Defined Commands
6962 @cindex user-defined command
6963 A @dfn{user-defined command} is a sequence of _GDBN__ commands to which you
6964 assign a new name as a command. This is done with the @code{define}
6968 @item define @var{commandname}
6970 Define a command named @var{commandname}. If there is already a command
6971 by that name, you are asked to confirm that you want to redefine it.
6973 The definition of the command is made up of other _GDBN__ command lines,
6974 which are given following the @code{define} command. The end of these
6975 commands is marked by a line containing @code{end}.
6977 @item document @var{commandname}
6979 Give documentation to the user-defined command @var{commandname}. The
6980 command @var{commandname} must already be defined. This command reads
6981 lines of documentation just as @code{define} reads the lines of the
6982 command definition, ending with @code{end}. After the @code{document}
6983 command is finished, @code{help} on command @var{commandname} will print
6984 the documentation you have specified.
6986 You may use the @code{document} command again to change the
6987 documentation of a command. Redefining the command with @code{define}
6988 does not change the documentation.
6990 @item help user-defined
6991 @kindex help user-defined
6992 List all user-defined commands, with the first line of the documentation
6996 @itemx show user @var{commandname}
6998 Display the _GDBN__ commands used to define @var{commandname} (but not its
6999 documentation). If no @var{commandname} is given, display the
7000 definitions for all user-defined commands.
7003 User-defined commands do not take arguments. When they are executed, the
7004 commands of the definition are not printed. An error in any command
7005 stops execution of the user-defined command.
7007 Commands that would ask for confirmation if used interactively proceed
7008 without asking when used inside a user-defined command. Many _GDBN__ commands
7009 that normally print messages to say what they are doing omit the messages
7010 when used in a user-defined command.
7013 @section Command Files
7015 @cindex command files
7016 A command file for _GDBN__ is a file of lines that are _GDBN__ commands. Comments
7017 (lines starting with @kbd{#}) may also be included. An empty line in a
7018 command file does nothing; it does not mean to repeat the last command, as
7019 it would from the terminal.
7022 @cindex @file{_GDBINIT__}
7023 When you start _GDBN__, it automatically executes commands from its
7024 @dfn{init files}. These are files named @file{_GDBINIT__}. _GDBN__ reads
7025 the init file (if any) in your home directory and then the init file
7026 (if any) in the current working directory. (The init files are not
7027 executed if you use the @samp{-nx} option; @pxref{Mode Options,
7028 ,Choosing Modes}.) You can also request the execution of a command
7029 file with the @code{source} command:
7032 @item source @var{filename}
7034 Execute the command file @var{filename}.
7037 The lines in a command file are executed sequentially. They are not
7038 printed as they are executed. An error in any command terminates execution
7039 of the command file.
7041 Commands that would ask for confirmation if used interactively proceed
7042 without asking when used in a command file. Many _GDBN__ commands that
7043 normally print messages to say what they are doing omit the messages
7044 when called from command files.
7047 @section Commands for Controlled Output
7049 During the execution of a command file or a user-defined command, normal
7050 _GDBN__ output is suppressed; the only output that appears is what is
7051 explicitly printed by the commands in the definition. This section
7052 describes three commands useful for generating exactly the output you
7056 @item echo @var{text}
7058 @c I do not consider backslash-space a standard C escape sequence
7059 @c because it is not in ANSI.
7060 Print @var{text}. Nonprinting characters can be included in
7061 @var{text} using C escape sequences, such as @samp{\n} to print a
7062 newline. @strong{No newline will be printed unless you specify one.}
7063 In addition to the standard C escape sequences, a backslash followed
7064 by a space stands for a space. This is useful for outputting a
7065 string with spaces at the beginning or the end, since leading and
7066 trailing spaces are otherwise trimmed from all arguments.
7067 To print @samp{@w{ }and foo =@w{ }}, use the command
7068 @samp{echo \@w{ }and foo = \@w{ }}.
7070 A backslash at the end of @var{text} can be used, as in C, to continue
7071 the command onto subsequent lines. For example,
7074 echo This is some text\n\
7075 which is continued\n\
7076 onto several lines.\n
7079 produces the same output as
7082 echo This is some text\n
7083 echo which is continued\n
7084 echo onto several lines.\n
7087 @item output @var{expression}
7089 Print the value of @var{expression} and nothing but that value: no
7090 newlines, no @samp{$@var{nn} = }. The value is not entered in the
7091 value history either. @xref{Expressions, ,Expressions}, for more information on
7094 @item output/@var{fmt} @var{expression}
7095 Print the value of @var{expression} in format @var{fmt}. You can use
7096 the same formats as for @code{print}; @pxref{Output formats}, for more
7099 @item printf @var{string}, @var{expressions}@dots{}
7101 Print the values of the @var{expressions} under the control of
7102 @var{string}. The @var{expressions} are separated by commas and may
7103 be either numbers or pointers. Their values are printed as specified
7104 by @var{string}, exactly as if your program were to execute
7107 printf (@var{string}, @var{expressions}@dots{});
7110 For example, you can print two values in hex like this:
7113 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
7116 The only backslash-escape sequences that you can use in the format
7117 string are the simple ones that consist of backslash followed by a
7123 @chapter Using _GDBN__ under GNU Emacs
7126 A special interface allows you to use GNU Emacs to view (and
7127 edit) the source files for the program you are debugging with
7130 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
7131 executable file you want to debug as an argument. This command starts
7132 _GDBN__ as a subprocess of Emacs, with input and output through a newly
7133 created Emacs buffer.
7135 Using _GDBN__ under Emacs is just like using _GDBN__ normally except for two
7140 All ``terminal'' input and output goes through the Emacs buffer.
7143 This applies both to _GDBN__ commands and their output, and to the input
7144 and output done by the program you are debugging.
7146 This is useful because it means that you can copy the text of previous
7147 commands and input them again; you can even use parts of the output
7150 All the facilities of Emacs' Shell mode are available for interacting
7151 with your program. In particular, you can send signals the usual
7152 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
7157 _GDBN__ displays source code through Emacs.
7160 Each time _GDBN__ displays a stack frame, Emacs automatically finds the
7161 source file for that frame and puts an arrow (_0__@samp{=>}_1__) at the
7162 left margin of the current line. Emacs uses a separate buffer for
7163 source display, and splits the window to show both your _GDBN__ session
7166 Explicit _GDBN__ @code{list} or search commands still produce output as
7167 usual, but you probably will have no reason to use them.
7170 @emph{Warning:} If the directory where your program resides is not your
7171 current directory, it can be easy to confuse Emacs about the location of
7172 the source files, in which case the auxiliary display buffer will not
7173 appear to show your source. _GDBN__ can find programs by searching your
7174 environment's @code{PATH} variable, so the _GDBN__ input and output
7175 session will proceed normally; but Emacs does not get enough information
7176 back from _GDBN__ to locate the source files in this situation. To
7177 avoid this problem, either start _GDBN__ mode from the directory where
7178 your program resides, or specify a full path name when prompted for the
7179 @kbd{M-x gdb} argument.
7181 A similar confusion can result if you use the _GDBN__ @code{file} command to
7182 switch to debugging a program in some other location, from an existing
7183 _GDBN__ buffer in Emacs.
7186 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
7187 you need to call _GDBN__ by a different name (for example, if you keep
7188 several configurations around, with different names) you can set the
7189 Emacs variable @code{gdb-command-name}; for example,
7192 (setq gdb-command-name "mygdb")
7196 (preceded by @kbd{ESC ESC}, or typed in the @code{*scratch*} buffer, or
7197 in your @file{.emacs} file) will make Emacs call the program named
7198 ``@code{mygdb}'' instead.
7200 In the _GDBN__ I/O buffer, you can use these special Emacs commands in
7201 addition to the standard Shell mode commands:
7205 Describe the features of Emacs' _GDBN__ Mode.
7208 Execute to another source line, like the _GDBN__ @code{step} command; also
7209 update the display window to show the current file and location.
7212 Execute to next source line in this function, skipping all function
7213 calls, like the _GDBN__ @code{next} command. Then update the display window
7214 to show the current file and location.
7217 Execute one instruction, like the _GDBN__ @code{stepi} command; update
7218 display window accordingly.
7221 Execute to next instruction, using the _GDBN__ @code{nexti} command; update
7222 display window accordingly.
7225 Execute until exit from the selected stack frame, like the _GDBN__
7226 @code{finish} command.
7229 Continue execution of your program, like the _GDBN__ @code{continue}
7232 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
7235 Go up the number of frames indicated by the numeric argument
7236 (@pxref{Arguments, , Numeric Arguments, emacs, The GNU Emacs Manual}),
7237 like the _GDBN__ @code{up} command.
7239 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
7242 Go down the number of frames indicated by the numeric argument, like the
7243 _GDBN__ @code{down} command.
7245 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
7248 Read the number where the cursor is positioned, and insert it at the end
7249 of the _GDBN__ I/O buffer. For example, if you wish to disassemble code
7250 around an address that was displayed earlier, type @kbd{disassemble};
7251 then move the cursor to the address display, and pick up the
7252 argument for @code{disassemble} by typing @kbd{C-x &}.
7254 You can customize this further on the fly by defining elements of the list
7255 @code{gdb-print-command}; once it is defined, you can format or
7256 otherwise process numbers picked up by @kbd{C-x &} before they are
7257 inserted. A numeric argument to @kbd{C-x &} will both indicate that you
7258 wish special formatting, and act as an index to pick an element of the
7259 list. If the list element is a string, the number to be inserted is
7260 formatted using the Emacs function @code{format}; otherwise the number
7261 is passed as an argument to the corresponding list element.
7264 In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
7265 tells _GDBN__ to set a breakpoint on the source line point is on.
7267 If you accidentally delete the source-display buffer, an easy way to get
7268 it back is to type the command @code{f} in the _GDBN__ buffer, to
7269 request a frame display; when you run under Emacs, this will recreate
7270 the source buffer if necessary to show you the context of the current
7273 The source files displayed in Emacs are in ordinary Emacs buffers
7274 which are visiting the source files in the usual way. You can edit
7275 the files with these buffers if you wish; but keep in mind that _GDBN__
7276 communicates with Emacs in terms of line numbers. If you add or
7277 delete lines from the text, the line numbers that _GDBN__ knows will cease
7278 to correspond properly to the code.
7280 @c The following dropped because Epoch is nonstandard. Reactivate
7281 @c if/when v19 does something similar. ---pesch@cygnus.com 19dec1990
7283 @kindex emacs epoch environment
7287 Version 18 of Emacs has a built-in window system called the @code{epoch}
7288 environment. Users of this environment can use a new command,
7289 @code{inspect} which performs identically to @code{print} except that
7290 each value is printed in its own window.
7296 @chapter Using _GDBN__ with Energize
7299 The Energize Programming System is an integrated development environment
7300 that includes a point-and-click interface to many programming tools.
7301 When you use _GDBN__ in this environment, you can use the standard
7302 Energize graphical interface to drive _GDBN__; you can also, if you
7303 choose, type _GDBN__ commands as usual in a debugging window. Even if
7304 you use the graphical interface, the debugging window (which uses Emacs,
7305 and resembles the standard Emacs interface to _GDBN__) displays the
7306 equivalent commands, so that the history of your debugging session is
7309 When Energize starts up a _GDBN__ session, it uses one of the
7310 command-line options @samp{-energize} or @samp{-cadillac} (``cadillac''
7311 is the name of the communications protocol used by the Energize system).
7312 This option makes _GDBN__ run as one of the tools in the Energize Tool
7313 Set: it sends all output to the Energize kernel, and accept input from
7316 See the user manual for the Energize Programming System for
7317 information on how to use the Energize graphical interface and the other
7318 development tools that Energize integrates with _GDBN__.
7323 @chapter Reporting Bugs in _GDBN__
7324 @cindex Bugs in _GDBN__
7325 @cindex Reporting Bugs in _GDBN__
7327 Your bug reports play an essential role in making _GDBN__ reliable.
7329 Reporting a bug may help you by bringing a solution to your problem, or it
7330 may not. But in any case the principal function of a bug report is to help
7331 the entire community by making the next version of _GDBN__ work better. Bug
7332 reports are your contribution to the maintenance of _GDBN__.
7334 In order for a bug report to serve its purpose, you must include the
7335 information that enables us to fix the bug.
7338 * Bug Criteria:: Have You Found a Bug?
7339 * Bug Reporting:: How to Report Bugs
7343 @section Have You Found a Bug?
7344 @cindex Bug Criteria
7346 If you are not sure whether you have found a bug, here are some guidelines:
7350 @cindex Fatal Signal
7352 If the debugger gets a fatal signal, for any input whatever, that is a
7353 _GDBN__ bug. Reliable debuggers never crash.
7356 @cindex error on Valid Input
7357 If _GDBN__ produces an error message for valid input, that is a bug.
7360 @cindex Invalid Input
7361 If _GDBN__ does not produce an error message for invalid input,
7362 that is a bug. However, you should note that your idea of
7363 ``invalid input'' might be our idea of ``an extension'' or ``support
7364 for traditional practice''.
7367 If you are an experienced user of debugging tools, your suggestions
7368 for improvement of _GDBN__ are welcome in any case.
7372 @section How to Report Bugs
7374 @cindex _GDBN__ Bugs, Reporting
7376 A number of companies and individuals offer support for GNU products.
7377 If you obtained _GDBN__ from a support organization, we recommend you
7378 contact that organization first.
7380 Contact information for many support companies and individuals is
7381 available in the file @file{etc/SERVICE} in the GNU Emacs distribution.
7383 In any event, we also recommend that you send bug reports for _GDBN__ to one
7387 bug-gdb@@prep.ai.mit.edu
7388 @{ucbvax|mit-eddie|uunet@}!prep.ai.mit.edu!bug-gdb
7391 @strong{Do not send bug reports to @samp{info-gdb}, or to
7392 @samp{help-gdb}, or to any newsgroups.} Most users of _GDBN__ do not want to
7393 receive bug reports. Those that do, have arranged to receive @samp{bug-gdb}.
7395 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
7396 serves as a repeater. The mailing list and the newsgroup carry exactly
7397 the same messages. Often people think of posting bug reports to the
7398 newsgroup instead of mailing them. This appears to work, but it has one
7399 problem which can be crucial: a newsgroup posting often lacks a mail
7400 path back to the sender. Thus, if we need to ask for more information,
7401 we may be unable to reach you. For this reason, it is better to send
7402 bug reports to the mailing list.
7404 As a last resort, send bug reports on paper to:
7408 Free Software Foundation
7413 The fundamental principle of reporting bugs usefully is this:
7414 @strong{report all the facts}. If you are not sure whether to state a
7415 fact or leave it out, state it!
7417 Often people omit facts because they think they know what causes the
7418 problem and assume that some details do not matter. Thus, you might
7419 assume that the name of the variable you use in an example does not matter.
7420 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
7421 stray memory reference which happens to fetch from the location where that
7422 name is stored in memory; perhaps, if the name were different, the contents
7423 of that location would fool the debugger into doing the right thing despite
7424 the bug. Play it safe and give a specific, complete example. That is the
7425 easiest thing for you to do, and the most helpful.
7427 Keep in mind that the purpose of a bug report is to enable us to fix
7428 the bug if it is new to us. It is not as important as what happens if
7429 the bug is already known. Therefore, always write your bug reports on
7430 the assumption that the bug has not been reported previously.
7432 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7433 bell?'' Those bug reports are useless, and we urge everyone to
7434 @emph{refuse to respond to them} except to chide the sender to report
7437 To enable us to fix the bug, you should include all these things:
7441 The version of _GDBN__. _GDBN__ announces it if you start with no
7442 arguments; you can also print it at any time using @code{show version}.
7444 Without this, we will not know whether there is any point in looking for
7445 the bug in the current version of _GDBN__.
7448 The type of machine you are using, and the operating system name and
7452 What compiler (and its version) was used to compile _GDBN__---e.g.
7456 What compiler (and its version) was used to compile the program you
7457 are debugging---e.g. ``_GCC__-2.0''.
7460 The command arguments you gave the compiler to compile your example and
7461 observe the bug. For example, did you use @samp{-O}? To guarantee
7462 you will not omit something important, list them all. A copy of the
7463 Makefile (or the output from make) is sufficient.
7465 If we were to try to guess the arguments, we would probably guess wrong
7466 and then we might not encounter the bug.
7469 A complete input script, and all necessary source files, that will
7473 A description of what behavior you observe that you believe is
7474 incorrect. For example, ``It gets a fatal signal.''
7476 Of course, if the bug is that _GDBN__ gets a fatal signal, then we will
7477 certainly notice it. But if the bug is incorrect output, we might not
7478 notice unless it is glaringly wrong. We are human, after all. You
7479 might as well not give us a chance to make a mistake.
7481 Even if the problem you experience is a fatal signal, you should still
7482 say so explicitly. Suppose something strange is going on, such as,
7483 your copy of _GDBN__ is out of synch, or you have encountered a
7484 bug in the C library on your system. (This has happened!) Your copy
7485 might crash and ours would not. If you told us to expect a crash,
7486 then when ours fails to crash, we would know that the bug was not
7487 happening for us. If you had not told us to expect a crash, then we
7488 would not be able to draw any conclusion from our observations.
7491 If you wish to suggest changes to the _GDBN__ source, send us context
7492 diffs. If you even discuss something in the _GDBN__ source, refer to
7493 it by context, not by line number.
7495 The line numbers in our development sources will not match those in your
7496 sources. Your line numbers would convey no useful information to us.
7499 Here are some things that are not necessary:
7503 A description of the envelope of the bug.
7505 Often people who encounter a bug spend a lot of time investigating
7506 which changes to the input file will make the bug go away and which
7507 changes will not affect it.
7509 This is often time consuming and not very useful, because the way we
7510 will find the bug is by running a single example under the debugger
7511 with breakpoints, not by pure deduction from a series of examples.
7512 We recommend that you save your time for something else.
7514 Of course, if you can find a simpler example to report @emph{instead}
7515 of the original one, that is a convenience for us. Errors in the
7516 output will be easier to spot, running under the debugger will take
7519 However, simplification is not vital; if you do not want to do this,
7520 report the bug anyway and send us the entire test case you used.
7523 A patch for the bug.
7525 A patch for the bug does help us if it is a good one. But do not omit
7526 the necessary information, such as the test case, on the assumption that
7527 a patch is all we need. We might see problems with your patch and decide
7528 to fix the problem another way, or we might not understand it at all.
7530 Sometimes with a program as complicated as _GDBN__ it is very hard to
7531 construct an example that will make the program follow a certain path
7532 through the code. If you do not send us the example, we will not be able
7533 to construct one, so we will not be able to verify that the bug is fixed.
7535 And if we cannot understand what bug you are trying to fix, or why your
7536 patch should be an improvement, we will not install it. A test case will
7537 help us to understand.
7540 A guess about what the bug is or what it depends on.
7542 Such guesses are usually wrong. Even we cannot guess right about such
7543 things without first using the debugger to find the facts.
7546 @c Note: no need to update nodes for rdl-apps.texi since it appears
7547 @c *only* in the TeX version of the manual.
7548 @c Note: eventually, make a cross reference to the readline Info nodes.
7550 @c appendices describing GNU readline. Distributed with readline code.
7551 @include rluser.texinfo
7552 @include inc-hist.texi
7555 _if__(_GENERIC__||!_H8__)
7556 @node Renamed Commands
7557 @appendix Renamed Commands
7559 The following commands were renamed in GDB 4, in order to make the
7560 command set as a whole more consistent and easier to use and remember:
7563 @kindex delete environment
7564 @kindex info copying
7565 @kindex info convenience
7566 @kindex info directories
7567 @kindex info editing
7568 @kindex info history
7569 @kindex info targets
7571 @kindex info version
7572 @kindex info warranty
7573 @kindex set addressprint
7574 @kindex set arrayprint
7575 @kindex set prettyprint
7576 @kindex set screen-height
7577 @kindex set screen-width
7578 @kindex set unionprint
7579 @kindex set vtblprint
7580 @kindex set demangle
7581 @kindex set asm-demangle
7582 @kindex set sevenbit-strings
7583 @kindex set array-max
7585 @kindex set history write
7586 @kindex show addressprint
7587 @kindex show arrayprint
7588 @kindex show prettyprint
7589 @kindex show screen-height
7590 @kindex show screen-width
7591 @kindex show unionprint
7592 @kindex show vtblprint
7593 @kindex show demangle
7594 @kindex show asm-demangle
7595 @kindex show sevenbit-strings
7596 @kindex show array-max
7597 @kindex show caution
7598 @kindex show history write
7603 @c END TEXI2ROFF-KILL
7605 OLD COMMAND NEW COMMAND
7607 --------------- -------------------------------
7608 @c END TEXI2ROFF-KILL
7609 add-syms add-symbol-file
7610 delete environment unset environment
7611 info convenience show convenience
7612 info copying show copying
7613 info directories show directories
7614 info editing show commands
7615 info history show values
7616 info targets help target
7617 info values show values
7618 info version show version
7619 info warranty show warranty
7620 set/show addressprint set/show print address
7621 set/show array-max set/show print elements
7622 set/show arrayprint set/show print array
7623 set/show asm-demangle set/show print asm-demangle
7624 set/show caution set/show confirm
7625 set/show demangle set/show print demangle
7626 set/show history write set/show history save
7627 set/show prettyprint set/show print pretty
7628 set/show screen-height set/show height
7629 set/show screen-width set/show width
7630 set/show sevenbit-strings set/show print sevenbit-strings
7631 set/show unionprint set/show print union
7632 set/show vtblprint set/show print vtbl
7634 unset [No longer an alias for delete]
7640 \vskip \parskip\vskip \baselineskip
7641 \halign{\tt #\hfil &\qquad#&\tt #\hfil\cr
7642 {\bf Old Command} &&{\bf New Command}\cr
7643 add-syms &&add-symbol-file\cr
7644 delete environment &&unset environment\cr
7645 info convenience &&show convenience\cr
7646 info copying &&show copying\cr
7647 info directories &&show directories \cr
7648 info editing &&show commands\cr
7649 info history &&show values\cr
7650 info targets &&help target\cr
7651 info values &&show values\cr
7652 info version &&show version\cr
7653 info warranty &&show warranty\cr
7654 set{\rm / }show addressprint &&set{\rm / }show print address\cr
7655 set{\rm / }show array-max &&set{\rm / }show print elements\cr
7656 set{\rm / }show arrayprint &&set{\rm / }show print array\cr
7657 set{\rm / }show asm-demangle &&set{\rm / }show print asm-demangle\cr
7658 set{\rm / }show caution &&set{\rm / }show confirm\cr
7659 set{\rm / }show demangle &&set{\rm / }show print demangle\cr
7660 set{\rm / }show history write &&set{\rm / }show history save\cr
7661 set{\rm / }show prettyprint &&set{\rm / }show print pretty\cr
7662 set{\rm / }show screen-height &&set{\rm / }show height\cr
7663 set{\rm / }show screen-width &&set{\rm / }show width\cr
7664 set{\rm / }show sevenbit-strings &&set{\rm / }show print sevenbit-strings\cr
7665 set{\rm / }show unionprint &&set{\rm / }show print union\cr
7666 set{\rm / }show vtblprint &&set{\rm / }show print vtbl\cr
7668 unset &&\rm(No longer an alias for delete)\cr
7671 @c END TEXI2ROFF-KILL
7672 _fi__(_GENERIC__||!_H8__)
7674 @node Formatting Documentation
7675 @appendix Formatting the Documentation
7677 @cindex GDB reference card
7678 @cindex reference card
7679 The GDB 4 release includes an already-formatted reference card, ready
7680 for printing with PostScript or GhostScript, in the @file{gdb}
7681 subdirectory of the main source directory---in
7682 @file{gdb-_GDB_VN__/gdb/refcard.ps} of the version _GDB_VN__ release.
7683 If you can use PostScript or GhostScript with your printer, you can
7684 print the reference card immediately with @file{refcard.ps}.
7686 The release also includes the source for the reference card. You
7687 can format it, using @TeX{}, by typing:
7693 The GDB reference card is designed to print in landscape mode on US
7694 ``letter'' size paper; that is, on a sheet 11 inches wide by 8.5 inches
7695 high. You will need to specify this form of printing as an option to
7696 your @sc{dvi} output program.
7698 @cindex documentation
7700 All the documentation for GDB comes as part of the machine-readable
7701 distribution. The documentation is written in Texinfo format, which is
7702 a documentation system that uses a single source file to produce both
7703 on-line information and a printed manual. You can use one of the Info
7704 formatting commands to create the on-line version of the documentation
7705 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
7707 GDB includes an already formatted copy of the on-line Info version of
7708 this manual in the @file{gdb} subdirectory. The main Info file is
7709 @file{gdb-@var{version-number}/gdb/gdb.info}, and it refers to
7710 subordinate files matching @samp{gdb.info*} in the same directory. If
7711 necessary, you can print out these files, or read them with any editor;
7712 but they are easier to read using the @code{info} subsystem in GNU Emacs
7713 or the standalone @code{info} program, available as part of the GNU
7714 Texinfo distribution.
7716 If you want to format these Info files yourself, you need one of the
7717 Info formatting programs, such as @code{texinfo-format-buffer} or
7720 If you have @code{makeinfo} installed, and are in the top level GDB
7721 source directory (@file{gdb-_GDB_VN__}, in the case of version _GDB_VN__), you can
7722 make the Info file by typing:
7729 If you want to typeset and print copies of this manual, you need
7730 @TeX{}, a printing program such as @code{lpr}, and @file{texinfo.tex},
7731 the Texinfo definitions file.
7733 @TeX{} is typesetting program; it does not print files directly, but
7734 produces output files called @sc{dvi} files. To print a typeset
7735 document, you need a program to print @sc{dvi} files. If your system
7736 has @TeX{} installed, chances are it has such a program. The precise
7737 command to use depends on your system; @kbd{lpr -d} is common; another
7738 is @kbd{dvips}. The @sc{dvi} print command may require a file name
7739 without any extension or a @samp{.dvi} extension.
7741 @TeX{} also requires a macro definitions file called
7742 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
7743 written in Texinfo format. On its own, @TeX{} cannot read, much less
7744 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
7745 and is located in the @file{gdb-@var{version-number}/texinfo}
7748 If you have @TeX{} and a @sc{dvi} printer program installed, you can
7749 typeset and print this manual. First switch to the the @file{gdb}
7750 subdirectory of the main source directory (for example, to
7751 @file{gdb-_GDB_VN__/gdb}) and then type:
7757 @node Installing GDB
7758 @appendix Installing GDB
7759 @cindex configuring GDB
7760 @cindex installation
7763 @c irrelevant in info file; it's as current as the code it lives with.
7765 @emph{Warning:} These installation instructions are current as of
7766 GDB version _GDB_VN__. If you're installing a more recent release
7767 of GDB, we may have improved the installation procedures since
7768 printing this manual; see the @file{README} file included in your
7769 release for the most recent instructions.
7773 GDB comes with a @code{configure} script that automates the process
7774 of preparing GDB for installation; you can then use @code{make} to
7777 The GDB distribution includes all the source code you need for GDB in
7778 a single directory, whose name is usually composed by appending the
7779 version number to @samp{gdb}.
7781 For example, the GDB version _GDB_VN__ distribution is in the @file{gdb-_GDB_VN__}
7782 directory. That directory contains:
7785 @item gdb-_GDB_VN__/configure @r{(and supporting files)}
7786 script for configuring GDB and all its supporting libraries.
7788 @item gdb-_GDB_VN__/gdb
7789 the source specific to GDB itself
7791 @item gdb-_GDB_VN__/bfd
7792 source for the Binary File Descriptor library
7794 @item gdb-_GDB_VN__/include
7797 @item gdb-_GDB_VN__/libiberty
7798 source for the @samp{-liberty} free software library
7800 @item gdb-_GDB_VN__/readline
7801 source for the GNU command-line interface
7803 @item gdb-_GDB_VN__/glob
7804 source for the GNU filename pattern-matching subroutine
7806 @item gdb-_GDB_VN__/mmalloc
7807 source for the GNU memory-mapped malloc package
7810 The simplest way to configure and build GDB is to run @code{configure}
7811 from the @file{gdb-@var{version-number}} source directory, which in
7812 this example is the @file{gdb-_GDB_VN__} directory.
7814 First switch to the @file{gdb-@var{version-number}} source directory
7815 if you are not already in it; then run @code{configure}. Pass the
7816 identifier for the platform on which GDB will run as an
7823 ./configure @var{host}
7828 where @var{host} is an identifier such as @samp{sun4} or
7829 @samp{decstation}, that identifies the platform where GDB will run.
7831 Running @samp{configure @var{host}} followed by @code{make} builds the
7832 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
7833 libraries, then @code{gdb} itself. The configured source files, and the
7834 binaries, are left in the corresponding source directories.
7836 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
7837 system does not recognize this automatically when you run a different
7838 shell, you may need to run @code{sh} on it explicitly:
7841 sh configure @var{host}
7844 If you run @code{configure} from a directory that contains source
7845 directories for multiple libraries or programs, such as the
7846 @file{gdb-_GDB_VN__} source directory for version _GDB_VN__, @code{configure}
7847 creates configuration files for every directory level underneath (unless
7848 you tell it not to, with the @samp{--norecursion} option).
7850 You can run the @code{configure} script from any of the
7851 subordinate directories in the GDB distribution, if you only want to
7852 configure that subdirectory; but be sure to specify a path to it.
7854 For example, with version _GDB_VN__, type the following to configure only
7855 the @code{bfd} subdirectory:
7859 cd gdb-_GDB_VN__/bfd
7860 ../configure @var{host}
7864 You can install @code{_GDBP__} anywhere; it has no hardwired paths.
7865 However, you should make sure that the shell on your path (named by
7866 the @samp{SHELL} environment variable) is publicly readable. Remember
7867 that GDB uses the shell to start your program---some systems refuse to
7868 let GDB debug child processes whose programs are not readable.
7871 * Separate Objdir:: Compiling GDB in another directory
7872 * Config Names:: Specifying names for hosts and targets
7873 * configure Options:: Summary of options for configure
7876 @node Separate Objdir
7877 @section Compiling GDB in Another Directory
7879 If you want to run GDB versions for several host or target machines,
7880 you'll need a different @code{gdb} compiled for each combination of
7881 host and target. @code{configure} is designed to make this easy by
7882 allowing you to generate each configuration in a separate subdirectory,
7883 rather than in the source directory. If your @code{make} program
7884 handles the @samp{VPATH} feature (GNU @code{make} does), running
7885 @code{make} in each of these directories then builds the @code{gdb}
7886 program specified there.
7888 To build @code{gdb} in a separate directory, run @code{configure}
7889 with the @samp{--srcdir} option to specify where to find the source.
7890 (You'll also need to specify a path to find @code{configure}
7891 itself from your working directory. If the path to @code{configure}
7892 would be the same as the argument to @samp{--srcdir}, you can leave out
7893 the @samp{--srcdir} option; it will be assumed.)
7895 For example, with version _GDB_VN__, you can build GDB in a separate
7896 directory for a Sun 4 like this:
7903 ../gdb-_GDB_VN__/configure sun4
7908 When @code{configure} builds a configuration using a remote source
7909 directory, it creates a tree for the binaries with the same structure
7910 (and using the same names) as the tree under the source directory. In
7911 the example, you'd find the Sun 4 library @file{libiberty.a} in the
7912 directory @file{gdb-sun4/libiberty}, and GDB itself in
7913 @file{gdb-sun4/gdb}.
7915 One popular reason to build several GDB configurations in separate
7916 directories is to configure GDB for cross-compiling (where GDB
7917 runs on one machine---the host---while debugging programs that run on
7918 another machine---the target). You specify a cross-debugging target by
7919 giving the @samp{--target=@var{target}} option to @code{configure}.
7921 When you run @code{make} to build a program or library, you must run
7922 it in a configured directory---whatever directory you were in when you
7923 called @code{configure} (or one of its subdirectories).
7925 The @code{Makefile} generated by @code{configure} for each source
7926 directory also runs recursively. If you type @code{make} in a source
7927 directory such as @file{gdb-_GDB_VN__} (or in a separate configured
7928 directory configured with @samp{--srcdir=@var{path}/gdb-_GDB_VN__}), you
7929 will build all the required libraries, then build GDB.
7931 When you have multiple hosts or targets configured in separate
7932 directories, you can run @code{make} on them in parallel (for example,
7933 if they are NFS-mounted on each of the hosts); they will not interfere
7937 @section Specifying Names for Hosts and Targets
7939 The specifications used for hosts and targets in the @code{configure}
7940 script are based on a three-part naming scheme, but some short predefined
7941 aliases are also supported. The full naming scheme encodes three pieces
7942 of information in the following pattern:
7945 @var{architecture}-@var{vendor}-@var{os}
7948 For example, you can use the alias @code{sun4} as a @var{host} argument
7949 or in a @code{--target=@var{target}} option, but the equivalent full name
7950 is @samp{sparc-sun-sunos4}.
7952 The @code{configure} script accompanying GDB does not provide
7953 any query facility to list all supported host and target names or
7954 aliases. @code{configure} calls the Bourne shell script
7955 @code{config.sub} to map abbreviations to full names; you can read the
7956 script, if you wish, or you can use it to test your guesses on
7957 abbreviations---for example:
7960 % sh config.sub sun4
7962 % sh config.sub sun3
7964 % sh config.sub decstation
7966 % sh config.sub hp300bsd
7968 % sh config.sub i386v
7970 % sh config.sub i786v
7971 Invalid configuration `i786v': machine `i786v' not recognized
7975 @code{config.sub} is also distributed in the GDB source
7976 directory (@file{gdb-_GDB_VN__}, for version _GDB_VN__).
7978 @node configure Options
7979 @section @code{configure} Options
7981 Here is a summary of the @code{configure} options and arguments that
7982 are most often useful for building _GDBN__. @code{configure} also has
7983 several other options not listed here. @inforef{What Configure
7984 Does,,configure.info}, for a full explanation of @code{configure}.
7985 @c FIXME: Would this be more, or less, useful as an xref (ref to printed
7986 @c manual in the printed manual, ref to info file only from the info file)?
7989 configure @r{[}--help@r{]}
7990 @r{[}--prefix=@var{dir}@r{]}
7991 @r{[}--srcdir=@var{path}@r{]}
7992 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
7993 @r{[}--target=@var{target}@r{]} @var{host}
7997 You may introduce options with a single @samp{-} rather than
7998 @samp{--} if you prefer; but you may abbreviate option names if you use
8003 Display a quick summary of how to invoke @code{configure}.
8005 @item -prefix=@var{dir}
8006 Configure the source to install programs and files under directory
8009 @item --srcdir=@var{path}
8010 @strong{Warning: using this option requires GNU @code{make}, or another
8011 @code{make} that implements the @code{VPATH} feature.}@*
8012 Use this option to make configurations in directories separate from the
8013 GDB source directories. Among other things, you can use this to
8014 build (or maintain) several configurations simultaneously, in separate
8015 directories. @code{configure} writes configuration specific files in
8016 the current directory, but arranges for them to use the source in the
8017 directory @var{path}. @code{configure} will create directories under
8018 the working directory in parallel to the source directories below
8022 Configure only the directory level where @code{configure} is executed; do not
8023 propagate configuration to subdirectories.
8026 Remove the configuration that the other arguments specify.
8028 @c This does not work (yet if ever). FIXME.
8029 @c @item --parse=@var{lang} @dots{}
8030 @c Configure the GDB expression parser to parse the listed languages.
8031 @c @samp{all} configures GDB for all supported languages. To get a
8032 @c list of all supported languages, omit the argument. Without this
8033 @c option, GDB is configured to parse all supported languages.
8035 @item --target=@var{target}
8036 Configure GDB for cross-debugging programs running on the specified
8037 @var{target}. Without this option, GDB is configured to debug
8038 programs that run on the same machine (@var{host}) as GDB itself.
8040 There is no convenient way to generate a list of all available targets.
8042 @item @var{host} @dots{}
8043 Configure GDB to run on the specified @var{host}.
8045 There is no convenient way to generate a list of all available hosts.
8049 @code{configure} accepts other options, for compatibility with
8050 configuring other GNU tools recursively; but these are the only
8051 options that affect GDB or its supporting libraries.
8054 @unnumbered GNU GENERAL PUBLIC LICENSE
8055 @center Version 2, June 1991
8058 Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc.
8059 675 Mass Ave, Cambridge, MA 02139, USA
8061 Everyone is permitted to copy and distribute verbatim copies
8062 of this license document, but changing it is not allowed.
8065 @unnumberedsec Preamble
8067 The licenses for most software are designed to take away your
8068 freedom to share and change it. By contrast, the GNU General Public
8069 License is intended to guarantee your freedom to share and change free
8070 software---to make sure the software is free for all its users. This
8071 General Public License applies to most of the Free Software
8072 Foundation's software and to any other program whose authors commit to
8073 using it. (Some other Free Software Foundation software is covered by
8074 the GNU Library General Public License instead.) You can apply it to
8077 When we speak of free software, we are referring to freedom, not
8078 price. Our General Public Licenses are designed to make sure that you
8079 have the freedom to distribute copies of free software (and charge for
8080 this service if you wish), that you receive source code or can get it
8081 if you want it, that you can change the software or use pieces of it
8082 in new free programs; and that you know you can do these things.
8084 To protect your rights, we need to make restrictions that forbid
8085 anyone to deny you these rights or to ask you to surrender the rights.
8086 These restrictions translate to certain responsibilities for you if you
8087 distribute copies of the software, or if you modify it.
8089 For example, if you distribute copies of such a program, whether
8090 gratis or for a fee, you must give the recipients all the rights that
8091 you have. You must make sure that they, too, receive or can get the
8092 source code. And you must show them these terms so they know their
8095 We protect your rights with two steps: (1) copyright the software, and
8096 (2) offer you this license which gives you legal permission to copy,
8097 distribute and/or modify the software.
8099 Also, for each author's protection and ours, we want to make certain
8100 that everyone understands that there is no warranty for this free
8101 software. If the software is modified by someone else and passed on, we
8102 want its recipients to know that what they have is not the original, so
8103 that any problems introduced by others will not reflect on the original
8104 authors' reputations.
8106 Finally, any free program is threatened constantly by software
8107 patents. We wish to avoid the danger that redistributors of a free
8108 program will individually obtain patent licenses, in effect making the
8109 program proprietary. To prevent this, we have made it clear that any
8110 patent must be licensed for everyone's free use or not licensed at all.
8112 The precise terms and conditions for copying, distribution and
8113 modification follow.
8116 @unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
8119 @center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
8124 This License applies to any program or other work which contains
8125 a notice placed by the copyright holder saying it may be distributed
8126 under the terms of this General Public License. The ``Program'', below,
8127 refers to any such program or work, and a ``work based on the Program''
8128 means either the Program or any derivative work under copyright law:
8129 that is to say, a work containing the Program or a portion of it,
8130 either verbatim or with modifications and/or translated into another
8131 language. (Hereinafter, translation is included without limitation in
8132 the term ``modification''.) Each licensee is addressed as ``you''.
8134 Activities other than copying, distribution and modification are not
8135 covered by this License; they are outside its scope. The act of
8136 running the Program is not restricted, and the output from the Program
8137 is covered only if its contents constitute a work based on the
8138 Program (independent of having been made by running the Program).
8139 Whether that is true depends on what the Program does.
8142 You may copy and distribute verbatim copies of the Program's
8143 source code as you receive it, in any medium, provided that you
8144 conspicuously and appropriately publish on each copy an appropriate
8145 copyright notice and disclaimer of warranty; keep intact all the
8146 notices that refer to this License and to the absence of any warranty;
8147 and give any other recipients of the Program a copy of this License
8148 along with the Program.
8150 You may charge a fee for the physical act of transferring a copy, and
8151 you may at your option offer warranty protection in exchange for a fee.
8154 You may modify your copy or copies of the Program or any portion
8155 of it, thus forming a work based on the Program, and copy and
8156 distribute such modifications or work under the terms of Section 1
8157 above, provided that you also meet all of these conditions:
8161 You must cause the modified files to carry prominent notices
8162 stating that you changed the files and the date of any change.
8165 You must cause any work that you distribute or publish, that in
8166 whole or in part contains or is derived from the Program or any
8167 part thereof, to be licensed as a whole at no charge to all third
8168 parties under the terms of this License.
8171 If the modified program normally reads commands interactively
8172 when run, you must cause it, when started running for such
8173 interactive use in the most ordinary way, to print or display an
8174 announcement including an appropriate copyright notice and a
8175 notice that there is no warranty (or else, saying that you provide
8176 a warranty) and that users may redistribute the program under
8177 these conditions, and telling the user how to view a copy of this
8178 License. (Exception: if the Program itself is interactive but
8179 does not normally print such an announcement, your work based on
8180 the Program is not required to print an announcement.)
8183 These requirements apply to the modified work as a whole. If
8184 identifiable sections of that work are not derived from the Program,
8185 and can be reasonably considered independent and separate works in
8186 themselves, then this License, and its terms, do not apply to those
8187 sections when you distribute them as separate works. But when you
8188 distribute the same sections as part of a whole which is a work based
8189 on the Program, the distribution of the whole must be on the terms of
8190 this License, whose permissions for other licensees extend to the
8191 entire whole, and thus to each and every part regardless of who wrote it.
8193 Thus, it is not the intent of this section to claim rights or contest
8194 your rights to work written entirely by you; rather, the intent is to
8195 exercise the right to control the distribution of derivative or
8196 collective works based on the Program.
8198 In addition, mere aggregation of another work not based on the Program
8199 with the Program (or with a work based on the Program) on a volume of
8200 a storage or distribution medium does not bring the other work under
8201 the scope of this License.
8204 You may copy and distribute the Program (or a work based on it,
8205 under Section 2) in object code or executable form under the terms of
8206 Sections 1 and 2 above provided that you also do one of the following:
8210 Accompany it with the complete corresponding machine-readable
8211 source code, which must be distributed under the terms of Sections
8212 1 and 2 above on a medium customarily used for software interchange; or,
8215 Accompany it with a written offer, valid for at least three
8216 years, to give any third party, for a charge no more than your
8217 cost of physically performing source distribution, a complete
8218 machine-readable copy of the corresponding source code, to be
8219 distributed under the terms of Sections 1 and 2 above on a medium
8220 customarily used for software interchange; or,
8223 Accompany it with the information you received as to the offer
8224 to distribute corresponding source code. (This alternative is
8225 allowed only for noncommercial distribution and only if you
8226 received the program in object code or executable form with such
8227 an offer, in accord with Subsection b above.)
8230 The source code for a work means the preferred form of the work for
8231 making modifications to it. For an executable work, complete source
8232 code means all the source code for all modules it contains, plus any
8233 associated interface definition files, plus the scripts used to
8234 control compilation and installation of the executable. However, as a
8235 special exception, the source code distributed need not include
8236 anything that is normally distributed (in either source or binary
8237 form) with the major components (compiler, kernel, and so on) of the
8238 operating system on which the executable runs, unless that component
8239 itself accompanies the executable.
8241 If distribution of executable or object code is made by offering
8242 access to copy from a designated place, then offering equivalent
8243 access to copy the source code from the same place counts as
8244 distribution of the source code, even though third parties are not
8245 compelled to copy the source along with the object code.
8248 You may not copy, modify, sublicense, or distribute the Program
8249 except as expressly provided under this License. Any attempt
8250 otherwise to copy, modify, sublicense or distribute the Program is
8251 void, and will automatically terminate your rights under this License.
8252 However, parties who have received copies, or rights, from you under
8253 this License will not have their licenses terminated so long as such
8254 parties remain in full compliance.
8257 You are not required to accept this License, since you have not
8258 signed it. However, nothing else grants you permission to modify or
8259 distribute the Program or its derivative works. These actions are
8260 prohibited by law if you do not accept this License. Therefore, by
8261 modifying or distributing the Program (or any work based on the
8262 Program), you indicate your acceptance of this License to do so, and
8263 all its terms and conditions for copying, distributing or modifying
8264 the Program or works based on it.
8267 Each time you redistribute the Program (or any work based on the
8268 Program), the recipient automatically receives a license from the
8269 original licensor to copy, distribute or modify the Program subject to
8270 these terms and conditions. You may not impose any further
8271 restrictions on the recipients' exercise of the rights granted herein.
8272 You are not responsible for enforcing compliance by third parties to
8276 If, as a consequence of a court judgment or allegation of patent
8277 infringement or for any other reason (not limited to patent issues),
8278 conditions are imposed on you (whether by court order, agreement or
8279 otherwise) that contradict the conditions of this License, they do not
8280 excuse you from the conditions of this License. If you cannot
8281 distribute so as to satisfy simultaneously your obligations under this
8282 License and any other pertinent obligations, then as a consequence you
8283 may not distribute the Program at all. For example, if a patent
8284 license would not permit royalty-free redistribution of the Program by
8285 all those who receive copies directly or indirectly through you, then
8286 the only way you could satisfy both it and this License would be to
8287 refrain entirely from distribution of the Program.
8289 If any portion of this section is held invalid or unenforceable under
8290 any particular circumstance, the balance of the section is intended to
8291 apply and the section as a whole is intended to apply in other
8294 It is not the purpose of this section to induce you to infringe any
8295 patents or other property right claims or to contest validity of any
8296 such claims; this section has the sole purpose of protecting the
8297 integrity of the free software distribution system, which is
8298 implemented by public license practices. Many people have made
8299 generous contributions to the wide range of software distributed
8300 through that system in reliance on consistent application of that
8301 system; it is up to the author/donor to decide if he or she is willing
8302 to distribute software through any other system and a licensee cannot
8305 This section is intended to make thoroughly clear what is believed to
8306 be a consequence of the rest of this License.
8309 If the distribution and/or use of the Program is restricted in
8310 certain countries either by patents or by copyrighted interfaces, the
8311 original copyright holder who places the Program under this License
8312 may add an explicit geographical distribution limitation excluding
8313 those countries, so that distribution is permitted only in or among
8314 countries not thus excluded. In such case, this License incorporates
8315 the limitation as if written in the body of this License.
8318 The Free Software Foundation may publish revised and/or new versions
8319 of the General Public License from time to time. Such new versions will
8320 be similar in spirit to the present version, but may differ in detail to
8321 address new problems or concerns.
8323 Each version is given a distinguishing version number. If the Program
8324 specifies a version number of this License which applies to it and ``any
8325 later version'', you have the option of following the terms and conditions
8326 either of that version or of any later version published by the Free
8327 Software Foundation. If the Program does not specify a version number of
8328 this License, you may choose any version ever published by the Free Software
8332 If you wish to incorporate parts of the Program into other free
8333 programs whose distribution conditions are different, write to the author
8334 to ask for permission. For software which is copyrighted by the Free
8335 Software Foundation, write to the Free Software Foundation; we sometimes
8336 make exceptions for this. Our decision will be guided by the two goals
8337 of preserving the free status of all derivatives of our free software and
8338 of promoting the sharing and reuse of software generally.
8341 @heading NO WARRANTY
8348 BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
8349 FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
8350 OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
8351 PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
8352 OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
8353 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS
8354 TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE
8355 PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
8356 REPAIR OR CORRECTION.
8359 IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
8360 WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
8361 REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
8362 INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
8363 OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
8364 TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
8365 YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
8366 PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
8367 POSSIBILITY OF SUCH DAMAGES.
8371 @heading END OF TERMS AND CONDITIONS
8374 @center END OF TERMS AND CONDITIONS
8378 @unnumberedsec Applying These Terms to Your New Programs
8380 If you develop a new program, and you want it to be of the greatest
8381 possible use to the public, the best way to achieve this is to make it
8382 free software which everyone can redistribute and change under these terms.
8384 To do so, attach the following notices to the program. It is safest
8385 to attach them to the start of each source file to most effectively
8386 convey the exclusion of warranty; and each file should have at least
8387 the ``copyright'' line and a pointer to where the full notice is found.
8390 @var{one line to give the program's name and an idea of what it does.}
8391 Copyright (C) 19@var{yy} @var{name of author}
8393 This program is free software; you can redistribute it and/or
8394 modify it under the terms of the GNU General Public License
8395 as published by the Free Software Foundation; either version 2
8396 of the License, or (at your option) any later version.
8398 This program is distributed in the hope that it will be useful,
8399 but WITHOUT ANY WARRANTY; without even the implied warranty of
8400 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
8401 GNU General Public License for more details.
8403 You should have received a copy of the GNU General Public License
8404 along with this program; if not, write to the
8405 Free Software Foundation, Inc., 675 Mass Ave,
8406 Cambridge, MA 02139, USA.
8409 Also add information on how to contact you by electronic and paper mail.
8411 If the program is interactive, make it output a short notice like this
8412 when it starts in an interactive mode:
8415 Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author}
8416 Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
8417 type `show w'. This is free software, and you are welcome
8418 to redistribute it under certain conditions; type `show c'
8422 The hypothetical commands @samp{show w} and @samp{show c} should show
8423 the appropriate parts of the General Public License. Of course, the
8424 commands you use may be called something other than @samp{show w} and
8425 @samp{show c}; they could even be mouse-clicks or menu items---whatever
8428 You should also get your employer (if you work as a programmer) or your
8429 school, if any, to sign a ``copyright disclaimer'' for the program, if
8430 necessary. Here is a sample; alter the names:
8433 Yoyodyne, Inc., hereby disclaims all copyright
8434 interest in the program `Gnomovision'
8435 (which makes passes at compilers) written
8438 @var{signature of Ty Coon}, 1 April 1989
8439 Ty Coon, President of Vice
8442 This General Public License does not permit incorporating your program into
8443 proprietary programs. If your program is a subroutine library, you may
8444 consider it more useful to permit linking proprietary applications with the
8445 library. If this is what you want to do, use the GNU Library General
8446 Public License instead of this License.
8454 % I think something like @colophon should be in texinfo. In the
8456 \long\def\colophon{\hbox to0pt{}\vfill
8457 \centerline{The body of this manual is set in}
8458 \centerline{\fontname\tenrm,}
8459 \centerline{with headings in {\bf\fontname\tenbf}}
8460 \centerline{and examples in {\tt\fontname\tentt}.}
8461 \centerline{{\it\fontname\tenit\/},}
8462 \centerline{{\bf\fontname\tenbf}, and}
8463 \centerline{{\sl\fontname\tensl\/}}
8464 \centerline{are used for emphasis.}\vfill}
8466 % Blame: pesch@cygnus.com, 1991.