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__
179 _if__(_GENERIC__||!_H8__)
181 _fi__(_GENERIC__||!_H8__)
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, Intel 80386, and Sparc remote
325 systems; 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 function
328 vector to mediate access to different targets; if you need to add your
329 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.
701 The command-line options described here are designed
702 to cover a variety of situations; in some environments, some of these
703 options may effectively be unavailable.
706 The most usual way to start _GDBN__ is with one argument,
707 specifying an executable program:
710 _GDBP__ @var{program}
715 You can also start with both an executable program and a core file
719 _GDBP__ @var{program} @var{core}
722 You can, instead, specify a process ID as a second argument, if you want
723 to debug a running process:
726 _GDBP__ @var{program} 1234
730 would attach _GDBN__ to process @code{1234} (unless you also have a file
731 named @file{1234}; _GDBN__ does check for a core file first).
733 Taking advantage of the second command-line argument requires a fairly
734 complete operating system; when you use _GDBN__ as a remote debugger
735 attached to a bare board, there may not be any notion of ``process'',
736 and there is often no way to get a core dump.
740 You can further control how _GDBN__ starts up by using command-line
741 options. _GDBN__ itself can remind you of the options available.
751 to display all available options and briefly describe their use
752 (@samp{_GDBP__ -h} is a shorter equivalent).
754 All options and command line arguments you give are processed
755 in sequential order. The order makes a difference when the
756 @samp{-x} option is used.
760 _include__(gdbinv-m.m4)_dnl__
762 * File Options:: Choosing Files
763 * Mode Options:: Choosing Modes
767 _include__(gdbinv-s.m4)
771 @subsection Choosing Files
774 When _GDBN__ starts, it reads any arguments other than options as
775 specifying an executable file and core file (or process ID). This is
776 the same as if the arguments were specified by the @samp{-se} and
777 @samp{-c} options respectively. (_GDBN__ reads the first argument
778 that does not have an associated option flag as equivalent to the
779 @samp{-se} option followed by that argument; and the second argument
780 that does not have an associated option flag, if any, as equivalent to
781 the @samp{-c} option followed by that argument.)
784 When _GDBN__ starts, it reads any argument other than options as
785 specifying an executable file. This is the same as if the argument was
786 specified by the @samp{-se} option.
789 Many options have both long and short forms; both are shown in the
790 following list. _GDBN__ also recognizes the long forms if you truncate
791 them, so long as enough of the option is present to be unambiguous.
792 (If you prefer, you can flag option arguments with @samp{--} rather
793 than @samp{-}, though we illustrate the more usual convention.)
796 @item -symbols=@var{file}
798 Read symbol table from file @var{file}.
800 @item -exec=@var{file}
802 Use file @var{file} as the executable file to execute when
803 appropriate, and for examining pure data in conjunction with a core
807 Read symbol table from file @var{file} and use it as the executable
811 @item -core=@var{file}
813 Use file @var{file} as a core dump to examine.
816 @item -command=@var{file}
818 Execute _GDBN__ commands from file @var{file}. @xref{Command Files}.
820 @item -directory=@var{directory}
821 @itemx -d @var{directory}
822 Add @var{directory} to the path to search for source files.
827 @emph{Warning: this option depends on operating system facilities that are not
828 supported on all systems.}@*
829 If memory-mapped files are available on your system through the @code{mmap}
830 system call, you can use this option
831 to have _GDBN__ write the symbols from your
832 program into a reusable file in the current directory. If the program you are debugging is
833 called @file{/tmp/fred}, the mapped symbol file will be @file{./fred.syms}.
834 Future _GDBN__ debugging sessions will notice the presence of this file,
835 and will quickly map in symbol information from it, rather than reading
836 the symbol table from the executable program.
838 The @file{.syms} file is specific to the host machine on which _GDBN__ is run.
839 It holds an exact image of _GDBN__'s internal symbol table. It cannot be
840 shared across multiple host platforms.
845 Read each symbol file's entire symbol table immediately, rather than
846 the default, which is to read it incrementally as it is needed.
847 This makes startup slower, but makes future operations faster.
851 The @code{-mapped} and @code{-readnow} options are typically combined in order to
852 build a @file{.syms} file that contains complete symbol information.
853 A simple GDB invocation to do nothing but build a @file{.syms} file for future
857 gdb -batch -nx -mapped -readnow programname
862 @subsection Choosing Modes
864 You can run _GDBN__ in various alternative modes---for example, in
865 batch mode or quiet mode.
870 Do not execute commands from any @file{_GDBINIT__} initialization files.
871 Normally, the commands in these files are executed after all the
872 command options and arguments have been processed.
873 @xref{Command Files}.
877 ``Quiet''. Do not print the introductory and copyright messages. These
878 messages are also suppressed in batch mode.
881 Run in batch mode. Exit with status @code{0} after processing all the command
882 files specified with @samp{-x} (and @file{_GDBINIT__}, if not inhibited).
883 Exit with nonzero status if an error occurs in executing the _GDBN__
884 commands in the command files.
886 Batch mode may be useful for running _GDBN__ as a filter, for example to
887 download and run a program on another computer; in order to make this
888 more useful, the message
891 Program exited normally.
895 (which is ordinarily issued whenever a program running under _GDBN__ control
896 terminates) is not issued when running in batch mode.
898 @item -cd=@var{directory}
899 Run _GDBN__ using @var{directory} as its working directory,
900 instead of the current directory.
903 @item -context @var{authentication}
904 When the Energize programming system starts up _GDBN__, it uses this
905 option to trigger an alternate mode of interaction.
906 @var{authentication} is a pair of numeric codes that identify _GDBN__
907 as a client in the Energize environment. Avoid this option when you run
908 _GDBN__ directly from the command line. See @ref{Energize,,Using
909 _GDBN__ with Energize} for more discussion of using _GDBN__ with Energize.
914 Emacs sets this option when it runs _GDBN__ as a subprocess. It tells _GDBN__
915 to output the full file name and line number in a standard,
916 recognizable fashion each time a stack frame is displayed (which
917 includes each time your program stops). This recognizable format looks
918 like two @samp{\032} characters, followed by the file name, line number
919 and character position separated by colons, and a newline. The
920 Emacs-to-_GDBN__ interface program uses the two @samp{\032} characters as
921 a signal to display the source code for the frame.
923 _if__(_GENERIC__ || !_H8__)
925 Set the line speed (baud rate or bits per second) of any serial
926 interface used by _GDBN__ for remote debugging.
928 @item -tty=@var{device}
929 Run using @var{device} for your program's standard input and output.
930 @c FIXME: kingdon thinks there is more to -tty. Investigate.
931 _fi__(_GENERIC__ || !_H8__)
934 @node Leaving _GDBN__
935 @section Leaving _GDBN__
936 @cindex exiting _GDBN__
942 To exit _GDBN__, use the @code{quit} command (abbreviated @code{q}), or type
943 an end-of-file character (usually @kbd{C-d}).
947 An interrupt (often @kbd{C-c}) will not exit from _GDBN__, but rather
948 will terminate the action of any _GDBN__ command that is in progress and
949 return to _GDBN__ command level. It is safe to type the interrupt
950 character at any time because _GDBN__ does not allow it to take effect
951 until a time when it is safe.
954 If you have been using _GDBN__ to control an attached process or device, you
955 can release it with the @code{detach} command; @pxref{Attach,
956 ,Debugging an Already-Running Process}..
961 @section Shell Commands
963 If you need to execute occasional shell commands during your
964 debugging session, there is no need to leave or suspend _GDBN__; you can
965 just use the @code{shell} command.
968 @item shell @var{command string}
971 Directs _GDBN__ to invoke an inferior shell to execute @var{command
972 string}. If it exists, the environment variable @code{SHELL} is used
973 for the name of the shell to run. Otherwise _GDBN__ uses
977 The utility @code{make} is often needed in development environments.
978 You do not have to use the @code{shell} command for this purpose in _GDBN__:
981 @item make @var{make-args}
984 Causes _GDBN__ to execute an inferior @code{make} program with the specified
985 arguments. This is equivalent to @samp{shell make @var{make-args}}.
990 @chapter _GDBN__ Commands
992 You can abbreviate a _GDBN__ command to the first few letters of the command
993 name, if that abbreviation is unambiguous; and you can repeat certain
994 _GDBN__ commands by typing just @key{RET}. You can also use the @key{TAB}
995 key to get _GDBN__ to fill out the rest of a word in a command (or to
996 show you the alternatives available, if there's more than one possibility).
999 * Command Syntax:: Command Syntax
1000 * Completion:: Command Completion
1001 * Help:: Getting Help
1004 @node Command Syntax
1005 @section Command Syntax
1007 A _GDBN__ command is a single line of input. There is no limit on how long
1008 it can be. It starts with a command name, which is followed by arguments
1009 whose meaning depends on the command name. For example, the command
1010 @code{step} accepts an argument which is the number of times to step,
1011 as in @samp{step 5}. You can also use the @code{step} command with
1012 no arguments. Some command names do not allow any arguments.
1014 @cindex abbreviation
1015 _GDBN__ command names may always be truncated if that abbreviation is
1016 unambiguous. Other possible command abbreviations are listed in the
1017 documentation for individual commands. In some cases, even ambiguous
1018 abbreviations are allowed; for example, @code{s} is specially defined as
1019 equivalent to @code{step} even though there are other commands whose
1020 names start with @code{s}. You can test abbreviations by using them as
1021 arguments to the @code{help} command.
1023 @cindex repeating commands
1025 A blank line as input to _GDBN__ (typing just @key{RET}) means to
1026 repeat the previous command. Certain commands (for example, @code{run})
1027 will not repeat this way; these are commands for which unintentional
1028 repetition might cause trouble and which you are unlikely to want to
1031 The @code{list} and @code{x} commands, when you repeat them with
1032 @key{RET}, construct new arguments rather than repeating
1033 exactly as typed. This permits easy scanning of source or memory.
1035 _GDBN__ can also use @key{RET} in another way: to partition lengthy
1036 output, in a way similar to the common utility @code{more}
1037 (@pxref{Screen Size}). Since it is easy to press one @key{RET} too many
1038 in this situation, _GDBN__ disables command repetition after any command
1039 that generates this sort of display.
1043 A line of input starting with @kbd{#} is a comment; it does nothing.
1044 This is useful mainly in command files (@pxref{Command Files}).
1047 @section Command Completion
1050 @cindex word completion
1051 _GDBN__ can fill in the rest of a word in a command for you, if there's
1052 only one possibility; it can also show you what the valid possibilities
1053 are for the next word in a command, at any time. This works for _GDBN__
1054 commands, _GDBN__ subcommands, and the names of symbols in your program.
1056 Press the @key{TAB} key whenever you want _GDBN__ to fill out the rest
1057 of a word. If there's only one possibility, _GDBN__ will fill in the
1058 word, and wait for you to finish the command (or press @key{RET} to
1059 enter it). For example, if you type
1061 @c FIXME "@key" doesn't distinguish its argument sufficiently to permit
1062 @c complete accuracy in these examples; space introduced for clarity.
1063 @c If texinfo enhancements make it unnecessary, it would be nice to
1064 @c replace " @key" by "@key" in the following...
1066 (_GDBP__) info bre @key{TAB}
1070 _GDBN__ fills in the rest of the word @samp{breakpoints}, since that's
1071 the only @code{info} subcommand beginning with @samp{bre}:
1074 (_GDBP__) info breakpoints
1078 You can either press @key{RET} at this point, to run the @code{info
1079 breakpoints} command, or backspace and enter something else, if
1080 @samp{breakpoints} doesn't look like the command you expected. (If you
1081 were sure you wanted @code{info breakpoints} in the first place, you
1082 might as well just type @key{RET} immediately after @samp{info bre},
1083 to exploit command abbreviations rather than command completion).
1085 If there is more than one possibility for the next word when you press
1086 @key{TAB}, _GDBN__ will sound a bell. You can either supply more
1087 characters and try again, or just press @key{TAB} a second time, and
1088 _GDBN__ will display all the possible completions for that word. For
1089 example, you might want to set a breakpoint on a subroutine whose name
1090 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} _GDBN__
1091 just sounds the bell. Typing @key{TAB} again will display all the
1092 function names in your program that begin with those characters, for
1096 (_GDBP__) b make_ @key{TAB}
1097 @exdent _GDBN__ sounds bell; press @key{TAB} again, to see:
1098 make_a_section_from_file make_environ
1099 make_abs_section make_function_type
1100 make_blockvector make_pointer_type
1101 make_cleanup make_reference_type
1102 make_command make_symbol_completion_list
1107 After displaying the available possibilities, _GDBN__ copies your
1108 partial input (@samp{b make_} in the example) so you can finish the
1111 If you just want to see the list of alternatives in the first place, you
1112 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1113 means @kbd{@key{META} ?}. You can type this either by holding down a
1114 key designated as the @key{META} shift on your keyboard (if there is
1115 one) while typing @kbd{?}, or by typing @key{ESC} followed by @kbd{?}.
1117 @cindex quotes in commands
1118 @cindex completion of quoted strings
1119 Sometimes the string you need, while logically a ``word'', may contain
1120 parentheses or other characters that _GDBN__ normally excludes from its
1121 notion of a word. To permit word completion to work in this situation,
1122 you may enclose words in @code{'} (single quote marks) in _GDBN__ commands.
1124 The most likely situation where you might need this is in typing the
1125 name of a C++ function. This is because C++ allows function overloading
1126 (multiple definitions of the same function, distinguished by argument
1127 type). For example, when you want to set a breakpoint you may need to
1128 distinguish whether you mean the version of @code{name} that takes an
1129 @code{int} parameter, @code{name(int)}, or the version that takes a
1130 @code{float} parameter, @code{name(float)}. To use the word-completion
1131 facilities in this situation, type a single quote @code{'} at the
1132 beginning of the function name. This alerts _GDBN__ that it may need to
1133 consider more information than usual when you press @key{TAB} or
1134 @kbd{M-?} to request word completion:
1137 (_GDBP__) b 'bubble( @key{M-?}
1138 bubble(double,double) bubble(int,int)
1139 (_GDBP__) b 'bubble(
1142 In some cases, _GDBN__ can tell that completing a name will require
1143 quotes. When this happens, _GDBN__ will insert the quote for you (while
1144 completing as much as it can) if you do not type the quote in the first
1148 (_GDBP__) b bub @key{TAB}
1149 @exdent _GDBN__ alters your input line to the following, and rings a bell:
1150 (_GDBP__) b 'bubble(
1154 In general, _GDBN__ can tell that a quote is needed (and inserts it) if
1155 you have not yet started typing the argument list when you ask for
1156 completion on an overloaded symbol.
1160 @section Getting Help
1161 @cindex online documentation
1164 You can always ask _GDBN__ itself for information on its commands, using the
1165 command @code{help}.
1171 You can use @code{help} (abbreviated @code{h}) with no arguments to
1172 display a short list of named classes of commands:
1176 List of classes of commands:
1178 running -- Running the program
1179 stack -- Examining the stack
1180 data -- Examining data
1181 breakpoints -- Making program stop at certain points
1182 files -- Specifying and examining files
1183 status -- Status inquiries
1184 support -- Support facilities
1185 user-defined -- User-defined commands
1186 aliases -- Aliases of other commands
1187 obscure -- Obscure features
1189 Type "help" followed by a class name for a list of
1190 commands in that class.
1191 Type "help" followed by command name for full
1193 Command name abbreviations are allowed if unambiguous.
1197 @item help @var{class}
1198 Using one of the general help classes as an argument, you can get a
1199 list of the individual commands in that class. For example, here is the
1200 help display for the class @code{status}:
1203 (_GDBP__) help status
1208 show -- Generic command for showing things set with "set"
1209 info -- Generic command for printing status
1211 Type "help" followed by command name for full
1213 Command name abbreviations are allowed if unambiguous.
1217 @item help @var{command}
1218 With a command name as @code{help} argument, _GDBN__ will display a
1219 short paragraph on how to use that command.
1222 In addition to @code{help}, you can use the _GDBN__ commands @code{info}
1223 and @code{show} to inquire about the state of your program, or the state
1224 of _GDBN__ itself. Each command supports many topics of inquiry; this
1225 manual introduces each of them in the appropriate context. The listings
1226 under @code{info} and under @code{show} in the Index point to
1227 all the sub-commands. @xref{Index}.
1234 This command (abbreviated @code{i}) is for describing the state of your
1235 program; for example, it can list the arguments given to your program
1236 (@code{info args}), the registers currently in use (@code{info
1237 registers}), or the breakpoints you have set (@code{info breakpoints}).
1238 You can get a complete list of the @code{info} sub-commands with
1239 @w{@code{help info}}.
1243 In contrast, @code{show} is for describing the state of _GDBN__ itself.
1244 You can change most of the things you can @code{show}, by using the
1245 related command @code{set}; for example, you can control what number
1246 system is used for displays with @code{set radix}, or simply inquire
1247 which is currently in use with @code{show radix}.
1250 To display all the settable parameters and their current
1251 values, you can use @code{show} with no arguments; you may also use
1252 @code{info set}. Both commands produce the same display.
1253 @c FIXME: "info set" violates the rule that "info" is for state of
1254 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1255 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1259 Here are three miscellaneous @code{show} subcommands, all of which are
1260 exceptional in lacking corresponding @code{set} commands:
1263 @kindex show version
1264 @cindex version number
1266 Show what version of _GDBN__ is running. You should include this
1267 information in _GDBN__ bug-reports. If multiple versions of _GDBN__ are in
1268 use at your site, you may occasionally want to make sure what version
1269 of _GDBN__ you are running; as _GDBN__ evolves, new commands are introduced,
1270 and old ones may wither away. The version number is also announced
1271 when you start _GDBN__ with no arguments.
1273 @kindex show copying
1275 Display information about permission for copying _GDBN__.
1277 @kindex show warranty
1279 Display the GNU ``NO WARRANTY'' statement.
1283 @chapter Running Programs Under _GDBN__
1285 To debug a program, you must run it under _GDBN__.
1288 * Compilation:: Compiling for Debugging
1289 * Starting:: Starting your Program
1291 * Arguments:: Your Program's Arguments
1292 * Environment:: Your Program's Environment
1293 * Working Directory:: Your Program's Working Directory
1294 * Input/Output:: Your Program's Input and Output
1295 * Attach:: Debugging an Already-Running Process
1296 * Kill Process:: Killing the Child Process
1297 * Process Information:: Additional Process Information
1302 @section Compiling for Debugging
1304 In order to debug a program effectively, you need to generate
1305 debugging information when you compile it. This debugging information
1306 is stored in the object file; it describes the data type of each
1307 variable or function and the correspondence between source line numbers
1308 and addresses in the executable code.
1310 To request debugging information, specify the @samp{-g} option when you run
1313 Many C compilers are unable to handle the @samp{-g} and @samp{-O}
1314 options together. Using those compilers, you cannot generate optimized
1315 executables containing debugging information.
1317 _GCC__, the GNU C compiler, supports @samp{-g} with or without
1318 @samp{-O}, making it possible to debug optimized code. We recommend
1319 that you @emph{always} use @samp{-g} whenever you compile a program.
1320 You may think your program is correct, but there is no sense in pushing
1323 @cindex optimized code, debugging
1324 @cindex debugging optimized code
1325 When you debug a program compiled with @samp{-g -O}, remember that the
1326 optimizer is rearranging your code; the debugger will show you what's
1327 really there. Don't be too surprised when the execution path doesn't
1328 exactly match your source file! An extreme example: if you define a
1329 variable, but never use it, _GDBN__ will never see that
1330 variable---because the compiler optimizes it out of existence.
1332 Some things do not work as well with @samp{-g -O} as with just
1333 @samp{-g}, particularly on machines with instruction scheduling. If in
1334 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
1335 please report it as a bug (including a test case!).
1337 Older versions of the GNU C compiler permitted a variant option
1338 @w{@samp{-gg}} for debugging information. _GDBN__ no longer supports this
1339 format; if your GNU C compiler has this option, do not use it.
1342 @comment As far as I know, there are no cases in which _GDBN__ will
1343 @comment produce strange output in this case. (but no promises).
1344 If your program includes archives made with the @code{ar} program, and
1345 if the object files used as input to @code{ar} were compiled without the
1346 @samp{-g} option and have names longer than 15 characters, _GDBN__ will get
1347 confused reading your program's symbol table. No error message will be
1348 given, but _GDBN__ may behave strangely. The reason for this problem is a
1349 deficiency in the Unix archive file format, which cannot represent file
1350 names longer than 15 characters.
1352 To avoid this problem, compile the archive members with the @samp{-g}
1353 option or use shorter file names. Alternatively, use a version of GNU
1354 @code{ar} dated more recently than August 1989.
1358 @section Starting your Program
1366 Use the @code{run} command to start your program under _GDBN__. You must
1367 first specify the program name
1372 _GDBN__ (@pxref{Invocation, ,Getting In and Out of _GDBN__}), or by using the
1373 @code{file} or @code{exec-file} command (@pxref{Files, ,Commands to
1379 If you are running your program in an execution environment that
1380 supports processes, @code{run} creates an inferior process and makes
1381 that process run your program. (In environments without processes,
1382 @code{run} jumps to the start of your program.)
1384 The execution of a program is affected by certain information it
1385 receives from its superior. _GDBN__ provides ways to specify this
1386 information, which you must do @emph{before} starting your program. (You
1387 can change it after starting your program, but such changes will only affect
1388 your program the next time you start it.) This information may be
1389 divided into four categories:
1392 @item The @emph{arguments.}
1393 Specify the arguments to give your program as the arguments of the
1394 @code{run} command. If a shell is available on your target, the shell
1395 is used to pass the arguments, so that you may use normal conventions
1396 (such as wildcard expansion or variable substitution) in describing
1397 the arguments. In Unix systems, you can control which shell is used
1398 with the @code{SHELL} environment variable. @xref{Arguments, ,Your
1399 Program's Arguments}.
1401 @item The @emph{environment.}
1402 Your program normally inherits its environment from _GDBN__, but you can
1403 use the _GDBN__ commands @code{set environment} and @code{unset
1404 environment} to change parts of the environment that will be given to
1405 your program. @xref{Environment, ,Your Program's Environment}.
1407 @item The @emph{working directory.}
1408 Your program inherits its working directory from _GDBN__. You can set
1409 _GDBN__'s working directory with the @code{cd} command in _GDBN__.
1410 @xref{Working Directory, ,Your Program's Working Directory}.
1412 @item The @emph{standard input and output.}
1413 Your program normally uses the same device for standard input and
1414 standard output as _GDBN__ is using. You can redirect input and output
1415 in the @code{run} command line, or you can use the @code{tty} command to
1416 set a different device for your program.
1417 @xref{Input/Output, ,Your Program's Input and Output}.
1420 @emph{Warning:} While input and output redirection work, you cannot use
1421 pipes to pass the output of the program you are debugging to another
1422 program; if you attempt this, _GDBN__ is likely to wind up debugging the
1427 When you issue the @code{run} command, your program begins to execute
1428 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
1429 of how to arrange for your program to stop. Once your program has
1430 stopped, you may calls functions in your program, using the @code{print}
1431 or @code{call} commands. @xref{Data, ,Examining Data}.
1433 If the modification time of your symbol file has changed since the
1434 last time _GDBN__ read its symbols, _GDBN__ will discard its symbol table and
1435 re-read it. When it does this, _GDBN__ tries to retain your current
1440 @section Your Program's Arguments
1442 @cindex arguments (to your program)
1443 The arguments to your program can be specified by the arguments of the
1444 @code{run} command. They are passed to a shell, which expands wildcard
1445 characters and performs redirection of I/O, and thence to your program.
1446 _GDBN__ uses the shell indicated by your environment variable
1447 @code{SHELL} if it exists; otherwise, _GDBN__ uses @code{/bin/sh}.
1449 @code{run} with no arguments uses the same arguments used by the previous
1450 @code{run}, or those set by the @code{set args} command.
1455 Specify the arguments to be used the next time your program is run. If
1456 @code{set args} has no arguments, @code{run} will execute your program
1457 with no arguments. Once you have run your program with arguments,
1458 using @code{set args} before the next @code{run} is the only way to run
1459 it again without arguments.
1463 Show the arguments to give your program when it is started.
1467 @section Your Program's Environment
1469 @cindex environment (of your program)
1470 The @dfn{environment} consists of a set of environment variables and
1471 their values. Environment variables conventionally record such things as
1472 your user name, your home directory, your terminal type, and your search
1473 path for programs to run. Usually you set up environment variables with
1474 the shell and they are inherited by all the other programs you run. When
1475 debugging, it can be useful to try running your program with a modified
1476 environment without having to start _GDBN__ over again.
1479 @item path @var{directory}
1481 Add @var{directory} to the front of the @code{PATH} environment variable
1482 (the search path for executables), for both _GDBN__ and your program.
1483 You may specify several directory names, separated by @samp{:} or
1484 whitespace. If @var{directory} is already in the path, it is moved to
1485 the front, so it will be searched sooner.
1487 You can use the string @samp{$cwd} to refer to whatever is the current
1488 working directory at the time _GDBN__ searches the path. If you use
1489 @samp{.} instead, it refers to the directory where you executed the
1490 @code{path} command. _GDBN__ fills in the current path where needed in
1491 the @var{directory} argument, before adding it to the search path.
1492 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
1493 @c document that, since repeating it would be a no-op.
1497 Display the list of search paths for executables (the @code{PATH}
1498 environment variable).
1500 @item show environment @r{[}@var{varname}@r{]}
1501 @kindex show environment
1502 Print the value of environment variable @var{varname} to be given to
1503 your program when it starts. If you do not supply @var{varname},
1504 print the names and values of all environment variables to be given to
1505 your program. You can abbreviate @code{environment} as @code{env}.
1507 @item set environment @var{varname} @r{[}=@r{]} @var{value}
1508 @kindex set environment
1509 Sets environment variable @var{varname} to @var{value}. The value
1510 changes for your program only, not for _GDBN__ itself. @var{value} may
1511 be any string; the values of environment variables are just strings, and
1512 any interpretation is supplied by your program itself. The @var{value}
1513 parameter is optional; if it is eliminated, the variable is set to a
1515 @c "any string" here does not include leading, trailing
1516 @c blanks. Gnu asks: does anyone care?
1518 For example, this command:
1525 tells a Unix program, when subsequently run, that its user is named
1526 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
1527 are not actually required.)
1529 @item unset environment @var{varname}
1530 @kindex unset environment
1531 Remove variable @var{varname} from the environment to be passed to your
1532 program. This is different from @samp{set env @var{varname} =};
1533 @code{unset environment} removes the variable from the environment,
1534 rather than assigning it an empty value.
1537 @node Working Directory
1538 @section Your Program's Working Directory
1540 @cindex working directory (of your program)
1541 Each time you start your program with @code{run}, it inherits its
1542 working directory from the current working directory of _GDBN__. _GDBN__'s
1543 working directory is initially whatever it inherited from its parent
1544 process (typically the shell), but you can specify a new working
1545 directory in _GDBN__ with the @code{cd} command.
1547 The _GDBN__ working directory also serves as a default for the commands
1548 that specify files for _GDBN__ to operate on. @xref{Files, ,Commands to
1552 @item cd @var{directory}
1554 Set _GDBN__'s working directory to @var{directory}.
1558 Print _GDBN__'s working directory.
1562 @section Your Program's Input and Output
1567 By default, the program you run under _GDBN__ does input and output to
1568 the same terminal that _GDBN__ uses. _GDBN__ switches the terminal to
1569 its own terminal modes to interact with you, but it records the terminal
1570 modes your program was using and switches back to them when you continue
1571 running your program.
1575 @kindex info terminal
1576 Displays _GDBN__'s recorded information about the terminal modes your
1580 You can redirect your program's input and/or output using shell
1581 redirection with the @code{run} command. For example,
1588 starts your program, diverting its output to the file @file{outfile}.
1591 @cindex controlling terminal
1592 Another way to specify where your program should do input and output is
1593 with the @code{tty} command. This command accepts a file name as
1594 argument, and causes this file to be the default for future @code{run}
1595 commands. It also resets the controlling terminal for the child
1596 process, for future @code{run} commands. For example,
1603 directs that processes started with subsequent @code{run} commands
1604 default to do input and output on the terminal @file{/dev/ttyb} and have
1605 that as their controlling terminal.
1607 An explicit redirection in @code{run} overrides the @code{tty} command's
1608 effect on the input/output device, but not its effect on the controlling
1611 When you use the @code{tty} command or redirect input in the @code{run}
1612 command, only the input @emph{for your program} is affected. The input
1613 for _GDBN__ still comes from your terminal.
1616 @section Debugging an Already-Running Process
1621 @item attach @var{process-id}
1623 attaches to a running process---one that was started outside _GDBN__.
1624 (@code{info files} will show your active targets.) The command takes as
1625 argument a process ID. The usual way to find out the process-id of
1626 a Unix process is with the @code{ps} utility, or with the @samp{jobs -l}
1629 @code{attach} will not repeat if you press @key{RET} a second time after
1630 executing the command.
1633 To use @code{attach}, you must be debugging in an environment which
1634 supports processes. You must also have permission to send the process a
1635 signal, and it must have the same effective user ID as the _GDBN__
1638 When using @code{attach}, you should first use the @code{file} command
1639 to specify the program running in the process and load its symbol table.
1640 @xref{Files, ,Commands to Specify Files}.
1642 The first thing _GDBN__ does after arranging to debug the specified
1643 process is to stop it. You can examine and modify an attached process
1644 with all the _GDBN__ commands that are ordinarily available when you start
1645 processes with @code{run}. You can insert breakpoints; you can step and
1646 continue; you can modify storage. If you would rather the process
1647 continue running, you may use the @code{continue} command after
1648 attaching _GDBN__ to the process.
1653 When you have finished debugging the attached process, you can use the
1654 @code{detach} command to release it from _GDBN__'s control. Detaching
1655 the process continues its execution. After the @code{detach} command,
1656 that process and _GDBN__ become completely independent once more, and you
1657 are ready to @code{attach} another process or start one with @code{run}.
1658 @code{detach} will not repeat if you press @key{RET} again after
1659 executing the command.
1662 If you exit _GDBN__ or use the @code{run} command while you have an attached
1663 process, you kill that process. By default, you will be asked for
1664 confirmation if you try to do either of these things; you can control
1665 whether or not you need to confirm by using the @code{set confirm} command
1666 (@pxref{Messages/Warnings, ,Optional Warnings and Messages}).
1670 @section Killing the Child Process
1675 Kill the child process in which your program is running under _GDBN__.
1678 This command is useful if you wish to debug a core dump instead of a
1679 running process. _GDBN__ ignores any core dump file while your program
1683 On some operating systems, a program cannot be executed outside _GDBN__
1684 while you have breakpoints set on it inside _GDBN__. You can use the
1685 @code{kill} command in this situation to permit running your program
1686 outside the debugger.
1688 The @code{kill} command is also useful if you wish to recompile and
1689 relink your program, since on many systems it is impossible to modify an
1690 executable file while it is running in a process. In this case, when you
1691 next type @code{run}, _GDBN__ will notice that the file has changed, and
1692 will re-read the symbol table (while trying to preserve your current
1693 breakpoint settings).
1695 @node Process Information
1696 @section Additional Process Information
1699 @cindex process image
1700 Some operating systems provide a facility called @samp{/proc} that can
1701 be used to examine the image of a running process using file-system
1702 subroutines. If _GDBN__ is configured for an operating system with this
1703 facility, the command @code{info proc} is available to report on several
1704 kinds of information about the process running your program.
1709 Summarize available information about the process.
1711 @item info proc mappings
1712 @kindex info proc mappings
1713 Report on the address ranges accessible in the program, with information
1714 on whether your program may read, write, or execute each range.
1716 @item info proc times
1717 @kindex info proc times
1718 Starting time, user CPU time, and system CPU time for your program and
1722 @kindex info proc id
1723 Report on the process ID's related to your program: its own process id,
1724 the id of its parent, the process group id, and the session id.
1726 @item info proc status
1727 @kindex info proc status
1728 General information on the state of the process. If the process is
1729 stopped, this report includes the reason for stopping, and any signal
1733 Show all the above information about the process.
1738 @chapter Stopping and Continuing
1740 The principal purpose of using a debugger is so that you can stop your
1741 program before it terminates; or so that, if your program runs into
1742 trouble, you can investigate and find out why.
1744 Inside _GDBN__, your program may stop for any of several reasons, such
1745 as a signal, a breakpoint, or reaching a new line after a _GDBN__
1746 command such as @code{step}. You may then examine and change
1747 variables, set new breakpoints or remove old ones, and then continue
1748 execution. Usually, the messages shown by _GDBN__ provide ample
1749 explanation of the status of your program---but you can also explicitly
1750 request this information at any time.
1754 @kindex info program
1755 Display information about the status of your program: whether it is
1756 running or not, what process it is, and why it stopped.
1760 * Breakpoints:: Breakpoints, Watchpoints, and Exceptions
1761 * Continuing and Stepping:: Resuming Execution
1762 _if__(_GENERIC__ || !_H8__)
1764 _fi__(_GENERIC__ || !_H8__)
1768 @section Breakpoints, Watchpoints, and Exceptions
1771 A @dfn{breakpoint} makes your program stop whenever a certain point in
1772 the program is reached. For each breakpoint, you can add various
1773 conditions to control in finer detail whether your program will stop.
1774 You can set breakpoints with the @code{break} command and its variants
1775 (@pxref{Set Breaks, ,Setting Breakpoints}), to specify the place where
1776 your program should stop by line number, function name or exact address
1777 in the program. In languages with exception handling (such as GNU
1778 C++), you can also set breakpoints where an exception is raised
1779 (@pxref{Exception Handling, ,Breakpoints and Exceptions}).
1782 @cindex memory tracing
1783 @cindex breakpoint on memory address
1784 @cindex breakpoint on variable modification
1785 A @dfn{watchpoint} is a special breakpoint that stops your program
1786 when the value of an expression changes. You must use a different
1787 command to set watchpoints (@pxref{Set Watchpoints, ,Setting
1788 Watchpoints}), but aside from that, you can manage a watchpoint like
1789 any other breakpoint: you enable, disable, and delete both breakpoints
1790 and watchpoints using the same commands.
1792 @cindex breakpoint numbers
1793 @cindex numbers for breakpoints
1794 _GDBN__ assigns a number to each breakpoint or watchpoint when you
1795 create it; these numbers are successive integers starting with one. In
1796 many of the commands for controlling various features of breakpoints you
1797 use the breakpoint number to say which breakpoint you want to change.
1798 Each breakpoint may be @dfn{enabled} or @dfn{disabled}; if disabled, it has
1799 no effect on your program until you enable it again.
1802 * Set Breaks:: Setting Breakpoints
1803 * Set Watchpoints:: Setting Watchpoints
1804 * Exception Handling:: Breakpoints and Exceptions
1805 * Delete Breaks:: Deleting Breakpoints
1806 * Disabling:: Disabling Breakpoints
1807 * Conditions:: Break Conditions
1808 * Break Commands:: Breakpoint Command Lists
1809 * Breakpoint Menus:: Breakpoint Menus
1810 * Error in Breakpoints::
1814 @subsection Setting Breakpoints
1816 @c FIXME LMB what does GDB do if no code on line of breakpt?
1817 @c consider in particular declaration with/without initialization.
1819 @c FIXME 2 is there stuff on this already? break at fun start, already init?
1824 @cindex latest breakpoint
1825 Breakpoints are set with the @code{break} command (abbreviated
1826 @code{b}). The debugger convenience variable @samp{$bpnum} records the
1827 number of the beakpoint you've set most recently; see @ref{Convenience
1828 Vars,, Convenience Variables}, for a discussion of what you can do with
1829 convenience variables.
1831 You have several ways to say where the breakpoint should go.
1834 @item break @var{function}
1835 Set a breakpoint at entry to function @var{function}. When using source
1836 languages that permit overloading of symbols, such as C++,
1837 @var{function} may refer to more than one possible place to break.
1838 @xref{Breakpoint Menus}, for a discussion of that situation.
1840 @item break +@var{offset}
1841 @itemx break -@var{offset}
1842 Set a breakpoint some number of lines forward or back from the position
1843 at which execution stopped in the currently selected frame.
1845 @item break @var{linenum}
1846 Set a breakpoint at line @var{linenum} in the current source file.
1847 That file is the last file whose source text was printed. This
1848 breakpoint will stop your program just before it executes any of the
1851 @item break @var{filename}:@var{linenum}
1852 Set a breakpoint at line @var{linenum} in source file @var{filename}.
1854 @item break @var{filename}:@var{function}
1855 Set a breakpoint at entry to function @var{function} found in file
1856 @var{filename}. Specifying a file name as well as a function name is
1857 superfluous except when multiple files contain similarly named
1860 @item break *@var{address}
1861 Set a breakpoint at address @var{address}. You can use this to set
1862 breakpoints in parts of your program which do not have debugging
1863 information or source files.
1866 When called without any arguments, @code{break} sets a breakpoint at
1867 the next instruction to be executed in the selected stack frame
1868 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
1869 innermost, this will cause your program to stop as soon as control
1870 returns to that frame. This is similar to the effect of a
1871 @code{finish} command in the frame inside the selected frame---except
1872 that @code{finish} does not leave an active breakpoint. If you use
1873 @code{break} without an argument in the innermost frame, _GDBN__ will stop
1874 the next time it reaches the current location; this may be useful
1877 _GDBN__ normally ignores breakpoints when it resumes execution, until at
1878 least one instruction has been executed. If it did not do this, you
1879 would be unable to proceed past a breakpoint without first disabling the
1880 breakpoint. This rule applies whether or not the breakpoint already
1881 existed when your program stopped.
1883 @item break @dots{} if @var{cond}
1884 Set a breakpoint with condition @var{cond}; evaluate the expression
1885 @var{cond} each time the breakpoint is reached, and stop only if the
1886 value is nonzero---that is, if @var{cond} evaluates as true.
1887 @samp{@dots{}} stands for one of the possible arguments described
1888 above (or no argument) specifying where to break. @xref{Conditions,
1889 ,Break Conditions}, for more information on breakpoint conditions.
1891 @item tbreak @var{args}
1893 Set a breakpoint enabled only for one stop. @var{args} are the
1894 same as for the @code{break} command, and the breakpoint is set in the same
1895 way, but the breakpoint is automatically disabled after the first time your
1896 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
1898 @item rbreak @var{regex}
1900 @cindex regular expression
1901 @c FIXME what kind of regexp?
1902 Set breakpoints on all functions matching the regular expression
1903 @var{regex}. This command
1904 sets an unconditional breakpoint on all matches, printing a list of all
1905 breakpoints it set. Once these breakpoints are set, they are treated
1906 just like the breakpoints set with the @code{break} command. They can
1907 be deleted, disabled, made conditional, etc., in the standard ways.
1909 When debugging C++ programs, @code{rbreak} is useful for setting
1910 breakpoints on overloaded functions that are not members of any special
1913 @kindex info breakpoints
1914 @cindex @code{$_} and @code{info breakpoints}
1915 @item info breakpoints @r{[}@var{n}@r{]}
1916 @itemx info break @r{[}@var{n}@r{]}
1917 @itemx info watchpoints @r{[}@var{n}@r{]}
1918 Print a table of all breakpoints and watchpoints set and not
1919 deleted, with the following columns for each breakpoint:
1922 @item Breakpoint Numbers
1924 Breakpoint or watchpoint.
1926 Whether the breakpoint is marked to be disabled or deleted when hit.
1927 @item Enabled or Disabled
1928 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
1929 that are not enabled.
1931 Where the breakpoint is in your program, as a memory address
1933 Where the breakpoint is in the source for your program, as a file and
1938 Breakpoint commands, if any, are listed after the line for the
1939 corresponding breakpoint.
1942 @code{info break} with a breakpoint
1943 number @var{n} as argument lists only that breakpoint. The
1944 convenience variable @code{$_} and the default examining-address for
1945 the @code{x} command are set to the address of the last breakpoint
1946 listed (@pxref{Memory, ,Examining Memory}).
1949 _GDBN__ allows you to set any number of breakpoints at the same place in
1950 your program. There is nothing silly or meaningless about this. When
1951 the breakpoints are conditional, this is even useful
1952 (@pxref{Conditions, ,Break Conditions}).
1954 @cindex negative breakpoint numbers
1955 @cindex internal _GDBN__ breakpoints
1956 _GDBN__ itself sometimes sets breakpoints in your program for special
1957 purposes, such as proper handling of @code{longjmp} (in C programs).
1958 These internal breakpoints are assigned negative numbers, starting with
1959 @code{-1}; @samp{info breakpoints} does not display them.
1961 You can see these breakpoints with the _GDBN__ maintenance command
1962 @samp{maint info breakpoints}.
1965 @kindex maint info breakpoints
1966 @item maint info breakpoints
1967 Using the same format as @samp{info breakpoints}, display both the
1968 breakpoints you've set explicitly, and those _GDBN__ is using for
1969 internal purposes. Internal breakpoints are shown with negative
1970 breakpoint numbers. The type column identifies what kind of breakpoint
1975 Normal, explicitly set breakpoint.
1978 Normal, explicitly set watchpoint.
1981 Internal breakpoint, used to handle correctly stepping through
1982 @code{longjmp} calls.
1984 @item longjmp resume
1985 Internal breakpoint at the target of a @code{longjmp}.
1988 Temporary internal breakpoint used by the _GDBN__ @code{until} command.
1991 Temporary internal breakpoint used by the _GDBN__ @code{finish} command.
1997 @node Set Watchpoints
1998 @subsection Setting Watchpoints
1999 @cindex setting watchpoints
2001 You can use a watchpoint to stop execution whenever the value of an
2002 expression changes, without having to predict a particular place
2003 where this may happen.
2005 Watchpoints currently execute two orders of magnitude more slowly than
2006 other breakpoints, but this can well be worth it to catch errors where
2007 you have no clue what part of your program is the culprit. Some
2008 processors provide special hardware to support watchpoint evaluation; future
2009 releases of _GDBN__ will use such hardware if it is available.
2013 @item watch @var{expr}
2014 Set a watchpoint for an expression.
2016 @kindex info watchpoints
2017 @item info watchpoints
2018 This command prints a list of watchpoints and breakpoints; it is the
2019 same as @code{info break}.
2022 @node Exception Handling
2023 @subsection Breakpoints and Exceptions
2024 @cindex exception handlers
2026 Some languages, such as GNU C++, implement exception handling. You can
2027 use _GDBN__ to examine what caused your program to raise an exception,
2028 and to list the exceptions your program is prepared to handle at a
2029 given point in time.
2032 @item catch @var{exceptions}
2034 You can set breakpoints at active exception handlers by using the
2035 @code{catch} command. @var{exceptions} is a list of names of exceptions
2039 You can use @code{info catch} to list active exception handlers.
2040 @xref{Frame Info, ,Information About a Frame}.
2042 There are currently some limitations to exception handling in _GDBN__.
2043 These will be corrected in a future release.
2047 If you call a function interactively, _GDBN__ normally returns
2048 control to you when the function has finished executing. If the call
2049 raises an exception, however, the call may bypass the mechanism that
2050 returns control to you and cause your program to simply continue
2051 running until it hits a breakpoint, catches a signal that _GDBN__ is
2052 listening for, or exits.
2054 You cannot raise an exception interactively.
2056 You cannot interactively install an exception handler.
2059 @cindex raise exceptions
2060 Sometimes @code{catch} is not the best way to debug exception handling:
2061 if you need to know exactly where an exception is raised, it is better to
2062 stop @emph{before} the exception handler is called, since that way you
2063 can see the stack before any unwinding takes place. If you set a
2064 breakpoint in an exception handler instead, it may not be easy to find
2065 out where the exception was raised.
2067 To stop just before an exception handler is called, you need some
2068 knowledge of the implementation. In the case of GNU C++, exceptions are
2069 raised by calling a library function named @code{__raise_exception}
2070 which has the following ANSI C interface:
2073 /* @var{addr} is where the exception identifier is stored.
2074 ID is the exception identifier. */
2075 void __raise_exception (void **@var{addr}, void *@var{id});
2079 To make the debugger catch all exceptions before any stack
2080 unwinding takes place, set a breakpoint on @code{__raise_exception}
2081 (@pxref{Breakpoints, ,Breakpoints Watchpoints and Exceptions}).
2083 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
2084 that depends on the value of @var{id}, you can stop your program when
2085 a specific exception is raised. You can use multiple conditional
2086 breakpoints to stop your program when any of a number of exceptions are
2090 @subsection Deleting Breakpoints
2092 @cindex clearing breakpoints, watchpoints
2093 @cindex deleting breakpoints, watchpoints
2094 It is often necessary to eliminate a breakpoint or watchpoint once it
2095 has done its job and you no longer want your program to stop there. This
2096 is called @dfn{deleting} the breakpoint. A breakpoint that has been
2097 deleted no longer exists; it is forgotten.
2099 With the @code{clear} command you can delete breakpoints according to
2100 where they are in your program. With the @code{delete} command you can
2101 delete individual breakpoints or watchpoints by specifying their
2104 It is not necessary to delete a breakpoint to proceed past it. _GDBN__
2105 automatically ignores breakpoints on the first instruction to be executed
2106 when you continue execution without changing the execution address.
2111 Delete any breakpoints at the next instruction to be executed in the
2112 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
2113 the innermost frame is selected, this is a good way to delete a
2114 breakpoint where your program just stopped.
2116 @item clear @var{function}
2117 @itemx clear @var{filename}:@var{function}
2118 Delete any breakpoints set at entry to the function @var{function}.
2120 @item clear @var{linenum}
2121 @itemx clear @var{filename}:@var{linenum}
2122 Delete any breakpoints set at or within the code of the specified line.
2124 @item delete @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]}
2125 @cindex delete breakpoints
2128 Delete the breakpoints or watchpoints of the numbers specified as
2129 arguments. If no argument is specified, delete all breakpoints (_GDBN__
2130 asks confirmation, unless you have @code{set confirm off}). You
2131 can abbreviate this command as @code{d}.
2135 @subsection Disabling Breakpoints
2137 @cindex disabled breakpoints
2138 @cindex enabled breakpoints
2139 Rather than deleting a breakpoint or watchpoint, you might prefer to
2140 @dfn{disable} it. This makes the breakpoint inoperative as if it had
2141 been deleted, but remembers the information on the breakpoint so that
2142 you can @dfn{enable} it again later.
2144 You disable and enable breakpoints and watchpoints with the
2145 @code{enable} and @code{disable} commands, optionally specifying one or
2146 more breakpoint numbers as arguments. Use @code{info break} or
2147 @code{info watch} to print a list of breakpoints or watchpoints if you
2148 do not know which numbers to use.
2150 A breakpoint or watchpoint can have any of four different states of
2155 Enabled. The breakpoint will stop your program. A breakpoint set
2156 with the @code{break} command starts out in this state.
2158 Disabled. The breakpoint has no effect on your program.
2160 Enabled once. The breakpoint will stop your program, but
2161 when it does so it will become disabled. A breakpoint set
2162 with the @code{tbreak} command starts out in this state.
2164 Enabled for deletion. The breakpoint will stop your program, but
2165 immediately after it does so it will be deleted permanently.
2168 You can use the following commands to enable or disable breakpoints and
2172 @item disable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]}
2173 @kindex disable breakpoints
2176 Disable the specified breakpoints---or all breakpoints, if none are
2177 listed. A disabled breakpoint has no effect but is not forgotten. All
2178 options such as ignore-counts, conditions and commands are remembered in
2179 case the breakpoint is enabled again later. You may abbreviate
2180 @code{disable} as @code{dis}.
2182 @item enable @r{[}breakpoints@r{]} @r{[}@var{bnums}@dots{}@r{]}
2183 @kindex enable breakpoints
2185 Enable the specified breakpoints (or all defined breakpoints). They
2186 become effective once again in stopping your program.
2188 @item enable @r{[}breakpoints@r{]} once @var{bnums}@dots{}
2189 Enable the specified breakpoints temporarily. Each will be disabled
2190 again the next time it stops your program.
2192 @item enable @r{[}breakpoints@r{]} delete @var{bnums}@dots{}
2193 Enable the specified breakpoints to work once and then die. Each of
2194 the breakpoints will be deleted the next time it stops your program.
2197 Save for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
2198 ,Setting Breakpoints}), breakpoints that you set are initially
2199 enabled; subsequently, they become disabled or enabled only when you
2200 use one of the commands above. (The command @code{until} can set and
2201 delete a breakpoint of its own, but it will not change the state of
2202 your other breakpoints; see @ref{Continuing and Stepping, ,Continuing and Stepping}.)
2205 @subsection Break Conditions
2206 @cindex conditional breakpoints
2207 @cindex breakpoint conditions
2209 @c FIXME what is scope of break condition expr? Context where wanted?
2210 @c in particular for a watchpoint?
2211 The simplest sort of breakpoint breaks every time your program reaches a
2212 specified place. You can also specify a @dfn{condition} for a
2213 breakpoint. A condition is just a Boolean expression in your
2214 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
2215 a condition evaluates the expression each time your program reaches it,
2216 and your program stops only if the condition is @emph{true}.
2218 This is the converse of using assertions for program validation; in that
2219 situation, you want to stop when the assertion is violated---that is,
2220 when the condition is false. In C, if you want to test an assertion expressed
2221 by the condition @var{assert}, you should set the condition
2222 @samp{! @var{assert}} on the appropriate breakpoint.
2224 Conditions are also accepted for watchpoints; you may not need them,
2225 since a watchpoint is inspecting the value of an expression anyhow---but
2226 it might be simpler, say, to just set a watchpoint on a variable name,
2227 and specify a condition that tests whether the new value is an interesting
2230 Break conditions can have side effects, and may even call functions in
2231 your program. This can be useful, for example, to activate functions
2232 that log program progress, or to use your own print functions to
2233 format special data structures. The effects are completely predictable
2234 unless there is another enabled breakpoint at the same address. (In
2235 that case, _GDBN__ might see the other breakpoint first and stop your
2236 program without checking the condition of this one.) Note that
2237 breakpoint commands are usually more convenient and flexible for the
2238 purpose of performing side effects when a breakpoint is reached
2239 (@pxref{Break Commands, ,Breakpoint Command Lists}).
2241 Break conditions can be specified when a breakpoint is set, by using
2242 @samp{if} in the arguments to the @code{break} command. @xref{Set
2243 Breaks, ,Setting Breakpoints}. They can also be changed at any time
2244 with the @code{condition} command. The @code{watch} command does not
2245 recognize the @code{if} keyword; @code{condition} is the only way to
2246 impose a further condition on a watchpoint.
2249 @item condition @var{bnum} @var{expression}
2251 Specify @var{expression} as the break condition for breakpoint or
2252 watchpoint number @var{bnum}. From now on, this breakpoint will stop
2253 your program only if the value of @var{expression} is true (nonzero, in
2254 C). When you use @code{condition}, _GDBN__ checks @var{expression}
2255 immediately for syntactic correctness, and to determine whether symbols
2256 in it have referents in the context of your breakpoint.
2257 @c FIXME so what does GDB do if there is no referent? Moreover, what
2258 @c about watchpoints?
2260 not actually evaluate @var{expression} at the time the @code{condition}
2261 command is given, however. @xref{Expressions, ,Expressions}.
2263 @item condition @var{bnum}
2264 Remove the condition from breakpoint number @var{bnum}. It becomes
2265 an ordinary unconditional breakpoint.
2268 @cindex ignore count (of breakpoint)
2269 A special case of a breakpoint condition is to stop only when the
2270 breakpoint has been reached a certain number of times. This is so
2271 useful that there is a special way to do it, using the @dfn{ignore
2272 count} of the breakpoint. Every breakpoint has an ignore count, which
2273 is an integer. Most of the time, the ignore count is zero, and
2274 therefore has no effect. But if your program reaches a breakpoint whose
2275 ignore count is positive, then instead of stopping, it just decrements
2276 the ignore count by one and continues. As a result, if the ignore count
2277 value is @var{n}, the breakpoint will not stop the next @var{n} times it
2281 @item ignore @var{bnum} @var{count}
2283 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
2284 The next @var{count} times the breakpoint is reached, your program's
2285 execution will not stop; other than to decrement the ignore count, _GDBN__
2288 To make the breakpoint stop the next time it is reached, specify
2291 @item continue @var{count}
2292 @itemx c @var{count}
2293 @itemx fg @var{count}
2294 @kindex continue @var{count}
2295 Continue execution of your program, setting the ignore count of the
2296 breakpoint where your program stopped to @var{count} minus one.
2297 Thus, your program will not stop at this breakpoint until the
2298 @var{count}'th time it is reached.
2300 An argument to this command is meaningful only when your program stopped
2301 due to a breakpoint. At other times, the argument to @code{continue} is
2304 The synonym @code{fg} is provided purely for convenience, and has
2305 exactly the same behavior as other forms of the command.
2308 If a breakpoint has a positive ignore count and a condition, the condition
2309 is not checked. Once the ignore count reaches zero, the condition will
2312 You could achieve the effect of the ignore count with a condition such
2313 as _0__@w{@samp{$foo-- <= 0}}_1__ using a debugger convenience variable that
2314 is decremented each time. @xref{Convenience Vars, ,Convenience
2317 @node Break Commands
2318 @subsection Breakpoint Command Lists
2320 @cindex breakpoint commands
2321 You can give any breakpoint (or watchpoint) a series of commands to
2322 execute when your program stops due to that breakpoint. For example, you
2323 might want to print the values of certain expressions, or enable other
2327 @item commands @r{[}@var{bnum}@r{]}
2328 @itemx @dots{} @var{command-list} @dots{}
2332 Specify a list of commands for breakpoint number @var{bnum}. The commands
2333 themselves appear on the following lines. Type a line containing just
2334 @code{end} to terminate the commands.
2336 To remove all commands from a breakpoint, type @code{commands} and
2337 follow it immediately with @code{end}; that is, give no commands.
2339 With no @var{bnum} argument, @code{commands} refers to the last
2340 breakpoint or watchpoint set (not to the breakpoint most recently
2344 Pressing @key{RET} as a means of repeating the last _GDBN__ command is
2345 disabled within a @var{command-list}.
2347 You can use breakpoint commands to start your program up again. Simply
2348 use the @code{continue} command, or @code{step}, or any other command
2349 that resumes execution. Subsequent commands in the command list are
2353 If the first command specified is @code{silent}, the usual message about
2354 stopping at a breakpoint is not printed. This may be desirable for
2355 breakpoints that are to print a specific message and then continue.
2356 If the remaining commands too print nothing, you will see no sign that
2357 the breakpoint was reached at all. @code{silent} is meaningful only
2358 at the beginning of a breakpoint command list.
2360 The commands @code{echo} and @code{output} that allow you to print
2361 precisely controlled output are often useful in silent breakpoints.
2362 @xref{Output, ,Commands for Controlled Output}.
2364 For example, here is how you could use breakpoint commands to print the
2365 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
2378 One application for breakpoint commands is to compensate for one bug so
2379 you can test for another. Put a breakpoint just after the erroneous line
2380 of code, give it a condition to detect the case in which something
2381 erroneous has been done, and give it commands to assign correct values
2382 to any variables that need them. End with the @code{continue} command
2383 so that your program does not stop, and start with the @code{silent}
2384 command so that no output is produced. Here is an example:
2396 One deficiency in the operation of automatically continuing breakpoints
2397 under Unix appears when your program uses raw mode for the terminal.
2398 _GDBN__ switches back to its own terminal modes (not raw) before executing
2399 commands, and then must switch back to raw mode when your program is
2400 continued. This causes any pending terminal input to be lost.
2401 @c FIXME: revisit below when GNU sys avail.
2402 @c In the GNU system, this will be fixed by changing the behavior of
2405 Under Unix, you can get around this problem by writing actions into
2406 the breakpoint condition rather than in commands. For example
2409 condition 5 (x = y + 4), 0
2413 specifies a condition expression (@pxref{Expressions, ,Expressions}) that will
2414 change @code{x} as needed, then always have the value zero so your
2415 program will not stop. No input is lost here, because _GDBN__ evaluates
2416 break conditions without changing the terminal modes. When you want
2417 to have nontrivial conditions for performing the side effects, the
2418 operators @samp{&&}, @samp{||} and @samp{?@dots{}:} may be useful.
2420 @node Breakpoint Menus
2421 @subsection Breakpoint Menus
2423 @cindex symbol overloading
2425 Some programming languages (notably C++) permit a single function name
2426 to be defined several times, for application in different contexts.
2427 This is called @dfn{overloading}. When a function name is overloaded,
2428 @samp{break @var{function}} is not enough to tell _GDBN__ where you want
2429 a breakpoint. If you realize this will be a problem, you can use
2430 something like @samp{break @var{function}(@var{types})} to specify which
2431 particular version of the function you want. Otherwise, _GDBN__ offers
2432 you a menu of numbered choices for different possible breakpoints, and
2433 waits for your selection with the prompt @samp{>}. The first two
2434 options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1}
2435 sets a breakpoint at each definition of @var{function}, and typing
2436 @kbd{0} aborts the @code{break} command without setting any new
2439 For example, the following session excerpt shows an attempt to set a
2440 breakpoint at the overloaded symbol @code{String::after}.
2441 We choose three particular definitions of that function name:
2443 @c FIXME! This is likely to change to show arg type lists, at least
2445 (_GDBP__) b String::after
2448 [2] file:String.cc; line number:867
2449 [3] file:String.cc; line number:860
2450 [4] file:String.cc; line number:875
2451 [5] file:String.cc; line number:853
2452 [6] file:String.cc; line number:846
2453 [7] file:String.cc; line number:735
2455 Breakpoint 1 at 0xb26c: file String.cc, line 867.
2456 Breakpoint 2 at 0xb344: file String.cc, line 875.
2457 Breakpoint 3 at 0xafcc: file String.cc, line 846.
2458 Multiple breakpoints were set.
2459 Use the "delete" command to delete unwanted breakpoints.
2463 @node Error in Breakpoints
2464 @subsection ``Cannot Insert Breakpoints''
2466 @c FIXME: "cannot insert breakpoints" error, v unclear.
2467 @c Q in pending mail to Gilmore. ---pesch@cygnus.com, 26mar91
2468 @c some light may be shed by looking at instances of
2469 @c ONE_PROCESS_WRITETEXT. But error message seems possible otherwise
2470 @c too. pesch, 20sep91
2471 Under some operating systems, breakpoints cannot be used in a program if
2472 any other process is running that program. In this situation,
2473 attempting to run or continue a program with a breakpoint causes _GDBN__
2474 to stop the other process.
2476 When this happens, you have three ways to proceed:
2480 Remove or disable the breakpoints, then continue.
2483 Suspend _GDBN__, and copy the file containing your program to a new name.
2484 Resume _GDBN__ and use the @code{exec-file} command to specify that _GDBN__
2485 should run your program under that name. Then start your program again.
2487 @c FIXME: RMS commented here "Show example". Maybe when someone
2488 @c explains the first FIXME: in this section...
2491 Relink your program so that the text segment is nonsharable, using the
2492 linker option @samp{-N}. The operating system limitation may not apply
2493 to nonsharable executables.
2496 @node Continuing and Stepping
2497 @section Continuing and Stepping
2501 @cindex resuming execution
2502 @dfn{Continuing} means resuming program execution until your program
2503 completes normally. In contrast, @dfn{stepping} means executing just
2504 one more ``step'' of your program, where ``step'' may mean either one
2505 line of source code, or one machine instruction (depending on what
2506 particular command you use). Either when continuing
2507 or when stepping, your program may stop even sooner, due to
2512 a breakpoint or to a signal. (If due to a signal, you may want to use
2513 @code{handle}, or use @samp{signal 0} to resume execution.
2514 @xref{Signals, ,Signals}.)
2518 @item continue @r{[}@var{ignore-count}@r{]}
2520 Resume program execution, at the address where your program last stopped;
2521 any breakpoints set at that address are bypassed. The optional argument
2522 @var{ignore-count} allows you to specify a further number of times to
2523 ignore a breakpoint at this location; its effect is like that of
2524 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
2526 To resume execution at a different place, you can use @code{return}
2527 (@pxref{Returning, ,Returning from a Function}) to go back to the
2528 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
2529 Different Address}) to go to an arbitrary location in your program.
2532 A typical technique for using stepping is to set a breakpoint
2533 (@pxref{Breakpoints, ,Breakpoints Watchpoints and Exceptions}) at the
2534 beginning of the function or the section of your program where a
2535 problem is believed to lie, run your program until it stops at that
2536 breakpoint, and then step through the suspect area, examining the
2537 variables that are interesting, until you see the problem happen.
2543 Continue running your program until control reaches a different source
2544 line, then stop it and return control to _GDBN__. This command is
2545 abbreviated @code{s}.
2548 @emph{Warning:} If you use the @code{step} command while control is
2549 within a function that was compiled without debugging information,
2550 execution will proceed until control reaches another function.
2553 @item step @var{count}
2554 Continue running as in @code{step}, but do so @var{count} times. If a
2555 breakpoint is reached or a signal not related to stepping occurs before
2556 @var{count} steps, stepping stops right away.
2558 @item next @r{[}@var{count}@r{]}
2561 Continue to the next source line in the current (innermost) stack frame.
2562 Similar to @code{step}, but any function calls appearing within the line
2563 of code are executed without stopping. Execution stops when control
2564 reaches a different line of code at the stack level which was executing
2565 when the @code{next} command was given. This command is abbreviated
2568 An argument @var{count} is a repeat count, as for @code{step}.
2570 @code{next} within a function that lacks debugging information acts like
2571 @code{step}, but any function calls appearing within the code of the
2572 function are executed without stopping.
2576 Continue running until just after function in the selected stack frame
2577 returns. Print the returned value (if any).
2579 Contrast this with the @code{return} command (@pxref{Returning,
2580 ,Returning from a Function}).
2586 Continue running until a source line past the current line, in the
2587 current stack frame, is reached. This command is used to avoid single
2588 stepping through a loop more than once. It is like the @code{next}
2589 command, except that when @code{until} encounters a jump, it
2590 automatically continues execution until the program counter is greater
2591 than the address of the jump.
2593 This means that when you reach the end of a loop after single stepping
2594 though it, @code{until} will cause your program to continue execution
2595 until the loop is exited. In contrast, a @code{next} command at the end
2596 of a loop will simply step back to the beginning of the loop, which
2597 would force you to step through the next iteration.
2599 @code{until} always stops your program if it attempts to exit the current
2602 @code{until} may produce somewhat counterintuitive results if the order
2603 of machine code does not match the order of the source lines. For
2604 example, in the following excerpt from a debugging session, the @code{f}
2605 (@code{frame}) command shows that execution is stopped at line
2606 @code{206}; yet when we use @code{until}, we get to line @code{195}:
2610 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
2613 195 for ( ; argc > 0; NEXTARG) @{
2616 This happened because, for execution efficiency, the compiler had
2617 generated code for the loop closure test at the end, rather than the
2618 start, of the loop---even though the test in a C @code{for}-loop is
2619 written before the body of the loop. The @code{until} command appeared
2620 to step back to the beginning of the loop when it advanced to this
2621 expression; however, it has not really gone to an earlier
2622 statement---not in terms of the actual machine code.
2624 @code{until} with no argument works by means of single
2625 instruction stepping, and hence is slower than @code{until} with an
2628 @item until @var{location}
2629 @item u @var{location}
2630 Continue running your program until either the specified location is
2631 reached, or the current stack frame returns. @var{location} is any of
2632 the forms of argument acceptable to @code{break} (@pxref{Set Breaks,
2633 ,Setting Breakpoints}). This form of the command uses breakpoints,
2634 and hence is quicker than @code{until} without an argument.
2640 Execute one machine instruction, then stop and return to the debugger.
2642 It is often useful to do @samp{display/i $pc} when stepping by machine
2643 instructions. This will cause the next instruction to be executed to
2644 be displayed automatically at each stop. @xref{Auto Display,
2645 ,Automatic Display}.
2647 An argument is a repeat count, as in @code{step}.
2653 Execute one machine instruction, but if it is a function call,
2654 proceed until the function returns.
2656 An argument is a repeat count, as in @code{next}.
2659 _if__(_GENERIC__ || !_H8__)
2664 A signal is an asynchronous event that can happen in a program. The
2665 operating system defines the possible kinds of signals, and gives each
2666 kind a name and a number. For example, in Unix @code{SIGINT} is the
2667 signal a program gets when you type an interrupt (often @kbd{C-c});
2668 @code{SIGSEGV} is the signal a program gets from referencing a place in
2669 memory far away from all the areas in use; @code{SIGALRM} occurs when
2670 the alarm clock timer goes off (which happens only if your program has
2671 requested an alarm).
2673 @cindex fatal signals
2674 Some signals, including @code{SIGALRM}, are a normal part of the
2675 functioning of your program. Others, such as @code{SIGSEGV}, indicate
2676 errors; these signals are @dfn{fatal} (kill your program immediately) if the
2677 program has not specified in advance some other way to handle the signal.
2678 @code{SIGINT} does not indicate an error in your program, but it is normally
2679 fatal so it can carry out the purpose of the interrupt: to kill the program.
2681 _GDBN__ has the ability to detect any occurrence of a signal in your
2682 program. You can tell _GDBN__ in advance what to do for each kind of
2685 @cindex handling signals
2686 Normally, _GDBN__ is set up to ignore non-erroneous signals like @code{SIGALRM}
2687 (so as not to interfere with their role in the functioning of your program)
2688 but to stop your program immediately whenever an error signal happens.
2689 You can change these settings with the @code{handle} command.
2693 @kindex info signals
2694 Print a table of all the kinds of signals and how _GDBN__ has been told to
2695 handle each one. You can use this to see the signal numbers of all
2696 the defined types of signals.
2698 @item handle @var{signal} @var{keywords}@dots{}
2700 Change the way _GDBN__ handles signal @var{signal}. @var{signal} can be the
2701 number of a signal or its name (with or without the @samp{SIG} at the
2702 beginning). The @var{keywords} say what change to make.
2706 The keywords allowed by the @code{handle} command can be abbreviated.
2707 Their full names are:
2711 _GDBN__ should not stop your program when this signal happens. It may
2712 still print a message telling you that the signal has come in.
2715 _GDBN__ should stop your program when this signal happens. This implies
2716 the @code{print} keyword as well.
2719 _GDBN__ should print a message when this signal happens.
2722 _GDBN__ should not mention the occurrence of the signal at all. This
2723 implies the @code{nostop} keyword as well.
2726 _GDBN__ should allow your program to see this signal; your program will be
2727 able to handle the signal, or may be terminated if the signal is fatal
2731 _GDBN__ should not allow your program to see this signal.
2735 When a signal has been set to stop your program, your program cannot see the
2736 signal until you continue. It will see the signal then, if @code{pass} is
2737 in effect for the signal in question @emph{at that time}. In other words,
2738 after _GDBN__ reports a signal, you can use the @code{handle} command with
2739 @code{pass} or @code{nopass} to control whether that signal will be seen by
2740 your program when you later continue it.
2742 You can also use the @code{signal} command to prevent your program from
2743 seeing a signal, or cause it to see a signal it normally would not see,
2744 or to give it any signal at any time. For example, if your program stopped
2745 due to some sort of memory reference error, you might store correct
2746 values into the erroneous variables and continue, hoping to see more
2747 execution; but your program would probably terminate immediately as
2748 a result of the fatal signal once it saw the signal. To prevent this,
2749 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
2751 _fi__(_GENERIC__ || !_H8__)
2754 @chapter Examining the Stack
2756 When your program has stopped, the first thing you need to know is where it
2757 stopped and how it got there.
2760 Each time your program performs a function call, the information about
2761 where in your program the call was made from is saved in a block of data
2762 called a @dfn{stack frame}. The frame also contains the arguments of the
2763 call and the local variables of the function that was called. All the
2764 stack frames are allocated in a region of memory called the @dfn{call
2767 When your program stops, the _GDBN__ commands for examining the stack allow you
2768 to see all of this information.
2770 @cindex selected frame
2771 One of the stack frames is @dfn{selected} by _GDBN__ and many _GDBN__ commands
2772 refer implicitly to the selected frame. In particular, whenever you ask
2773 _GDBN__ for the value of a variable in your program, the value is found in the
2774 selected frame. There are special _GDBN__ commands to select whichever frame
2775 you are interested in.
2777 When your program stops, _GDBN__ automatically selects the currently executing
2778 frame and describes it briefly as the @code{frame} command does
2779 (@pxref{Frame Info, ,Information About a Frame}).
2782 * Frames:: Stack Frames
2783 * Backtrace:: Backtraces
2784 * Selection:: Selecting a Frame
2785 * Frame Info:: Information on a Frame
2789 @section Stack Frames
2793 The call stack is divided up into contiguous pieces called @dfn{stack
2794 frames}, or @dfn{frames} for short; each frame is the data associated
2795 with one call to one function. The frame contains the arguments given
2796 to the function, the function's local variables, and the address at
2797 which the function is executing.
2799 @cindex initial frame
2800 @cindex outermost frame
2801 @cindex innermost frame
2802 When your program is started, the stack has only one frame, that of the
2803 function @code{main}. This is called the @dfn{initial} frame or the
2804 @dfn{outermost} frame. Each time a function is called, a new frame is
2805 made. Each time a function returns, the frame for that function invocation
2806 is eliminated. If a function is recursive, there can be many frames for
2807 the same function. The frame for the function in which execution is
2808 actually occurring is called the @dfn{innermost} frame. This is the most
2809 recently created of all the stack frames that still exist.
2811 @cindex frame pointer
2812 Inside your program, stack frames are identified by their addresses. A
2813 stack frame consists of many bytes, each of which has its own address; each
2814 kind of computer has a convention for choosing one of those bytes whose
2815 address serves as the address of the frame. Usually this address is kept
2816 in a register called the @dfn{frame pointer register} while execution is
2817 going on in that frame.
2819 @cindex frame number
2820 _GDBN__ assigns numbers to all existing stack frames, starting with
2821 zero for the innermost frame, one for the frame that called it,
2822 and so on upward. These numbers do not really exist in your program;
2823 they are assigned by _GDBN__ to give you a way of designating stack
2824 frames in _GDBN__ commands.
2826 @cindex frameless execution
2827 Some compilers allow functions to be compiled so that they operate
2828 without stack frames. (For example, the @code{_GCC__} option
2829 @samp{-fomit-frame-pointer} will generate functions without a frame.)
2830 This is occasionally done with heavily used library functions to save
2831 the frame setup time. _GDBN__ has limited facilities for dealing with
2832 these function invocations. If the innermost function invocation has no
2833 stack frame, _GDBN__ will nevertheless regard it as though it had a
2834 separate frame, which is numbered zero as usual, allowing correct
2835 tracing of the function call chain. However, _GDBN__ has no provision
2836 for frameless functions elsewhere in the stack.
2841 A backtrace is a summary of how your program got where it is. It shows one
2842 line per frame, for many frames, starting with the currently executing
2843 frame (frame zero), followed by its caller (frame one), and on up the
2851 Print a backtrace of the entire stack: one line per frame for all
2852 frames in the stack.
2854 You can stop the backtrace at any time by typing the system interrupt
2855 character, normally @kbd{C-c}.
2857 @item backtrace @var{n}
2859 Similar, but print only the innermost @var{n} frames.
2861 @item backtrace -@var{n}
2863 Similar, but print only the outermost @var{n} frames.
2869 The names @code{where} and @code{info stack} (abbreviated @code{info s})
2870 are additional aliases for @code{backtrace}.
2872 Each line in the backtrace shows the frame number and the function name.
2873 The program counter value is also shown---unless you use @code{set
2874 print address off}. The backtrace also shows the source file name and
2875 line number, as well as the arguments to the function. The program
2876 counter value is omitted if it is at the beginning of the code for that
2879 Here is an example of a backtrace. It was made with the command
2880 @samp{bt 3}, so it shows the innermost three frames.
2884 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
2886 #1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242
2887 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
2889 (More stack frames follow...)
2894 The display for frame zero does not begin with a program counter
2895 value, indicating that your program has stopped at the beginning of the
2896 code for line @code{993} of @code{builtin.c}.
2899 @section Selecting a Frame
2901 Most commands for examining the stack and other data in your program work on
2902 whichever stack frame is selected at the moment. Here are the commands for
2903 selecting a stack frame; all of them finish by printing a brief description
2904 of the stack frame just selected.
2911 Select frame number @var{n}. Recall that frame zero is the innermost
2912 (currently executing) frame, frame one is the frame that called the
2913 innermost one, and so on. The highest-numbered frame is @code{main}'s
2916 @item frame @var{addr}
2918 Select the frame at address @var{addr}. This is useful mainly if the
2919 chaining of stack frames has been damaged by a bug, making it
2920 impossible for _GDBN__ to assign numbers properly to all frames. In
2921 addition, this can be useful when your program has multiple stacks and
2922 switches between them.
2925 On the SPARC architecture, @code{frame} needs two addresses to
2926 select an arbitrary frame: a frame pointer and a stack pointer.
2927 @c note to future updaters: this is conditioned on a flag
2928 @c FRAME_SPECIFICATION_DYADIC in the tm-*.h files, currently only used
2929 @c by SPARC, hence the specific attribution. Generalize or list all
2930 @c possibilities if more supported machines start doing this.
2935 Move @var{n} frames up the stack. For positive numbers @var{n}, this
2936 advances toward the outermost frame, to higher frame numbers, to frames
2937 that have existed longer. @var{n} defaults to one.
2942 Move @var{n} frames down the stack. For positive numbers @var{n}, this
2943 advances toward the innermost frame, to lower frame numbers, to frames
2944 that were created more recently. @var{n} defaults to one. You may
2945 abbreviate @code{down} as @code{do}.
2948 All of these commands end by printing two lines of output describing the
2949 frame. The first line shows the frame number, the function name, the
2950 arguments, and the source file and line number of execution in that
2951 frame. The second line shows the text of that source line. For
2957 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
2959 10 read_input_file (argv[i]);
2963 After such a printout, the @code{list} command with no arguments will
2964 print ten lines centered on the point of execution in the frame.
2965 @xref{List, ,Printing Source Lines}.
2968 @item up-silently @var{n}
2969 @itemx down-silently @var{n}
2970 @kindex down-silently
2972 These two commands are variants of @code{up} and @code{down},
2973 respectively; they differ in that they do their work silently, without
2974 causing display of the new frame. They are intended primarily for use
2975 in _GDBN__ command scripts, where the output might be unnecessary and
2980 @section Information About a Frame
2982 There are several other commands to print information about the selected
2988 When used without any argument, this command does not change which
2989 frame is selected, but prints a brief description of the currently
2990 selected stack frame. It can be abbreviated @code{f}. With an
2991 argument, this command is used to select a stack frame
2992 (@pxref{Selection, ,Selecting a Frame}).
2998 This command prints a verbose description of the selected stack frame,
2999 including the address of the frame, the addresses of the next frame down
3000 (called by this frame) and the next frame up (caller of this frame), the
3001 language that the source code corresponding to this frame was written in,
3002 the address of the frame's arguments, the program counter saved in it
3003 (the address of execution in the caller frame), and which registers
3004 were saved in the frame. The verbose description is useful when
3005 something has gone wrong that has made the stack format fail to fit
3006 the usual conventions.
3008 @item info frame @var{addr}
3009 @itemx info f @var{addr}
3010 Print a verbose description of the frame at address @var{addr},
3011 without selecting that frame. The selected frame remains unchanged by
3016 Print the arguments of the selected frame, each on a separate line.
3020 Print the local variables of the selected frame, each on a separate
3021 line. These are all variables declared static or automatic within all
3022 program blocks that execution in this frame is currently inside of.
3026 @cindex catch exceptions
3027 @cindex exception handlers
3028 Print a list of all the exception handlers that are active in the
3029 current stack frame at the current point of execution. To see other
3030 exception handlers, visit the associated frame (using the @code{up},
3031 @code{down}, or @code{frame} commands); then type @code{info catch}.
3032 @xref{Exception Handling, ,Breakpoints and Exceptions}.
3036 @chapter Examining Source Files
3038 _GDBN__ can print parts of your program's source, since the debugging
3039 information recorded in your program tells _GDBN__ what source files were
3040 used to build it. When your program stops, _GDBN__ spontaneously prints
3041 the line where it stopped. Likewise, when you select a stack frame
3042 (@pxref{Selection, ,Selecting a Frame}), _GDBN__ prints the line where
3043 execution in that frame has stopped. You can print other portions of
3044 source files by explicit command.
3047 If you use _GDBN__ through its GNU Emacs interface, you may prefer to use
3048 Emacs facilities to view source; @pxref{Emacs, ,Using _GDBN__ under GNU
3053 * List:: Printing Source Lines
3054 _if__(_GENERIC__ || !_H8__)
3055 * Search:: Searching Source Files
3056 _fi__(_GENERIC__ || !_H8__)
3057 * Source Path:: Specifying Source Directories
3058 * Machine Code:: Source and Machine Code
3062 @section Printing Source Lines
3066 To print lines from a source file, use the @code{list} command
3067 (abbreviated @code{l}). There are several ways to specify what part
3068 of the file you want to print.
3070 Here are the forms of the @code{list} command most commonly used:
3073 @item list @var{linenum}
3074 Print lines centered around line number @var{linenum} in the
3075 current source file.
3077 @item list @var{function}
3078 Print lines centered around the beginning of function
3082 Print more lines. If the last lines printed were printed with a
3083 @code{list} command, this prints lines following the last lines
3084 printed; however, if the last line printed was a solitary line printed
3085 as part of displaying a stack frame (@pxref{Stack, ,Examining the
3086 Stack}), this prints lines centered around that line.
3089 Print lines just before the lines last printed.
3092 By default, _GDBN__ prints ten source lines with any of these forms of
3093 the @code{list} command. You can change this using @code{set listsize}:
3096 @item set listsize @var{count}
3097 @kindex set listsize
3098 Make the @code{list} command display @var{count} source lines (unless
3099 the @code{list} argument explicitly specifies some other number).
3102 @kindex show listsize
3103 Display the number of lines that @code{list} will currently display by
3107 Repeating a @code{list} command with @key{RET} discards the argument,
3108 so it is equivalent to typing just @code{list}. This is more useful
3109 than listing the same lines again. An exception is made for an
3110 argument of @samp{-}; that argument is preserved in repetition so that
3111 each repetition moves up in the source file.
3114 In general, the @code{list} command expects you to supply zero, one or two
3115 @dfn{linespecs}. Linespecs specify source lines; there are several ways
3116 of writing them but the effect is always to specify some source line.
3117 Here is a complete description of the possible arguments for @code{list}:
3120 @item list @var{linespec}
3121 Print lines centered around the line specified by @var{linespec}.
3123 @item list @var{first},@var{last}
3124 Print lines from @var{first} to @var{last}. Both arguments are
3127 @item list ,@var{last}
3128 Print lines ending with @var{last}.
3130 @item list @var{first},
3131 Print lines starting with @var{first}.
3134 Print lines just after the lines last printed.
3137 Print lines just before the lines last printed.
3140 As described in the preceding table.
3143 Here are the ways of specifying a single source line---all the
3148 Specifies line @var{number} of the current source file.
3149 When a @code{list} command has two linespecs, this refers to
3150 the same source file as the first linespec.
3153 Specifies the line @var{offset} lines after the last line printed.
3154 When used as the second linespec in a @code{list} command that has
3155 two, this specifies the line @var{offset} lines down from the
3159 Specifies the line @var{offset} lines before the last line printed.
3161 @item @var{filename}:@var{number}
3162 Specifies line @var{number} in the source file @var{filename}.
3164 @item @var{function}
3165 @c FIXME: "of the open-brace" is C-centric. When we add other langs...
3166 Specifies the line of the open-brace that begins the body of the
3167 function @var{function}.
3169 @item @var{filename}:@var{function}
3170 Specifies the line of the open-brace that begins the body of the
3171 function @var{function} in the file @var{filename}. You only need the
3172 file name with a function name to avoid ambiguity when there are
3173 identically named functions in different source files.
3175 @item *@var{address}
3176 Specifies the line containing the program address @var{address}.
3177 @var{address} may be any expression.
3180 _if__(_GENERIC__ || !_H8__)
3182 @section Searching Source Files
3184 @kindex reverse-search
3186 There are two commands for searching through the current source file for a
3190 @item forward-search @var{regexp}
3191 @itemx search @var{regexp}
3193 @kindex forward-search
3194 The command @samp{forward-search @var{regexp}} checks each line,
3195 starting with the one following the last line listed, for a match for
3196 @var{regexp}. It lists the line that is found. You can use
3197 synonym @samp{search @var{regexp}} or abbreviate the command name as
3200 @item reverse-search @var{regexp}
3201 The command @samp{reverse-search @var{regexp}} checks each line, starting
3202 with the one before the last line listed and going backward, for a match
3203 for @var{regexp}. It lists the line that is found. You can abbreviate
3204 this command as @code{rev}.
3206 _fi__(_GENERIC__ || !_H8__)
3209 @section Specifying Source Directories
3212 @cindex directories for source files
3213 Executable programs sometimes do not record the directories of the source
3214 files from which they were compiled, just the names. Even when they do,
3215 the directories could be moved between the compilation and your debugging
3216 session. _GDBN__ has a list of directories to search for source files;
3217 this is called the @dfn{source path}. Each time _GDBN__ wants a source file,
3218 it tries all the directories in the list, in the order they are present
3219 in the list, until it finds a file with the desired name. Note that
3220 the executable search path is @emph{not} used for this purpose. Neither is
3221 the current working directory, unless it happens to be in the source
3224 If _GDBN__ cannot find a source file in the source path, and the object
3225 program records a directory, _GDBN__ tries that directory too. If the
3226 source path is empty, and there is no record of the compilation
3227 directory, _GDBN__ will, as a last resort, look in the current
3230 Whenever you reset or rearrange the source path, _GDBN__ will clear out
3231 any information it has cached about where source files are found, where
3232 each line is in the file, etc.
3235 When you start _GDBN__, its source path is empty.
3236 To add other directories, use the @code{directory} command.
3239 @item directory @var{dirname} @dots{}
3240 Add directory @var{dirname} to the front of the source path. Several
3241 directory names may be given to this command, separated by @samp{:} or
3242 whitespace. You may specify a directory that is already in the source
3243 path; this moves it forward, so it will be searched sooner.
3245 You can use the string @samp{$cdir} to refer to the compilation
3246 directory (if one is recorded), and @samp{$cwd} to refer to the current
3247 working directory. @samp{$cwd} is not the same as @samp{.}---the former
3248 tracks the current working directory as it changes during your _GDBN__
3249 session, while the latter is immediately expanded to the current
3250 directory at the time you add an entry to the source path.
3253 Reset the source path to empty again. This requires confirmation.
3255 @c RET-repeat for @code{directory} is explicitly disabled, but since
3256 @c repeating it would be a no-op we do not say that. (thanks to RMS)
3258 @item show directories
3259 @kindex show directories
3260 Print the source path: show which directories it contains.
3263 If your source path is cluttered with directories that are no longer of
3264 interest, _GDBN__ may sometimes cause confusion by finding the wrong
3265 versions of source. You can correct the situation as follows:
3269 Use @code{directory} with no argument to reset the source path to empty.
3272 Use @code{directory} with suitable arguments to reinstall the
3273 directories you want in the source path. You can add all the
3274 directories in one command.
3278 @section Source and Machine Code
3280 You can use the command @code{info line} to map source lines to program
3281 addresses (and viceversa), and the command @code{disassemble} to display
3282 a range of addresses as machine instructions.
3285 @item info line @var{linespec}
3287 Print the starting and ending addresses of the compiled code for
3288 source line @var{linespec}. You can specify source lines in any of
3289 the ways understood by the @code{list} command (@pxref{List, ,Printing
3293 For example, we can use @code{info line} to discover the location of
3294 the object code for the first line of function
3295 @code{m4_changequote}:
3298 (_GDBP__) info line m4_changecom
3299 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
3303 We can also inquire (using @code{*@var{addr}} as the form for
3304 @var{linespec}) what source line covers a particular address:
3306 (_GDBP__) info line *0x63ff
3307 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
3310 @cindex @code{$_} and @code{info line}
3311 After @code{info line}, the default address for the @code{x} command
3312 is changed to the starting address of the line, so that @samp{x/i} is
3313 sufficient to begin examining the machine code (@pxref{Memory,
3314 ,Examining Memory}). Also, this address is saved as the value of the
3315 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
3321 This specialized command dumps a range of memory as machine
3322 instructions. The default memory range is the function surrounding the
3323 program counter of the selected frame. A single argument to this
3324 command is a program counter value; the function surrounding this value
3325 will be dumped. Two arguments specify a range of addresses (first
3326 inclusive, second exclusive) to dump.
3329 _if__(_GENERIC__||!_H8__)
3330 We can use @code{disassemble} to inspect the object code
3331 range shown in the last @code{info line} example (the example
3332 shows SPARC machine instructions):
3336 (_GDBP__) disas 0x63e4 0x6404
3337 Dump of assembler code from 0x63e4 to 0x6404:
3338 0x63e4 <builtin_init+5340>: ble 0x63f8 <builtin_init+5360>
3339 0x63e8 <builtin_init+5344>: sethi %hi(0x4c00), %o0
3340 0x63ec <builtin_init+5348>: ld [%i1+4], %o0
3341 0x63f0 <builtin_init+5352>: b 0x63fc <builtin_init+5364>
3342 0x63f4 <builtin_init+5356>: ld [%o0+4], %o0
3343 0x63f8 <builtin_init+5360>: or %o0, 0x1a4, %o0
3344 0x63fc <builtin_init+5364>: call 0x9288 <path_search>
3345 0x6400 <builtin_init+5368>: nop
3346 End of assembler dump.
3349 _fi__(_GENERIC__||!_H8__)
3351 _if__(!_GENERIC__||_H8__)
3352 For example, here is the beginning of the output for the
3353 disassembly of a function @code{fact}:
3357 (_GDBP__) disas fact
3358 Dump of assembler code for function fact:
3360 0x802c <fact>: 6d f2 mov.w r2,@@-r7
3361 0x802e <fact+2>: 6d f3 mov.w r3,@@-r7
3362 0x8030 <fact+4>: 6d f6 mov.w r6,@@-r7
3363 0x8032 <fact+6>: 0d 76 mov.w r7,r6
3364 0x8034 <fact+8>: 6f 70 00 08 mov.w @@(0x8,r7),r0
3365 0x8038 <fact+12> 19 11 sub.w r1,r1
3371 _fi__(!_GENERIC__||_H8__)
3375 @chapter Examining Data
3377 @cindex printing data
3378 @cindex examining data
3381 @c "inspect" is not quite a synonym if you are using Epoch, which we do not
3382 @c document because it is nonstandard... Under Epoch it displays in a
3383 @c different window or something like that.
3384 The usual way to examine data in your program is with the @code{print}
3385 command (abbreviated @code{p}), or its synonym @code{inspect}.
3387 It evaluates and prints the value of an expression of the language your
3388 program is written in (@pxref{Languages, ,Using _GDBN__ with Different
3393 @item print @var{exp}
3394 @itemx print /@var{f} @var{exp}
3395 @var{exp} is an expression (in the source language). By default
3396 the value of @var{exp} is printed in a format appropriate to its data
3397 type; you can choose a different format by specifying @samp{/@var{f}},
3398 where @var{f} is a letter specifying the format; @pxref{Output formats}.
3401 @itemx print /@var{f}
3402 If you omit @var{exp}, _GDBN__ displays the last value again (from the
3403 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
3404 conveniently inspect the same value in an alternative format.
3407 A more low-level way of examining data is with the @code{x} command.
3408 It examines data in memory at a specified address and prints it in a
3409 specified format. @xref{Memory, ,Examining Memory}.
3411 If you are interested in information about types, or about how the fields
3412 of a struct or class are declared, use the @code{ptype @var{exp}}
3413 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol Table}.
3416 * Expressions:: Expressions
3417 * Variables:: Program Variables
3418 * Arrays:: Artificial Arrays
3419 * Output formats:: Output formats
3420 * Memory:: Examining Memory
3421 * Auto Display:: Automatic Display
3422 * Print Settings:: Print Settings
3423 * Value History:: Value History
3424 * Convenience Vars:: Convenience Variables
3425 * Registers:: Registers
3426 _if__(_GENERIC__ || !_H8__)
3427 * Floating Point Hardware:: Floating Point Hardware
3428 _fi__(_GENERIC__ || !_H8__)
3432 @section Expressions
3435 @code{print} and many other _GDBN__ commands accept an expression and
3436 compute its value. Any kind of constant, variable or operator defined
3437 by the programming language you are using is legal in an expression in
3438 _GDBN__. This includes conditional expressions, function calls, casts
3439 and string constants. It unfortunately does not include symbols defined
3440 by preprocessor @code{#define} commands.
3443 Because C is so widespread, most of the expressions shown in examples in
3444 this manual are in C. @xref{Languages, , Using _GDBN__ with Different
3445 Languages}, for information on how to use expressions in other
3448 In this section, we discuss operators that you can use in _GDBN__
3449 expressions regardless of your programming language.
3451 Casts are supported in all languages, not just in C, because it is so
3452 useful to cast a number into a pointer so as to examine a structure
3453 at that address in memory.
3454 @c FIXME: casts supported---Mod2 true?
3457 _GDBN__ supports these operators in addition to those of programming
3462 @samp{@@} is a binary operator for treating parts of memory as arrays.
3463 @xref{Arrays, ,Artificial Arrays}, for more information.
3466 @samp{::} allows you to specify a variable in terms of the file or
3467 function where it is defined. @xref{Variables, ,Program Variables}.
3469 @item @{@var{type}@} @var{addr}
3470 Refers to an object of type @var{type} stored at address @var{addr} in
3471 memory. @var{addr} may be any expression whose value is an integer or
3472 pointer (but parentheses are required around binary operators, just as in
3473 a cast). This construct is allowed regardless of what kind of data is
3474 normally supposed to reside at @var{addr}.
3478 @section Program Variables
3480 The most common kind of expression to use is the name of a variable
3483 Variables in expressions are understood in the selected stack frame
3484 (@pxref{Selection, ,Selecting a Frame}); they must either be global
3485 (or static) or be visible according to the scope rules of the
3486 programming language from the point of execution in that frame. This
3487 means that in the function
3502 the variable @code{a} is usable whenever your program is executing
3503 within the function @code{foo}, but the variable @code{b} is visible
3504 only while your program is executing inside the block in which @code{b}
3507 @cindex variable name conflict
3508 There is an exception: you can refer to a variable or function whose
3509 scope is a single source file even if the current execution point is not
3510 in this file. But it is possible to have more than one such variable or
3511 function with the same name (in different source files). If that
3512 happens, referring to that name has unpredictable effects. If you wish,
3513 you can specify a static variable in a particular function or file,
3514 using the colon-colon notation:
3518 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
3522 @var{file}::@var{variable}
3523 @var{function}::@var{variable}
3527 Here @var{file} or @var{function} is the name of the context for the
3528 static @var{variable}. In the case of file names, you can use quotes to
3529 make sure _GDBN__ parses the file name as a single word---for example,
3530 to print a global value of @code{x} defined in @file{f2.c}:
3533 (_GDBP__) p 'f2.c'::x
3536 @cindex C++ scope resolution
3537 This use of @samp{::} is very rarely in conflict with the very similar
3538 use of the same notation in C++. _GDBN__ also supports use of the C++
3539 scope resolution operator in _GDBN__ expressions.
3541 @cindex wrong values
3542 @cindex variable values, wrong
3544 @emph{Warning:} Occasionally, a local variable may appear to have the
3545 wrong value at certain points in a function---just after entry to the
3546 function, and just before exit. You may see this problem when you are
3547 stepping by machine instructions. This is because on most machines, it
3548 takes more than one instruction to set up a stack frame (including local
3549 variable definitions); if you are stepping by machine instructions,
3550 variables may appear to have the wrong values until the stack frame is
3551 completely built. On function exit, it usually also takes more than one
3552 machine instruction to destroy a stack frame; after you begin stepping
3553 through that group of instructions, local variable definitions may be
3558 @section Artificial Arrays
3560 @cindex artificial array
3562 It is often useful to print out several successive objects of the
3563 same type in memory; a section of an array, or an array of
3564 dynamically determined size for which only a pointer exists in the
3567 This can be done by constructing an @dfn{artificial array} with the
3568 binary operator @samp{@@}. The left operand of @samp{@@} should be
3569 the first element of the desired array, as an individual object.
3570 The right operand should be the desired length of the array. The result is
3571 an array value whose elements are all of the type of the left argument.
3572 The first element is actually the left argument; the second element
3573 comes from bytes of memory immediately following those that hold the
3574 first element, and so on. Here is an example. If a program says
3577 int *array = (int *) malloc (len * sizeof (int));
3581 you can print the contents of @code{array} with
3587 The left operand of @samp{@@} must reside in memory. Array values made
3588 with @samp{@@} in this way behave just like other arrays in terms of
3589 subscripting, and are coerced to pointers when used in expressions.
3590 Artificial arrays most often appear in expressions via the value history
3591 (@pxref{Value History, ,Value History}), after printing one out.)
3593 Sometimes the artificial array mechanism is not quite enough; in
3594 moderately complex data structures, the elements of interest may not
3595 actually be adjacent---for example, if you are interested in the values
3596 of pointers in an array. One useful work-around in this situation is
3597 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
3598 Variables}) as a counter in an expression that prints the first
3599 interesting value, and then repeat that expression via @key{RET}. For
3600 instance, suppose you have an array @code{dtab} of pointers to
3601 structures, and you are interested in the values of a field @code{fv}
3602 in each structure. Here is an example of what you might type:
3612 @node Output formats
3613 @section Output formats
3615 @cindex formatted output
3616 @cindex output formats
3617 By default, _GDBN__ prints a value according to its data type. Sometimes
3618 this is not what you want. For example, you might want to print a number
3619 in hex, or a pointer in decimal. Or you might want to view data in memory
3620 at a certain address as a character string or as an instruction. To do
3621 these things, specify an @dfn{output format} when you print a value.
3623 The simplest use of output formats is to say how to print a value
3624 already computed. This is done by starting the arguments of the
3625 @code{print} command with a slash and a format letter. The format
3626 letters supported are:
3630 Regard the bits of the value as an integer, and print the integer in
3634 Print as integer in signed decimal.
3637 Print as integer in unsigned decimal.
3640 Print as integer in octal.
3643 Print as integer in binary. The letter @samp{t} stands for ``two''.
3646 Print as an address, both absolute in hex and as an offset from the
3647 nearest preceding symbol. This format can be used to discover where (in
3648 what function) an unknown address is located:
3651 (_GDBP__) p/a 0x54320
3652 _0__$3 = 0x54320 <_initialize_vx+396>_1__
3656 Regard as an integer and print it as a character constant.
3659 Regard the bits of the value as a floating point number and print
3660 using typical floating point syntax.
3663 For example, to print the program counter in hex (@pxref{Registers}), type
3670 Note that no space is required before the slash; this is because command
3671 names in _GDBN__ cannot contain a slash.
3673 To reprint the last value in the value history with a different format,
3674 you can use the @code{print} command with just a format and no
3675 expression. For example, @samp{p/x} reprints the last value in hex.
3678 @section Examining Memory
3680 You can use the command @code{x} (for ``examine'') to examine memory in
3681 any of several formats, independently of your program's data types.
3683 @cindex examining memory
3686 @item x/@var{nfu} @var{addr}
3689 Use the command @code{x} to examine memory.
3692 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
3693 much memory to display and how to format it; @var{addr} is an
3694 expression giving the address where you want to start displaying memory.
3695 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
3696 Several commands set convenient defaults for @var{addr}.
3699 @item @var{n}, the repeat count
3700 The repeat count is a decimal integer; the default is 1. It specifies
3701 how much memory (counting by units @var{u}) to display.
3702 @c This really is **decimal**; unaffected by 'set radix' as of GDB
3705 @item @var{f}, the display format
3706 The display format is one of the formats used by @code{print},
3707 or @samp{s} (null-terminated string) or @samp{i} (machine instruction).
3708 The default is @samp{x} (hexadecimal) initially, or the format from the
3709 last time you used either @code{x} or @code{print}.
3711 @item @var{u}, the unit size
3712 The unit size is any of
3717 Halfwords (two bytes).
3719 Words (four bytes). This is the initial default.
3721 Giant words (eight bytes).
3724 Each time you specify a unit size with @code{x}, that size becomes the
3725 default unit the next time you use @code{x}. (For the @samp{s} and
3726 @samp{i} formats, the unit size is ignored and is normally not written.)
3728 @item @var{addr}, starting display address
3729 @var{addr} is the address where you want _GDBN__ to begin displaying
3730 memory. The expression need not have a pointer value (though it may);
3731 it is always interpreted as an integer address of a byte of memory.
3732 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
3733 @var{addr} is usually just after the last address examined---but several
3734 other commands also set the default address: @code{info breakpoints} (to
3735 the address of the last breakpoint listed), @code{info line} (to the
3736 starting address of a line), and @code{print} (if you use it to display
3737 a value from memory).
3740 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
3741 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
3742 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
3743 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
3744 @pxref{Registers}) in hexadecimal (@samp{x}).
3746 Since the letters indicating unit sizes are all distinct from the
3747 letters specifying output formats, you do not have to remember whether
3748 unit size or format comes first; either order will work. The output
3749 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
3750 (However, the count @var{n} must come first; @samp{wx4} will not work.)
3752 Even though the unit size @var{u} is ignored for the formats @samp{s}
3753 and @samp{i}, you might still want to use a count @var{n}; for example,
3754 @samp{3i} specifies that you want to see three machine instructions,
3755 including any operands. The command @code{disassemble} gives an
3756 alternative way of inspecting machine instructions; @pxref{Machine
3759 All the defaults for the arguments to @code{x} are designed to make it
3760 easy to continue scanning memory with minimal specifications each time
3761 you use @code{x}. For example, after you have inspected three machine
3762 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
3763 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
3764 the repeat count @var{n} is used again; the other arguments default as
3765 for successive uses of @code{x}.
3767 @cindex @code{$_}, @code{$__}, and value history
3768 The addresses and contents printed by the @code{x} command are not saved
3769 in the value history because there is often too much of them and they
3770 would get in the way. Instead, _GDBN__ makes these values available for
3771 subsequent use in expressions as values of the convenience variables
3772 @code{$_} and @code{$__}. After an @code{x} command, the last address
3773 examined is available for use in expressions in the convenience variable
3774 @code{$_}. The contents of that address, as examined, are available in
3775 the convenience variable @code{$__}.
3777 If the @code{x} command has a repeat count, the address and contents saved
3778 are from the last memory unit printed; this is not the same as the last
3779 address printed if several units were printed on the last line of output.
3782 @section Automatic Display
3783 @cindex automatic display
3784 @cindex display of expressions
3786 If you find that you want to print the value of an expression frequently
3787 (to see how it changes), you might want to add it to the @dfn{automatic
3788 display list} so that _GDBN__ will print its value each time your program stops.
3789 Each expression added to the list is given a number to identify it;
3790 to remove an expression from the list, you specify that number.
3791 The automatic display looks like this:
3795 3: bar[5] = (struct hack *) 0x3804
3799 showing item numbers, expressions and their current values. As with
3800 displays you request manually using @code{x} or @code{print}, you can
3801 specify the output format you prefer; in fact, @code{display} decides
3802 whether to use @code{print} or @code{x} depending on how elaborate your
3803 format specification is---it uses @code{x} if you specify a unit size,
3804 or one of the two formats (@samp{i} and @samp{s}) that are only
3805 supported by @code{x}; otherwise it uses @code{print}.
3808 @item display @var{exp}
3810 Add the expression @var{exp} to the list of expressions to display
3811 each time your program stops. @xref{Expressions, ,Expressions}.
3813 @code{display} will not repeat if you press @key{RET} again after using it.
3815 @item display/@var{fmt} @var{exp}
3816 For @var{fmt} specifying only a display format and not a size or
3817 count, add the expression @var{exp} to the auto-display list but
3818 arranges to display it each time in the specified format @var{fmt}.
3819 @xref{Output formats}.
3821 @item display/@var{fmt} @var{addr}
3822 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
3823 number of units, add the expression @var{addr} as a memory address to
3824 be examined each time your program stops. Examining means in effect
3825 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
3828 For example, @samp{display/i $pc} can be helpful, to see the machine
3829 instruction about to be executed each time execution stops (@samp{$pc}
3830 is a common name for the program counter; @pxref{Registers}).
3833 @item undisplay @var{dnums}@dots{}
3834 @itemx delete display @var{dnums}@dots{}
3835 @kindex delete display
3837 Remove item numbers @var{dnums} from the list of expressions to display.
3839 @code{undisplay} will not repeat if you press @key{RET} after using it.
3840 (Otherwise you would just get the error @samp{No display number @dots{}}.)
3842 @item disable display @var{dnums}@dots{}
3843 @kindex disable display
3844 Disable the display of item numbers @var{dnums}. A disabled display
3845 item is not printed automatically, but is not forgotten. It may be
3846 enabled again later.
3848 @item enable display @var{dnums}@dots{}
3849 @kindex enable display
3850 Enable display of item numbers @var{dnums}. It becomes effective once
3851 again in auto display of its expression, until you specify otherwise.
3854 Display the current values of the expressions on the list, just as is
3855 done when your program stops.
3858 @kindex info display
3859 Print the list of expressions previously set up to display
3860 automatically, each one with its item number, but without showing the
3861 values. This includes disabled expressions, which are marked as such.
3862 It also includes expressions which would not be displayed right now
3863 because they refer to automatic variables not currently available.
3866 If a display expression refers to local variables, then it does not make
3867 sense outside the lexical context for which it was set up. Such an
3868 expression is disabled when execution enters a context where one of its
3869 variables is not defined. For example, if you give the command
3870 @code{display last_char} while inside a function with an argument
3871 @code{last_char}, then this argument will be displayed while your program
3872 continues to stop inside that function. When it stops elsewhere---where
3873 there is no variable @code{last_char}---display is disabled. The next time
3874 your program stops where @code{last_char} is meaningful, you can enable the
3875 display expression once again.
3877 @node Print Settings
3878 @section Print Settings
3880 @cindex format options
3881 @cindex print settings
3882 _GDBN__ provides the following ways to control how arrays, structures,
3883 and symbols are printed.
3886 These settings are useful for debugging programs in any language:
3889 @item set print address
3890 @item set print address on
3891 @kindex set print address
3892 _GDBN__ will print memory addresses showing the location of stack
3893 traces, structure values, pointer values, breakpoints, and so forth,
3894 even when it also displays the contents of those addresses. The default
3895 is on. For example, this is what a stack frame display looks like, with
3896 @code{set print address on}:
3901 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
3903 530 if (lquote != def_lquote)
3907 @item set print address off
3908 Do not print addresses when displaying their contents. For example,
3909 this is the same stack frame displayed with @code{set print address off}:
3913 (_GDBP__) set print addr off
3915 #0 set_quotes (lq="<<", rq=">>") at input.c:530
3916 530 if (lquote != def_lquote)
3920 @item show print address
3921 @kindex show print address
3922 Show whether or not addresses are to be printed.
3924 @item set print array
3925 @itemx set print array on
3926 @kindex set print array
3927 _GDBN__ will pretty print arrays. This format is more convenient to read,
3928 but uses more space. The default is off.
3930 @item set print array off.
3931 Return to compressed format for arrays.
3933 @item show print array
3934 @kindex show print array
3935 Show whether compressed or pretty format is selected for displaying
3938 @item set print elements @var{number-of-elements}
3939 @kindex set print elements
3940 If _GDBN__ is printing a large array, it will stop printing after it has
3941 printed the number of elements set by the @code{set print elements} command.
3942 This limit also applies to the display of strings.
3944 @item show print elements
3945 @kindex show print elements
3946 Display the number of elements of a large array that _GDBN__ will print
3947 before losing patience.
3949 @item set print pretty on
3950 @kindex set print pretty
3951 Cause _GDBN__ to print structures in an indented format with one member per
3967 @item set print pretty off
3968 Cause _GDBN__ to print structures in a compact format, like this:
3972 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
3973 meat = 0x54 "Pork"@}
3978 This is the default format.
3980 @item show print pretty
3981 @kindex show print pretty
3982 Show which format _GDBN__ will use to print structures.
3984 @item set print sevenbit-strings on
3985 @kindex set print sevenbit-strings
3986 Print using only seven-bit characters; if this option is set,
3987 _GDBN__ will display any eight-bit characters (in strings or character
3988 values) using the notation @code{\}@var{nnn}. For example, @kbd{M-a} is
3989 displayed as @code{\341}.
3991 @item set print sevenbit-strings off
3992 Print using either seven-bit or eight-bit characters, as required. This
3995 @item show print sevenbit-strings
3996 @kindex show print sevenbit-strings
3997 Show whether or not _GDBN__ will print only seven-bit characters.
3999 @item set print union on
4000 @kindex set print union
4001 Tell _GDBN__ to print unions which are contained in structures. This is the
4004 @item set print union off
4005 Tell _GDBN__ not to print unions which are contained in structures.
4007 @item show print union
4008 @kindex show print union
4009 Ask _GDBN__ whether or not it will print unions which are contained in
4012 For example, given the declarations
4015 typedef enum @{Tree, Bug@} Species;
4016 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
4017 typedef enum @{Caterpillar, Cocoon, Butterfly@}
4028 struct thing foo = @{Tree, @{Acorn@}@};
4032 with @code{set print union on} in effect @samp{p foo} would print
4035 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
4039 and with @code{set print union off} in effect it would print
4042 $1 = @{it = Tree, form = @{...@}@}
4047 These settings are of interest when debugging C++ programs:
4050 @item set print demangle
4051 @itemx set print demangle on
4052 @kindex set print demangle
4053 Print C++ names in their source form rather than in the mangled form
4054 in which they are passed to the assembler and linker for type-safe linkage.
4057 @item show print demangle
4058 @kindex show print demangle
4059 Show whether C++ names will be printed in mangled or demangled form.
4061 @item set print asm-demangle
4062 @itemx set print asm-demangle on
4063 @kindex set print asm-demangle
4064 Print C++ names in their source form rather than their mangled form, even
4065 in assembler code printouts such as instruction disassemblies.
4068 @item show print asm-demangle
4069 @kindex show print asm-demangle
4070 Show whether C++ names in assembly listings will be printed in mangled
4073 @item set print object
4074 @itemx set print object on
4075 @kindex set print object
4076 When displaying a pointer to an object, identify the @emph{actual}
4077 (derived) type of the object rather than the @emph{declared} type, using
4078 the virtual function table.
4080 @item set print object off
4081 Display only the declared type of objects, without reference to the
4082 virtual function table. This is the default setting.
4084 @item show print object
4085 @kindex show print object
4086 Show whether actual, or declared, object types will be displayed.
4088 @item set print vtbl
4089 @itemx set print vtbl on
4090 @kindex set print vtbl
4091 Pretty print C++ virtual function tables. The default is off.
4093 @item set print vtbl off
4094 Do not pretty print C++ virtual function tables.
4096 @item show print vtbl
4097 @kindex show print vtbl
4098 Show whether C++ virtual function tables are pretty printed, or not.
4102 @section Value History
4104 @cindex value history
4105 Values printed by the @code{print} command are saved in _GDBN__'s @dfn{value
4106 history} so that you can refer to them in other expressions. Values are
4107 kept until the symbol table is re-read or discarded (for example with
4108 the @code{file} or @code{symbol-file} commands). When the symbol table
4109 changes, the value history is discarded, since the values may contain
4110 pointers back to the types defined in the symbol table.
4114 @cindex history number
4115 The values printed are given @dfn{history numbers} for you to refer to them
4116 by. These are successive integers starting with one. @code{print} shows you
4117 the history number assigned to a value by printing @samp{$@var{num} = }
4118 before the value; here @var{num} is the history number.
4120 To refer to any previous value, use @samp{$} followed by the value's
4121 history number. The way @code{print} labels its output is designed to
4122 remind you of this. Just @code{$} refers to the most recent value in
4123 the history, and @code{$$} refers to the value before that.
4124 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
4125 is the value just prior to @code{$$}, @code{$$1} is equivalent to
4126 @code{$$}, and @code{$$0} is equivalent to @code{$}.
4128 For example, suppose you have just printed a pointer to a structure and
4129 want to see the contents of the structure. It suffices to type
4135 If you have a chain of structures where the component @code{next} points
4136 to the next one, you can print the contents of the next one with this:
4143 You can print successive links in the chain by repeating this
4144 command---which you can do by just typing @key{RET}.
4146 Note that the history records values, not expressions. If the value of
4147 @code{x} is 4 and you type these commands:
4155 then the value recorded in the value history by the @code{print} command
4156 remains 4 even though the value of @code{x} has changed.
4161 Print the last ten values in the value history, with their item numbers.
4162 This is like @samp{p@ $$9} repeated ten times, except that @code{show
4163 values} does not change the history.
4165 @item show values @var{n}
4166 Print ten history values centered on history item number @var{n}.
4169 Print ten history values just after the values last printed. If no more
4170 values are available, produces no display.
4173 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
4174 same effect as @samp{show values +}.
4176 @node Convenience Vars
4177 @section Convenience Variables
4179 @cindex convenience variables
4180 _GDBN__ provides @dfn{convenience variables} that you can use within
4181 _GDBN__ to hold on to a value and refer to it later. These variables
4182 exist entirely within _GDBN__; they are not part of your program, and
4183 setting a convenience variable has no direct effect on further execution
4184 of your program. That is why you can use them freely.
4186 Convenience variables are prefixed with @samp{$}. Any name preceded by
4187 @samp{$} can be used for a convenience variable, unless it is one of
4188 the predefined machine-specific register names (@pxref{Registers}).
4189 (Value history references, in contrast, are @emph{numbers} preceded
4190 by @samp{$}. @xref{Value History, ,Value History}.)
4192 You can save a value in a convenience variable with an assignment
4193 expression, just as you would set a variable in your program. Example:
4196 set $foo = *object_ptr
4200 would save in @code{$foo} the value contained in the object pointed to by
4203 Using a convenience variable for the first time creates it; but its value
4204 is @code{void} until you assign a new value. You can alter the value with
4205 another assignment at any time.
4207 Convenience variables have no fixed types. You can assign a convenience
4208 variable any type of value, including structures and arrays, even if
4209 that variable already has a value of a different type. The convenience
4210 variable, when used as an expression, has the type of its current value.
4213 @item show convenience
4214 @kindex show convenience
4215 Print a list of convenience variables used so far, and their values.
4216 Abbreviated @code{show con}.
4219 One of the ways to use a convenience variable is as a counter to be
4220 incremented or a pointer to be advanced. For example, to print
4221 a field from successive elements of an array of structures:
4225 print bar[$i++]->contents
4226 @i{@dots{} repeat that command by typing @key{RET}.}
4229 Some convenience variables are created automatically by _GDBN__ and given
4230 values likely to be useful.
4235 The variable @code{$_} is automatically set by the @code{x} command to
4236 the last address examined (@pxref{Memory, ,Examining Memory}). Other
4237 commands which provide a default address for @code{x} to examine also
4238 set @code{$_} to that address; these commands include @code{info line}
4239 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
4240 except when set by the @code{x} command, in which case it is a pointer
4241 to the type of @code{$__}.
4245 The variable @code{$__} is automatically set by the @code{x} command
4246 to the value found in the last address examined. Its type is chosen
4247 to match the format in which the data was printed.
4254 You can refer to machine register contents, in expressions, as variables
4255 with names starting with @samp{$}. The names of registers are different
4256 for each machine; use @code{info registers} to see the names used on
4260 @item info registers
4261 @kindex info registers
4262 Print the names and values of all registers except floating-point
4263 registers (in the selected stack frame).
4265 @item info all-registers
4266 @kindex info all-registers
4267 @cindex floating point registers
4268 Print the names and values of all registers, including floating-point
4271 @item info registers @var{regname} @dots{}
4272 Print the relativized value of each specified register @var{regname}.
4273 @var{regname} may be any register name valid on the machine you are using, with
4274 or without the initial @samp{$}.
4277 _GDBN__ has four ``standard'' register names that are available (in
4278 expressions) on most machines---whenever they do not conflict with an
4279 architecture's canonical mnemonics for registers. The register names
4280 @code{$pc} and @code{$sp} are used for the program counter register and
4281 the stack pointer. @code{$fp} is used for a register that contains a
4282 pointer to the current stack frame, and @code{$ps} is used for a
4283 register that contains the processor status. For example,
4284 you could print the program counter in hex with
4291 or print the instruction to be executed next with
4298 or add four to the stack pointer @footnote{This is a way of removing
4299 one word from the stack, on machines where stacks grow downward in
4300 memory (most machines, nowadays). This assumes that the innermost
4301 stack frame is selected; setting @code{$sp} is not allowed when other
4302 stack frames are selected. To pop entire frames off the stack,
4303 regardless of machine architecture, use @code{return};
4304 @pxref{Returning, ,Returning from a Function}.} with
4310 Whenever possible, these four standard register names are available on
4311 your machine even though the machine has different canonical mnemonics,
4312 so long as there is no conflict. The @code{info registers} command
4313 shows the canonical names. For example, on the SPARC, @code{info
4314 registers} displays the processor status register as @code{$psr} but you
4315 can also refer to it as @code{$ps}.
4317 _GDBN__ always considers the contents of an ordinary register as an
4318 integer when the register is examined in this way. Some machines have
4319 special registers which can hold nothing but floating point; these
4320 registers are considered to have floating point values. There is no way
4321 to refer to the contents of an ordinary register as floating point value
4322 (although you can @emph{print} it as a floating point value with
4323 @samp{print/f $@var{regname}}).
4325 Some registers have distinct ``raw'' and ``virtual'' data formats. This
4326 means that the data format in which the register contents are saved by
4327 the operating system is not the same one that your program normally
4328 sees. For example, the registers of the 68881 floating point
4329 coprocessor are always saved in ``extended'' (raw) format, but all C
4330 programs expect to work with ``double'' (virtual) format. In such
4331 cases, _GDBN__ normally works with the virtual format only (the format that
4332 makes sense for your program), but the @code{info registers} command
4333 prints the data in both formats.
4335 Normally, register values are relative to the selected stack frame
4336 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
4337 value that the register would contain if all stack frames farther in
4338 were exited and their saved registers restored. In order to see the
4339 true contents of hardware registers, you must select the innermost
4340 frame (with @samp{frame 0}).
4342 However, _GDBN__ must deduce where registers are saved, from the machine
4343 code generated by your compiler. If some registers are not saved, or if
4344 _GDBN__ is unable to locate the saved registers, the selected stack
4345 frame will make no difference.
4349 @item set rstack_high_address @var{address}
4350 @kindex set rstack_high_address
4351 @cindex AMD 29K register stack
4352 @cindex register stack, AMD29K
4353 On AMD 29000 family processors, registers are saved in a separate
4354 ``register stack''. There is no way for _GDBN__ to determine the extent
4355 of this stack. Normally, _GDBN__ just assumes that the stack is ``large
4356 enough''. This may result in _GDBN__ referencing memory locations that
4357 don't exist. If necessary, you can get around this problem by
4358 specifying the ending address of the register stack with the @code{set
4359 rstack_high_address} command. The argument should be an address, which
4360 you will probably want to precede with @samp{0x} to specify in
4363 @item show rstack_high_address
4364 @kindex show rstack_high_address
4365 Display the current limit of the register stack, on AMD 29000 family
4370 _if__(_GENERIC__ || !_H8__)
4371 @node Floating Point Hardware
4372 @section Floating Point Hardware
4373 @cindex floating point
4375 Depending on the host machine architecture, _GDBN__ may be able to give
4376 you more information about the status of the floating point hardware.
4381 If available, provides hardware-dependent information about the floating
4382 point unit. The exact contents and layout vary depending on the
4383 floating point chip.
4385 @c FIXME: this is a cop-out. Try to get examples, explanations. Only
4386 @c FIXME...supported currently on arm's and 386's. Mark properly with
4387 @c FIXME... m4 macros to isolate general statements from hardware-dep,
4388 @c FIXME... at that point.
4389 _fi__(_GENERIC__ || !_H8__)
4393 @chapter Using _GDBN__ with Different Languages
4396 Although programming languages generally have common aspects, they are
4397 rarely expressed in the same manner. For instance, in ANSI C,
4398 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
4399 Modula-2, it is accomplished by @code{p^}. Values can also be
4400 represented (and displayed) differently. Hex numbers in C are written
4401 like @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
4403 @cindex working language
4404 Language-specific information is built into _GDBN__ for some languages,
4405 allowing you to express operations like the above in your program's
4406 native language, and allowing _GDBN__ to output values in a manner
4407 consistent with the syntax of your program's native language. The
4408 language you use to build expressions, called the @dfn{working
4409 language}, can be selected manually, or _GDBN__ can set it
4413 * Setting:: Switching between source languages
4414 * Show:: Displaying the language
4415 * Checks:: Type and Range checks
4416 * Support:: Supported languages
4420 @section Switching between source languages
4422 There are two ways to control the working language---either have _GDBN__
4423 set it automatically, or select it manually yourself. You can use the
4424 @code{set language} command for either purpose. On startup, _GDBN__
4425 defaults to setting the language automatically.
4428 * Manually:: Setting the working language manually
4429 * Automatically:: Having _GDBN__ infer the source language
4433 @subsection Setting the working language
4435 @kindex set language
4436 To set the language, issue the command @samp{set language @var{lang}},
4437 where @var{lang} is the name of a language: @code{c} or @code{modula-2}.
4438 For a list of the supported languages, type @samp{set language}.
4440 Setting the language manually prevents _GDBN__ from updating the working
4441 language automatically. This can lead to confusion if you try
4442 to debug a program when the working language is not the same as the
4443 source language, when an expression is acceptable to both
4444 languages---but means different things. For instance, if the current
4445 source file were written in C, and _GDBN__ was parsing Modula-2, a
4453 might not have the effect you intended. In C, this means to add
4454 @code{b} and @code{c} and place the result in @code{a}. The result
4455 printed would be the value of @code{a}. In Modula-2, this means to compare
4456 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
4458 If you allow _GDBN__ to set the language automatically, then
4459 you can count on expressions evaluating the same way in your debugging
4460 session and in your program.
4463 @subsection Having _GDBN__ infer the source language
4465 To have _GDBN__ set the working language automatically, use @samp{set
4466 language local} or @samp{set language auto}. _GDBN__ then infers the
4467 language that a program was written in by looking at the name of its
4468 source files, and examining their extensions:
4472 Modula-2 source file
4482 This information is recorded for each function or procedure in a source
4483 file. When your program stops in a frame (usually by encountering a
4484 breakpoint), _GDBN__ sets the working language to the language recorded
4485 for the function in that frame. If the language for a frame is unknown
4486 (that is, if the function or block corresponding to the frame was
4487 defined in a source file that does not have a recognized extension), the
4488 current working language is not changed, and _GDBN__ issues a warning.
4490 This may not seem necessary for most programs, which are written
4491 entirely in one source language. However, program modules and libraries
4492 written in one source language can be used by a main program written in
4493 a different source language. Using @samp{set language auto} in this
4494 case frees you from having to set the working language manually.
4497 @section Displaying the language
4499 The following commands will help you find out which language is the
4500 working language, and also what language source files were written in.
4502 @kindex show language
4507 Display the current working language. This is the
4508 language you can use with commands such as @code{print} to
4509 build and compute expressions that may involve variables in your program.
4512 Among the other information listed here (@pxref{Frame Info, ,Information
4513 about a Frame}) is the source language for this frame. This is the
4514 language that will become the working language if you ever use an
4515 identifier that is in this frame.
4518 Among the other information listed here (@pxref{Symbols, ,Examining the
4519 Symbol Table}) is the source language of this source file.
4523 @section Type and range Checking
4526 @emph{Warning:} In this release, the _GDBN__ commands for type and range
4527 checking are included, but they do not yet have any effect. This
4528 section documents the intended facilities.
4530 @c FIXME remove warning when type/range code added
4532 Some languages are designed to guard you against making seemingly common
4533 errors through a series of compile- and run-time checks. These include
4534 checking the type of arguments to functions and operators, and making
4535 sure mathematical overflows are caught at run time. Checks such as
4536 these help to ensure a program's correctness once it has been compiled
4537 by eliminating type mismatches, and providing active checks for range
4538 errors when your program is running.
4540 _GDBN__ can check for conditions like the above if you wish.
4541 Although _GDBN__ will not check the statements in your program, it
4542 can check expressions entered directly into _GDBN__ for evaluation via
4543 the @code{print} command, for example. As with the working language,
4544 _GDBN__ can also decide whether or not to check automatically based on
4545 your program's source language. @xref{Support, ,Supported Languages},
4546 for the default settings of supported languages.
4549 * Type Checking:: An overview of type checking
4550 * Range Checking:: An overview of range checking
4553 @cindex type checking
4554 @cindex checks, type
4556 @subsection An overview of type checking
4558 Some languages, such as Modula-2, are strongly typed, meaning that the
4559 arguments to operators and functions have to be of the correct type,
4560 otherwise an error occurs. These checks prevent type mismatch
4561 errors from ever causing any run-time problems. For example,
4569 The second example fails because the @code{CARDINAL} 1 is not
4570 type-compatible with the @code{REAL} 2.3.
4572 For expressions you use in _GDBN__ commands, you can tell the _GDBN__
4573 type checker to skip checking; to treat any mismatches as errors and
4574 abandon the expression; or only issue warnings when type mismatches
4575 occur, but evaluate the expression anyway. When you choose the last of
4576 these, _GDBN__ evaluates expressions like the second example above, but
4577 also issues a warning.
4579 Even though you may turn type checking off, other type-based reasons may
4580 prevent _GDBN__ from evaluating an expression. For instance, _GDBN__ does not
4581 know how to add an @code{int} and a @code{struct foo}. These particular
4582 type errors have nothing to do with the language in use, and usually
4583 arise from expressions, such as the one described above, which make
4584 little sense to evaluate anyway.
4586 Each language defines to what degree it is strict about type. For
4587 instance, both Modula-2 and C require the arguments to arithmetical
4588 operators to be numbers. In C, enumerated types and pointers can be
4589 represented as numbers, so that they are valid arguments to mathematical
4590 operators. @xref{Support, ,Supported Languages}, for further
4591 details on specific languages.
4593 _GDBN__ provides some additional commands for controlling the type checker:
4596 @kindex set check type
4597 @kindex show check type
4599 @item set check type auto
4600 Set type checking on or off based on the current working language.
4601 @xref{Support, ,Supported Languages}, for the default settings for
4604 @item set check type on
4605 @itemx set check type off
4606 Set type checking on or off, overriding the default setting for the
4607 current working language. Issue a warning if the setting does not
4608 match the language's default. If any type mismatches occur in
4609 evaluating an expression while typechecking is on, _GDBN__ prints a
4610 message and aborts evaluation of the expression.
4612 @item set check type warn
4613 Cause the type checker to issue warnings, but to always attempt to
4614 evaluate the expression. Evaluating the expression may still
4615 be impossible for other reasons. For example, _GDBN__ cannot add
4616 numbers and structures.
4619 Show the current setting of the type checker, and whether or not _GDBN__ is
4620 setting it automatically.
4623 @cindex range checking
4624 @cindex checks, range
4625 @node Range Checking
4626 @subsection An overview of Range Checking
4628 In some languages (such as Modula-2), it is an error to exceed the
4629 bounds of a type; this is enforced with run-time checks. Such range
4630 checking is meant to ensure program correctness by making sure
4631 computations do not overflow, or indices on an array element access do
4632 not exceed the bounds of the array.
4634 For expressions you use in _GDBN__ commands, you can tell _GDBN__ to
4635 ignore range errors; to always treat them as errors and abandon the
4636 expression; or to issue warnings when a range error occurs but evaluate
4637 the expression anyway.
4639 A range error can result from numerical overflow, from exceeding an
4640 array index bound, or when you type in a constant that is not a member
4641 of any type. Some languages, however, do not treat overflows as an
4642 error. In many implementations of C, mathematical overflow causes the
4643 result to ``wrap around'' to lower values---for example, if @var{m} is
4644 the largest integer value, and @var{s} is the smallest, then
4647 @var{m} + 1 @result{} @var{s}
4650 This, too, is specific to individual languages, and in some cases
4651 specific to individual compilers or machines. @xref{Support, ,
4652 Supported Languages}, for further details on specific languages.
4654 _GDBN__ provides some additional commands for controlling the range checker:
4657 @kindex set check range
4658 @kindex show check range
4660 @item set check range auto
4661 Set range checking on or off based on the current working language.
4662 @xref{Support, ,Supported Languages}, for the default settings for
4665 @item set check range on
4666 @itemx set check range off
4667 Set range checking on or off, overriding the default setting for the
4668 current working language. A warning is issued if the setting does not
4669 match the language's default. If a range error occurs, then a message
4670 is printed and evaluation of the expression is aborted.
4672 @item set check range warn
4673 Output messages when the _GDBN__ range checker detects a range error,
4674 but attempt to evaluate the expression anyway. Evaluating the
4675 expression may still be impossible for other reasons, such as accessing
4676 memory that the process does not own (a typical example from many UNIX
4680 Show the current setting of the range checker, and whether or not it is
4681 being set automatically by _GDBN__.
4685 @section Supported Languages
4687 _GDBN__ 4 supports C, C++, and Modula-2. Some _GDBN__
4688 features may be used in expressions regardless of the language you
4689 use: the _GDBN__ @code{@@} and @code{::} operators, and the
4690 @samp{@{type@}addr} construct (@pxref{Expressions, ,Expressions}) can be
4691 used with the constructs of any of the supported languages.
4693 The following sections detail to what degree each of these
4694 source languages is supported by _GDBN__. These sections are
4695 not meant to be language tutorials or references, but serve only as a
4696 reference guide to what the _GDBN__ expression parser will accept, and
4697 what input and output formats should look like for different languages.
4698 There are many good books written on each of these languages; please
4699 look to these for a language reference or tutorial.
4703 * Modula-2:: Modula-2
4707 @subsection C and C++
4715 @cindex expressions in C or C++
4716 Since C and C++ are so closely related, many features of _GDBN__ apply
4717 to both languages. Whenever this is the case, we discuss both languages
4723 The C++ debugging facilities are jointly implemented by the GNU C++
4724 compiler and _GDBN__. Therefore, to debug your C++ code effectively,
4725 you must compile your C++ programs with the GNU C++ compiler,
4729 * C Operators:: C and C++ Operators
4730 * C Constants:: C and C++ Constants
4731 * Cplusplus expressions:: C++ Expressions
4733 * C Defaults:: Default settings for C and C++
4735 * C Checks:: C and C++ Type and Range Checks
4736 * Debugging C:: _GDBN__ and C
4737 * Debugging C plus plus:: Special features for C++
4740 @cindex C and C++ operators
4743 @subsubsection C and C++ Operators
4746 @section C and C++ Operators
4749 Operators must be defined on values of specific types. For instance,
4750 @code{+} is defined on numbers, but not on structures. Operators are
4751 often defined on groups of types. For the purposes of C and C++, the
4752 following definitions hold:
4756 @emph{Integral types} include @code{int} with any of its storage-class
4757 specifiers, @code{char}, and @code{enum}s.
4760 @emph{Floating-point types} include @code{float} and @code{double}.
4763 @emph{Pointer types} include all types defined as @code{(@var{type}
4767 @emph{Scalar types} include all of the above.
4771 The following operators are supported. They are listed here
4772 in order of increasing precedence:
4776 The comma or sequencing operator. Expressions in a comma-separated list
4777 are evaluated from left to right, with the result of the entire
4778 expression being the last expression evaluated.
4781 Assignment. The value of an assignment expression is the value
4782 assigned. Defined on scalar types.
4785 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
4786 and translated to @w{@code{@var{a} = @var{a op b}}}.
4787 @w{@code{@var{op}=}} and @code{=} have the same precendence.
4788 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
4789 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
4792 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
4793 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
4797 Logical @sc{or}. Defined on integral types.
4800 Logical @sc{and}. Defined on integral types.
4803 Bitwise @sc{or}. Defined on integral types.
4806 Bitwise exclusive-@sc{or}. Defined on integral types.
4809 Bitwise @sc{and}. Defined on integral types.
4812 Equality and inequality. Defined on scalar types. The value of these
4813 expressions is 0 for false and non-zero for true.
4815 @item <@r{, }>@r{, }<=@r{, }>=
4816 Less than, greater than, less than or equal, greater than or equal.
4817 Defined on scalar types. The value of these expressions is 0 for false
4818 and non-zero for true.
4821 left shift, and right shift. Defined on integral types.
4824 The _GDBN__ ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
4827 Addition and subtraction. Defined on integral types, floating-point types and
4830 @item *@r{, }/@r{, }%
4831 Multiplication, division, and modulus. Multiplication and division are
4832 defined on integral and floating-point types. Modulus is defined on
4836 Increment and decrement. When appearing before a variable, the
4837 operation is performed before the variable is used in an expression;
4838 when appearing after it, the variable's value is used before the
4839 operation takes place.
4842 Pointer dereferencing. Defined on pointer types. Same precedence as
4846 Address operator. Defined on variables. Same precedence as @code{++}.
4848 For debugging C++, _GDBN__ implements a use of @samp{&} beyond what's
4849 allowed in the C++ language itself: you can use @samp{&(&@var{ref})}
4850 (or, if you prefer, simply @samp{&&@var{ref}} to examine the address
4851 where a C++ reference variable (declared with @samp{&@var{ref}}) is
4855 Negative. Defined on integral and floating-point types. Same
4856 precedence as @code{++}.
4859 Logical negation. Defined on integral types. Same precedence as
4863 Bitwise complement operator. Defined on integral types. Same precedence as
4867 Structure member, and pointer-to-structure member. For convenience,
4868 _GDBN__ regards the two as equivalent, choosing whether to dereference a
4869 pointer based on the stored type information.
4870 Defined on @code{struct}s and @code{union}s.
4873 Array indexing. @code{@var{a}[@var{i}]} is defined as
4874 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
4877 Function parameter list. Same precedence as @code{->}.
4880 C++ scope resolution operator. Defined on
4881 @code{struct}, @code{union}, and @code{class} types.
4884 The _GDBN__ scope operator (@pxref{Expressions, ,Expressions}). Same precedence as
4885 @code{::}, above._1__
4888 @cindex C and C++ constants
4891 @subsubsection C and C++ Constants
4894 @section C and C++ Constants
4897 _GDBN__ allows you to express the constants of C and C++ in the
4902 Integer constants are a sequence of digits. Octal constants are
4903 specified by a leading @samp{0} (ie. zero), and hexadecimal constants by
4904 a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
4905 @samp{l}, specifying that the constant should be treated as a
4909 Floating point constants are a sequence of digits, followed by a decimal
4910 point, followed by a sequence of digits, and optionally followed by an
4911 exponent. An exponent is of the form:
4912 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
4913 sequence of digits. The @samp{+} is optional for positive exponents.
4916 Enumerated constants consist of enumerated identifiers, or their
4917 integral equivalents.
4920 Character constants are a single character surrounded by single quotes
4921 (@code{'}), or a number---the ordinal value of the corresponding character
4922 (usually its @sc{ASCII} value). Within quotes, the single character may
4923 be represented by a letter or by @dfn{escape sequences}, which are of
4924 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
4925 of the character's ordinal value; or of the form @samp{\@var{x}}, where
4926 @samp{@var{x}} is a predefined special character---for example,
4927 @samp{\n} for newline.
4930 String constants are a sequence of character constants surrounded
4931 by double quotes (@code{"}).
4934 Pointer constants are an integral value.
4937 @node Cplusplus expressions
4939 @subsubsection C++ Expressions
4942 @section C++ Expressions
4945 @cindex expressions in C++
4946 _GDBN__'s expression handling has a number of extensions to
4947 interpret a significant subset of C++ expressions.
4949 @cindex C++ support, not in @sc{coff}
4950 @cindex @sc{coff} versus C++
4951 @cindex C++ and object formats
4952 @cindex object formats and C++
4953 @cindex a.out and C++
4954 @cindex @sc{ecoff} and C++
4955 @cindex @sc{xcoff} and C++
4956 @cindex @sc{elf}/stabs and C++
4957 @cindex @sc{elf}/@sc{dwarf} and C++
4959 @emph{Warning:} Most of these extensions depend on the use of additional
4960 debugging information in the symbol table, and thus require a rich,
4961 extendable object code format. In particular, if your system uses
4962 a.out, MIPS @sc{ecoff}, RS/6000 @sc{xcoff}, or Sun @sc{elf} with stabs
4963 extensions to the symbol table, these facilities are all available.
4964 Where the object code format is standard @sc{coff}, on the other hand,
4965 most of the C++ support in _GDBN__ will @emph{not} work, nor can it.
4966 For the standard SVr4 debugging format, @sc{dwarf} in @sc{elf}, the
4967 standard is still evolving, so the C++ support in _GDBN__ is still
4968 fragile; when this debugging format stabilizes, however, C++ support
4969 will also be available on systems that use it.
4974 @cindex member functions
4976 Member function calls are allowed; you can use expressions like
4979 count = aml->GetOriginal(x, y)
4983 @cindex namespace in C++
4985 While a member function is active (in the selected stack frame), your
4986 expressions have the same namespace available as the member function;
4987 that is, _GDBN__ allows implicit references to the class instance
4988 pointer @code{this} following the same rules as C++.
4990 @cindex call overloaded functions
4991 @cindex type conversions in C++
4993 You can call overloaded functions; _GDBN__ will resolve the function
4994 call to the right definition, with one restriction---you must use
4995 arguments of the type required by the function that you want to call.
4996 _GDBN__ will not perform conversions requiring constructors or
4997 user-defined type operators.
4999 @cindex reference declarations
5001 _GDBN__ understands variables declared as C++ references; you can use them in
5002 expressions just as you do in C++ source---they are automatically
5005 In the parameter list shown when _GDBN__ displays a frame, the values of
5006 reference variables are not displayed (unlike other variables); this
5007 avoids clutter, since references are often used for large structures.
5008 The @emph{address} of a reference variable is always shown, unless
5009 you have specified @samp{set print address off}.
5012 _GDBN__ supports the C++ name resolution operator @code{::}---your
5013 expressions can use it just as expressions in your program do. Since
5014 one scope may be defined in another, you can use @code{::} repeatedly if
5015 necessary, for example in an expression like
5016 @samp{@var{scope1}::@var{scope2}::@var{name}}. _GDBN__ also allows
5017 resolving name scope by reference to source files, in both C and C++
5018 debugging (@pxref{Variables, ,Program Variables}).
5023 @subsubsection C and C++ Defaults
5024 @cindex C and C++ defaults
5026 If you allow _GDBN__ to set type and range checking automatically, they
5027 both default to @code{off} whenever the working language changes to
5028 C or C++. This happens regardless of whether you, or _GDBN__,
5029 selected the working language.
5031 If you allow _GDBN__ to set the language automatically, it sets the
5032 working language to C or C++ on entering code compiled from a source file
5033 whose name ends with @file{.c}, @file{.C}, or @file{.cc}.
5034 @xref{Automatically, ,Having _GDBN__ infer the source language}, for
5040 @subsubsection C and C++ Type and Range Checks
5043 @section C and C++ Type and Range Checks
5045 @cindex C and C++ checks
5048 @emph{Warning:} in this release, _GDBN__ does not yet perform type or
5051 @c FIXME remove warning when type/range checks added
5053 By default, when _GDBN__ parses C or C++ expressions, type checking
5054 is not used. However, if you turn type checking on, _GDBN__ will
5055 consider two variables type equivalent if:
5059 The two variables are structured and have the same structure, union, or
5063 Two two variables have the same type name, or types that have been
5064 declared equivalent through @code{typedef}.
5067 @c leaving this out because neither J Gilmore nor R Pesch understand it.
5070 The two @code{struct}, @code{union}, or @code{enum} variables are
5071 declared in the same declaration. (Note: this may not be true for all C
5076 Range checking, if turned on, is done on mathematical operations. Array
5077 indices are not checked, since they are often used to index a pointer
5078 that is not itself an array.
5082 @subsubsection _GDBN__ and C
5085 @section _GDBN__ and C
5088 The @code{set print union} and @code{show print union} commands apply to
5089 the @code{union} type. When set to @samp{on}, any @code{union} that is
5090 inside a @code{struct} or @code{class} will also be printed.
5091 Otherwise, it will appear as @samp{@{...@}}.
5093 The @code{@@} operator aids in the debugging of dynamic arrays, formed
5094 with pointers and a memory allocation function. (@pxref{Expressions, ,Expressions})
5096 @node Debugging C plus plus
5098 @subsubsection _GDBN__ Features for C++
5101 @section _GDBN__ Features for C++
5104 @cindex commands for C++
5105 Some _GDBN__ commands are particularly useful with C++, and some are
5106 designed specifically for use with C++. Here is a summary:
5109 @cindex break in overloaded functions
5110 @item @r{breakpoint menus}
5111 When you want a breakpoint in a function whose name is overloaded,
5112 _GDBN__'s breakpoint menus help you specify which function definition
5113 you want. @xref{Breakpoint Menus}.
5115 @cindex overloading in C++
5116 @item rbreak @var{regex}
5117 Setting breakpoints using regular expressions is helpful for setting
5118 breakpoints on overloaded functions that are not members of any special
5120 @xref{Set Breaks, ,Setting Breakpoints}.
5122 @cindex C++ exception handling
5123 @item catch @var{exceptions}
5125 Debug C++ exception handling using these commands. @xref{Exception
5126 Handling, ,Breakpoints and Exceptions}.
5129 @item ptype @var{typename}
5130 Print inheritance relationships as well as other information for type
5132 @xref{Symbols, ,Examining the Symbol Table}.
5134 @cindex C++ symbol display
5135 @item set print demangle
5136 @itemx show print demangle
5137 @itemx set print asm-demangle
5138 @itemx show print asm-demangle
5139 Control whether C++ symbols display in their source form, both when
5140 displaying code as C++ source and when displaying disassemblies.
5141 @xref{Print Settings, ,Print Settings}.
5143 @item set print object
5144 @itemx show print object
5145 Choose whether to print derived (actual) or declared types of objects.
5146 @xref{Print Settings, ,Print Settings}.
5148 @item set print vtbl
5149 @itemx show print vtbl
5150 Control the format for printing virtual function tables.
5151 @xref{Print Settings, ,Print Settings}.
5153 @item @r{Overloaded symbol names}
5154 You can specify a particular definition of an overloaded symbol, using
5155 the same notation that's used to declare such symbols in C++: type
5156 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
5157 also use _GDBN__'s command-line word completion facilities to list the
5158 available choices, or to finish the type list for you.
5159 @xref{Completion,, Command Completion}, for details on how to do this.
5164 @subsection Modula-2
5167 The extensions made to _GDBN__ to support Modula-2 support output
5168 from the GNU Modula-2 compiler (which is currently being developed).
5169 Other Modula-2 compilers are not currently supported, and attempting to
5170 debug executables produced by them will most likely result in an error
5171 as _GDBN__ reads in the executable's symbol table.
5173 @cindex expressions in Modula-2
5175 * M2 Operators:: Built-in operators
5176 * Built-In Func/Proc:: Built-in Functions and Procedures
5177 * M2 Constants:: Modula-2 Constants
5178 * M2 Defaults:: Default settings for Modula-2
5179 * Deviations:: Deviations from standard Modula-2
5180 * M2 Checks:: Modula-2 Type and Range Checks
5181 * M2 Scope:: The scope operators @code{::} and @code{.}
5182 * GDB/M2:: _GDBN__ and Modula-2
5186 @subsubsection Operators
5187 @cindex Modula-2 operators
5189 Operators must be defined on values of specific types. For instance,
5190 @code{+} is defined on numbers, but not on structures. Operators are
5191 often defined on groups of types. For the purposes of Modula-2, the
5192 following definitions hold:
5197 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
5201 @emph{Character types} consist of @code{CHAR} and its subranges.
5204 @emph{Floating-point types} consist of @code{REAL}.
5207 @emph{Pointer types} consist of anything declared as @code{POINTER TO
5211 @emph{Scalar types} consist of all of the above.
5214 @emph{Set types} consist of @code{SET}s and @code{BITSET}s.
5217 @emph{Boolean types} consist of @code{BOOLEAN}.
5221 The following operators are supported, and appear in order of
5222 increasing precedence:
5226 Function argument or array index separator.
5229 Assignment. The value of @var{var} @code{:=} @var{value} is
5233 Less than, greater than on integral, floating-point, or enumerated
5237 Less than, greater than, less than or equal to, greater than or equal to
5238 on integral, floating-point and enumerated types, or set inclusion on
5239 set types. Same precedence as @code{<}.
5241 @item =@r{, }<>@r{, }#
5242 Equality and two ways of expressing inequality, valid on scalar types.
5243 Same precedence as @code{<}. In _GDBN__ scripts, only @code{<>} is
5244 available for inequality, since @code{#} conflicts with the script
5248 Set membership. Defined on set types and the types of their members.
5249 Same precedence as @code{<}.
5252 Boolean disjunction. Defined on boolean types.
5255 Boolean conjuction. Defined on boolean types.
5258 The _GDBN__ ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
5261 Addition and subtraction on integral and floating-point types, or union
5262 and difference on set types.
5265 Multiplication on integral and floating-point types, or set intersection
5269 Division on floating-point types, or symmetric set difference on set
5270 types. Same precedence as @code{*}.
5273 Integer division and remainder. Defined on integral types. Same
5274 precedence as @code{*}.
5277 Negative. Defined on @code{INTEGER}s and @code{REAL}s.
5280 Pointer dereferencing. Defined on pointer types.
5283 Boolean negation. Defined on boolean types. Same precedence as
5287 @code{RECORD} field selector. Defined on @code{RECORD}s. Same
5288 precedence as @code{^}.
5291 Array indexing. Defined on @code{ARRAY}s. Same precedence as @code{^}.
5294 Procedure argument list. Defined on @code{PROCEDURE}s. Same precedence
5298 _GDBN__ and Modula-2 scope operators.
5302 @emph{Warning:} Sets and their operations are not yet supported, so _GDBN__
5303 will treat the use of the operator @code{IN}, or the use of operators
5304 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
5305 @code{<=}, and @code{>=} on sets as an error.
5308 @cindex Modula-2 built-ins
5309 @node Built-In Func/Proc
5310 @subsubsection Built-in Functions and Procedures
5312 Modula-2 also makes available several built-in procedures and functions.
5313 In describing these, the following metavariables are used:
5318 represents an @code{ARRAY} variable.
5321 represents a @code{CHAR} constant or variable.
5324 represents a variable or constant of integral type.
5327 represents an identifier that belongs to a set. Generally used in the
5328 same function with the metavariable @var{s}. The type of @var{s} should
5329 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}.
5332 represents a variable or constant of integral or floating-point type.
5335 represents a variable or constant of floating-point type.
5341 represents a variable.
5344 represents a variable or constant of one of many types. See the
5345 explanation of the function for details.
5348 All Modula-2 built-in procedures also return a result, described below.
5352 Returns the absolute value of @var{n}.
5355 If @var{c} is a lower case letter, it returns its upper case
5356 equivalent, otherwise it returns its argument
5359 Returns the character whose ordinal value is @var{i}.
5362 Decrements the value in the variable @var{v}. Returns the new value.
5364 @item DEC(@var{v},@var{i})
5365 Decrements the value in the variable @var{v} by @var{i}. Returns the
5368 @item EXCL(@var{m},@var{s})
5369 Removes the element @var{m} from the set @var{s}. Returns the new
5372 @item FLOAT(@var{i})
5373 Returns the floating point equivalent of the integer @var{i}.
5376 Returns the index of the last member of @var{a}.
5379 Increments the value in the variable @var{v}. Returns the new value.
5381 @item INC(@var{v},@var{i})
5382 Increments the value in the variable @var{v} by @var{i}. Returns the
5385 @item INCL(@var{m},@var{s})
5386 Adds the element @var{m} to the set @var{s} if it is not already
5387 there. Returns the new set.
5390 Returns the maximum value of the type @var{t}.
5393 Returns the minimum value of the type @var{t}.
5396 Returns boolean TRUE if @var{i} is an odd number.
5399 Returns the ordinal value of its argument. For example, the ordinal
5400 value of a character is its ASCII value (on machines supporting the
5401 ASCII character set). @var{x} must be of an ordered type, which include
5402 integral, character and enumerated types.
5405 Returns the size of its argument. @var{x} can be a variable or a type.
5407 @item TRUNC(@var{r})
5408 Returns the integral part of @var{r}.
5410 @item VAL(@var{t},@var{i})
5411 Returns the member of the type @var{t} whose ordinal value is @var{i}.
5415 @emph{Warning:} Sets and their operations are not yet supported, so
5416 _GDBN__ will treat the use of procedures @code{INCL} and @code{EXCL} as
5420 @cindex Modula-2 constants
5422 @subsubsection Constants
5424 _GDBN__ allows you to express the constants of Modula-2 in the following
5430 Integer constants are simply a sequence of digits. When used in an
5431 expression, a constant is interpreted to be type-compatible with the
5432 rest of the expression. Hexadecimal integers are specified by a
5433 trailing @samp{H}, and octal integers by a trailing @samp{B}.
5436 Floating point constants appear as a sequence of digits, followed by a
5437 decimal point and another sequence of digits. An optional exponent can
5438 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
5439 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
5440 digits of the floating point constant must be valid decimal (base 10)
5444 Character constants consist of a single character enclosed by a pair of
5445 like quotes, either single (@code{'}) or double (@code{"}). They may
5446 also be expressed by their ordinal value (their ASCII value, usually)
5447 followed by a @samp{C}.
5450 String constants consist of a sequence of characters enclosed by a
5451 pair of like quotes, either single (@code{'}) or double (@code{"}).
5452 Escape sequences in the style of C are also allowed. @xref{C
5453 Constants, ,C and C++ Constants}, for a brief explanation of escape
5457 Enumerated constants consist of an enumerated identifier.
5460 Boolean constants consist of the identifiers @code{TRUE} and
5464 Pointer constants consist of integral values only.
5467 Set constants are not yet supported.
5471 @subsubsection Modula-2 Defaults
5472 @cindex Modula-2 defaults
5474 If type and range checking are set automatically by _GDBN__, they
5475 both default to @code{on} whenever the working language changes to
5476 Modula-2. This happens regardless of whether you, or _GDBN__,
5477 selected the working language.
5479 If you allow _GDBN__ to set the language automatically, then entering
5480 code compiled from a file whose name ends with @file{.mod} will set the
5481 working language to Modula-2. @xref{Automatically, ,Having _GDBN__ set
5482 the language automatically}, for further details.
5485 @subsubsection Deviations from Standard Modula-2
5486 @cindex Modula-2, deviations from
5488 A few changes have been made to make Modula-2 programs easier to debug.
5489 This is done primarily via loosening its type strictness:
5493 Unlike in standard Modula-2, pointer constants can be formed by
5494 integers. This allows you to modify pointer variables during
5495 debugging. (In standard Modula-2, the actual address contained in a
5496 pointer variable is hidden from you; it can only be modified
5497 through direct assignment to another pointer variable or expression that
5498 returned a pointer.)
5501 C escape sequences can be used in strings and characters to represent
5502 non-printable characters. _GDBN__ will print out strings with these
5503 escape sequences embedded. Single non-printable characters are
5504 printed using the @samp{CHR(@var{nnn})} format.
5507 The assignment operator (@code{:=}) returns the value of its right-hand
5511 All built-in procedures both modify @emph{and} return their argument.
5515 @subsubsection Modula-2 Type and Range Checks
5516 @cindex Modula-2 checks
5519 @emph{Warning:} in this release, _GDBN__ does not yet perform type or
5522 @c FIXME remove warning when type/range checks added
5524 _GDBN__ considers two Modula-2 variables type equivalent if:
5528 They are of types that have been declared equivalent via a @code{TYPE
5529 @var{t1} = @var{t2}} statement
5532 They have been declared on the same line. (Note: This is true of the
5533 GNU Modula-2 compiler, but it may not be true of other compilers.)
5536 As long as type checking is enabled, any attempt to combine variables
5537 whose types are not equivalent is an error.
5539 Range checking is done on all mathematical operations, assignment, array
5540 index bounds, and all built-in functions and procedures.
5543 @subsubsection The scope operators @code{::} and @code{.}
5546 @cindex colon, doubled as scope operator
5549 @c Info cannot handoe :: but TeX can.
5555 There are a few subtle differences between the Modula-2 scope operator
5556 (@code{.}) and the _GDBN__ scope operator (@code{::}). The two have
5561 @var{module} . @var{id}
5562 @var{scope} :: @var{id}
5566 where @var{scope} is the name of a module or a procedure,
5567 @var{module} the name of a module, and @var{id} is any declared
5568 identifier within your program, except another module.
5570 Using the @code{::} operator makes _GDBN__ search the scope
5571 specified by @var{scope} for the identifier @var{id}. If it is not
5572 found in the specified scope, then _GDBN__ will search all scopes
5573 enclosing the one specified by @var{scope}.
5575 Using the @code{.} operator makes _GDBN__ search the current scope for
5576 the identifier specified by @var{id} that was imported from the
5577 definition module specified by @var{module}. With this operator, it is
5578 an error if the identifier @var{id} was not imported from definition
5579 module @var{module}, or if @var{id} is not an identifier in
5583 @subsubsection _GDBN__ and Modula-2
5585 Some _GDBN__ commands have little use when debugging Modula-2 programs.
5586 Five subcommands of @code{set print} and @code{show print} apply
5587 specifically to C and C++: @samp{vtbl}, @samp{demangle},
5588 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
5589 apply to C++, and the last to C's @code{union} type, which has no direct
5590 analogue in Modula-2.
5592 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
5593 while using any language, is not useful with Modula-2. Its
5594 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
5595 created in Modula-2 as they can in C or C++. However, because an
5596 address can be specified by an integral constant, the construct
5597 @samp{@{@var{type}@}@var{adrexp}} is still useful. (@pxref{Expressions, ,Expressions})
5599 @cindex @code{#} in Modula-2
5600 In _GDBN__ scripts, the Modula-2 inequality operator @code{#} is
5601 interpreted as the beginning of a comment. Use @code{<>} instead.
5606 @chapter Examining the Symbol Table
5608 The commands described in this section allow you to inquire about the
5609 symbols (names of variables, functions and types) defined in your
5610 program. This information is inherent in the text of your program and
5611 does not change as your program executes. _GDBN__ finds it in your
5612 program's symbol table, in the file indicated when you started _GDBN__
5613 (@pxref{File Options, ,Choosing Files}), or by one of the
5614 file-management commands (@pxref{Files, ,Commands to Specify Files}).
5616 @c FIXME! This might be intentionally specific to C and C++; if so, move
5617 @c to someplace in C section of lang chapter.
5618 @cindex symbol names
5619 @cindex names of symbols
5620 @cindex quoting names
5621 Occasionally, you may need to refer to symbols that contain unusual
5622 characters, which _GDBN__ ordinarily treats as word delimiters. The
5623 most frequent case is in referring to static variables in other
5624 source files (@pxref{Variables,,Program Variables}). File names
5625 are recorded in object files as debugging symbols, but _GDBN__ would
5626 ordinarily parse a typical file name, like @file{foo.c}, as the three words
5627 @samp{foo} @samp{.} @samp{c}. To allow _GDBN__ to recognize
5628 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
5635 looks up the value of @code{x} in the scope of the file @file{foo.c}.
5638 @item info address @var{symbol}
5639 @kindex info address
5640 Describe where the data for @var{symbol} is stored. For a register
5641 variable, this says which register it is kept in. For a non-register
5642 local variable, this prints the stack-frame offset at which the variable
5645 Note the contrast with @samp{print &@var{symbol}}, which does not work
5646 at all for a register variables, and for a stack local variable prints
5647 the exact address of the current instantiation of the variable.
5649 @item whatis @var{exp}
5651 Print the data type of expression @var{exp}. @var{exp} is not
5652 actually evaluated, and any side-effecting operations (such as
5653 assignments or function calls) inside it do not take place.
5654 @xref{Expressions, ,Expressions}.
5657 Print the data type of @code{$}, the last value in the value history.
5659 @item ptype @var{typename}
5661 Print a description of data type @var{typename}. @var{typename} may be
5662 the name of a type, or for C code it may have the form
5663 @samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or
5664 @samp{enum @var{enum-tag}}.
5666 @item ptype @var{exp}
5668 Print a description of the type of expression @var{exp}. @code{ptype}
5669 differs from @code{whatis} by printing a detailed description, instead
5670 of just the name of the type. For example, if your program declares a
5674 struct complex @{double real; double imag;@} v;
5678 compare the output of the two commands:
5683 type = struct complex
5685 type = struct complex @{
5693 As with @code{whatis}, using @code{ptype} without an argument refers to
5694 the type of @code{$}, the last value in the value history.
5696 @item info types @var{regexp}
5699 Print a brief description of all types whose name matches @var{regexp}
5700 (or all types in your program, if you supply no argument). Each
5701 complete typename is matched as though it were a complete line; thus,
5702 @samp{i type value} gives information on all types in your program whose
5703 name includes the string @code{value}, but @samp{i type ^value$} gives
5704 information only on types whose complete name is @code{value}.
5706 This command differs from @code{ptype} in two ways: first, like
5707 @code{whatis}, it does not print a detailed description; second, it
5708 lists all source files where a type is defined.
5712 Show the name of the current source file---that is, the source file for
5713 the function containing the current point of execution---and the language
5717 @kindex info sources
5718 Print the names of all source files in your program for which there is
5719 debugging information, organized into two lists: files whose symbols
5720 have already been read, and files whose symbols will be read when needed.
5722 @item info functions
5723 @kindex info functions
5724 Print the names and data types of all defined functions.
5726 @item info functions @var{regexp}
5727 Print the names and data types of all defined functions
5728 whose names contain a match for regular expression @var{regexp}.
5729 Thus, @samp{info fun step} finds all functions whose names
5730 include @code{step}; @samp{info fun ^step} finds those whose names
5731 start with @code{step}.
5733 @item info variables
5734 @kindex info variables
5735 Print the names and data types of all variables that are declared
5736 outside of functions (i.e., excluding local variables).
5738 @item info variables @var{regexp}
5739 Print the names and data types of all variables (except for local
5740 variables) whose names contain a match for regular expression
5744 This was never implemented.
5746 @itemx info methods @var{regexp}
5747 @kindex info methods
5748 The @code{info methods} command permits the user to examine all defined
5749 methods within C++ program, or (with the @var{regexp} argument) a
5750 specific set of methods found in the various C++ classes. Many
5751 C++ classes provide a large number of methods. Thus, the output
5752 from the @code{ptype} command can be overwhelming and hard to use. The
5753 @code{info-methods} command filters the methods, printing only those
5754 which match the regular-expression @var{regexp}.
5757 @item maint print symbols @var{filename}
5758 @itemx maint print psymbols @var{filename}
5759 @itemx maint print msymbols @var{filename}
5760 @kindex maint print symbols
5762 @kindex maint print psymbols
5763 @cindex partial symbol dump
5764 Write a dump of debugging symbol data into the file @var{filename}.
5765 These commands are used to debug the _GDBN__ symbol-reading code. Only
5766 symbols with debugging data are included. If you use @samp{maint print
5767 symbols}, _GDBN__ includes all the symbols for which it has already
5768 collected full details: that is, @var{filename} reflects symbols for
5769 only those files whose symbols _GDBN__ has read. You can use the
5770 command @code{info sources} to find out which files these are. If you
5771 use @samp{maint print psymbols} instead, the dump shows information about
5772 symbols that _GDBN__ only knows partially---that is, symbols defined in
5773 files that _GDBN__ has skimmed, but not yet read completely. Finally,
5774 @samp{maint print msymbols} dumps just the minimal symbol information
5775 required for each object file from which _GDBN__ has read some symbols.
5776 The description of @code{symbol-file} explains how _GDBN__ reads
5777 symbols; both @code{info source} and @code{symbol-file} are described in
5778 @ref{Files, ,Commands to Specify Files}.
5782 @chapter Altering Execution
5784 Once you think you have found an error in your program, you might want to
5785 find out for certain whether correcting the apparent error would lead to
5786 correct results in the rest of the run. You can find the answer by
5787 experiment, using the _GDBN__ features for altering execution of the
5790 For example, you can store new values into variables or memory
5791 locations, give your program a signal, restart it at a different address,
5792 or even return prematurely from a function to its caller.
5795 * Assignment:: Assignment to Variables
5796 * Jumping:: Continuing at a Different Address
5798 * Signaling:: Giving your program a Signal
5800 * Returning:: Returning from a Function
5801 * Calling:: Calling your Program's Functions
5802 * Patching:: Patching your Program
5806 @section Assignment to Variables
5809 @cindex setting variables
5810 To alter the value of a variable, evaluate an assignment expression.
5811 @xref{Expressions, ,Expressions}. For example,
5818 stores the value 4 into the variable @code{x}, and then prints the
5819 value of the assignment expression (which is 4).
5821 @xref{Languages, ,Using _GDBN__ with Different Languages}, for more
5822 information on operators in supported languages.
5825 @kindex set variable
5826 @cindex variables, setting
5827 If you are not interested in seeing the value of the assignment, use the
5828 @code{set} command instead of the @code{print} command. @code{set} is
5829 really the same as @code{print} except that the expression's value is not
5830 printed and is not put in the value history (@pxref{Value History, ,Value History}). The
5831 expression is evaluated only for its effects.
5833 If the beginning of the argument string of the @code{set} command
5834 appears identical to a @code{set} subcommand, use the @code{set
5835 variable} command instead of just @code{set}. This command is identical
5836 to @code{set} except for its lack of subcommands. For example, a
5837 program might well have a variable @code{width}---which leads to
5838 an error if we try to set a new value with just @samp{set width=13}, as
5839 we might if @code{set width} did not happen to be a _GDBN__ command:
5842 (_GDBP__) whatis width
5846 (_GDBP__) set width=47
5847 Invalid syntax in expression.
5851 The invalid expression, of course, is @samp{=47}. What we can do in
5852 order to actually set our program's variable @code{width} is
5855 (_GDBP__) set var width=47
5858 _GDBN__ allows more implicit conversions in assignments than C; you can
5859 freely store an integer value into a pointer variable or vice versa,
5860 and any structure can be converted to any other structure that is the
5861 same length or shorter.
5862 @comment FIXME: how do structs align/pad in these conversions?
5863 @comment /pesch@cygnus.com 18dec1990
5865 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
5866 construct to generate a value of specified type at a specified address
5867 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
5868 to memory location @code{0x83040} as an integer (which implies a certain size
5869 and representation in memory), and
5872 set @{int@}0x83040 = 4
5876 stores the value 4 into that memory location.
5879 @section Continuing at a Different Address
5881 Ordinarily, when you continue your program, you do so at the place where
5882 it stopped, with the @code{continue} command. You can instead continue at
5883 an address of your own choosing, with the following commands:
5886 @item jump @var{linespec}
5888 Resume execution at line @var{linespec}. Execution will stop
5889 immediately if there is a breakpoint there. @xref{List, ,Printing
5890 Source Lines}, for a description of the different forms of
5893 The @code{jump} command does not change the current stack frame, or
5894 the stack pointer, or the contents of any memory location or any
5895 register other than the program counter. If line @var{linespec} is in
5896 a different function from the one currently executing, the results may
5897 be bizarre if the two functions expect different patterns of arguments or
5898 of local variables. For this reason, the @code{jump} command requests
5899 confirmation if the specified line is not in the function currently
5900 executing. However, even bizarre results are predictable if you are
5901 well acquainted with the machine-language code of your program.
5903 @item jump *@var{address}
5904 Resume execution at the instruction at address @var{address}.
5907 You can get much the same effect as the @code{jump} command by storing a
5908 new value into the register @code{$pc}. The difference is that this
5909 does not start your program running; it only changes the address where it
5910 @emph{will} run when it is continued. For example,
5917 causes the next @code{continue} command or stepping command to execute at
5918 address @code{0x485}, rather than at the address where your program stopped.
5919 @xref{Continuing and Stepping, ,Continuing and Stepping}.
5921 The most common occasion to use the @code{jump} command is to back up,
5922 perhaps with more breakpoints set, over a portion of a program that has
5923 already executed, in order to examine its execution in more detail.
5928 @section Giving your program a Signal
5931 @item signal @var{signalnum}
5933 Resume execution where your program stopped, but give it immediately the
5934 signal number @var{signalnum}.
5936 Alternatively, if @var{signalnum} is zero, continue execution without
5937 giving a signal. This is useful when your program stopped on account of
5938 a signal and would ordinary see the signal when resumed with the
5939 @code{continue} command; @samp{signal 0} causes it to resume without a
5942 @code{signal} does not repeat when you press @key{RET} a second time
5943 after executing the command.
5949 @section Returning from a Function
5953 @itemx return @var{expression}
5954 @cindex returning from a function
5956 You can cancel execution of a function call with the @code{return}
5957 command. If you give an
5958 @var{expression} argument, its value is used as the function's return
5962 When you use @code{return}, _GDBN__ discards the selected stack frame
5963 (and all frames within it). You can think of this as making the
5964 discarded frame return prematurely. If you wish to specify a value to
5965 be returned, give that value as the argument to @code{return}.
5967 This pops the selected stack frame (@pxref{Selection, ,Selecting a
5968 Frame}), and any other frames inside of it, leaving its caller as the
5969 innermost remaining frame. That frame becomes selected. The
5970 specified value is stored in the registers used for returning values
5973 The @code{return} command does not resume execution; it leaves the
5974 program stopped in the state that would exist if the function had just
5975 returned. In contrast, the @code{finish} command (@pxref{Continuing
5976 and Stepping, ,Continuing and Stepping}) resumes execution until the
5977 selected stack frame returns naturally.
5980 @section Calling your Program's Functions
5982 @cindex calling functions
5985 @item call @var{expr}
5986 Evaluate the expression @var{expr} without displaying @code{void}
5990 You can use this variant of the @code{print} command if you want to
5991 execute a function from your program, but without cluttering the output
5992 with @code{void} returned values. The result is printed and saved in
5993 the value history, if it is not void.
5996 @section Patching your Program
5997 @cindex patching binaries
5998 @cindex writing into executables
5999 @cindex writing into corefiles
6001 By default, _GDBN__ opens the file containing your program's executable
6002 code (or the corefile) read-only. This prevents accidental alterations
6003 to machine code; but it also prevents you from intentionally patching
6004 your program's binary.
6006 If you'd like to be able to patch the binary, you can specify that
6007 explicitly with the @code{set write} command. For example, you might
6008 want to turn on internal debugging flags, or even to make emergency
6013 @itemx set write off
6015 If you specify @samp{set write on}, _GDBN__ will open executable and
6016 core files for both reading and writing; if you specify @samp{set write
6017 off} (the default), _GDBN__ will open them read-only.
6019 If you have already loaded a file, you must load it
6020 again (using the @code{exec-file} or @code{core-file} command) after
6021 changing @code{set write}, for your new setting to take effect.
6025 Display whether executable files and core files will be opened for
6026 writing as well as reading.
6030 @chapter _GDBN__'s Files
6032 _GDBN__ needs to know the file name of the program to be debugged, both in
6033 order to read its symbol table and in order to start your program.
6035 To debug a core dump of a previous run, _GDBN__ must be told the file
6036 name of the core dump.
6040 * Files:: Commands to Specify Files
6041 * Symbol Errors:: Errors Reading Symbol Files
6045 @section Commands to Specify Files
6046 @cindex core dump file
6047 @cindex symbol table
6050 The usual way to specify executable and core dump file names is with
6051 the command arguments given when you start _GDBN__, (@pxref{Invocation,
6052 ,Getting In and Out of _GDBN__}.
6055 The usual way to specify an executable file name is with
6056 the command argument given when you start _GDBN__, (@pxref{Invocation,
6057 ,Getting In and Out of _GDBN__}.
6060 Occasionally it is necessary to change to a different file during a
6061 _GDBN__ session. Or you may run _GDBN__ and forget to specify a file you
6062 want to use. In these situations the _GDBN__ commands to specify new files
6066 @item file @var{filename}
6067 @cindex executable file
6069 Use @var{filename} as the program to be debugged. It is read for its
6070 symbols and for the contents of pure memory. It is also the program
6071 executed when you use the @code{run} command. If you do not specify a
6072 directory and the file is not found in _GDBN__'s working directory, _GDBN__
6073 uses the environment variable @code{PATH} as a list of directories to
6074 search, just as the shell does when looking for a program to run. You
6075 can change the value of this variable, for both _GDBN__ and your program,
6076 using the @code{path} command.
6078 On systems with memory-mapped files, an auxiliary symbol table file
6079 @file{@var{filename}.syms} may be available for @var{filename}. If it
6080 is, _GDBN__ will map in the symbol table from
6081 @file{@var{filename}.syms}, starting up more quickly. See the
6082 descriptions of the options @samp{-mapped} and @samp{-readnow} (available
6083 on the command line, and with the commands @code{file}, @code{symbol-file},
6084 or @code{add-symbol-file}), for more information.
6087 @code{file} with no argument makes _GDBN__ discard any information it
6088 has on both executable file and the symbol table.
6090 @item exec-file @r{[} @var{filename} @r{]}
6092 Specify that the program to be run (but not the symbol table) is found
6093 in @var{filename}. _GDBN__ will search the environment variable @code{PATH}
6094 if necessary to locate your program. Omitting @var{filename} means to
6095 discard information on the executable file.
6097 @item symbol-file @r{[} @var{filename} @r{]}
6099 Read symbol table information from file @var{filename}. @code{PATH} is
6100 searched when necessary. Use the @code{file} command to get both symbol
6101 table and program to run from the same file.
6103 @code{symbol-file} with no argument clears out _GDBN__'s information on your
6104 program's symbol table.
6106 The @code{symbol-file} command causes _GDBN__ to forget the contents of its
6107 convenience variables, the value history, and all breakpoints and
6108 auto-display expressions. This is because they may contain pointers to
6109 the internal data recording symbols and data types, which are part of
6110 the old symbol table data being discarded inside _GDBN__.
6112 @code{symbol-file} will not repeat if you press @key{RET} again after
6115 When _GDBN__ is configured for a particular environment, it will
6116 understand debugging information in whatever format is the standard
6117 generated for that environment; you may use either a GNU compiler, or
6118 other compilers that adhere to the local conventions. Best results are
6119 usually obtained from GNU compilers; for example, using @code{_GCC__}
6120 you can generate debugging information for optimized code.
6122 On some kinds of object files, the @code{symbol-file} command does not
6123 normally read the symbol table in full right away. Instead, it scans
6124 the symbol table quickly to find which source files and which symbols
6125 are present. The details are read later, one source file at a time,
6128 The purpose of this two-stage reading strategy is to make _GDBN__ start up
6129 faster. For the most part, it is invisible except for occasional
6130 pauses while the symbol table details for a particular source file are
6131 being read. (The @code{set verbose} command can turn these pauses
6132 into messages if desired. @xref{Messages/Warnings, ,Optional Warnings
6135 When the symbol table is stored in COFF format, @code{symbol-file} does
6136 read the symbol table data in full right away. We have not implemented
6137 the two-stage strategy for COFF yet.
6139 @item symbol-file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
6140 @itemx file @var{filename} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
6142 @cindex reading symbols immediately
6143 @cindex symbols, reading immediately
6145 @cindex memory-mapped symbol file
6146 @cindex saving symbol table
6147 You can override the _GDBN__ two-stage strategy for reading symbol
6148 tables by using the @samp{-readnow} option with any of the commands that
6149 load symbol table information, if you want to be sure _GDBN__ has the
6150 entire symbol table available.
6153 If memory-mapped files are available on your system through the
6154 @code{mmap} system call, you can use another option, @samp{-mapped}, to
6155 cause _GDBN__ to write the symbols for your program into a reusable
6156 file. Future _GDBN__ debugging sessions will map in symbol information
6157 from this auxiliary symbol file (if the program hasn't changed), rather
6158 than spending time reading the symbol table from the executable
6159 program. Using the @samp{-mapped} option has the same effect as
6160 starting _GDBN__ with the @samp{-mapped} command-line option.
6162 You can use both options together, to make sure the auxiliary symbol
6163 file has all the symbol information for your program.
6165 The @code{.syms} file is specific to the host machine on which GDB is run.
6166 It holds an exact image of GDB's internal symbol table. It cannot be
6167 shared across multiple host platforms.
6169 The auxiliary symbol file for a program called @var{myprog} is called
6170 @samp{@var{myprog}.syms}. Once this file exists (so long as it is newer
6171 than the corresponding executable), _GDBN__ will always attempt to use
6172 it when you debug @var{myprog}; no special options or commands are
6174 @c FIXME: for now no mention of directories, since this seems to be in
6175 @c flux. 13mar1992 status is that in theory GDB would look either in
6176 @c current dir or in same dir as myprog; but issues like competing
6177 @c GDB's, or clutter in system dirs, mean that in practice right now
6178 @c only current dir is used. FFish says maybe a special GDB hierarchy
6179 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
6182 @item core-file @r{[} @var{filename} @r{]}
6185 Specify the whereabouts of a core dump file to be used as the ``contents
6186 of memory''. Traditionally, core files contain only some parts of the
6187 address space of the process that generated them; _GDBN__ can access the
6188 executable file itself for other parts.
6190 @code{core-file} with no argument specifies that no core file is
6193 Note that the core file is ignored when your program is actually running
6194 under _GDBN__. So, if you have been running your program and you wish to
6195 debug a core file instead, you must kill the subprocess in which the
6196 program is running. To do this, use the @code{kill} command
6197 (@pxref{Kill Process, ,Killing the Child Process}).
6200 @item load @var{filename}
6203 Depending on what remote debugging facilities are configured into
6204 _GDBN__, the @code{load} command may be available. Where it exists, it
6205 is meant to make @var{filename} (an executable) available for debugging
6206 on the remote system---by downloading, or dynamic linking, for example.
6207 @code{load} also records @var{filename}'s symbol table in _GDBN__, like
6208 the @code{add-symbol-file} command.
6210 If @code{load} is not available on your _GDBN__, attempting to execute
6211 it gets the error message ``@code{You can't do that when your target is
6216 On VxWorks, @code{load} will dynamically link @var{filename} on the
6217 current target system as well as adding its symbols in _GDBN__.
6221 @cindex download to Nindy-960
6222 With the Nindy interface to an Intel 960 board, @code{load} will
6223 download @var{filename} to the 960 as well as adding its symbols in
6228 @cindex download to H8/300
6229 @cindex H8/300 download
6230 When you select remote debugging to a Hitachi H8/300 board (@pxref{Hitachi
6231 H8/300 Remote,,_GDBN__ and the Hitachi H8/300}), the
6232 @code{load} command downloads your program to the H8/300 and also opens
6233 it as the current executable target for _GDBN__ on your host (like the
6234 @code{file} command).
6237 @code{load} will not repeat if you press @key{RET} again after using it.
6239 @item add-symbol-file @var{filename} @var{address}
6240 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]} @r{[} -mapped @r{]}
6241 @kindex add-symbol-file
6242 @cindex dynamic linking
6243 The @code{add-symbol-file} command reads additional symbol table information
6244 from the file @var{filename}. You would use this command when @var{filename}
6245 has been dynamically loaded (by some other means) into the program that
6246 is running. @var{address} should be the memory address at which the
6247 file has been loaded; _GDBN__ cannot figure this out for itself.
6249 The symbol table of the file @var{filename} is added to the symbol table
6250 originally read with the @code{symbol-file} command. You can use the
6251 @code{add-symbol-file} command any number of times; the new symbol data thus
6252 read keeps adding to the old. To discard all old symbol data instead,
6253 use the @code{symbol-file} command.
6255 @code{add-symbol-file} will not repeat if you press @key{RET} after using it.
6257 You can use the @samp{-mapped} and @samp{-readnow} options just as with
6258 the @code{symbol-file} command, to change how _GDBN__ manages the symbol
6259 tabl einformation for @var{filename}.
6265 @code{info files} and @code{info target} are synonymous; both print
6266 the current targets (@pxref{Targets, ,Specifying a Debugging Target}),
6267 including the names of the executable and core dump files currently in
6268 use by _GDBN__, and the files from which symbols were loaded. The command
6269 @code{help targets} lists all possible targets rather than current
6274 All file-specifying commands allow both absolute and relative file names
6275 as arguments. _GDBN__ always converts the file name to an absolute path
6276 name and remembers it that way.
6279 @cindex shared libraries
6280 _GDBN__ supports SunOS, SVR4, and IBM RS/6000 shared libraries.
6281 _GDBN__ automatically loads symbol definitions from shared libraries
6282 when you use the @code{run} command, or when you examine a core file.
6283 (Before you issue the @code{run} command, _GDBN__ will not understand
6284 references to a function in a shared library, however---unless you are
6285 debugging a core file).
6286 @c FIXME: next _GDBN__ release should permit some refs to undef
6287 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared lib
6291 @itemx info sharedlibrary
6292 @kindex info sharedlibrary
6294 Print the names of the shared libraries which are currently loaded.
6296 @item sharedlibrary @var{regex}
6297 @itemx share @var{regex}
6298 @kindex sharedlibrary
6300 This is an obsolescent command; you can use it to explicitly
6301 load shared object library symbols for files matching a UNIX regular
6302 expression, but as with files loaded automatically, it will only load
6303 shared libraries required by your program for a core file or after
6304 typing @code{run}. If @var{regex} is omitted all shared libraries
6305 required by your program are loaded.
6310 @section Errors Reading Symbol Files
6312 While reading a symbol file, _GDBN__ will occasionally encounter problems,
6313 such as symbol types it does not recognize, or known bugs in compiler
6314 output. By default, _GDBN__ does not notify you of such problems, since
6315 they are relatively common and primarily of interest to people
6316 debugging compilers. If you are interested in seeing information
6317 about ill-constructed symbol tables, you can either ask _GDBN__ to print
6318 only one message about each such type of problem, no matter how many
6319 times the problem occurs; or you can ask _GDBN__ to print more messages,
6320 to see how many times the problems occur, with the @code{set
6321 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
6324 The messages currently printed, and their meanings, are:
6327 @item inner block not inside outer block in @var{symbol}
6329 The symbol information shows where symbol scopes begin and end
6330 (such as at the start of a function or a block of statements). This
6331 error indicates that an inner scope block is not fully contained
6332 in its outer scope blocks.
6334 _GDBN__ circumvents the problem by treating the inner block as if it had
6335 the same scope as the outer block. In the error message, @var{symbol}
6336 may be shown as ``@code{(don't know)}'' if the outer block is not a
6339 @item block at @var{address} out of order
6341 The symbol information for symbol scope blocks should occur in
6342 order of increasing addresses. This error indicates that it does not
6345 _GDBN__ does not circumvent this problem, and will have trouble locating
6346 symbols in the source file whose symbols being read. (You can often
6347 determine what source file is affected by specifying @code{set verbose
6348 on}. @xref{Messages/Warnings, ,Optional Warnings and Messages}.)
6350 @item bad block start address patched
6352 The symbol information for a symbol scope block has a start address
6353 smaller than the address of the preceding source line. This is known
6354 to occur in the SunOS 4.1.1 (and earlier) C compiler.
6356 _GDBN__ circumvents the problem by treating the symbol scope block as
6357 starting on the previous source line.
6359 @item bad string table offset in symbol @var{n}
6362 Symbol number @var{n} contains a pointer into the string table which is
6363 larger than the size of the string table.
6365 _GDBN__ circumvents the problem by considering the symbol to have the
6366 name @code{foo}, which may cause other problems if many symbols end up
6369 @item unknown symbol type @code{0x@var{nn}}
6371 The symbol information contains new data types that _GDBN__ does not yet
6372 know how to read. @code{0x@var{nn}} is the symbol type of the misunderstood
6373 information, in hexadecimal.
6375 _GDBN__ circumvents the error by ignoring this symbol information. This
6376 will usually allow your program to be debugged, though certain symbols
6377 will not be accessible. If you encounter such a problem and feel like
6378 debugging it, you can debug @code{_GDBP__} with itself, breakpoint on
6379 @code{complain}, then go up to the function @code{read_dbx_symtab} and
6380 examine @code{*bufp} to see the symbol.
6382 @item stub type has NULL name
6383 _GDBN__ could not find the full definition for a struct or class.
6385 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
6387 The symbol information for a C++ member function is missing some
6388 information that recent versions of the compiler should have output
6391 @item info mismatch between compiler and debugger
6393 _GDBN__ could not parse a type specification output by the compiler.
6397 @chapter Specifying a Debugging Target
6398 @cindex debugging target
6401 A @dfn{target} is the execution environment occupied by your program.
6402 Often, _GDBN__ runs in the same host environment as your program; in
6403 that case, the debugging target is specified as a side effect when you
6404 use the @code{file} or @code{core} commands. When you need more
6405 flexibility---for example, running _GDBN__ on a physically separate
6406 host, or controlling a standalone system over a serial port or a
6407 realtime system over a TCP/IP connection---you can use the @code{target}
6408 command to specify one of the target types configured for _GDBN__
6409 (@pxref{Target Commands, ,Commands for Managing Targets}).
6412 * Active Targets:: Active Targets
6413 * Target Commands:: Commands for Managing Targets
6414 * Remote:: Remote Debugging
6417 @node Active Targets
6418 @section Active Targets
6419 @cindex stacking targets
6420 @cindex active targets
6421 @cindex multiple targets
6423 There are three classes of targets: processes, core files, and
6424 executable files. _GDBN__ can work concurrently on up to three active
6425 targets, one in each class. This allows you to (for example) start a
6426 process and inspect its activity without abandoning your work on a core
6429 If, for example, you execute @samp{gdb a.out}, then the executable file
6430 @code{a.out} is the only active target. If you designate a core file as
6431 well---presumably from a prior run that crashed and coredumped---then
6432 _GDBN__ has two active targets and will use them in tandem, looking
6433 first in the corefile target, then in the executable file, to satisfy
6434 requests for memory addresses. (Typically, these two classes of target
6435 are complementary, since core files contain only a program's
6436 read-write memory---variables and so on---plus machine status, while
6437 executable files contain only the program text and initialized data.)
6439 When you type @code{run}, your executable file becomes an active process
6440 target as well. When a process target is active, all _GDBN__ commands
6441 requesting memory addresses refer to that target; addresses in an active
6442 core file or executable file target are obscured while the process
6446 Use the @code{exec-file} command to select a
6447 new executable target (@pxref{Files, ,Commands to Specify
6451 Use the @code{core-file} and @code{exec-file} commands to select a
6452 new core file or executable target (@pxref{Files, ,Commands to Specify
6453 Files}). To specify as a target a process that is already running, use
6454 the @code{attach} command (@pxref{Attach, ,Debugging an
6455 Already-Running Process}.).
6458 @node Target Commands
6459 @section Commands for Managing Targets
6462 @item target @var{type} @var{parameters}
6463 Connects the _GDBN__ host environment to a target machine or process. A
6464 target is typically a protocol for talking to debugging facilities. You
6465 use the argument @var{type} to specify the type or protocol of the
6468 Further @var{parameters} are interpreted by the target protocol, but
6469 typically include things like device names or host names to connect
6470 with, process numbers, and baud rates.
6472 The @code{target} command will not repeat if you press @key{RET} again
6473 after executing the command.
6477 Displays the names of all targets available. To display targets
6478 currently selected, use either @code{info target} or @code{info files}
6479 (@pxref{Files, ,Commands to Specify Files}).
6481 @item help target @var{name}
6482 Describe a particular target, including any parameters necessary to
6486 Here are some common targets (available, or not, depending on the GDB
6490 @item target exec @var{prog}
6492 An executable file. @samp{target exec @var{prog}} is the same as
6493 @samp{exec-file @var{prog}}.
6495 @item target core @var{filename}
6497 A core dump file. @samp{target core @var{filename}} is the same as
6498 @samp{core-file @var{filename}}.
6500 @item target remote @var{dev}
6501 @kindex target remote
6502 Remote serial target in GDB-specific protocol. The argument @var{dev}
6503 specifies what serial device to use for the connection (e.g.
6504 @file{/dev/ttya}). @xref{Remote, ,Remote Debugging}.
6507 @item target amd-eb @var{dev} @var{speed} @var{PROG}
6508 @kindex target amd-eb
6510 Remote PC-resident AMD EB29K board, attached over serial lines.
6511 @var{dev} is the serial device, as for @code{target remote};
6512 @var{speed} allows you to specify the linespeed; and @var{PROG} is the
6513 name of the program to be debugged, as it appears to DOS on the PC.
6514 @xref{EB29K Remote, ,_GDBN__ with a Remote EB29K}.
6518 @cindex UDI interface to 29K
6520 Remote AMD 29K board, attached over the AMD ``Universal Debug
6521 Interface'', a protocol based on TCP/IP. @xref{UDI29K Remote,,_GDBN__
6522 and the UDI 29K protocol}.
6527 A Hitachi H8/300 board, attached via serial line to your host. Use
6528 special commands @code{device} and @code{speed} to control the serial
6529 line and the communications speed used. @xref{Hitachi H8/300
6530 Remote,,_GDBN__ and the Hitachi H8/300}.
6534 @item target nindy @var{devicename}
6535 @kindex target nindy
6536 An Intel 960 board controlled by a Nindy Monitor. @var{devicename} is
6537 the name of the serial device to use for the connection, e.g.
6538 @file{/dev/ttya}. @xref{i960-Nindy Remote, ,_GDBN__ with a Remote i960 (Nindy)}.
6542 @item target st2000 @var{dev} @var{speed}
6543 @kindex target st2000
6544 A Tandem ST2000 phone switch, running Tandem's STDBUG protocol. @var{dev}
6545 is the name of the device attached to the ST2000 serial line;
6546 @var{speed} is the communication line speed. The arguments are not used
6547 if _GDBN__ is configured to connect to the ST2000 using TCP or Telnet.
6548 @xref{ST2000 Remote,,_GDBN__ with a Tandem ST2000}.
6552 @item target vxworks @var{machinename}
6553 @kindex target vxworks
6554 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
6555 is the target system's machine name or IP address.
6556 @xref{VxWorks Remote, ,_GDBN__ and VxWorks}.
6561 Different targets are available on different configurations of _GDBN__; your
6562 configuration may have more or fewer targets.
6566 @section Remote Debugging
6567 @cindex remote debugging
6569 If you are trying to debug a program running on a machine that cannot run
6570 GDB in the usual way, it is often useful to use remote debugging. For
6571 example, you might use remote debugging on an operating system kernel, or on
6572 a small system which does not have a general purpose operating system
6573 powerful enough to run a full-featured debugger.
6575 Some configurations of GDB have special serial or TCP/IP interfaces
6576 to make this work with particular debugging targets. In addition,
6577 GDB comes with a generic serial protocol (specific to GDB, but
6578 not specific to any particular target system) which you can use if you
6579 write the remote stubs---the code that will run on the remote system to
6580 communicate with GDB.
6582 Other remote targets may be available in your
6583 configuration of GDB; use @code{help targets} to list them.
6586 _dnl__ Text on starting up GDB in various specific cases; it goes up front
6587 _dnl__ in manuals configured for any of those particular situations, here
6590 _include__(gdbinv-m.m4)<>_dnl__
6592 _include__(gdbinv-s.m4)
6595 @node Controlling _GDBN__
6596 @chapter Controlling _GDBN__
6598 You can alter many aspects of _GDBN__'s interaction with you by using
6599 the @code{set} command. For commands controlling how _GDBN__ displays
6600 data, @pxref{Print Settings, ,Print Settings}; other settings are described here.
6604 * Editing:: Command Editing
6605 * History:: Command History
6606 * Screen Size:: Screen Size
6608 * Messages/Warnings:: Optional Warnings and Messages
6615 _GDBN__ indicates its readiness to read a command by printing a string
6616 called the @dfn{prompt}. This string is normally @samp{(_GDBP__)}. You
6617 can change the prompt string with the @code{set prompt} command. For
6618 instance, when debugging _GDBN__ with _GDBN__, it is useful to change
6619 the prompt in one of the _GDBN__<>s so that you can always tell which
6620 one you are talking to.
6623 @item set prompt @var{newprompt}
6625 Directs _GDBN__ to use @var{newprompt} as its prompt string henceforth.
6628 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
6632 @section Command Editing
6634 @cindex command line editing
6636 _GDBN__ reads its input commands via the @dfn{readline} interface. This
6637 GNU library provides consistent behavior for programs which provide a
6638 command line interface to the user. Advantages are @code{emacs}-style
6639 or @code{vi}-style inline editing of commands, @code{csh}-like history
6640 substitution, and a storage and recall of command history across
6643 You may control the behavior of command line editing in _GDBN__ with the
6650 @itemx set editing on
6651 Enable command line editing (enabled by default).
6653 @item set editing off
6654 Disable command line editing.
6656 @kindex show editing
6658 Show whether command line editing is enabled.
6662 @section Command History
6665 @cindex history substitution
6666 @cindex history file
6667 @kindex set history filename
6668 @item set history filename @var{fname}
6669 Set the name of the _GDBN__ command history file to @var{fname}. This is
6670 the file from which _GDBN__ will read an initial command history
6671 list or to which it will write this list when it exits. This list is
6672 accessed through history expansion or through the history
6673 command editing characters listed below. This file defaults to the
6674 value of the environment variable @code{GDBHISTFILE}, or to
6675 @file{./.gdb_history} if this variable is not set.
6677 @cindex history save
6678 @kindex set history save
6679 @item set history save
6680 @itemx set history save on
6681 Record command history in a file, whose name may be specified with the
6682 @code{set history filename} command. By default, this option is disabled.
6684 @item set history save off
6685 Stop recording command history in a file.
6687 @cindex history size
6688 @kindex set history size
6689 @item set history size @var{size}
6690 Set the number of commands which _GDBN__ will keep in its history list.
6691 This defaults to the value of the environment variable
6692 @code{HISTSIZE}, or to 256 if this variable is not set.
6695 @cindex history expansion
6696 History expansion assigns special meaning to the character @kbd{!}.
6698 @xref{Event Designators}.
6700 Since @kbd{!} is also the logical not operator in C, history expansion
6701 is off by default. If you decide to enable history expansion with the
6702 @code{set history expansion on} command, you may sometimes need to
6703 follow @kbd{!} (when it is used as logical not, in an expression) with
6704 a space or a tab to prevent it from being expanded. The readline
6705 history facilities will not attempt substitution on the strings
6706 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
6708 The commands to control history expansion are:
6712 @kindex set history expansion
6713 @item set history expansion on
6714 @itemx set history expansion
6715 Enable history expansion. History expansion is off by default.
6717 @item set history expansion off
6718 Disable history expansion.
6720 The readline code comes with more complete documentation of
6721 editing and history expansion features. Users unfamiliar with @code{emacs}
6722 or @code{vi} may wish to read it.
6724 @xref{Command Line Editing}.
6728 @kindex show history
6730 @itemx show history filename
6731 @itemx show history save
6732 @itemx show history size
6733 @itemx show history expansion
6734 These commands display the state of the _GDBN__ history parameters.
6735 @code{show history} by itself displays all four states.
6740 @kindex show commands
6742 Display the last ten commands in the command history.
6744 @item show commands @var{n}
6745 Print ten commands centered on command number @var{n}.
6747 @item show commands +
6748 Print ten commands just after the commands last printed.
6752 @section Screen Size
6753 @cindex size of screen
6754 @cindex pauses in output
6756 Certain commands to _GDBN__ may produce large amounts of information
6757 output to the screen. To help you read all of it, _GDBN__ pauses and
6758 asks you for input at the end of each page of output. Type @key{RET}
6759 when you want to continue the output. _GDBN__ also uses the screen
6760 width setting to determine when to wrap lines of output. Depending on
6761 what is being printed, it tries to break the line at a readable place,
6762 rather than simply letting it overflow onto the following line.
6764 Normally _GDBN__ knows the size of the screen from the termcap data base
6765 together with the value of the @code{TERM} environment variable and the
6766 @code{stty rows} and @code{stty cols} settings. If this is not correct,
6767 you can override it with the @code{set height} and @code{set
6771 @item set height @var{lpp}
6773 @itemx set width @var{cpl}
6779 These @code{set} commands specify a screen height of @var{lpp} lines and
6780 a screen width of @var{cpl} characters. The associated @code{show}
6781 commands display the current settings.
6783 If you specify a height of zero lines, _GDBN__ will not pause during output
6784 no matter how long the output is. This is useful if output is to a file
6785 or to an editor buffer.
6790 @cindex number representation
6791 @cindex entering numbers
6793 You can always enter numbers in octal, decimal, or hexadecimal in _GDBN__ by
6794 the usual conventions: octal numbers begin with @samp{0}, decimal
6795 numbers end with @samp{.}, and hexadecimal numbers begin with @samp{0x}.
6796 Numbers that begin with none of these are, by default, entered in base
6797 10; likewise, the default display for numbers---when no particular
6798 format is specified---is base 10. You can change the default base for
6799 both input and output with the @code{set radix} command.
6803 @item set radix @var{base}
6804 Set the default base for numeric input and display. Supported choices
6805 for @var{base} are decimal 2, 8, 10, 16. @var{base} must itself be
6806 specified either unambiguously or using the current default radix; for
6817 will set the base to decimal. On the other hand, @samp{set radix 10}
6818 will leave the radix unchanged no matter what it was.
6822 Display the current default base for numeric input and display.
6825 @node Messages/Warnings
6826 @section Optional Warnings and Messages
6828 By default, _GDBN__ is silent about its inner workings. If you are running
6829 on a slow machine, you may want to use the @code{set verbose} command.
6830 It will make _GDBN__ tell you when it does a lengthy internal operation, so
6831 you will not think it has crashed.
6833 Currently, the messages controlled by @code{set verbose} are those
6834 which announce that the symbol table for a source file is being read;
6835 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
6839 @item set verbose on
6840 Enables _GDBN__'s output of certain informational messages.
6842 @item set verbose off
6843 Disables _GDBN__'s output of certain informational messages.
6845 @kindex show verbose
6847 Displays whether @code{set verbose} is on or off.
6850 By default, if _GDBN__ encounters bugs in the symbol table of an object
6851 file, it is silent; but if you are debugging a compiler, you may find
6852 this information useful (@pxref{Symbol Errors, ,Errors Reading Symbol Files}).
6855 @kindex set complaints
6856 @item set complaints @var{limit}
6857 Permits _GDBN__ to output @var{limit} complaints about each type of unusual
6858 symbols before becoming silent about the problem. Set @var{limit} to
6859 zero to suppress all complaints; set it to a large number to prevent
6860 complaints from being suppressed.
6862 @kindex show complaints
6863 @item show complaints
6864 Displays how many symbol complaints _GDBN__ is permitted to produce.
6867 By default, _GDBN__ is cautious, and asks what sometimes seems to be a
6868 lot of stupid questions to confirm certain commands. For example, if
6869 you try to run a program which is already running:
6873 The program being debugged has been started already.
6874 Start it from the beginning? (y or n)
6877 If you are willing to unflinchingly face the consequences of your own
6878 commands, you can disable this ``feature'':
6883 @cindex confirmation
6884 @cindex stupid questions
6885 @item set confirm off
6886 Disables confirmation requests.
6888 @item set confirm on
6889 Enables confirmation requests (the default).
6892 @kindex show confirm
6893 Displays state of confirmation requests.
6896 @c FIXME this does not really belong here. But where *does* it belong?
6897 @cindex reloading symbols
6898 Some systems allow individual object files that make up your program to
6899 be replaced without stopping and restarting your program.
6901 For example, in VxWorks you can simply recompile a defective object file
6902 and keep on running.
6904 If you are running on one of these systems, you can allow _GDBN__ to
6905 reload the symbols for automatically relinked modules:
6908 @kindex set symbol-reloading
6909 @item set symbol-reloading on
6910 Replace symbol definitions for the corresponding source file when an
6911 object file with a particular name is seen again.
6913 @item set symbol-reloading off
6914 Do not replace symbol definitions when re-encountering object files of
6915 the same name. This is the default state; if you are not running on a
6916 system that permits automatically relinking modules, you should leave
6917 @code{symbol-reloading} off, since otherwise _GDBN__ may discard symbols
6918 when linking large programs, that may contain several modules (from
6919 different directories or libraries) with the same name.
6921 @item show symbol-reloading
6922 Show the current @code{on} or @code{off} setting.
6926 @chapter Canned Sequences of Commands
6928 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
6929 Command Lists}), _GDBN__ provides two ways to store sequences of commands
6930 for execution as a unit: user-defined commands and command files.
6933 * Define:: User-Defined Commands
6934 * Command Files:: Command Files
6935 * Output:: Commands for Controlled Output
6939 @section User-Defined Commands
6941 @cindex user-defined command
6942 A @dfn{user-defined command} is a sequence of _GDBN__ commands to which you
6943 assign a new name as a command. This is done with the @code{define}
6947 @item define @var{commandname}
6949 Define a command named @var{commandname}. If there is already a command
6950 by that name, you are asked to confirm that you want to redefine it.
6952 The definition of the command is made up of other _GDBN__ command lines,
6953 which are given following the @code{define} command. The end of these
6954 commands is marked by a line containing @code{end}.
6956 @item document @var{commandname}
6958 Give documentation to the user-defined command @var{commandname}. The
6959 command @var{commandname} must already be defined. This command reads
6960 lines of documentation just as @code{define} reads the lines of the
6961 command definition, ending with @code{end}. After the @code{document}
6962 command is finished, @code{help} on command @var{commandname} will print
6963 the documentation you have specified.
6965 You may use the @code{document} command again to change the
6966 documentation of a command. Redefining the command with @code{define}
6967 does not change the documentation.
6969 @item help user-defined
6970 @kindex help user-defined
6971 List all user-defined commands, with the first line of the documentation
6975 @itemx show user @var{commandname}
6977 Display the _GDBN__ commands used to define @var{commandname} (but not its
6978 documentation). If no @var{commandname} is given, display the
6979 definitions for all user-defined commands.
6982 User-defined commands do not take arguments. When they are executed, the
6983 commands of the definition are not printed. An error in any command
6984 stops execution of the user-defined command.
6986 Commands that would ask for confirmation if used interactively proceed
6987 without asking when used inside a user-defined command. Many _GDBN__ commands
6988 that normally print messages to say what they are doing omit the messages
6989 when used in a user-defined command.
6992 @section Command Files
6994 @cindex command files
6995 A command file for _GDBN__ is a file of lines that are _GDBN__ commands. Comments
6996 (lines starting with @kbd{#}) may also be included. An empty line in a
6997 command file does nothing; it does not mean to repeat the last command, as
6998 it would from the terminal.
7001 @cindex @file{_GDBINIT__}
7002 When you start _GDBN__, it automatically executes commands from its
7003 @dfn{init files}. These are files named @file{_GDBINIT__}. _GDBN__ reads
7004 the init file (if any) in your home directory and then the init file
7005 (if any) in the current working directory. (The init files are not
7006 executed if you use the @samp{-nx} option; @pxref{Mode Options,
7007 ,Choosing Modes}.) You can also request the execution of a command
7008 file with the @code{source} command:
7011 @item source @var{filename}
7013 Execute the command file @var{filename}.
7016 The lines in a command file are executed sequentially. They are not
7017 printed as they are executed. An error in any command terminates execution
7018 of the command file.
7020 Commands that would ask for confirmation if used interactively proceed
7021 without asking when used in a command file. Many _GDBN__ commands that
7022 normally print messages to say what they are doing omit the messages
7023 when called from command files.
7026 @section Commands for Controlled Output
7028 During the execution of a command file or a user-defined command, normal
7029 _GDBN__ output is suppressed; the only output that appears is what is
7030 explicitly printed by the commands in the definition. This section
7031 describes three commands useful for generating exactly the output you
7035 @item echo @var{text}
7037 @c I do not consider backslash-space a standard C escape sequence
7038 @c because it is not in ANSI.
7039 Print @var{text}. Nonprinting characters can be included in
7040 @var{text} using C escape sequences, such as @samp{\n} to print a
7041 newline. @strong{No newline will be printed unless you specify one.}
7042 In addition to the standard C escape sequences, a backslash followed
7043 by a space stands for a space. This is useful for outputting a
7044 string with spaces at the beginning or the end, since leading and
7045 trailing spaces are otherwise trimmed from all arguments.
7046 To print @samp{@w{ }and foo =@w{ }}, use the command
7047 @samp{echo \@w{ }and foo = \@w{ }}.
7049 A backslash at the end of @var{text} can be used, as in C, to continue
7050 the command onto subsequent lines. For example,
7053 echo This is some text\n\
7054 which is continued\n\
7055 onto several lines.\n
7058 produces the same output as
7061 echo This is some text\n
7062 echo which is continued\n
7063 echo onto several lines.\n
7066 @item output @var{expression}
7068 Print the value of @var{expression} and nothing but that value: no
7069 newlines, no @samp{$@var{nn} = }. The value is not entered in the
7070 value history either. @xref{Expressions, ,Expressions}, for more information on
7073 @item output/@var{fmt} @var{expression}
7074 Print the value of @var{expression} in format @var{fmt}. You can use
7075 the same formats as for @code{print}; @pxref{Output formats}, for more
7078 @item printf @var{string}, @var{expressions}@dots{}
7080 Print the values of the @var{expressions} under the control of
7081 @var{string}. The @var{expressions} are separated by commas and may
7082 be either numbers or pointers. Their values are printed as specified
7083 by @var{string}, exactly as if your program were to execute
7086 printf (@var{string}, @var{expressions}@dots{});
7089 For example, you can print two values in hex like this:
7092 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
7095 The only backslash-escape sequences that you can use in the format
7096 string are the simple ones that consist of backslash followed by a
7102 @chapter Using _GDBN__ under GNU Emacs
7105 A special interface allows you to use GNU Emacs to view (and
7106 edit) the source files for the program you are debugging with
7109 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
7110 executable file you want to debug as an argument. This command starts
7111 _GDBN__ as a subprocess of Emacs, with input and output through a newly
7112 created Emacs buffer.
7114 Using _GDBN__ under Emacs is just like using _GDBN__ normally except for two
7119 All ``terminal'' input and output goes through the Emacs buffer.
7122 This applies both to _GDBN__ commands and their output, and to the input
7123 and output done by the program you are debugging.
7125 This is useful because it means that you can copy the text of previous
7126 commands and input them again; you can even use parts of the output
7129 All the facilities of Emacs' Shell mode are available for interacting
7130 with your program. In particular, you can send signals the usual
7131 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
7136 _GDBN__ displays source code through Emacs.
7139 Each time _GDBN__ displays a stack frame, Emacs automatically finds the
7140 source file for that frame and puts an arrow (_0__@samp{=>}_1__) at the
7141 left margin of the current line. Emacs uses a separate buffer for
7142 source display, and splits the window to show both your _GDBN__ session
7145 Explicit _GDBN__ @code{list} or search commands still produce output as
7146 usual, but you probably will have no reason to use them.
7149 @emph{Warning:} If the directory where your program resides is not your
7150 current directory, it can be easy to confuse Emacs about the location of
7151 the source files, in which case the auxiliary display buffer will not
7152 appear to show your source. _GDBN__ can find programs by searching your
7153 environment's @code{PATH} variable, so the _GDBN__ input and output
7154 session will proceed normally; but Emacs does not get enough information
7155 back from _GDBN__ to locate the source files in this situation. To
7156 avoid this problem, either start _GDBN__ mode from the directory where
7157 your program resides, or specify a full path name when prompted for the
7158 @kbd{M-x gdb} argument.
7160 A similar confusion can result if you use the _GDBN__ @code{file} command to
7161 switch to debugging a program in some other location, from an existing
7162 _GDBN__ buffer in Emacs.
7165 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If
7166 you need to call _GDBN__ by a different name (for example, if you keep
7167 several configurations around, with different names) you can set the
7168 Emacs variable @code{gdb-command-name}; for example,
7171 (setq gdb-command-name "mygdb")
7175 (preceded by @kbd{ESC ESC}, or typed in the @code{*scratch*} buffer, or
7176 in your @file{.emacs} file) will make Emacs call the program named
7177 ``@code{mygdb}'' instead.
7179 In the _GDBN__ I/O buffer, you can use these special Emacs commands in
7180 addition to the standard Shell mode commands:
7184 Describe the features of Emacs' _GDBN__ Mode.
7187 Execute to another source line, like the _GDBN__ @code{step} command; also
7188 update the display window to show the current file and location.
7191 Execute to next source line in this function, skipping all function
7192 calls, like the _GDBN__ @code{next} command. Then update the display window
7193 to show the current file and location.
7196 Execute one instruction, like the _GDBN__ @code{stepi} command; update
7197 display window accordingly.
7200 Execute to next instruction, using the _GDBN__ @code{nexti} command; update
7201 display window accordingly.
7204 Execute until exit from the selected stack frame, like the _GDBN__
7205 @code{finish} command.
7208 Continue execution of your program, like the _GDBN__ @code{continue}
7211 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}.
7214 Go up the number of frames indicated by the numeric argument
7215 (@pxref{Arguments, , Numeric Arguments, emacs, The GNU Emacs Manual}),
7216 like the _GDBN__ @code{up} command.
7218 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-u}.
7221 Go down the number of frames indicated by the numeric argument, like the
7222 _GDBN__ @code{down} command.
7224 @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-d}.
7227 Read the number where the cursor is positioned, and insert it at the end
7228 of the _GDBN__ I/O buffer. For example, if you wish to disassemble code
7229 around an address that was displayed earlier, type @kbd{disassemble};
7230 then move the cursor to the address display, and pick up the
7231 argument for @code{disassemble} by typing @kbd{C-x &}.
7233 You can customize this further on the fly by defining elements of the list
7234 @code{gdb-print-command}; once it is defined, you can format or
7235 otherwise process numbers picked up by @kbd{C-x &} before they are
7236 inserted. A numeric argument to @kbd{C-x &} will both indicate that you
7237 wish special formatting, and act as an index to pick an element of the
7238 list. If the list element is a string, the number to be inserted is
7239 formatted using the Emacs function @code{format}; otherwise the number
7240 is passed as an argument to the corresponding list element.
7243 In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break})
7244 tells _GDBN__ to set a breakpoint on the source line point is on.
7246 If you accidentally delete the source-display buffer, an easy way to get
7247 it back is to type the command @code{f} in the _GDBN__ buffer, to
7248 request a frame display; when you run under Emacs, this will recreate
7249 the source buffer if necessary to show you the context of the current
7252 The source files displayed in Emacs are in ordinary Emacs buffers
7253 which are visiting the source files in the usual way. You can edit
7254 the files with these buffers if you wish; but keep in mind that _GDBN__
7255 communicates with Emacs in terms of line numbers. If you add or
7256 delete lines from the text, the line numbers that _GDBN__ knows will cease
7257 to correspond properly to the code.
7259 @c The following dropped because Epoch is nonstandard. Reactivate
7260 @c if/when v19 does something similar. ---pesch@cygnus.com 19dec1990
7262 @kindex emacs epoch environment
7266 Version 18 of Emacs has a built-in window system called the @code{epoch}
7267 environment. Users of this environment can use a new command,
7268 @code{inspect} which performs identically to @code{print} except that
7269 each value is printed in its own window.
7275 @chapter Using _GDBN__ with Energize
7278 The Energize Programming System is an integrated development environment
7279 that includes a point-and-click interface to many programming tools.
7280 When you use _GDBN__ in this environment, you can use the standard
7281 Energize graphical interface to drive _GDBN__; you can also, if you
7282 choose, type _GDBN__ commands as usual in a debugging window. Even if
7283 you use the graphical interface, the debugging window (which uses Emacs,
7284 and resembles the standard Emacs interface to _GDBN__) displays the
7285 equivalent commands, so that the history of your debugging session is
7288 When Energize starts up a _GDBN__ session, it uses one of the
7289 command-line options @samp{-energize} or @samp{-cadillac} (``cadillac''
7290 is the name of the communications protocol used by the Energize system).
7291 This option makes _GDBN__ run as one of the tools in the Energize Tool
7292 Set: it sends all output to the Energize kernel, and accept input from
7295 See the user manual for the Energize Programming System for
7296 information on how to use the Energize graphical interface and the other
7297 development tools that Energize integrates with _GDBN__.
7302 @chapter Reporting Bugs in _GDBN__
7303 @cindex Bugs in _GDBN__
7304 @cindex Reporting Bugs in _GDBN__
7306 Your bug reports play an essential role in making _GDBN__ reliable.
7308 Reporting a bug may help you by bringing a solution to your problem, or it
7309 may not. But in any case the principal function of a bug report is to help
7310 the entire community by making the next version of _GDBN__ work better. Bug
7311 reports are your contribution to the maintenance of _GDBN__.
7313 In order for a bug report to serve its purpose, you must include the
7314 information that enables us to fix the bug.
7317 * Bug Criteria:: Have You Found a Bug?
7318 * Bug Reporting:: How to Report Bugs
7322 @section Have You Found a Bug?
7323 @cindex Bug Criteria
7325 If you are not sure whether you have found a bug, here are some guidelines:
7329 @cindex Fatal Signal
7331 If the debugger gets a fatal signal, for any input whatever, that is a
7332 _GDBN__ bug. Reliable debuggers never crash.
7335 @cindex error on Valid Input
7336 If _GDBN__ produces an error message for valid input, that is a bug.
7339 @cindex Invalid Input
7340 If _GDBN__ does not produce an error message for invalid input,
7341 that is a bug. However, you should note that your idea of
7342 ``invalid input'' might be our idea of ``an extension'' or ``support
7343 for traditional practice''.
7346 If you are an experienced user of debugging tools, your suggestions
7347 for improvement of _GDBN__ are welcome in any case.
7351 @section How to Report Bugs
7353 @cindex _GDBN__ Bugs, Reporting
7355 A number of companies and individuals offer support for GNU products.
7356 If you obtained _GDBN__ from a support organization, we recommend you
7357 contact that organization first.
7359 Contact information for many support companies and individuals is
7360 available in the file @file{etc/SERVICE} in the GNU Emacs distribution.
7362 In any event, we also recommend that you send bug reports for _GDBN__ to one
7366 bug-gdb@@prep.ai.mit.edu
7367 @{ucbvax|mit-eddie|uunet@}!prep.ai.mit.edu!bug-gdb
7370 @strong{Do not send bug reports to @samp{info-gdb}, or to
7371 @samp{help-gdb}, or to any newsgroups.} Most users of _GDBN__ do not want to
7372 receive bug reports. Those that do, have arranged to receive @samp{bug-gdb}.
7374 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
7375 serves as a repeater. The mailing list and the newsgroup carry exactly
7376 the same messages. Often people think of posting bug reports to the
7377 newsgroup instead of mailing them. This appears to work, but it has one
7378 problem which can be crucial: a newsgroup posting often lacks a mail
7379 path back to the sender. Thus, if we need to ask for more information,
7380 we may be unable to reach you. For this reason, it is better to send
7381 bug reports to the mailing list.
7383 As a last resort, send bug reports on paper to:
7387 Free Software Foundation
7392 The fundamental principle of reporting bugs usefully is this:
7393 @strong{report all the facts}. If you are not sure whether to state a
7394 fact or leave it out, state it!
7396 Often people omit facts because they think they know what causes the
7397 problem and assume that some details do not matter. Thus, you might
7398 assume that the name of the variable you use in an example does not matter.
7399 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
7400 stray memory reference which happens to fetch from the location where that
7401 name is stored in memory; perhaps, if the name were different, the contents
7402 of that location would fool the debugger into doing the right thing despite
7403 the bug. Play it safe and give a specific, complete example. That is the
7404 easiest thing for you to do, and the most helpful.
7406 Keep in mind that the purpose of a bug report is to enable us to fix
7407 the bug if it is new to us. It is not as important as what happens if
7408 the bug is already known. Therefore, always write your bug reports on
7409 the assumption that the bug has not been reported previously.
7411 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7412 bell?'' Those bug reports are useless, and we urge everyone to
7413 @emph{refuse to respond to them} except to chide the sender to report
7416 To enable us to fix the bug, you should include all these things:
7420 The version of _GDBN__. _GDBN__ announces it if you start with no
7421 arguments; you can also print it at any time using @code{show version}.
7423 Without this, we will not know whether there is any point in looking for
7424 the bug in the current version of _GDBN__.
7427 The type of machine you are using, and the operating system name and
7431 What compiler (and its version) was used to compile _GDBN__---e.g.
7435 What compiler (and its version) was used to compile the program you
7436 are debugging---e.g. ``_GCC__-2.0''.
7439 The command arguments you gave the compiler to compile your example and
7440 observe the bug. For example, did you use @samp{-O}? To guarantee
7441 you will not omit something important, list them all. A copy of the
7442 Makefile (or the output from make) is sufficient.
7444 If we were to try to guess the arguments, we would probably guess wrong
7445 and then we might not encounter the bug.
7448 A complete input script, and all necessary source files, that will
7452 A description of what behavior you observe that you believe is
7453 incorrect. For example, ``It gets a fatal signal.''
7455 Of course, if the bug is that _GDBN__ gets a fatal signal, then we will
7456 certainly notice it. But if the bug is incorrect output, we might not
7457 notice unless it is glaringly wrong. We are human, after all. You
7458 might as well not give us a chance to make a mistake.
7460 Even if the problem you experience is a fatal signal, you should still
7461 say so explicitly. Suppose something strange is going on, such as,
7462 your copy of _GDBN__ is out of synch, or you have encountered a
7463 bug in the C library on your system. (This has happened!) Your copy
7464 might crash and ours would not. If you told us to expect a crash,
7465 then when ours fails to crash, we would know that the bug was not
7466 happening for us. If you had not told us to expect a crash, then we
7467 would not be able to draw any conclusion from our observations.
7470 If you wish to suggest changes to the _GDBN__ source, send us context
7471 diffs. If you even discuss something in the _GDBN__ source, refer to
7472 it by context, not by line number.
7474 The line numbers in our development sources will not match those in your
7475 sources. Your line numbers would convey no useful information to us.
7478 Here are some things that are not necessary:
7482 A description of the envelope of the bug.
7484 Often people who encounter a bug spend a lot of time investigating
7485 which changes to the input file will make the bug go away and which
7486 changes will not affect it.
7488 This is often time consuming and not very useful, because the way we
7489 will find the bug is by running a single example under the debugger
7490 with breakpoints, not by pure deduction from a series of examples.
7491 We recommend that you save your time for something else.
7493 Of course, if you can find a simpler example to report @emph{instead}
7494 of the original one, that is a convenience for us. Errors in the
7495 output will be easier to spot, running under the debugger will take
7498 However, simplification is not vital; if you do not want to do this,
7499 report the bug anyway and send us the entire test case you used.
7502 A patch for the bug.
7504 A patch for the bug does help us if it is a good one. But do not omit
7505 the necessary information, such as the test case, on the assumption that
7506 a patch is all we need. We might see problems with your patch and decide
7507 to fix the problem another way, or we might not understand it at all.
7509 Sometimes with a program as complicated as _GDBN__ it is very hard to
7510 construct an example that will make the program follow a certain path
7511 through the code. If you do not send us the example, we will not be able
7512 to construct one, so we will not be able to verify that the bug is fixed.
7514 And if we cannot understand what bug you are trying to fix, or why your
7515 patch should be an improvement, we will not install it. A test case will
7516 help us to understand.
7519 A guess about what the bug is or what it depends on.
7521 Such guesses are usually wrong. Even we cannot guess right about such
7522 things without first using the debugger to find the facts.
7525 @c Note: no need to update nodes for rdl-apps.texi since it appears
7526 @c *only* in the TeX version of the manual.
7527 @c Note: eventually, make a cross reference to the readline Info nodes.
7529 @c appendices describing GNU readline. Distributed with readline code.
7530 @include rluser.texinfo
7531 @include inc-hist.texi
7534 _if__(_GENERIC__||!_H8__)
7535 @node Renamed Commands
7536 @appendix Renamed Commands
7538 The following commands were renamed in GDB 4, in order to make the
7539 command set as a whole more consistent and easier to use and remember:
7542 @kindex delete environment
7543 @kindex info copying
7544 @kindex info convenience
7545 @kindex info directories
7546 @kindex info editing
7547 @kindex info history
7548 @kindex info targets
7550 @kindex info version
7551 @kindex info warranty
7552 @kindex set addressprint
7553 @kindex set arrayprint
7554 @kindex set prettyprint
7555 @kindex set screen-height
7556 @kindex set screen-width
7557 @kindex set unionprint
7558 @kindex set vtblprint
7559 @kindex set demangle
7560 @kindex set asm-demangle
7561 @kindex set sevenbit-strings
7562 @kindex set array-max
7564 @kindex set history write
7565 @kindex show addressprint
7566 @kindex show arrayprint
7567 @kindex show prettyprint
7568 @kindex show screen-height
7569 @kindex show screen-width
7570 @kindex show unionprint
7571 @kindex show vtblprint
7572 @kindex show demangle
7573 @kindex show asm-demangle
7574 @kindex show sevenbit-strings
7575 @kindex show array-max
7576 @kindex show caution
7577 @kindex show history write
7582 @c END TEXI2ROFF-KILL
7584 OLD COMMAND NEW COMMAND
7586 --------------- -------------------------------
7587 @c END TEXI2ROFF-KILL
7588 add-syms add-symbol-file
7589 delete environment unset environment
7590 info convenience show convenience
7591 info copying show copying
7592 info directories show directories
7593 info editing show commands
7594 info history show values
7595 info targets help target
7596 info values show values
7597 info version show version
7598 info warranty show warranty
7599 set/show addressprint set/show print address
7600 set/show array-max set/show print elements
7601 set/show arrayprint set/show print array
7602 set/show asm-demangle set/show print asm-demangle
7603 set/show caution set/show confirm
7604 set/show demangle set/show print demangle
7605 set/show history write set/show history save
7606 set/show prettyprint set/show print pretty
7607 set/show screen-height set/show height
7608 set/show screen-width set/show width
7609 set/show sevenbit-strings set/show print sevenbit-strings
7610 set/show unionprint set/show print union
7611 set/show vtblprint set/show print vtbl
7613 unset [No longer an alias for delete]
7619 \vskip \parskip\vskip \baselineskip
7620 \halign{\tt #\hfil &\qquad#&\tt #\hfil\cr
7621 {\bf Old Command} &&{\bf New Command}\cr
7622 add-syms &&add-symbol-file\cr
7623 delete environment &&unset environment\cr
7624 info convenience &&show convenience\cr
7625 info copying &&show copying\cr
7626 info directories &&show directories \cr
7627 info editing &&show commands\cr
7628 info history &&show values\cr
7629 info targets &&help target\cr
7630 info values &&show values\cr
7631 info version &&show version\cr
7632 info warranty &&show warranty\cr
7633 set{\rm / }show addressprint &&set{\rm / }show print address\cr
7634 set{\rm / }show array-max &&set{\rm / }show print elements\cr
7635 set{\rm / }show arrayprint &&set{\rm / }show print array\cr
7636 set{\rm / }show asm-demangle &&set{\rm / }show print asm-demangle\cr
7637 set{\rm / }show caution &&set{\rm / }show confirm\cr
7638 set{\rm / }show demangle &&set{\rm / }show print demangle\cr
7639 set{\rm / }show history write &&set{\rm / }show history save\cr
7640 set{\rm / }show prettyprint &&set{\rm / }show print pretty\cr
7641 set{\rm / }show screen-height &&set{\rm / }show height\cr
7642 set{\rm / }show screen-width &&set{\rm / }show width\cr
7643 set{\rm / }show sevenbit-strings &&set{\rm / }show print sevenbit-strings\cr
7644 set{\rm / }show unionprint &&set{\rm / }show print union\cr
7645 set{\rm / }show vtblprint &&set{\rm / }show print vtbl\cr
7647 unset &&\rm(No longer an alias for delete)\cr
7650 @c END TEXI2ROFF-KILL
7651 _fi__(_GENERIC__||!_H8__)
7653 @node Formatting Documentation
7654 @appendix Formatting the Documentation
7656 @cindex GDB reference card
7657 @cindex reference card
7658 The GDB 4 release includes an already-formatted reference card, ready
7659 for printing with PostScript or GhostScript, in the @file{gdb}
7660 subdirectory of the main source directory---in
7661 @file{gdb-_GDB_VN__/gdb/refcard.ps} of the version _GDB_VN__ release.
7662 If you can use PostScript or GhostScript with your printer, you can
7663 print the reference card immediately with @file{refcard.ps}.
7665 The release also includes the source for the reference card. You
7666 can format it, using @TeX{}, by typing:
7672 The GDB reference card is designed to print in landscape mode on US
7673 ``letter'' size paper; that is, on a sheet 11 inches wide by 8.5 inches
7674 high. You will need to specify this form of printing as an option to
7675 your @sc{dvi} output program.
7677 @cindex documentation
7679 All the documentation for GDB comes as part of the machine-readable
7680 distribution. The documentation is written in Texinfo format, which is
7681 a documentation system that uses a single source file to produce both
7682 on-line information and a printed manual. You can use one of the Info
7683 formatting commands to create the on-line version of the documentation
7684 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
7686 GDB includes an already formatted copy of the on-line Info version of
7687 this manual in the @file{gdb} subdirectory. The main Info file is
7688 @file{gdb-@var{version-number}/gdb/gdb.info}, and it refers to
7689 subordinate files matching @samp{gdb.info*} in the same directory. If
7690 necessary, you can print out these files, or read them with any editor;
7691 but they are easier to read using the @code{info} subsystem in GNU Emacs
7692 or the standalone @code{info} program, available as part of the GNU
7693 Texinfo distribution.
7695 If you want to format these Info files yourself, you need one of the
7696 Info formatting programs, such as @code{texinfo-format-buffer} or
7699 If you have @code{makeinfo} installed, and are in the top level GDB
7700 source directory (@file{gdb-_GDB_VN__}, in the case of version _GDB_VN__), you can
7701 make the Info file by typing:
7708 If you want to typeset and print copies of this manual, you need
7709 @TeX{}, a printing program such as @code{lpr}, and @file{texinfo.tex},
7710 the Texinfo definitions file.
7712 @TeX{} is typesetting program; it does not print files directly, but
7713 produces output files called @sc{dvi} files. To print a typeset
7714 document, you need a program to print @sc{dvi} files. If your system
7715 has @TeX{} installed, chances are it has such a program. The precise
7716 command to use depends on your system; @kbd{lpr -d} is common; another
7717 is @kbd{dvips}. The @sc{dvi} print command may require a file name
7718 without any extension or a @samp{.dvi} extension.
7720 @TeX{} also requires a macro definitions file called
7721 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
7722 written in Texinfo format. On its own, @TeX{} cannot read, much less
7723 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
7724 and is located in the @file{gdb-@var{version-number}/texinfo}
7727 If you have @TeX{} and a @sc{dvi} printer program installed, you can
7728 typeset and print this manual. First switch to the the @file{gdb}
7729 subdirectory of the main source directory (for example, to
7730 @file{gdb-_GDB_VN__/gdb}) and then type:
7736 @node Installing GDB
7737 @appendix Installing GDB
7738 @cindex configuring GDB
7739 @cindex installation
7742 @c irrelevant in info file; it's as current as the code it lives with.
7744 @emph{Warning:} These installation instructions are current as of
7745 GDB version _GDB_VN__. If you're installing a more recent release
7746 of GDB, we may have improved the installation procedures since
7747 printing this manual; see the @file{README} file included in your
7748 release for the most recent instructions.
7752 GDB comes with a @code{configure} script that automates the process
7753 of preparing GDB for installation; you can then use @code{make} to
7756 The GDB distribution includes all the source code you need for GDB in
7757 a single directory, whose name is usually composed by appending the
7758 version number to @samp{gdb}.
7760 For example, the GDB version _GDB_VN__ distribution is in the @file{gdb-_GDB_VN__}
7761 directory. That directory contains:
7764 @item gdb-_GDB_VN__/configure @r{(and supporting files)}
7765 script for configuring GDB and all its supporting libraries.
7767 @item gdb-_GDB_VN__/gdb
7768 the source specific to GDB itself
7770 @item gdb-_GDB_VN__/bfd
7771 source for the Binary File Descriptor library
7773 @item gdb-_GDB_VN__/include
7776 @item gdb-_GDB_VN__/libiberty
7777 source for the @samp{-liberty} free software library
7779 @item gdb-_GDB_VN__/readline
7780 source for the GNU command-line interface
7782 @item gdb-_GDB_VN__/glob
7783 source for the GNU filename pattern-matching subroutine
7785 @item gdb-_GDB_VN__/mmalloc
7786 source for the GNU memory-mapped malloc package
7789 The simplest way to configure and build GDB is to run @code{configure}
7790 from the @file{gdb-@var{version-number}} source directory, which in
7791 this example is the @file{gdb-_GDB_VN__} directory.
7793 First switch to the @file{gdb-@var{version-number}} source directory
7794 if you are not already in it; then run @code{configure}. Pass the
7795 identifier for the platform on which GDB will run as an
7802 ./configure @var{host}
7807 where @var{host} is an identifier such as @samp{sun4} or
7808 @samp{decstation}, that identifies the platform where GDB will run.
7810 Running @samp{configure @var{host}} followed by @code{make} builds the
7811 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
7812 libraries, then @code{gdb} itself. The configured source files, and the
7813 binaries, are left in the corresponding source directories.
7815 @code{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
7816 system does not recognize this automatically when you run a different
7817 shell, you may need to run @code{sh} on it explicitly:
7820 sh configure @var{host}
7823 If you run @code{configure} from a directory that contains source
7824 directories for multiple libraries or programs, such as the
7825 @file{gdb-_GDB_VN__} source directory for version _GDB_VN__, @code{configure}
7826 creates configuration files for every directory level underneath (unless
7827 you tell it not to, with the @samp{--norecursion} option).
7829 You can run the @code{configure} script from any of the
7830 subordinate directories in the GDB distribution, if you only want to
7831 configure that subdirectory; but be sure to specify a path to it.
7833 For example, with version _GDB_VN__, type the following to configure only
7834 the @code{bfd} subdirectory:
7838 cd gdb-_GDB_VN__/bfd
7839 ../configure @var{host}
7843 You can install @code{_GDBP__} anywhere; it has no hardwired paths.
7844 However, you should make sure that the shell on your path (named by
7845 the @samp{SHELL} environment variable) is publicly readable. Remember
7846 that GDB uses the shell to start your program---some systems refuse to
7847 let GDB debug child processes whose programs are not readable.
7850 * Separate Objdir:: Compiling GDB in another directory
7851 * Config Names:: Specifying names for hosts and targets
7852 * configure Options:: Summary of options for configure
7855 @node Separate Objdir
7856 @section Compiling GDB in Another Directory
7858 If you want to run GDB versions for several host or target machines,
7859 you'll need a different @code{gdb} compiled for each combination of
7860 host and target. @code{configure} is designed to make this easy by
7861 allowing you to generate each configuration in a separate subdirectory,
7862 rather than in the source directory. If your @code{make} program
7863 handles the @samp{VPATH} feature (GNU @code{make} does), running
7864 @code{make} in each of these directories then builds the @code{gdb}
7865 program specified there.
7867 To build @code{gdb} in a separate directory, run @code{configure}
7868 with the @samp{--srcdir} option to specify where to find the source.
7869 (You'll also need to specify a path to find @code{configure}
7870 itself from your working directory. If the path to @code{configure}
7871 would be the same as the argument to @samp{--srcdir}, you can leave out
7872 the @samp{--srcdir} option; it will be assumed.)
7874 For example, with version _GDB_VN__, you can build GDB in a separate
7875 directory for a Sun 4 like this:
7882 ../gdb-_GDB_VN__/configure sun4
7887 When @code{configure} builds a configuration using a remote source
7888 directory, it creates a tree for the binaries with the same structure
7889 (and using the same names) as the tree under the source directory. In
7890 the example, you'd find the Sun 4 library @file{libiberty.a} in the
7891 directory @file{gdb-sun4/libiberty}, and GDB itself in
7892 @file{gdb-sun4/gdb}.
7894 One popular reason to build several GDB configurations in separate
7895 directories is to configure GDB for cross-compiling (where GDB
7896 runs on one machine---the host---while debugging programs that run on
7897 another machine---the target). You specify a cross-debugging target by
7898 giving the @samp{--target=@var{target}} option to @code{configure}.
7900 When you run @code{make} to build a program or library, you must run
7901 it in a configured directory---whatever directory you were in when you
7902 called @code{configure} (or one of its subdirectories).
7904 The @code{Makefile} generated by @code{configure} for each source
7905 directory also runs recursively. If you type @code{make} in a source
7906 directory such as @file{gdb-_GDB_VN__} (or in a separate configured
7907 directory configured with @samp{--srcdir=@var{path}/gdb-_GDB_VN__}), you
7908 will build all the required libraries, then build GDB.
7910 When you have multiple hosts or targets configured in separate
7911 directories, you can run @code{make} on them in parallel (for example,
7912 if they are NFS-mounted on each of the hosts); they will not interfere
7916 @section Specifying Names for Hosts and Targets
7918 The specifications used for hosts and targets in the @code{configure}
7919 script are based on a three-part naming scheme, but some short predefined
7920 aliases are also supported. The full naming scheme encodes three pieces
7921 of information in the following pattern:
7924 @var{architecture}-@var{vendor}-@var{os}
7927 For example, you can use the alias @code{sun4} as a @var{host} argument
7928 or in a @code{--target=@var{target}} option, but the equivalent full name
7929 is @samp{sparc-sun-sunos4}.
7931 The @code{configure} script accompanying GDB does not provide
7932 any query facility to list all supported host and target names or
7933 aliases. @code{configure} calls the Bourne shell script
7934 @code{config.sub} to map abbreviations to full names; you can read the
7935 script, if you wish, or you can use it to test your guesses on
7936 abbreviations---for example:
7939 % sh config.sub sun4
7941 % sh config.sub sun3
7943 % sh config.sub decstation
7945 % sh config.sub hp300bsd
7947 % sh config.sub i386v
7949 % sh config.sub i786v
7950 Invalid configuration `i786v': machine `i786v' not recognized
7954 @code{config.sub} is also distributed in the GDB source
7955 directory (@file{gdb-_GDB_VN__}, for version _GDB_VN__).
7957 @node configure Options
7958 @section @code{configure} Options
7960 Here is a summary of the @code{configure} options and arguments that
7961 are most often useful for building _GDBN__. @code{configure} also has
7962 several other options not listed here. @inforef{What Configure
7963 Does,,configure.info}, for a full explanation of @code{configure}.
7964 @c FIXME: Would this be more, or less, useful as an xref (ref to printed
7965 @c manual in the printed manual, ref to info file only from the info file)?
7968 configure @r{[}--help@r{]}
7969 @r{[}--prefix=@var{dir}@r{]}
7970 @r{[}--srcdir=@var{path}@r{]}
7971 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
7972 @r{[}--target=@var{target}@r{]} @var{host}
7976 You may introduce options with a single @samp{-} rather than
7977 @samp{--} if you prefer; but you may abbreviate option names if you use
7982 Display a quick summary of how to invoke @code{configure}.
7984 @item -prefix=@var{dir}
7985 Configure the source to install programs and files under directory
7988 @item --srcdir=@var{path}
7989 @strong{Warning: using this option requires GNU @code{make}, or another
7990 @code{make} that implements the @code{VPATH} feature.}@*
7991 Use this option to make configurations in directories separate from the
7992 GDB source directories. Among other things, you can use this to
7993 build (or maintain) several configurations simultaneously, in separate
7994 directories. @code{configure} writes configuration specific files in
7995 the current directory, but arranges for them to use the source in the
7996 directory @var{path}. @code{configure} will create directories under
7997 the working directory in parallel to the source directories below
8001 Configure only the directory level where @code{configure} is executed; do not
8002 propagate configuration to subdirectories.
8005 Remove the configuration that the other arguments specify.
8007 @c This does not work (yet if ever). FIXME.
8008 @c @item --parse=@var{lang} @dots{}
8009 @c Configure the GDB expression parser to parse the listed languages.
8010 @c @samp{all} configures GDB for all supported languages. To get a
8011 @c list of all supported languages, omit the argument. Without this
8012 @c option, GDB is configured to parse all supported languages.
8014 @item --target=@var{target}
8015 Configure GDB for cross-debugging programs running on the specified
8016 @var{target}. Without this option, GDB is configured to debug
8017 programs that run on the same machine (@var{host}) as GDB itself.
8019 There is no convenient way to generate a list of all available targets.
8021 @item @var{host} @dots{}
8022 Configure GDB to run on the specified @var{host}.
8024 There is no convenient way to generate a list of all available hosts.
8028 @code{configure} accepts other options, for compatibility with
8029 configuring other GNU tools recursively; but these are the only
8030 options that affect GDB or its supporting libraries.
8033 @unnumbered GNU GENERAL PUBLIC LICENSE
8034 @center Version 2, June 1991
8037 Copyright @copyright{} 1989, 1991 Free Software Foundation, Inc.
8038 675 Mass Ave, Cambridge, MA 02139, USA
8040 Everyone is permitted to copy and distribute verbatim copies
8041 of this license document, but changing it is not allowed.
8044 @unnumberedsec Preamble
8046 The licenses for most software are designed to take away your
8047 freedom to share and change it. By contrast, the GNU General Public
8048 License is intended to guarantee your freedom to share and change free
8049 software---to make sure the software is free for all its users. This
8050 General Public License applies to most of the Free Software
8051 Foundation's software and to any other program whose authors commit to
8052 using it. (Some other Free Software Foundation software is covered by
8053 the GNU Library General Public License instead.) You can apply it to
8056 When we speak of free software, we are referring to freedom, not
8057 price. Our General Public Licenses are designed to make sure that you
8058 have the freedom to distribute copies of free software (and charge for
8059 this service if you wish), that you receive source code or can get it
8060 if you want it, that you can change the software or use pieces of it
8061 in new free programs; and that you know you can do these things.
8063 To protect your rights, we need to make restrictions that forbid
8064 anyone to deny you these rights or to ask you to surrender the rights.
8065 These restrictions translate to certain responsibilities for you if you
8066 distribute copies of the software, or if you modify it.
8068 For example, if you distribute copies of such a program, whether
8069 gratis or for a fee, you must give the recipients all the rights that
8070 you have. You must make sure that they, too, receive or can get the
8071 source code. And you must show them these terms so they know their
8074 We protect your rights with two steps: (1) copyright the software, and
8075 (2) offer you this license which gives you legal permission to copy,
8076 distribute and/or modify the software.
8078 Also, for each author's protection and ours, we want to make certain
8079 that everyone understands that there is no warranty for this free
8080 software. If the software is modified by someone else and passed on, we
8081 want its recipients to know that what they have is not the original, so
8082 that any problems introduced by others will not reflect on the original
8083 authors' reputations.
8085 Finally, any free program is threatened constantly by software
8086 patents. We wish to avoid the danger that redistributors of a free
8087 program will individually obtain patent licenses, in effect making the
8088 program proprietary. To prevent this, we have made it clear that any
8089 patent must be licensed for everyone's free use or not licensed at all.
8091 The precise terms and conditions for copying, distribution and
8092 modification follow.
8095 @unnumberedsec TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
8098 @center TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
8103 This License applies to any program or other work which contains
8104 a notice placed by the copyright holder saying it may be distributed
8105 under the terms of this General Public License. The ``Program'', below,
8106 refers to any such program or work, and a ``work based on the Program''
8107 means either the Program or any derivative work under copyright law:
8108 that is to say, a work containing the Program or a portion of it,
8109 either verbatim or with modifications and/or translated into another
8110 language. (Hereinafter, translation is included without limitation in
8111 the term ``modification''.) Each licensee is addressed as ``you''.
8113 Activities other than copying, distribution and modification are not
8114 covered by this License; they are outside its scope. The act of
8115 running the Program is not restricted, and the output from the Program
8116 is covered only if its contents constitute a work based on the
8117 Program (independent of having been made by running the Program).
8118 Whether that is true depends on what the Program does.
8121 You may copy and distribute verbatim copies of the Program's
8122 source code as you receive it, in any medium, provided that you
8123 conspicuously and appropriately publish on each copy an appropriate
8124 copyright notice and disclaimer of warranty; keep intact all the
8125 notices that refer to this License and to the absence of any warranty;
8126 and give any other recipients of the Program a copy of this License
8127 along with the Program.
8129 You may charge a fee for the physical act of transferring a copy, and
8130 you may at your option offer warranty protection in exchange for a fee.
8133 You may modify your copy or copies of the Program or any portion
8134 of it, thus forming a work based on the Program, and copy and
8135 distribute such modifications or work under the terms of Section 1
8136 above, provided that you also meet all of these conditions:
8140 You must cause the modified files to carry prominent notices
8141 stating that you changed the files and the date of any change.
8144 You must cause any work that you distribute or publish, that in
8145 whole or in part contains or is derived from the Program or any
8146 part thereof, to be licensed as a whole at no charge to all third
8147 parties under the terms of this License.
8150 If the modified program normally reads commands interactively
8151 when run, you must cause it, when started running for such
8152 interactive use in the most ordinary way, to print or display an
8153 announcement including an appropriate copyright notice and a
8154 notice that there is no warranty (or else, saying that you provide
8155 a warranty) and that users may redistribute the program under
8156 these conditions, and telling the user how to view a copy of this
8157 License. (Exception: if the Program itself is interactive but
8158 does not normally print such an announcement, your work based on
8159 the Program is not required to print an announcement.)
8162 These requirements apply to the modified work as a whole. If
8163 identifiable sections of that work are not derived from the Program,
8164 and can be reasonably considered independent and separate works in
8165 themselves, then this License, and its terms, do not apply to those
8166 sections when you distribute them as separate works. But when you
8167 distribute the same sections as part of a whole which is a work based
8168 on the Program, the distribution of the whole must be on the terms of
8169 this License, whose permissions for other licensees extend to the
8170 entire whole, and thus to each and every part regardless of who wrote it.
8172 Thus, it is not the intent of this section to claim rights or contest
8173 your rights to work written entirely by you; rather, the intent is to
8174 exercise the right to control the distribution of derivative or
8175 collective works based on the Program.
8177 In addition, mere aggregation of another work not based on the Program
8178 with the Program (or with a work based on the Program) on a volume of
8179 a storage or distribution medium does not bring the other work under
8180 the scope of this License.
8183 You may copy and distribute the Program (or a work based on it,
8184 under Section 2) in object code or executable form under the terms of
8185 Sections 1 and 2 above provided that you also do one of the following:
8189 Accompany it with the complete corresponding machine-readable
8190 source code, which must be distributed under the terms of Sections
8191 1 and 2 above on a medium customarily used for software interchange; or,
8194 Accompany it with a written offer, valid for at least three
8195 years, to give any third party, for a charge no more than your
8196 cost of physically performing source distribution, a complete
8197 machine-readable copy of the corresponding source code, to be
8198 distributed under the terms of Sections 1 and 2 above on a medium
8199 customarily used for software interchange; or,
8202 Accompany it with the information you received as to the offer
8203 to distribute corresponding source code. (This alternative is
8204 allowed only for noncommercial distribution and only if you
8205 received the program in object code or executable form with such
8206 an offer, in accord with Subsection b above.)
8209 The source code for a work means the preferred form of the work for
8210 making modifications to it. For an executable work, complete source
8211 code means all the source code for all modules it contains, plus any
8212 associated interface definition files, plus the scripts used to
8213 control compilation and installation of the executable. However, as a
8214 special exception, the source code distributed need not include
8215 anything that is normally distributed (in either source or binary
8216 form) with the major components (compiler, kernel, and so on) of the
8217 operating system on which the executable runs, unless that component
8218 itself accompanies the executable.
8220 If distribution of executable or object code is made by offering
8221 access to copy from a designated place, then offering equivalent
8222 access to copy the source code from the same place counts as
8223 distribution of the source code, even though third parties are not
8224 compelled to copy the source along with the object code.
8227 You may not copy, modify, sublicense, or distribute the Program
8228 except as expressly provided under this License. Any attempt
8229 otherwise to copy, modify, sublicense or distribute the Program is
8230 void, and will automatically terminate your rights under this License.
8231 However, parties who have received copies, or rights, from you under
8232 this License will not have their licenses terminated so long as such
8233 parties remain in full compliance.
8236 You are not required to accept this License, since you have not
8237 signed it. However, nothing else grants you permission to modify or
8238 distribute the Program or its derivative works. These actions are
8239 prohibited by law if you do not accept this License. Therefore, by
8240 modifying or distributing the Program (or any work based on the
8241 Program), you indicate your acceptance of this License to do so, and
8242 all its terms and conditions for copying, distributing or modifying
8243 the Program or works based on it.
8246 Each time you redistribute the Program (or any work based on the
8247 Program), the recipient automatically receives a license from the
8248 original licensor to copy, distribute or modify the Program subject to
8249 these terms and conditions. You may not impose any further
8250 restrictions on the recipients' exercise of the rights granted herein.
8251 You are not responsible for enforcing compliance by third parties to
8255 If, as a consequence of a court judgment or allegation of patent
8256 infringement or for any other reason (not limited to patent issues),
8257 conditions are imposed on you (whether by court order, agreement or
8258 otherwise) that contradict the conditions of this License, they do not
8259 excuse you from the conditions of this License. If you cannot
8260 distribute so as to satisfy simultaneously your obligations under this
8261 License and any other pertinent obligations, then as a consequence you
8262 may not distribute the Program at all. For example, if a patent
8263 license would not permit royalty-free redistribution of the Program by
8264 all those who receive copies directly or indirectly through you, then
8265 the only way you could satisfy both it and this License would be to
8266 refrain entirely from distribution of the Program.
8268 If any portion of this section is held invalid or unenforceable under
8269 any particular circumstance, the balance of the section is intended to
8270 apply and the section as a whole is intended to apply in other
8273 It is not the purpose of this section to induce you to infringe any
8274 patents or other property right claims or to contest validity of any
8275 such claims; this section has the sole purpose of protecting the
8276 integrity of the free software distribution system, which is
8277 implemented by public license practices. Many people have made
8278 generous contributions to the wide range of software distributed
8279 through that system in reliance on consistent application of that
8280 system; it is up to the author/donor to decide if he or she is willing
8281 to distribute software through any other system and a licensee cannot
8284 This section is intended to make thoroughly clear what is believed to
8285 be a consequence of the rest of this License.
8288 If the distribution and/or use of the Program is restricted in
8289 certain countries either by patents or by copyrighted interfaces, the
8290 original copyright holder who places the Program under this License
8291 may add an explicit geographical distribution limitation excluding
8292 those countries, so that distribution is permitted only in or among
8293 countries not thus excluded. In such case, this License incorporates
8294 the limitation as if written in the body of this License.
8297 The Free Software Foundation may publish revised and/or new versions
8298 of the General Public License from time to time. Such new versions will
8299 be similar in spirit to the present version, but may differ in detail to
8300 address new problems or concerns.
8302 Each version is given a distinguishing version number. If the Program
8303 specifies a version number of this License which applies to it and ``any
8304 later version'', you have the option of following the terms and conditions
8305 either of that version or of any later version published by the Free
8306 Software Foundation. If the Program does not specify a version number of
8307 this License, you may choose any version ever published by the Free Software
8311 If you wish to incorporate parts of the Program into other free
8312 programs whose distribution conditions are different, write to the author
8313 to ask for permission. For software which is copyrighted by the Free
8314 Software Foundation, write to the Free Software Foundation; we sometimes
8315 make exceptions for this. Our decision will be guided by the two goals
8316 of preserving the free status of all derivatives of our free software and
8317 of promoting the sharing and reuse of software generally.
8320 @heading NO WARRANTY
8327 BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY
8328 FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN
8329 OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES
8330 PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED
8331 OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
8332 MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS
8333 TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE
8334 PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING,
8335 REPAIR OR CORRECTION.
8338 IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
8339 WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR
8340 REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES,
8341 INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING
8342 OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED
8343 TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY
8344 YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER
8345 PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE
8346 POSSIBILITY OF SUCH DAMAGES.
8350 @heading END OF TERMS AND CONDITIONS
8353 @center END OF TERMS AND CONDITIONS
8357 @unnumberedsec Applying These Terms to Your New Programs
8359 If you develop a new program, and you want it to be of the greatest
8360 possible use to the public, the best way to achieve this is to make it
8361 free software which everyone can redistribute and change under these terms.
8363 To do so, attach the following notices to the program. It is safest
8364 to attach them to the start of each source file to most effectively
8365 convey the exclusion of warranty; and each file should have at least
8366 the ``copyright'' line and a pointer to where the full notice is found.
8369 @var{one line to give the program's name and an idea of what it does.}
8370 Copyright (C) 19@var{yy} @var{name of author}
8372 This program is free software; you can redistribute it and/or
8373 modify it under the terms of the GNU General Public License
8374 as published by the Free Software Foundation; either version 2
8375 of the License, or (at your option) any later version.
8377 This program is distributed in the hope that it will be useful,
8378 but WITHOUT ANY WARRANTY; without even the implied warranty of
8379 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
8380 GNU General Public License for more details.
8382 You should have received a copy of the GNU General Public License
8383 along with this program; if not, write to the
8384 Free Software Foundation, Inc., 675 Mass Ave,
8385 Cambridge, MA 02139, USA.
8388 Also add information on how to contact you by electronic and paper mail.
8390 If the program is interactive, make it output a short notice like this
8391 when it starts in an interactive mode:
8394 Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author}
8395 Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
8396 type `show w'. This is free software, and you are welcome
8397 to redistribute it under certain conditions; type `show c'
8401 The hypothetical commands @samp{show w} and @samp{show c} should show
8402 the appropriate parts of the General Public License. Of course, the
8403 commands you use may be called something other than @samp{show w} and
8404 @samp{show c}; they could even be mouse-clicks or menu items---whatever
8407 You should also get your employer (if you work as a programmer) or your
8408 school, if any, to sign a ``copyright disclaimer'' for the program, if
8409 necessary. Here is a sample; alter the names:
8412 Yoyodyne, Inc., hereby disclaims all copyright
8413 interest in the program `Gnomovision'
8414 (which makes passes at compilers) written
8417 @var{signature of Ty Coon}, 1 April 1989
8418 Ty Coon, President of Vice
8421 This General Public License does not permit incorporating your program into
8422 proprietary programs. If your program is a subroutine library, you may
8423 consider it more useful to permit linking proprietary applications with the
8424 library. If this is what you want to do, use the GNU Library General
8425 Public License instead of this License.
8433 % I think something like @colophon should be in texinfo. In the
8435 \long\def\colophon{\hbox to0pt{}\vfill
8436 \centerline{The body of this manual is set in}
8437 \centerline{\fontname\tenrm,}
8438 \centerline{with headings in {\bf\fontname\tenbf}}
8439 \centerline{and examples in {\tt\fontname\tentt}.}
8440 \centerline{{\it\fontname\tenit\/},}
8441 \centerline{{\bf\fontname\tenbf}, and}
8442 \centerline{{\sl\fontname\tensl\/}}
8443 \centerline{are used for emphasis.}\vfill}
8445 % Blame: pesch@cygnus.com, 1991.