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diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index f9261e3..48ecdca 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -1,6 +1,9 @@ +_dnl__ -*-Texinfo-*- +_dnl__ Copyright (c) 1988 1989 1990 1991 Free Software Foundation, Inc. +_dnl__ This file controls overall layout of the GDB manual. +_dnl__ $Id$ \input texinfo @setfilename _GDBP__.info -@c $Id$ @c THIS MANUAL REQUIRES TEXINFO-2 macros and info-makers to format properly. @c @c NOTE: this manual is marked up for preprocessing with a collection @@ -11,6298 +14,37 @@ @c with all configurations, from wherever you got this). _if__(0) -THIS IS THE FULL SOURCE. The full source needs to be run through m4 -before either tex- or info- formatting: for example, +THIS IS THE SOURCE PRIOR TO PREPROCESSING. The full source needs to +be run through m4 before either tex- or info- formatting: for example, _0__ - m4 pretex.m4 none.m4 m680x0.m4 gdb.texinfo >gdb-680x0.texinfo + m4 pretex.m4 none.m4 m680x0.m4 gdb.texi-m4 >gdb-680x0.texinfo _1__ will produce (assuming your path finds either GNU or SysV m4; Berkeley won't do) a file suitable for formatting. See the text in "pretex.m4" for a fuller explanation (and the macro definitions). - To permit maximum flexibility, the full source also does not contain -any "info" markup that can be generated automatically; you should first -preprocess it as above, then run it through C-u texinfo-master-menu, -before actually info-formatting it. -_fi__(0) -@c -@syncodeindex ky cp -@c FOR UPDATES LEADING TO THIS DRAFT, GDB CHANGELOG CONSULTED BETWEEN: -@c Sun May 19 05:36:59 1991 John Gilmore (gnu at cygint.cygnus.com) -@c Sat Dec 22 02:51:40 1990 John Gilmore (gnu at cygint) -@ifinfo -This file documents the GNU debugger _GDBN__. - -Copyright (C) 1988, 1989, 1990, 1991 Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -@ignore -Permission is granted to process this file through TeX and print the -results, provided the printed document carries copying permission -notice identical to this one except for the removal of this paragraph -(this paragraph not being relevant to the printed manual). - -@end ignore -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -section entitled ``GNU General Public License'' is included exactly as -in the original, and provided that the entire resulting derived work is -distributed under the terms of a permission notice identical to this -one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions, -except that the section entitled ``GNU General Public License'' may be -included in a translation approved by the Free Software Foundation -instead of in the original English. -@end ifinfo -@smallbook -@setchapternewpage odd -_if__(_GENERIC__) -@settitle Using _GDBN__ (v4.0) -_fi__(_GENERIC__) -_if__(!_GENERIC__) -@settitle Using _GDBN__ v4.0 (_HOST__) -_fi__(!_GENERIC__) -@iftex -@c @finalout -@end iftex -@titlepage -@title{Using _GDBN__} -@subtitle{A Guide to the GNU Source-Level Debugger} -_if__(!_GENERIC__) -@subtitle{On _HOST__ Systems} -_fi__(!_GENERIC__) -@sp 1 -@c Maybe crank this up to "Fourth Edition" when released at FSF -@c @subtitle Third Edition---_GDBN__ version 4.0 -@subtitle _GDBN__ version 4.0 -@subtitle May 1991 -@author{Richard M. Stallman@qquad @hfill Free Software Foundation} -@author{Roland H. Pesch@qquad @hfill Cygnus Support} -@page - -@tex -\def\$#1${{#1}} % Kluge: collect RCS revision info without $...$ -\xdef\manvers{\$Revision$} % For use in headers, footers too -{\parskip=0pt -\hfill rms\@ai.mit.edu, pesch\@cygnus.com\par -\hfill {\it Using _GDBN__}, \manvers\par -\hfill \TeX{}info \texinfoversion\par -} -@end tex - -@vskip 0pt plus 1filll -Copyright @copyright{} 1988, 1989, 1990, 1991 Free Software Foundation, Inc. - -Permission is granted to make and distribute verbatim copies of -this manual provided the copyright notice and this permission notice -are preserved on all copies. - -Permission is granted to copy and distribute modified versions of this -manual under the conditions for verbatim copying, provided also that the -section entitled ``GNU General Public License'' is included exactly as -in the original, and provided that the entire resulting derived work is -distributed under the terms of a permission notice identical to this -one. - -Permission is granted to copy and distribute translations of this manual -into another language, under the above conditions for modified versions, -except that the section entitled ``GNU General Public License'' may be -included in a translation approved by the Free Software Foundation -instead of in the original English. -@end titlepage -@page - -@node Top, Summary, (dir), (dir) -@ifinfo -This file describes version 4.0 of GDB, the GNU symbolic debugger. -@end ifinfo - -@menu -* Summary:: Summary of _GDBN__ -* New Features:: New Features in _GDBN__ version 4.0 -* Sample Session:: A Sample _GDBN__ Session -* Invocation:: Getting In and Out of _GDBN__ -* Commands:: -* Running:: Running Programs Under _GDBN__ -* Stopping:: Stopping and Continuing -* Stack:: Examining the Stack -* Source:: Examining Source Files -* Data:: Examining Data -* Symbols:: Examining the Symbol Table -* Altering:: Altering Execution -* _GDBN__ Files:: -* Targets:: Specifying a Debugging Target -* Controlling _GDBN__:: Controlling _GDBN__ -* Sequences:: Canned Sequences of Commands -* Emacs:: Using _GDBN__ under GNU Emacs -* _GDBN__ Bugs:: Reporting Bugs in _GDBN__ -* Renamed Commands:: -* Installing _GDBN__:: Installing _GDBN__ -* Copying:: GNU GENERAL PUBLIC LICENSE -* Index:: Index -@end menu - -@node Summary, New Features, Top, Top -@unnumbered Summary of _GDBN__ - -The purpose of a debugger such as _GDBN__ is to allow you to see what is -going on ``inside'' another program while it executes---or what another -program was doing at the moment it crashed. - -_GDBN__ can do four main kinds of things (plus other things in support of -these) to help you catch bugs in the act: - -@itemize @bullet -@item -Start your program, specifying anything that might affect its behavior. - -@item -Make your program stop on specified conditions. - -@item -Examine what has happened, when your program has stopped. - -@item -Change things in your program, so you can experiment with correcting the -effects of one bug and go on to learn about another. -@end itemize - -_GDBN__ can be used to debug programs written in C and C++. Pascal support -is being implemented, and Fortran support will be added when a GNU -Fortran compiler is ready. - -@menu -* Free Software:: Free Software -* Contributors:: Contributors to GDB -@end menu - -@node Free Software, Contributors, Summary, Summary -@unnumberedsec Free Software -_GDBN__ is @dfn{free software}, protected by the GNU General Public License (GPL). -The GPL gives you the freedom to copy or adapt a licensed -program---but every person getting a copy also gets with it the -freedom to modify that copy (which means that they must get access to -the source code), and the freedom to distribute further copies. -Typical software companies use copyrights to limit your freedoms; the -Free Software Foundation uses the GPL to preserve these freedoms. - -Fundamentally, the General Public License is a license which says that -you have these freedoms and that you can't take these freedoms away -from anyone else. - -@c FIXME: (passim) go through all xrefs, expanding to use text headings -For full details, @pxref{Copying}. -@node Contributors, , Free Software, Summary -@unnumberedsec Contributors to GDB - -Richard Stallman was the original author of GDB, as with many GNU -programs. Many others have contributed to its development. This -section attempts to credit major contributors. One of the virtues of -free software is that everyone is free to contribute to it; with -regret, we cannot actually acknowledge everyone here. The file -@file{ChangeLog} in the GDB distribution approximates a blow-by-blow -account. - -Changes much prior to version 2.0 are lost in the mists of time. - -@quotation -@emph{Plea:} Additions to this section are particularly welcome. If you -or your friends (or enemies; let's be evenhanded) have been unfairly -omitted from this list, we would like to add your names! -@end quotation - -So that they may not regard their long labor as thankless, we -particularly thank those who shepherded GDB through major releases: -John Gilmore (release 4.0); Jim Kingdon (releases 3.9, 3.5, 3.4, 3.3); -and Randy Smith (releases 3.2, 3.1, 3.0). As major maintainer of GDB -for some period, each contributed significantly to the structure, -stability, and capabilities of the entire debugger. - -Richard Stallman, assisted at various times by Pete TerMaat, Chris -Hanson, and Richard Mlynarik, handled releases through 2.8. - -Michael Tiemann is the author of most of the GNU C++ support in GDB, -with significant additional contributions from Per Bothner. James -Clark wrote the GNU C++ demangler. Early work on C++ was by Peter -TerMaat (who also did much general update work leading to release 3.0). - -GDB 4.0 uses the BFD subroutine library to examine multiple -object-file formats; BFD was a joint project of V. Gumby -Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore. - -David Johnson wrote the original COFF support; Pace Willison did -the original support for encapsulated COFF. - -Adam de Boor and Bradley Davis contributed the ISI Optimum V support. -Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS -support. Jean-Daniel Fekete contributed Sun 386i support. Chris -Hanson improved the HP9000 support. Noboyuki Hikichi and Tomoyuki -Hasei contributed Sony/News OS 3 support. David Johnson contributed -Encore Umax support. Jyrki Kuoppala contributed Altos 3068 support. -Keith Packard contributed NS32K support. Doug Rabson contributed -Acorn Risc Machine support. Chris Smith contributed Convex support -(and Fortran debugging). Jonathan Stone contributed Pyramid support. -Michael Tiemann contributed SPARC support. Tim Tucker contributed -support for the Gould NP1 and Gould Powernode. Pace Willison -contributed Intel 386 support. Jay Vosburgh contributed Symmetry -support. - -Rich Schaefer helped with support of SunOS shared libraries. - -Jay Fenlason and Roland McGrath ensured that GDB and GAS agree about -several machine instruction sets. - -Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped -develop remote debugging. Intel Corporation and Wind River Systems -contributed remote debugging modules for their products. - -Brian Fox is the author of the readline libraries providing -command-line editing and command history. - -@node New Features, Sample Session, Summary, Top -@unnumbered New Features since _GDBN__ version 3.5 - -@table @emph -@item Targets -Using the new command @code{target}, you can select at runtime whether -you are debugging local files, local processes, standalone systems over -a serial port, realtime systems over a TCP/IP connection, etc. -Internally, _GDBN__ now uses a function vector to mediate access to -different targets; if you need to add your own support for a remote -protocol, this makes it much easier. - -@item Watchpoints -_GDBN__ now sports watchpoints as well as breakpoints. You can use a -watchpoint to stop execution whenever the value of an expression -changes, without having to predict a particular place in your program -where this may happen. - -@item Object Code Formats -_GDBN__ uses a new scheme called Binary File Descriptors (BFD) to permit -it to switch dynamically, without reconfiguration or recompilation, -between different object-file formats. Formats currently supported are -COFF, a.out, and the Intel 960 b.out; files may be read as .o's, archive -libraries, or core dumps. BFD is available as a subroutine library so -that other programs may take advantage of it, and the other GNU binary -utilities are being converted to use it. - -@item Configuration -Compile-time configuration (to select a particular architecture and -operating system) is much easier. The script @code{config.gdb} now -handles specification of separate host and target configurations. - -@item Interaction -The user interface to _GDBN__'s control variables has been simplified -and consolidated in two commands, @code{set} and @code{show}. Output -lines are now broken at readable places, rather than overflowing onto -the next line. You can suppress output of machine-level addresses, -displaying only source language information. - - -@item Source Language -_GDBN__ now has limited support for C++ exception handling: _GDBN__ can -break when an exception is raised, before the stack is peeled back to -the exception handler's context. - -@item Command Rationalization -Many _GDBN__ commands have been renamed to make them easier to remember -and use. In particular, the subcommands of @code{info} and -@code{show}/@code{set} are grouped to make the former refer to the state -of your program, and the latter refer to the state of _GDBN__ itself. -@xref{Renamed Commands}, for details on what commands were renamed. - -@item Ports -_GDBN__ has been ported to the following new architectures: AT&T 3b1, -Acorn RISC machine, HP300 running HPUX, big- and little-endian MIPS -machines, Motorola 88k, Sun 386i, and Sun 3 running SunOS 4. In -addition, the following are supported as targets only: AMD 29k, Intel -960, and Wind River's VxWorks. - -@item Shared Libraries -_GDBN__ 4.0 supports SunOS shared libraries. - -@item Work in Progress -Kernel debugging for BSD and Mach systems; Tahoe and HPPA architecture -support. - -@end table - -@node Sample Session, Invocation, New Features, Top -@chapter A Sample _GDBN__ Session - -You can use this manual at your leisure to read all about _GDBN__. -However, a handful of commands are enough to get started using the -debugger. This chapter illustrates these commands. - -@iftex -In this sample session, we emphasize user input like this: @i{input}, -to make it easier to pick out from the surrounding output. -@end iftex - -@c FIXME: this example may not be appropriate for some configs, where -@c FIXME...primary interest is in remote use. -_0__ -One of the preliminary versions of GNU @code{m4} (a generic macro -processor) exhibits the following bug: sometimes, when we change its -quote strings from the default, the commands used to capture one macro's -definition in another stop working. In the following short @code{m4} -session, we define a macro @code{foo} which expands to @code{0000}; we -then use the @code{m4} builtin @code{defn} to define @code{bar} as the -same thing. However, when we change the open quote string to -@code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same -procedure fails to define a new synonym @code{baz}: - -@smallexample -$ @i{cd gnu/m4} -$ @i{./m4} -@i{define(foo,0000)} - -@i{foo} -0000 -@i{define(bar,defn(`foo'))} - -@i{bar} -0000 -@i{changequote(<QUOTE>,<UNQUOTE>)} - -@i{define(baz,defn(<QUOTE>foo<UNQUOTE>))} -@i{baz} -@i{C-D} -m4: End of input: 0: fatal error: EOF in string -@end smallexample - -@noindent -Let's use _GDBN__ to try to see what's going on. - -@smallexample -$ @i{_GDBP__ m4} -Reading symbol data from m4...done. -(_GDBP__) -@end smallexample - -@noindent -_GDBN__ only reads enough symbol data to know where to find the rest -when needed; as a result, the first prompt comes up very quickly. We -then tell _GDBN__ to use a narrower display width than usual, so -that examples will fit in this manual. - -@smallexample -(_GDBP__) @i{set width 70} -@end smallexample - -@noindent -Let's see how the @code{m4} builtin @code{changequote} works. -Having looked at the source, we know the relevant subroutine is -@code{m4_changequote}, so we set a breakpoint there with _GDBN__'s -@code{break} command. - -@smallexample -(_GDBP__) @i{break m4_changequote} -Breakpoint 1 at 0x62f4: file builtin.c, line 879. -@end smallexample - -@noindent -Using the @code{run} command, we start @code{m4} running under _GDBN__ -control; as long as control does not reach the @code{m4_changequote} -subroutine, the program runs as usual: - -@smallexample -(_GDBP__) @i{run} -Starting program: /work/Editorial/gdb/gnu/m4/m4 -@i{define(foo,0000)} - -@i{foo} -0000 -@end smallexample - -@noindent -To trigger the breakpoint, we call @code{changequote}. _GDBN__ -suspends execution of @code{m4}, displaying information about the -context where it stops. - -@smallexample -@i{changequote(<QUOTE>,<UNQUOTE>)} - -Breakpoint 1, m4_changequote (argc=3, argv=0x33c70) at builtin.c:879 -879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]), argc, 1, 3)) -@end smallexample - -@noindent -Now we use the command @code{n} (@code{next}) to advance execution to -the next line of the current function. - -@smallexample -(_GDBP__) @i{n} -882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1]) : nil, -@end smallexample - -@noindent -@code{set_quotes} looks like a promising subroutine. We can go into it -by using the command @code{s} (@code{step}) instead of @code{next}. -@code{step} goes to the next line to be executed in @emph{any} -subroutine, so it steps into @code{set_quotes}. - -@smallexample -(_GDBP__) @i{s} -set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>") - at input.c:530 -530 if (lquote != def_lquote) -@end smallexample - -@noindent -The summary display showing the subroutine where @code{m4} is now -suspended (and its arguments) is called a stack frame display. We can -use the @code{backtrace} command (which can also be spelled @code{bt}), -to see where we are in the stack: it displays a stack frame for each -active subroutine. - -@smallexample -(_GDBP__) @i{bt} -#0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>") - at input.c:530 -#1 0x6344 in m4_changequote (argc=3, argv=0x33c70) at builtin.c:882 -#2 0x8174 in expand_macro (sym=0x33320) at macro.c:242 -#3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30) - at macro.c:71 -#4 0x79dc in expand_input () at macro.c:40 -#5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195 -@end smallexample - -@noindent -Let's step through a few more lines to see what happens. The first two -times, we can use @samp{s}; the next two times we use @code{n} to avoid -falling into the @code{xstrdup} subroutine. -@smallexample -(_GDBP__) @i{s} -0x3b5c 532 if (rquote != def_rquote) -(_GDBP__) @i{s} -0x3b80 535 lquote = (lq == nil || *lq == '\0') ? def_lquote :\ - xstrdup(lq); -(_GDBP__) @i{n} -536 rquote = (rq == nil || *rq == '\0') ? def_rquote : xstrdup\ -(rq); -(_GDBP__) @i{n} -538 len_lquote = strlen(rquote); -@end smallexample - -@noindent -The last line displayed looks a little odd; let's examine the variables -@code{lquote} and @code{rquote} to see if they are in fact the new left -and right quotes we specified. We can use the command @code{p} -(@code{print}) to see their values. - -@smallexample -(_GDBP__) @i{p lquote} -$1 = 0x35d40 "<QUOTE>" -(_GDBP__) @i{p rquote} -$2 = 0x35d50 "<UNQUOTE>" -@end smallexample - -@noindent -@code{lquote} and @code{rquote} are indeed the new left and right quotes. -Let's look at some context; we can display ten lines of source -surrounding the current line, with the @code{l} (@code{list}) command. - -@smallexample -(_GDBP__) @i{l} -533 xfree(rquote); -534 -535 lquote = (lq == nil || *lq == '\0') ? def_lquote : xstrdup\ -(lq); -536 rquote = (rq == nil || *rq == '\0') ? def_rquote : xstrdup\ -(rq); -537 -538 len_lquote = strlen(rquote); -539 len_rquote = strlen(lquote); -540 @} -541 -542 void -@end smallexample - -@noindent -Let's step past the two lines that set @code{len_lquote} and -@code{len_rquote}, and then examine the values of those variables. - -@smallexample -(_GDBP__) @i{n} -539 len_rquote = strlen(lquote); -(_GDBP__) @i{n} -540 @} -(_GDBP__) @i{p len_lquote} -$3 = 9 -(_GDBP__) @i{p len_rquote} -$4 = 7 -@end smallexample - -@noindent -That certainly looks wrong, assuming @code{len_lquote} and -@code{len_rquote} are meant to be the lengths of @code{lquote} and -@code{rquote} respectively. Let's try setting them to better values. -We can use the @code{p} command for this, since it'll print the value of -any expression---and that expression can include subroutine calls and -assignments. - -@smallexample -(_GDBP__) p len_lquote=strlen(lquote) -$5 = 7 -(_GDBP__) p len_rquote=strlen(rquote) -$6 = 9 -@end smallexample - -@noindent -Let's see if that fixes the problem of using the new quotes with the -@code{m4} built-in @code{defn}. We can allow @code{m4} to continue -executing with the @code{c} (@code{continue}) command, and then try the -example that caused trouble initially: - -@smallexample -(_GDBP__) @i{c} -Continuing. - -@i{define(baz,defn(<QUOTE>foo<UNQUOTE>))} - -baz -0000 -@end smallexample - -@noindent -Success! The new quotes now work just as well as the default ones. The -problem seems to have been just the two typos defining the wrong -lengths. We'll let @code{m4} exit by giving it an EOF as input. - -@smallexample -@i{C-D} -Program exited normally. -@end smallexample - -@noindent -The message @samp{Program exited normally.} is from _GDBN__; it -indicates @code{m4} has finished executing. We can end our _GDBN__ -session with the _GDBN__ @code{quit} command. - -@smallexample -(_GDBP__) @i{quit} - -$ -_1__@end smallexample - - -@node Invocation, Commands, Sample Session, Top -@chapter Getting In and Out of _GDBN__ - -@menu -* Starting _GDBN__:: Starting _GDBN__ -* Leaving _GDBN__:: Leaving _GDBN__ -* Shell Commands:: Shell Commands -@end menu - -@node Starting _GDBN__, Leaving _GDBN__, Invocation, Invocation -@section Starting _GDBN__ - -_GDBN__ is invoked with the shell command @code{_GDBP__}. Once started, -it reads commands from the terminal until you tell it to exit. - -You can run @code{_GDBP__} with no arguments or options; but the most -usual way to start _GDBN__ is with one argument or two, specifying an -executable program as the argument: -@example -_GDBP__ program -@end example -@noindent -You can also start with both an executable program and a core file specified: -@example -_GDBP__ program core -@end example - -@noindent -You can further control how _GDBN__ starts up by using command-line -options. _GDBN__ itself can remind you of the options available: -@example -_GDBP__ -help -@end example -@noindent -will display all available options and briefly describe their use -(@samp{_GDBP__ -h} is a shorter equivalent). - -All options and command line arguments you give are processed -in sequential order. The order makes a difference when the -@samp{-x} option is used. - -@menu -* File Options:: Choosing Files -* Mode Options:: Choosing Modes -_if__(_GENERIC__) -_divert__(1) -_fi__(_GENERIC__) -* i960-Nindy Remote:: -* EB29K Remote:: -* VxWorks Remote:: -_if__(_GENERIC__) -_divert__ -_fi__(_GENERIC__) -@end menu - -@node File Options, Mode Options, Starting _GDBN__, Starting _GDBN__ -@subsection Choosing Files - -As shown above, any arguments other than options specify an executable -file and core file; that is, the first argument encountered with no -associated option flag is equivalent to a @samp{-se} option, and the -second, if any, is equivalent to a @samp{-c} option. Many options have -both long and short forms; both are shown here. The long forms are also -recognized if you truncate them, so long as enough of the option is -present to be unambiguous. (If you prefer, you can flag option -arguments with @samp{+} rather than @samp{-}, though we illustrate the -more usual convention.) - -@table @code -@item -symbols=@var{file} -@itemx -s @var{file} -Read symbol table from file @var{file}. - -@item -exec=@var{file} -@itemx -e @var{file} -Use file @var{file} as the executable file to execute when -appropriate, and for examining pure data in conjunction with a core -dump. - -@item -se @var{file} -Read symbol table from file @var{file} and use it as the executable -file. - -@item -core=@var{file} -@itemx -c @var{file} -Use file @var{file} as a core dump to examine. - -@item -command=@var{file} -@itemx -x @var{file} -Execute _GDBN__ commands from file @var{file}. @xref{Command Files}. - -@item -directory=@var{directory} -@itemx -d @var{directory} -Add @var{directory} to the path to search for source files. -@end table - -@node Mode Options, i960-Nindy Remote, File Options, Starting _GDBN__ -@subsection Choosing Modes - -@table @code -@item -nx -@itemx -n -Do not execute commands from any @file{_GDBINIT__} initialization files. -Normally, the commands in these files are executed after all the -command options and arguments have been processed. @xref{Command -Files}. - -@item -quiet -@itemx -q -``Quiet''. Do not print the introductory and copyright messages. These -messages are also suppressed in batch mode, or if an executable file name is -specified on the _GDBN__ command line. - -@item -batch -Run in batch mode. Exit with status @code{0} after processing all the command -files specified with @samp{-x} (and @file{_GDBINIT__}, if not inhibited). -Exit with nonzero status if an error occurs in executing the _GDBN__ -commands in the command files. - -Batch mode may be useful for running _GDBN__ as a filter, for example to -download and run a program on another computer; in order to make this -more useful, the message -@example -Program exited normally. -@end example -@noindent -(which is ordinarily issued whenever a program running under _GDBN__ control -terminates) is not issued when running in batch mode. - -@item -cd @var{directory} -Run _GDBN__ using @var{directory} as its working directory, -instead of the current directory. - -@item -fullname -@itemx -f -This option is used when Emacs runs _GDBN__ as a subprocess. It tells _GDBN__ -to output the full file name and line number in a standard, -recognizable fashion each time a stack frame is displayed (which -includes each time the program stops). This recognizable format looks -like two @samp{\032} characters, followed by the file name, line number -and character position separated by colons, and a newline. The -Emacs-to-_GDBN__ interface program uses the two @samp{\032} characters as -a signal to display the source code for the frame. - -@item -b @var{bps} -Set the line speed (baud rate or bits per second) of any serial -interface used by _GDBN__ for remote debugging. - -@item -tty @var{device} -Run using @var{device} for your program's standard input and output. -@c FIXME: kingdon thinks there's more to -tty. Investigate. -@end table - -_if__(_GENERIC__) -_divert__(2) -@c This text diverted to "Remote Debugging" section in general case; -@c however, if we're doing a manual specifically for one of these, it -@c belongs up front (in "Getting In and Out" chapter). -_fi__(_GENERIC__) -_if__(_I960__) -@node i960-Nindy Remote, EB29K Remote, Mode Options, Starting _GDBN__ -@subsection _GDBN__ with a Remote i960 (Nindy) - -@cindex Nindy -@cindex i960 -@dfn{Nindy} is a ROM Monitor program for Intel 960 target systems. When -_GDBN__ is configured to control a remote Intel 960 using Nindy, you can -tell _GDBN__ how to connect to the 960 in several ways: - -@itemize @bullet -@item -Through command line options specifying serial port, version of the -Nindy protocol, and communications speed; - -@item -By responding to a prompt on startup; - -@item -By using the @code{target} command at any point during your _GDBN__ -session. @xref{Target Commands}. - -@end itemize - -@menu -* Nindy Startup:: Startup with Nindy -* Nindy Options:: Options for Nindy -* Nindy reset:: Nindy Reset Command -@end menu - -@node Nindy Startup, Nindy Options, i960-Nindy Remote, i960-Nindy Remote -@subsubsection Startup with Nindy - -If you simply start @code{_GDBN__} without using any command-line -options, you are prompted for what serial port to use, @emph{before} you -reach the ordinary _GDBN__ prompt: -@example -Attach /dev/ttyNN -- specify NN, or "quit" to quit: -@end example -@noindent -Respond to the prompt with whatever suffix (after @samp{/dev/tty}) -identifies the serial port you want to use. You can, if you choose, -simply start up with no Nindy connection by responding to the prompt -with an empty line. If you do this, and later wish to attach to Nindy, -use @code{target} (@pxref{Target Commands}). - -@node Nindy Options, Nindy reset, Nindy Startup, i960-Nindy Remote -@subsubsection Options for Nindy - -These are the startup options for beginning your _GDBN__ session with a -Nindy-960 board attached: - -@table @code -@item -r @var{port} -Specify the serial port name of a serial interface to be used to connect -to the target system. This option is only available when _GDBN__ is -configured for the Intel 960 target architecture. You may specify -@var{port} as any of: a full pathname (e.g. @samp{-r /dev/ttya}), a -device name in @file{/dev} (e.g. @samp{-r ttya}), or simply the unique -suffix for a specific @code{tty} (e.g. @samp{-r a}). - -@item -O -(An uppercase letter ``O'', not a zero.) Specify that _GDBN__ should use -the ``old'' Nindy monitor protocol to connect to the target system. -This option is only available when _GDBN__ is configured for the Intel 960 -target architecture. - -@quotation -@emph{Warning:} if you specify @samp{-O}, but are actually trying to -connect to a target system that expects the newer protocol, the connection -will fail, appearing to be a speed mismatch. _GDBN__ will repeatedly -attempt to reconnect at several different line speeds. You can abort -this process with an interrupt. -@end quotation - -@item -brk -Specify that _GDBN__ should first send a @code{BREAK} signal to the target -system, in an attempt to reset it, before connecting to a Nindy target. - -@quotation -@emph{Warning:} Many target systems do not have the hardware that this -requires; it only works with a few boards. -@end quotation - -@end table - -The standard @samp{-b} option controls the line speed used on the serial -port. - -@group -@node Nindy reset, , Nindy Options, i960-Nindy Remote -@subsubsection Nindy Reset Command -@table @code -@item reset -@kindex reset -For a Nindy target, this command sends a ``break'' to the remote target -system; this is only useful if the target has been equipped with a -circuit to perform a hard reset (or some other interesting action) when -a break is detected. -@end table -@end group -_fi__(_I960__) - -_if__(_AMD29K__) -@node EB29K Remote, VxWorks Remote, i960-Nindy Remote, Starting _GDBN__ -@subsection _GDBN__ with a Remote EB29K - -@cindex EB29K board -@cindex running 29K programs - -To use _GDBN__ from a Unix system to run programs on AMD's EB29K -board in a PC, you must first connect a serial cable between the PC -and a serial port on the Unix system. In the following, we assume -you've hooked the cable between the PC's @file{COM1} port and -@file{/dev/ttya} on the Unix system. - -@menu -* Comms (EB29K):: Communications Setup -* _GDBP__-EB29K:: EB29K cross-debugging -* Remote Log:: Remote Log -@end menu - -@node Comms (EB29K), _GDBP__-EB29K, EB29K Remote, EB29K Remote -@subsubsection Communications Setup -The next step is to set up the PC's port, by doing something like the -following in DOS on the PC: -_0__@example -C:\> MODE com1:9600,n,8,1,none -_1__@end example -@noindent -This example---run on an MS DOS 4.0 system---sets the PC port to 9600 -bps, no parity, eight data bits, one stop bit, and no ``retry'' action; -you must match the communications parameters when establishing the Unix -end of the connection as well. -@c FIXME: Who knows what this "no retry action" crud from the DOS manual may -@c mean? It's optional; leave it out? ---pesch@cygnus.com, 25feb91 - -To give control of the PC to the Unix side of the serial line, type -the following at the DOS console: -_0__@example -C:\> CTTY com1 -_1__@end example -@noindent -(Later, if you wish to return control to the DOS console, you can use -the command @code{CTTY con}---but you must send it over the device that -had control, in our example over the @file{COM1} serial line). - -From the Unix host, use a communications program such as @code{tip} or -@code{cu} to communicate with the PC; for example, -@example -cu -s 9600 -l /dev/ttya -@end example -@noindent -The @code{cu} options shown specify, respectively, the linespeed and the -serial port to use. If you use @code{tip} instead, your command line -may look something like the following: -@example -tip -9600 /dev/ttya -@end example -@noindent -Your system may define a different name where our example uses -@file{/dev/ttya} as the argument to @code{tip}. The communications -parameters, including what port to use, are associated with the -@code{tip} argument in the ``remote'' descriptions file---normally the -system table @file{/etc/remote}. -@c FIXME: What if anything needs doing to match the "n,8,1,none" part of -@c the DOS side's comms setup? cu can support -o (odd -@c parity), -e (even parity)---apparently no settings for no parity or -@c for character size. Taken from stty maybe...? John points out tip -@c can set these as internal variables, eg ~s parity=none; man stty -@c suggests that it *might* work to stty these options with stdin or -@c stdout redirected... ---pesch@cygnus.com, 25feb91 - -@kindex EBMON -Using the @code{tip} or @code{cu} connection, change the DOS working -directory to the directory containing a copy of your 29K program, then -start the PC program @code{EBMON} (an EB29K control program supplied -with your board by AMD). You should see an initial display from -@code{EBMON} similar to the one that follows, ending with the -@code{EBMON} prompt @samp{#}--- -_0__@example -C:\> G: - -G:\> CD \usr\joe\work29k - -G:\USR\JOE\WORK29K> EBMON -Am29000 PC Coprocessor Board Monitor, version 3.0-18 -Copyright 1990 Advanced Micro Devices, Inc. -Written by Gibbons and Associates, Inc. - -Enter '?' or 'H' for help - -PC Coprocessor Type = EB29K -I/O Base = 0x208 -Memory Base = 0xd0000 - -Data Memory Size = 2048KB -Available I-RAM Range = 0x8000 to 0x1fffff -Available D-RAM Range = 0x80002000 to 0x801fffff - -PageSize = 0x400 -Register Stack Size = 0x800 -Memory Stack Size = 0x1800 - -CPU PRL = 0x3 -Am29027 Available = No -Byte Write Available = Yes - -# ~. -_1__@end example - -Then exit the @code{cu} or @code{tip} program (done in the example by -typing @code{~.} at the @code{EBMON} prompt). @code{EBMON} will keep -running, ready for _GDBN__ to take over. - -For this example, we've assumed what is probably the most convenient -way to make sure the same 29K program is on both the PC and the Unix -system: a PC/NFS connection that establishes ``drive @code{G:}'' on the -PC as a file system on the Unix host. If you don't have PC/NFS or -something similar connecting the two systems, you must arrange some -other way---perhaps floppy-disk transfer---of getting the 29K program -from the Unix system to the PC; _GDBN__ will @emph{not} download it over the -serial line. - -@node _GDBP__-EB29K, Remote Log, Comms (EB29K), EB29K Remote -@subsubsection EB29K cross-debugging -Finally, @code{cd} to the directory containing an image of your 29K -program on the Unix system, and start _GDBN__---specifying as argument the -name of your 29K program: -@example -cd /usr/joe/work29k -_GDBP__ myfoo -@end example -Now you can use the @code{target} command: -@example -target amd-eb /dev/ttya 9600 MYFOO -@end example -@c FIXME: test above 'target amd-eb' as spelled, with caps! caps are meant to -@c emphasize that this is the name as seen by DOS (since I think DOS is -@c single-minded about case of letters). ---pesch@cygnus.com, 25feb91 - -@noindent -In this example, we've assumed your program is in a file called -@file{myfoo}. Note that the filename given as the last argument to -@code{target amd-eb} should be the name of the program as it appears to DOS. -In our example this is simply @code{MYFOO}, but in general it can include -a DOS path, and depending on your transfer mechanism may not resemble -the name on the Unix side. - -At this point, you can set any breakpoints you wish; when you're ready -to see your program run on the 29K board, use the _GDBN__ command -@code{run}. - -To stop debugging the remote program, use the _GDBN__ @code{detach} -command. - -To return control of the PC to its console, use @code{tip} or @code{cu} -once again, after your _GDBN__ session has concluded, to attach to -@code{EBMON}. You can then type the command @code{q} to shut down -@code{EBMON}, returning control to the DOS command-line interpreter. -Type @code{CTTY con} to return command input to the main DOS console, -and type @kbd{~.} to leave @code{tip} or @code{cu}. - -@node Remote Log, , _GDBP__-EB29K, EB29K Remote -@subsubsection Remote Log -@kindex eb.log -@cindex log file for EB29K -The @code{target amd-eb} command creates a file @file{eb.log} in the -current working directory, to help debug problems with the connection. -@file{eb.log} records all the output from @code{EBMON}, including echoes -of the commands sent to it. Running @samp{tail -f} on this file in -another window often helps to understand trouble with @code{EBMON}, or -unexpected events on the PC side of the connection. -_fi__(_AMD29K__) - -_if__(_VXWORKS__) -@node VxWorks Remote, , EB29K Remote, Starting _GDBN__ -@subsection _GDBN__ and VxWorks -@cindex VxWorks -_GDBN__ enables developers to spawn and debug tasks running on networked -VxWorks targets from a Unix host. Already-running tasks spawned from -the VxWorks shell can also be debugged. _GDBN__ uses code that runs on -both the UNIX host and on the VxWorks target. The program -@code{_GDBP__} is installed and executed on the UNIX host. - -The remote debugging interface (RDB) routines are installed and executed -on the VxWorks target. These routines are included in the VxWorks library -@file{rdb.a} and are incorporated into the system image when source-level -debugging is enabled in the VxWorks configuration. - -@kindex{INCLUDE_RDB} -Defining @code{INCLUDE_RDB} in the VxWorks configuration file -@file{configAll.h} includes the RDB interface routines and spawns the -source debugging task @code{tRdbTask} when VxWorks is booted. For more -information on configuring and remaking VxWorks, see the @cite{VxWorks -Programmer's Guide}. - -Once you have included the RDB interface in your VxWorks system image -and set your Unix execution search path to find _GDBN__, you are ready -to run _GDBN__. From your UNIX host, type: - -@smallexample -% _GDBP__ -@end smallexample - -_GDBN__ will come up showing the prompt: - -@smallexample -(_GDBP__) -@end smallexample - -@menu -* VxWorks connection:: Connecting to VxWorks -* VxWorks download:: VxWorks Download -* VxWorks attach:: Running Tasks -@end menu - -@node VxWorks connection, VxWorks download, VxWorks Remote, VxWorks Remote -@subsubsection Connecting to VxWorks - -The _GDBN__ command @code{target} lets you connect to a VxWorks target on the -network. To connect to a target whose host name is ``@code{tt}'', type: - -@smallexample -(_GDBP__) target vxworks tt -@end smallexample - -_GDBN__ will display a message similar to the following: - -@smallexample -Attaching remote machine across net... Success! -@end smallexample - -_GDBN__ will then attempt to read the symbol tables of any object -modules loaded into the VxWorks target since it was last booted. -_GDBN__ locates these files by searching the directories listed in the -command search path (@pxref{Environment}); if it fails to find an -object file, it will display a message such as: - -@smallexample -prog.o: No such file or directory. -@end smallexample - -This will cause the @code{target} command to abort. When this happens, -you should add the appropriate directory to the search path, with the -_GDBN__ command @code{path}, and execute the @code{target} command -again. - -@node VxWorks download, VxWorks attach, VxWorks connection, VxWorks Remote -@subsubsection VxWorks Download - -@cindex download to VxWorks -If you have connected to the VxWorks target and you want to debug an -object that has not yet been loaded, you can use the _GDBN__ @code{load} -command to download a file from UNIX to VxWorks incrementally. The -object file given as an argument to the @code{load} command is actually -opened twice: first by the VxWorks target in order to download the code, -then by _GDBN__ in order to read the symbol table. This can lead to -problems if the current working directories on the two systems differ. -It is simplest to set the working directory on both systems to the -directory in which the object file resides, and then to reference the -file by its name, without any path. Thus, to load a program -@file{prog.o}, residing in @file{wherever/vw/demo/rdb}, on VxWorks type: - -@smallexample --> cd "wherever/vw/demo/rdb" -@end smallexample - -On _GDBN__ type: - -@smallexample -(_GDBP__) cd wherever/vw/demo/rdb -(_GDBP__) load prog.o -@end smallexample - -_GDBN__ will display a response similar to the following: - -@smallexample -Reading symbol data from wherever/vw/demo/rdb/prog.o... done. -@end smallexample - -You can also use the @code{load} command to reload an object module -after editing and recompiling the corresponding source file. Note that -this will cause _GDBN__ to delete all currently-defined breakpoints, -auto-displays, and convenience variables, and to clear the value -history. (This is necessary in order to preserve the integrity of -debugger data structures that reference the target system's symbol -table.) - -@node VxWorks attach, , VxWorks download, VxWorks Remote -@subsubsection Running Tasks - -@cindex running VxWorks tasks -You can also attach to an existing task using the @code{attach} command as -follows: - -@smallexample -(_GDBP__) attach @var{task} -@end smallexample - -where @var{task} is the VxWorks hexadecimal task ID. The task can be running -or suspended when you attach to it. If running, it will be suspended at -the time of attachment. - -_fi__(_VXWORKS__) -_if__(_GENERIC__) -_divert__ -@c end of text diverted to section "Remote Debugging" for general case -_fi__(_GENERIC__) - -@node Leaving _GDBN__, Shell Commands, Starting _GDBN__, Invocation -@section Leaving _GDBN__ -@cindex exiting _GDBN__ -@table @code -@item quit -@kindex quit -@kindex q -To exit _GDBN__, use the @code{quit} command (abbreviated @code{q}), or type -an end-of-file character (usually @kbd{C-d}). -@end table - -@cindex interrupt -An interrupt (often @kbd{C-c}) will not exit from _GDBN__, but rather -will terminate the action of any _GDBN__ command that is in progress and -return to _GDBN__ command level. It is safe to type the interrupt -character at any time because _GDBN__ does not allow it to take effect -until a time when it is safe. - -If you've been using _GDBN__ to control an attached process or device, -you can release it with the @code{detach} command; @pxref{Attach}. - -@node Shell Commands, , Leaving _GDBN__, Invocation -@section Shell Commands -If you just need to execute occasional shell commands during your -debugging session, there's no need to leave or suspend _GDBN__; you can -just use the @code{shell} command. - -@table @code -@item shell @var{command string} -@kindex shell -@cindex shell escape -Directs _GDBN__ to invoke an inferior shell to execute @var{command -string}. If it exists, the environment variable @code{SHELL} is used -for the name of the shell to run. Otherwise _GDBN__ uses -@code{/bin/sh}. -@end table - -The utility @code{make} is often needed in development environments. -You don't have to use the @code{shell} command for this purpose in _GDBN__: - -@table @code -@item make @var{make-args} -@kindex make -@cindex calling make -Causes _GDBN__ to execute an inferior @code{make} program with the specified -arguments. This is equivalent to @samp{shell make @var{make-args}}. -@end table - -@node Commands, Running, Invocation, Top -@chapter _GDBN__ Commands - -@menu -* Command Syntax:: Command Syntax -* Help:: Getting Help -@end menu - -@node Command Syntax, Help, Commands, Commands -@section Command Syntax -A _GDBN__ command is a single line of input. There is no limit on how long -it can be. It starts with a command name, which is followed by arguments -whose meaning depends on the command name. For example, the command -@code{step} accepts an argument which is the number of times to step, -as in @samp{step 5}. You can also use the @code{step} command with -no arguments. Some command names do not allow any arguments. - -@cindex abbreviation -_GDBN__ command names may always be truncated if that abbreviation is -unambiguous. Other possible command abbreviations are listed in the -documentation for individual commands. Sometimes even ambiguous -abbreviations are allowed; for example, @code{s} is specially defined as -equivalent to @code{step} even though there are other commands whose -names start with @code{s}. - -@cindex repeating commands -A blank line as input to _GDBN__ means to repeat the previous command. -Certain commands (for example, @code{run}) will not repeat this way; -these are commands for which unintentional repetition might cause -trouble and which you are unlikely to want to repeat. - -The @code{list} and @code{x} commands construct new arguments when -repeated, rather than repeating exactly as typed, to permit easy -scanning of source or memory. - -@kindex # -@cindex comment -A line of input starting with @kbd{#} is a comment; it does nothing. -This is useful mainly in command files (@xref{Command Files}). - -@node Help, , Command Syntax, Commands -@section Getting Help -@cindex online documentation -@kindex help -You can always ask _GDBN__ itself for information on its commands, using the -command @code{help}. - -@table @code -@item help -@itemx h -@kindex h -You can use @code{help} (abbreviated @code{h}) with no arguments to -display a short list of named categories of commands: -@smallexample -(_GDBP__) help -List of classes of commands: - -running -- Running the program -stack -- Examining the stack -data -- Examining data -breakpoints -- Making program stop at certain points -files -- Specifying and examining files -status -- Status inquiries -support -- Support facilities -user-defined -- User-defined commands -aliases -- Aliases of other commands -obscure -- Obscure features - -Type "help" followed by a class name for a list of commands in that class. -Type "help" followed by command name for full documentation. -Command name abbreviations are allowed if unambiguous. -(_GDBP__) -@end smallexample - -@item help @var{category} -Using one of the general help categories as an argument, you can get a -list of the individual commands in a category. For example, here is the -help display for category @code{status}: -@smallexample -(_GDBP__) help status -Status inquiries. - -List of commands: - -show -- Generic command for showing things set with "set" -info -- Generic command for printing status - -Type "help" followed by command name for full documentation. -Command name abbreviations are allowed if unambiguous. -(_GDBP__) -@end smallexample - -@item help @var{command} -With a command name as @code{help} argument, _GDBN__ will display a -short paragraph on how to use that command. -@end table - -In addition to @code{help}, you can use the _GDBN__ commands @code{info} -and @code{show} to inquire about the state of your program, or the state -of _GDBN__ itself. Both commands support many topics of inquiry; this -manual introduces each of them in the appropriate context. The listings -under @code{info} and under @code{show} in the Index point to -all the sub-commands. -@c FIXME: @pxref{Index} used to be here, but even though it shows up in -@c FIXME...the 'aux' file with a pageno the xref can't find it. - -@table @code -@item info -@kindex info -@kindex i -This command (abbreviated @code{i}) is for describing the state of your -program; for example, it can list the arguments given to your program -(@code{info args}), the registers currently in use (@code{info -registers}), or the breakpoints you've set (@code{info breakpoints}). -You can get a complete list of the @code{info} sub-commands with -@code{help info}. - -@kindex show -@item show -In contrast, @code{show} is for describing the state of _GDBN__ itself. -You can change most of the things you can @code{show}, by using the -related command @code{set}; for example, you can control what number -system is used for displays with @code{set radix}, or simply inquire -which is currently in use with @code{show radix}. - -@kindex info set -To display all the settable parameters and their current -values, you can use @code{show} with no arguments; you may also use -@code{info set}. Both commands produce the same display. -@c FIXME: "info set" violates the rule that "info" is for state of -@c FIXME...program. Ck w/ GNU: "info set" to be called something else, -@c FIXME...or change desc of rule---eg "state of prog and debugging session"? -@end table - -Here are three miscellaneous @code{show} subcommands, all of which are -exceptional in lacking corresponding @code{set} commands: - -@table @code -@kindex show version -@item show version -Show what version of _GDBN__ is running. You should include this -information in _GDBN__ bug-reports. If multiple versions of _GDBN__ are -in use at your site, you may occasionally want to make sure what version -of _GDBN__ you're running; as _GDBN__ evolves, new commands are -introduced, and old ones may wither away. The version number is also -announced when you start _GDBN__ with no arguments. - -@kindex show copying -@item show copying -Display information about permission for copying _GDBN__. - -@kindex show warranty -@item show warranty -Display the GNU ``NO WARRANTY'' statement. -@end table - -@node Running, Stopping, Commands, Top -@chapter Running Programs Under _GDBN__ - -@menu -* Compilation:: Compiling for Debugging -* Starting:: Starting your Program -* Arguments:: Your Program's Arguments -* Environment:: Your Program's Environment -* Working Directory:: Your Program's Working Directory -* Input/Output:: Your Program's Input and Output -* Attach:: Debugging an Already-Running Process -* Kill Process:: Killing the Child Process -@end menu - -@node Compilation, Starting, Running, Running -@section Compiling for Debugging - -In order to debug a program effectively, you need to generate -debugging information when you compile it. This debugging information -is stored in the object file; it describes the data type of each -variable or function and the correspondence between source line numbers -and addresses in the executable code. - -To request debugging information, specify the @samp{-g} option when you run -the compiler. - -Many C compilers are unable to handle the @samp{-g} and @samp{-O} -options together. Using those compilers, you cannot generate optimized -executables containing debugging information. - -The GNU C compiler supports @samp{-g} with or without @samp{-O}, making it -possible to debug optimized code. We recommend that you @emph{always} use -@samp{-g} whenever you compile a program. You may think the program is -correct, but there's no sense in pushing your luck. - -Some things do not work as well with @samp{-g -O} as with just -@samp{-g}, particularly on machines with instruction scheduling. If in -doubt, recompile with @samp{-g} alone, and if this fixes the problem, -please report it as a bug (including a test case!). - -Older versions of the GNU C compiler permitted a variant option -@samp{-gg} for debugging information. _GDBN__ no longer supports this -format; if your GNU C compiler has this option, do not use it. - -@ignore -@comment As far as I know, there are no cases in which _GDBN__ will -@comment produce strange output in this case. (but no promises). -If your program includes archives made with the @code{ar} program, and -if the object files used as input to @code{ar} were compiled without the -@samp{-g} option and have names longer than 15 characters, _GDBN__ will get -confused reading the program's symbol table. No error message will be -given, but _GDBN__ may behave strangely. The reason for this problem is a -deficiency in the Unix archive file format, which cannot represent file -names longer than 15 characters. - -To avoid this problem, compile the archive members with the @samp{-g} -option or use shorter file names. Alternatively, use a version of GNU -@code{ar} dated more recently than August 1989. -@end ignore - - -@node Starting, Arguments, Compilation, Running -@section Starting your Program -@cindex starting -@cindex running -@table @code -@item run -@itemx r -@kindex run -Use the @code{run} command to start your program under _GDBN__. -_if__(_VXWORKS__) -Except on VxWorks, you -_fi__(_VXWORKS__) -_if__(!_VXWORKS__) -You -_fi__(!_VXWORKS__) -must first specify the program name with an argument to _GDBN__ -(@pxref{Invocation}), or using the @code{file} or @code{exec-file} -command (@pxref{Files}).@refill -@end table - -On targets that support processes, @code{run} creates an inferior -process and makes that process run your program. On other targets, -@code{run} jumps to the start of the program. - -The execution of a program is affected by certain information it -receives from its superior. _GDBN__ provides ways to specify this -information, which you must do @i{before} starting the program. (You -can change it after starting the program, but such changes will only affect -the program the next time you start it.) This information may be -divided into four categories: - -@table @asis -@item The @i{arguments.} -You specify the arguments to give your program as the arguments of the -@code{run} command. If a shell is available on your target, the shell -is used to pass the arguments, so that you may use normal conventions -(such as wildcard expansion or variable substitution) in -describing the arguments. In Unix systems, you can control which shell -is used with the @code{SHELL} environment variable. @xref{Arguments}.@refill - -@item The @i{environment.} -Your program normally inherits its environment from _GDBN__, but you can -use the _GDBN__ commands @code{set environment} and @code{unset -environment} to change parts of the environment that will be given to -the program. @xref{Environment}.@refill - -@item The @i{working directory.} -Your program inherits its working directory from _GDBN__. You can set -_GDBN__'s working directory with the @code{cd} command in _GDBN__. -@xref{Working Directory}. - -@item The @i{standard input and output.} -Your program normally uses the same device for standard input and -standard output as _GDBN__ is using. You can redirect input and output -in the @code{run} command line, or you can use the @code{tty} command to -set a different device for your program. -@xref{Input/Output}. -@end table - -When you issue the @code{run} command, your program begins to execute -immediately. @xref{Stopping}, for discussion of how to arrange for your -program to stop. Once your program has been started by the @code{run} -command (and then stopped), you may evaluate expressions that involve -calls to functions in the inferior, using the @code{print} or -@code{call} commands. @xref{Data}. - -If the modification time of your symbol file has changed since the last -time _GDBN__ read its symbols, _GDBN__ will discard its symbol table and re-read -it. In this process, it tries to retain your current breakpoints. - -@node Arguments, Environment, Starting, Running -@section Your Program's Arguments - -@cindex arguments (to your program) -The arguments to your program can be specified by the arguments of the -@code{run} command. They are passed to a shell, which expands wildcard -characters and performs redirection of I/O, and thence to the program. -_GDBN__ uses the shell indicated by your environment variable -@code{SHELL} if it exists; otherwise, _GDBN__ uses @code{/bin/sh}. - -@code{run} with no arguments uses the same arguments used by the previous -@code{run}, or those set by the @code{set args} command. - -@kindex set args -@table @code -@item set args -Specify the arguments to be used the next time your program is run. If -@code{set args} has no arguments, @code{run} will execute your program -with no arguments. Once you have run your program with arguments, this -is the only way to run it again without arguments. - -@item show args -@kindex show args -Show the arguments to give your program when it is started. -@end table - -@node Environment, Working Directory, Arguments, Running -@section Your Program's Environment - -@cindex environment (of your program) -The @dfn{environment} consists of a set of environment variables and -their values. Environment variables conventionally record such things as -your user name, your home directory, your terminal type, and your search -path for programs to run. Usually you set up environment variables with -the shell and they are inherited by all the other programs you run. When -debugging, it can be useful to try running the program with a modified -environment without having to start _GDBN__ over again. - -@table @code -@item path @var{directory} -@kindex path -Add @var{directory} to the front of the @code{PATH} environment variable -(the search path for executables), for both _GDBN__ and your program. -You may specify several directory names, separated by @samp{:} or -whitespace. If @var{directory} is already in the path, it is moved to -the front, so it will be searched sooner. You can use the string -@samp{$cwd} to refer to whatever is the current working directory at the -time _GDBN__ searches the path. @footnote{If you use @samp{.} instead, -it refers to the directory where you executed the @code{path} command. -_GDBN__ fills in the current path where needed in the @var{directory} -argument, before adding it to the search path.} -@c 'path' is explicitly nonrepeatable, but RMS points out it's silly to -@c document that, since repeating it would be a no-op. - -@item show paths -@kindex show paths -Display the list of search paths for executables (the @code{PATH} -environment variable). - -@item show environment @var{varname} -@kindex show environment -Print the value of environment variable @var{varname} to be given to -your program when it starts. - -@item show environment -Print the names and values of all environment variables to be given to -your program. - -@item set environment @var{varname} @var{value} -@itemx set environment @var{varname} = @var{value} -@kindex set environment -Sets environment variable @var{varname} to @var{value}. The value -changes for your program only, not for _GDBN__ itself. @var{value} may -be any string; the values of environment variables are just strings, and -any interpretation is supplied by your program itself. The @var{value} -parameter is optional; if it is eliminated, the variable is set to a -null value. -@c "any string" here doesn't include leading, trailing -@c blanks. Gnu asks: does anyone care? - -For example, this command: - -@example -set env USER = foo -@end example - -@noindent -tells a Unix program, when subsequently run, that its user is named -@samp{foo}. (The spaces around @samp{=} are used for clarity here; they -are not actually required.) - -@item unset environment @var{varname} -@kindex unset environment -Remove variable @var{varname} from the environment to be passed to your -program. This is different from @samp{set env @var{varname} =}; -@code{unset environment} removes the variable from the environment, -rather than assigning it an empty value. -@end table - -@node Working Directory, Input/Output, Environment, Running -@section Your Program's Working Directory - -@cindex working directory (of your program) -Each time you start your program with @code{run}, it inherits its -working directory from the current working directory of _GDBN__. _GDBN__'s -working directory is initially whatever it inherited from its parent -process (typically the shell), but you can specify a new working -directory in _GDBN__ with the @code{cd} command. - -The _GDBN__ working directory also serves as a default for the commands -that specify files for _GDBN__ to operate on. @xref{Files}. - -@table @code -@item cd @var{directory} -@kindex cd -Set _GDBN__'s working directory to @var{directory}. - -@item pwd -@kindex pwd -Print _GDBN__'s working directory. -@end table - -@node Input/Output, Attach, Working Directory, Running -@section Your Program's Input and Output - -@cindex redirection -@cindex i/o -@cindex terminal -@cindex controlling terminal -By default, the program you run under _GDBN__ does input and output to -the same terminal that _GDBN__ uses. _GDBN__ switches the terminal to -its own terminal modes to interact with you, but it records the terminal -modes your program was using and switches back to them when you continue -running your program. - -@table @code -@item info terminal -@kindex info terminal -Displays _GDBN__'s recorded information about the terminal modes your -program is using. -@end table - -You can redirect the program's input and/or output using shell -redirection with the @code{run} command. For example, - -_0__@example -run > outfile -_1__@end example - -@noindent -starts the program, diverting its output to the file @file{outfile}. - -@kindex tty -Another way to specify where the program should do input and output is -with the @code{tty} command. This command accepts a file name as -argument, and causes this file to be the default for future @code{run} -commands. It also resets the controlling terminal for the child -process, for future @code{run} commands. For example, - -@example -tty /dev/ttyb -@end example - -@noindent -directs that processes started with subsequent @code{run} commands -default to do input and output on the terminal @file{/dev/ttyb} and have -that as their controlling terminal. - -An explicit redirection in @code{run} overrides the @code{tty} command's -effect on the input/output device, but not its effect on the controlling -terminal. - -When you use the @code{tty} command or redirect input in the @code{run} -command, only the input @emph{for your program} is affected. The input -for _GDBN__ still comes from your terminal. - -@node Attach, Kill Process, Input/Output, Running -@section Debugging an Already-Running Process -@kindex attach -@cindex attach - -@table @code -@item attach @var{process-id} -This command -attaches to a running process---one that was started outside _GDBN__. -(@code{info files} will show your active targets.) The command takes as -argument a process ID. The usual way to find out the process-id of -a Unix process is with the @code{ps} utility, or with the @samp{jobs -l} -shell command. - -@code{attach} will not repeat if you press @key{RET} a second time after -executing the command. -@end table - -To use @code{attach}, you must be debugging in an environment which -supports processes. You must also have permission to send the process a -signal, and it must have the same effective user ID as the _GDBN__ -process. - -When using @code{attach}, you should first use the @code{file} command -to specify the program running in the process and load its symbol table. -@xref{Files}. - -The first thing _GDBN__ does after arranging to debug the specified -process is to stop it. You can examine and modify an attached process -with all the _GDBN__ commands that ordinarily available when you start -processes with @code{run}. You can insert breakpoints; you can step and -continue; you can modify storage. If you would rather the process -continue running, you may use the @code{continue} command after -attaching _GDBN__ to the process. - -@table @code -@item detach -@kindex detach -When you have finished debugging the attached process, you can use the -@code{detach} command to release it from _GDBN__'s control. Detaching -the process continues its execution. After the @code{detach} command, -that process and _GDBN__ become completely independent once more, and you -are ready to @code{attach} another process or start one with @code{run}. -@code{detach} will not repeat if you press @key{RET} again after -executing the command. -@end table - -If you exit _GDBN__ or use the @code{run} command while you have an attached -process, you kill that process. By default, you will be asked for -confirmation if you try to do either of these things; you can control -whether or not you need to confirm by using the @code{set confirm} command -(@pxref{Messages/Warnings}). - -@group -@node Kill Process, , Attach, Running -@section Killing the Child Process - -@table @code -@item kill -@kindex kill -Kill the child process in which your program is running under _GDBN__. -@end table - -This command is useful if you wish to debug a core dump instead of a -running process. _GDBN__ ignores any core dump file while your program -is running. -@end group - -On some operating systems, you can't execute your program in another -process while breakpoints are active inside _GDBN__. You can use the -@code{kill} command in this situation to permit running the program -outside the debugger. - -The @code{kill} command is also useful if you wish to recompile and -relink the program, since on many systems it is impossible to modify an -executable file which is running in a process. In this case, when you -next type @code{run}, _GDBN__ will notice that the file has changed, and -will re-read the symbol table (while trying to preserve your current -breakpoint settings). - -@node Stopping, Stack, Running, Top -@chapter Stopping and Continuing - -When you run a program normally, it runs until it terminates. The -principal purpose of using a debugger is so that you can stop your -program before it terminates; or so that, if the program runs into -trouble, you can investigate and find out why. - -Inside _GDBN__, your program may stop for any of several reasons, such -as a signal, a breakpoint, or reaching a new line after a _GDBN__ -command such as @code{step}. Usually, the messages shown by _GDBN__ -provide ample explanation of the status of your program---but you can -also explicitly request this information at any time. - -@table @code -@item info program -@kindex info program -Display information about the status of your program: whether it is -running or not, what process it is, and why it stopped. -@end table - -@menu -* Breakpoints:: Breakpoints, Watchpoints, and Exceptions -* Stepping:: Stepping -* Continuing:: Continuing -* Signals:: Signals -@end menu - -@node Breakpoints, Stepping, Stopping, Stopping -@section Breakpoints, Watchpoints, and Exceptions - -@cindex breakpoints -A @dfn{breakpoint} makes your program stop whenever a certain point in -the program is reached. For each breakpoint, you can add various -conditions to control in finer detail whether the program will stop. -You can set breakpoints with the @code{break} command and its variants -(@pxref{Set Breaks}), to specify the place where the program should stop -by line number, function name or exact address in the program. In -languages with exception handling (such as GNU C++), you can also set -breakpoints where an execption is raised (@pxref{Exception Handling}). - -@cindex watchpoints -A @dfn{watchpoint} is a special breakpoint that stops your program when -the value of an expression changes. You must use a different command to -set watchpoints (@pxref{Set Watchpoints}), but aside from that, you can -manage a watchpoint exactly like any other breakpoint: you enable, disable, and -delete both breakpoints and watchpoints using exactly the same commands. - -Each breakpoint or watchpoint is assigned a number when it is created; -these numbers are successive integers starting with one. In many of the -commands for controlling various features of breakpoints you use the -breakpoint number to say which breakpoint you want to change. Each -breakpoint may be @dfn{enabled} or @dfn{disabled}; if disabled, it has -no effect on the program until you enable it again. - -@menu -* Set Breaks:: Setting Breakpoints -* Set Watchpoints:: Setting Watchpoints -* Exception Handling:: Breakpoints and Exceptions -* Delete Breaks:: Deleting Breakpoints -* Disabling:: Disabling Breakpoints -* Conditions:: Break Conditions -* Break Commands:: Breakpoint Command Lists -* Breakpoint Menus:: Breakpoint Menus -* Error in Breakpoints:: -@end menu - -@node Set Breaks, Set Watchpoints, Breakpoints, Breakpoints -@subsection Setting Breakpoints - -@kindex break -@kindex b -Breakpoints are set with the @code{break} command (abbreviated @code{b}). - -You have several ways to say where the breakpoint should go. - -@table @code -@item break @var{function} -Set a breakpoint at entry to function @var{function}. When using source -languages that permit overloading of symbols, such as C++, -@var{function} may refer to more than one possible place to break. -@xref{Breakpoint Menus}, for a discussion of that situation. - -@item break +@var{offset} -@itemx break -@var{offset} -Set a breakpoint some number of lines forward or back from the position -at which execution stopped in the currently selected frame. - -@item break @var{linenum} -Set a breakpoint at line @var{linenum} in the current source file. -That file is the last file whose source text was printed. This -breakpoint will stop the program just before it executes any of the -code on that line. - -@item break @var{filename}:@var{linenum} -Set a breakpoint at line @var{linenum} in source file @var{filename}. - -@item break @var{filename}:@var{function} -Set a breakpoint at entry to function @var{function} found in file -@var{filename}. Specifying a file name as well as a function name is -superfluous except when multiple files contain similarly named -functions. - -@item break *@var{address} -Set a breakpoint at address @var{address}. You can use this to set -breakpoints in parts of the program which do not have debugging -information or source files. - -@item break -When called without any arguments, @code{break} sets a breakpoint at the -next instruction to be executed in the selected stack frame -(@pxref{Stack}). In any selected frame but the innermost, this will -cause the program to stop as soon as control returns to that frame. -This is similar to the effect of a @code{finish} command in the frame -inside the selected frame---except that @code{finish} doesn't leave an -active breakpoint. If you use @code{break} without an argument in the -innermost frame, _GDBN__ will stop the next time it reaches the current -location; this may be useful inside loops. - -_GDBN__ normally ignores breakpoints when it resumes execution, until at -least one instruction has been executed. If it did not do this, you -would be unable to proceed past a breakpoint without first disabling the -breakpoint. This rule applies whether or not the breakpoint already -existed when the program stopped. - -@item break @dots{} if @var{cond} -Set a breakpoint with condition @var{cond}; evaluate the expression -@var{cond} each time the breakpoint is reached, and stop only if the -value is nonzero. @samp{@dots{}} stands for one of the possible -arguments described above (or no argument) specifying where to break. -@xref{Conditions}, for more information on breakpoint conditions. - -@item tbreak @var{args} -@kindex tbreak -Set a breakpoint enabled only for one stop. @var{args} are the -same as in the @code{break} command, and the breakpoint is set in the same -way, but the breakpoint is automatically disabled the first time it -is hit. @xref{Disabling}. - -@item rbreak @var{regex} -@kindex rbreak -Set a breakpoint on all functions matching @var{regex}. This is -useful for setting breakpoints on overloaded functions that are not -members of any special classes. This command sets an unconditional -breakpoint on all matches, printing a list of all breakpoints it set. -Once these breakpoints are set, they are treated just like the -breakpoints set with the @code{break} command. They can be deleted, -disabled, made conditional, etc., in the standard ways. - -@kindex info breakpoints -@kindex $_ -@item info breakpoints -The command @code{info breakpoints} prints a list of all breakpoints -(but not watchpoints) set and not deleted, showing their numbers, where -in the program they are, and any special features in use for them. -Disabled breakpoints are included in the list, but marked as disabled. -@code{info break} with a breakpoint number as argument lists only that -breakpoint. The convenience variable @code{$_} and the default -examining-address for the @code{x} command are set to the address of the -last breakpoint listed (@pxref{Memory}). The equivalent command for -watchpoints is @code{info watch}. -@end table - -_GDBN__ allows you to set any number of breakpoints at the same place in the -program. There is nothing silly or meaningless about this. When the -breakpoints are conditional, this is even useful (@pxref{Conditions}). - -@node Set Watchpoints, Exception Handling, Set Breaks, Breakpoints -@subsection Setting Watchpoints -@cindex setting watchpoints -You can use a watchpoint to stop execution whenever the value of an -expression changes, without having to predict a particular place in the -inferior process where this may happen. - -Watchpoints currently execute two orders of magnitude more slowly than -other breakpoints, but this can well be worth it to catch errors where -you have no clue what part of your program is the culprit. Some -processors provide special hardware to implement this feature; future -releases of _GDBN__ will use such hardware if it is available. - -@table @code -@kindex watch -@item watch @var{expr} -Set a watchpoint for an expression. - -@kindex info watchpoints -@item info watchpoints -This command prints a list of watchpoints; it is otherwise similar to -@code{info break}. -@end table - -@node Exception Handling, Delete Breaks, Set Watchpoints, Breakpoints -@subsection Breakpoints and Exceptions -@cindex exception handlers - -Some languages, such as GNU C++, implement exception handling. _GDBN__ -can be used to examine what caused the program to raise an exception -and to list the exceptions the program is prepared to handle at a -given point in time. - -@table @code -@item catch @var{exceptions} -@kindex catch - -You can set breakpoints at active exception handlers by using the -@code{catch} command. @var{exceptions} is a list of names of exceptions -to catch. -@end table - -You can use @code{info catch} to list active exception handlers; -@pxref{Frame Info}. - -There are currently some limitations to exception handling in _GDBN__. -These will be corrected in a future release. - -@itemize @bullet -@item -If you call a function interactively, _GDBN__ normally returns -control to you when the function has finished executing. If the call -raises an exception, however, the call may bypass the mechanism that -returns control to the user and cause the program to simply continue -running until it hits a breakpoint, catches a signal that _GDBN__ is -listening for, or exits. -@item -You cannot raise an exception interactively. -@item -You cannot interactively install an exception handler. -@end itemize - -@cindex raise exceptions -Sometimes @code{catch} is not the best way to debug exception handling: -if you need to know exactly where an exception is raised, it's better to -stop @emph{before} the exception handler is called, since that way you -can see the stack before any unwinding takes place. If you set a -breakpoint in an exception handler instead, it may not be easy to find -out where the exception was raised. - -To stop just before an exception handler is called, you need some -knowledge of the implementation. In the case of GNU C++ exception are -raised by calling a library function named @code{__raise_exception} -which has the following ANSI C interface: - -@example - /* ADDR is where the exception identifier is stored. - ID is the exception identifier. */ - void __raise_exception (void **@var{addr}, void *@var{id}); -@end example - -@noindent -To make the debugger catch all exceptions before any stack -unwinding takes place, set a breakpoint on @code{__raise_exception} -(@pxref{Breakpoints}). - -With a conditional breakpoint (@xref{Conditions}) that depends on the -value of @var{id}, you can stop your program when a specific exception -is raised. You can use multiple conditional breakpoints to stop the -program when any of a number of exceptions are raised. - -@node Delete Breaks, Disabling, Exception Handling, Breakpoints -@subsection Deleting Breakpoints - -@cindex clearing breakpoints, watchpoints -@cindex deleting breakpoints, watchpoints -It is often necessary to eliminate a breakpoint or watchpoint once it -has done its job and you no longer want the program to stop there. This -is called @dfn{deleting} the breakpoint. A breakpoint that has been -deleted no longer exists in any sense; it is forgotten. - -With the @code{clear} command you can delete breakpoints according to -where they are in the program. With the @code{delete} command you can -delete individual breakpoints or watchpoints by specifying their -breakpoint numbers. - -It is not necessary to delete a breakpoint to proceed past it. _GDBN__ -automatically ignores breakpoints on the first instruction to be executed -when you continue execution without changing the execution address. - -@table @code -@item clear -@kindex clear -Delete any breakpoints at the next instruction to be executed in the -selected stack frame (@pxref{Selection}). When the innermost frame -is selected, this is a good way to delete a breakpoint that the program -just stopped at. - -@item clear @var{function} -@itemx clear @var{filename}:@var{function} -Delete any breakpoints set at entry to the function @var{function}. - -@item clear @var{linenum} -@itemx clear @var{filename}:@var{linenum} -Delete any breakpoints set at or within the code of the specified line. - -@item delete breakpoints @var{bnums}@dots{} -@itemx delete @var{bnums}@dots{} -@itemx delete -@cindex delete breakpoints -@kindex delete -@kindex d -Delete the breakpoints or watchpoints of the numbers specified as -arguments. If no argument is specified, delete all breakpoints. You -can abbreviate this command as @code{d}. -@end table - -@node Disabling, Conditions, Delete Breaks, Breakpoints -@subsection Disabling Breakpoints - -@cindex disabled breakpoints -@cindex enabled breakpoints -Rather than deleting a breakpoint or watchpoint, you might prefer to -@dfn{disable} it. This makes the breakpoint inoperative as if it had -been deleted, but remembers the information on the breakpoint so that -you can @dfn{enable} it again later. - -You disable and enable breakpoints and watchpoints with the -@code{enable} and @code{disable} commands, optionally specifying one or -more breakpoint numbers as arguments. Use @code{info break} or -@code{info watch} to print a list of breakpoints or watchpoints if you -don't know which numbers to use. - -A breakpoint or watchpoint can have any of four different states of -enablement: - -@itemize @bullet -@item -Enabled. The breakpoint will stop the program. A breakpoint made -with the @code{break} command starts out in this state. -@item -Disabled. The breakpoint has no effect on the program. -@item -Enabled once. The breakpoint will stop the program, but -when it does so it will become disabled. A breakpoint made -with the @code{tbreak} command starts out in this state. -@item -Enabled for deletion. The breakpoint will stop the program, but -immediately after it does so it will be deleted permanently. -@end itemize - -You can use the following commands to enable or disable breakpoints and -watchpoints: - -@table @code -@item disable breakpoints @var{bnums}@dots{} -@itemx disable @var{bnums}@dots{} -@itemx disable -@kindex disable breakpoints -@kindex disable -@kindex dis -Disable the specified breakpoints---or all breakpoints, if none are -listed. A disabled breakpoint has no effect but is not forgotten. All -options such as ignore-counts, conditions and commands are remembered in -case the breakpoint is enabled again later. You may abbreviate -@code{disable} as @code{dis}. - -@item enable breakpoints @var{bnums}@dots{} -@itemx enable @var{bnums}@dots{} -@itemx enable -@kindex enable breakpoints -@kindex enable -Enable the specified breakpoints (or all defined breakpoints). They -become effective once again in stopping the program, until you specify -otherwise. - -@item enable breakpoints once @var{bnums}@dots{} -@itemx enable once @var{bnums}@dots{} -Enable the specified breakpoints temporarily. Each will be disabled -again the next time it stops the program (unless you have used one of -these commands to specify a different state before that time comes). - -@item enable breakpoints delete @var{bnums}@dots{} -@itemx enable delete @var{bnums}@dots{} -Enable the specified breakpoints to work once and then die. Each of -the breakpoints will be deleted the next time it stops the program -(unless you have used one of these commands to specify a different -state before that time comes). -@end table - -Save for a breakpoint set with @code{tbreak} (@pxref{Set Breaks}), -breakpoints that you set initially enabled; subsequently, they become -disabled or enabled only when you use one of the commands above. (The -command @code{until} can set and delete a breakpoint of its own, but it -will not change the state of your other breakpoints; -@pxref{Stepping}.) - -@node Conditions, Break Commands, Disabling, Breakpoints -@subsection Break Conditions -@cindex conditional breakpoints -@cindex breakpoint conditions - -The simplest sort of breakpoint breaks every time the program reaches a -specified place. You can also specify a @dfn{condition} for a -breakpoint. A condition is just a Boolean expression in your -programming language. (@xref{Expressions}). A breakpoint with a -condition evaluates the expression each time the program reaches it, and -the program stops only if the condition is true. - -Conditions are also accepted for watchpoints; you may not need them, -since a watchpoint is inspecting the value of an expression anyhow---but -it might be simpler, say, to just set a watchpoint on a variable name, -then have a condition that tests whether the new value is an interesting -one. - -Break conditions may have side effects, and may even call functions in your -program. These may sound like strange things to do, but their effects are -completely predictable unless there is another enabled breakpoint at the -same address. (In that case, _GDBN__ might see the other breakpoint first and -stop the program without checking the condition of this one.) Note that -breakpoint commands are usually more convenient and flexible for the -purpose of performing side effects when a breakpoint is reached -(@pxref{Break Commands}). - -Break conditions can be specified when a breakpoint is set, by using -@samp{if} in the arguments to the @code{break} command. @xref{Set Breaks}. -They can also be changed at any time with the @code{condition} command. -The @code{watch} command doesn't recognize the @code{if} keyword; -@code{condition} is the only way to impose a further condition on a -watchpoint. - -@table @code -@item condition @var{bnum} @var{expression} -@kindex condition -Specify @var{expression} as the break condition for breakpoint or -watchpoint number @var{bnum}. From now on, this breakpoint will stop -the program only if the value of @var{expression} is true (nonzero, in -C). When you call @code{condition}, the expression you specify is -checked immediately for syntactic correctness, and to determine whether -symbols in it have referents in the context of your breakpoint. _GDBN__ -does not actually evaluate @var{expression} at the time the -@code{condition} command is given, however. @xref{Expressions}. - -@item condition @var{bnum} -Remove the condition from breakpoint number @var{bnum}. It becomes -an ordinary unconditional breakpoint. -@end table - -@cindex ignore count (of breakpoint) -A special case of a breakpoint condition is to stop only when the -breakpoint has been reached a certain number of times. This is so -useful that there is a special way to do it, using the @dfn{ignore -count} of the breakpoint. Every breakpoint has an ignore count, which -is an integer. Most of the time, the ignore count is zero, and -therefore has no effect. But if the program reaches a breakpoint whose -ignore count is positive, then instead of stopping, it just decrements -the ignore count by one and continues. As a result, if the ignore count -value is @var{n}, the breakpoint will not stop the next @var{n} times it -is reached. - -@table @code -@item ignore @var{bnum} @var{count} -@kindex ignore -Set the ignore count of breakpoint number @var{bnum} to @var{count}. -The next @var{count} times the breakpoint is reached, your program's -execution will not stop; other than to decrement the ignore count, _GDBN__ -takes no action. - -To make the breakpoint stop the next time it is reached, specify -a count of zero. - -@item continue @var{count} -@itemx c @var{count} -@itemx fg @var{count} -@kindex continue @var{count} -Continue execution of the program, setting the ignore count of the -breakpoint that the program stopped at to @var{count} minus one. -Thus, the program will not stop at this breakpoint until the -@var{count}'th time it is reached. - -An argument to this command is meaningful only when the program stopped -due to a breakpoint. At other times, the argument to @code{continue} is -ignored. - -The synonym @code{fg} is provided purely for convenience, and has -exactly the same behavior as other forms of the command. -@end table - -If a breakpoint has a positive ignore count and a condition, the condition -is not checked. Once the ignore count reaches zero, the condition will -be checked. - -You could achieve the effect of the ignore count with a -condition such as _0__@w{@samp{$foo-- <= 0}}_1__ using a debugger convenience -variable that is decremented each time. @xref{Convenience Vars}. - -@node Break Commands, Breakpoint Menus, Conditions, Breakpoints -@subsection Breakpoint Command Lists - -@cindex breakpoint commands -You can give any breakpoint (or watchpoint) a series of commands to -execute when the program stops due to that breakpoint. For example, you -might want to print the values of certain expressions, or enable other -breakpoints. - -@table @code -@item commands @var{bnum} -@itemx @dots{} @var{command-list} @dots{} -@itemx end -@kindex commands -@kindex end -Specify a list of commands for breakpoint number @var{bnum}. The commands -themselves appear on the following lines. Type a line containing just -@code{end} to terminate the commands. - -To remove all commands from a breakpoint, use the command -@code{commands} and follow it immediately by @code{end}; that is, give -no commands. - -With no @var{bnum} argument, @code{commands} refers to the last -breakpoint or watchpoint set (not to the breakpoint most recently -encountered). -@end table - -Pressing @key{RET} as a means of repeating the last _GDBN__ command is -disabled from the time you enter @code{commands} to just after the -corresponding @code{end}. - -You can use breakpoint commands to start the program up again. Simply -use the @code{continue} command, or @code{step}, or any other command to -resume execution. However, if you do this, any further commands in the -same breakpoint's command list are ignored. When the program stops -again, _GDBN__ will act according to the cause of that stop. - -@kindex silent -If the first command specified is @code{silent}, the usual message about -stopping at a breakpoint is not printed. This may be desirable for -breakpoints that are to print a specific message and then continue. -If the remaining commands too print nothing, you will see no sign that -the breakpoint was reached at all. @code{silent} is not really a command; -it is meaningful only at the beginning of the commands for a breakpoint. - -The commands @code{echo} and @code{output} that allow you to print precisely -controlled output are often useful in silent breakpoints. @xref{Output}. - -For example, here is how you could use breakpoint commands to print the -value of @code{x} at entry to @code{foo} whenever @code{x} is positive. - -_0__@example -break foo if x>0 -commands -silent -echo x is\040 -output x -echo \n -cont -end -_1__@end example - -One application for breakpoint commands is to correct one bug so you can -test another. Put a breakpoint just after the erroneous line of code, give -it a condition to detect the case in which something erroneous has been -done, and give it commands to assign correct values to any variables that -need them. End with the @code{continue} command so that the program does not -stop, and start with the @code{silent} command so that no output is -produced. Here is an example: - -@example -break 403 -commands -silent -set x = y + 4 -cont -end -@end example - -@cindex lost output -One deficiency in the operation of automatically continuing breakpoints -under Unix appears when your program uses raw mode for the terminal. -_GDBN__ switches back to its own terminal modes (not raw) before executing -commands, and then must switch back to raw mode when your program is -continued. This causes any pending terminal input to be lost. -In the GNU system, this will be fixed by changing the behavior of -terminal modes. - -Under Unix, when you have this problem, you might be able to get around -it by putting your actions into the breakpoint condition instead of -commands. For example - -@example -condition 5 (x = y + 4), 0 -@end example - -@noindent -specifies a condition expression (@xref{Expressions}) that will change -@code{x} as needed, then always have the value zero so the program will not -stop. Loss of input is avoided here because break conditions are -evaluated without changing the terminal modes. When you want to have -nontrivial conditions for performing the side effects, the operators -@samp{&&}, @samp{||} and @samp{?@dots{}:} may be useful. - -@node Breakpoint Menus, Error in Breakpoints, Break Commands, Breakpoints -@subsection Breakpoint Menus -@cindex C++ overloading -@cindex symbol overloading - -Some programming languages (notably C++) permit a single function name -to be defined several times, for application in different contexts. -This is called @dfn{overloading}. When a function name is overloaded, -@samp{break @var{function}} is not enough to tell _GDBN__ where you want -a breakpoint. _GDBN__ responds to this situation by offering you a menu -of numbered choices for different possible breakpoints, and waiting for -your selection with the prompt @samp{>}. The first two -options are always @samp{[0] cancel} and @samp{[1] all}. Typing @kbd{1} -will set a breakpoint at all the definitions available for -@var{function}, and typing @kbd{0} will abort the @code{break} command -without setting any new breakpoints. - -For example, the following session excerpt shows an attempt to set a -breakpoint at the overloaded symbol @code{String::after}. In the -example, we choose three particular definitions of the function: - -@example -(_GDBP__) b String::after -[0] cancel -[1] all -[2] file:String.cc; line number:867 -[3] file:String.cc; line number:860 -[4] file:String.cc; line number:875 -[5] file:String.cc; line number:853 -[6] file:String.cc; line number:846 -[7] file:String.cc; line number:735 -> 2 4 6 -Breakpoint 1 at 0xb26c: file String.cc, line 867. -Breakpoint 2 at 0xb344: file String.cc, line 875. -Breakpoint 3 at 0xafcc: file String.cc, line 846. -Multiple breakpoints were set. -Use the "delete" command to delete unwanted breakpoints. -(_GDBP__) -@end example - - -@node Error in Breakpoints, , Breakpoint Menus, Breakpoints -@subsection ``Cannot Insert Breakpoints'' - -@c FIXME: "cannot insert breakpoints" error, v unclear. -@c Q in pending mail to Gilmore. ---pesch@cygnus.com, 26mar91 -Under some operating systems, breakpoints cannot be used in a program if -any other process is running that program. In this situation, -attempting to run or continue a program with a breakpoint will cause _GDBN__ -to stop the other process. - -When this happens, you have three ways to proceed: - -@enumerate -@item -Remove or disable the breakpoints, then continue. - -@item -Suspend _GDBN__, and copy the file containing the program to a new name. -Resume _GDBN__ and use the @code{exec-file} command to specify that _GDBN__ -should run the program under that name. Then start the program again. - -@c FIXME: RMS commented here "Show example". Maybe when someone -@c explains the first FIXME: in this section... - -@item -Relink the program so that the text segment is nonsharable, using the -linker option @samp{-N}. The operating system limitation may not apply -to nonsharable executables. -@end enumerate - -@node Stepping, Continuing, Breakpoints, Stopping -@section Stepping - -@cindex stepping -@dfn{Stepping} means setting your program in motion for a limited time, -so that control will return automatically to _GDBN__ after one line of -code or one machine instruction. @footnote{Your program might stop even -sooner, during stepping, since a signal may arrive before your program -reaches the next source line. Also, since breakpoints are active during -stepping, your program will stop for them even if it has not gone as far -as the stepping command specifies.} - -A typical technique for using stepping is to put a breakpoint -(@pxref{Breakpoints}) at the beginning of the function or the section of -the program in which a problem is believed to lie, run the program until -it stops at that breakpoint, and then step through the suspect area, -examining the variables that are interesting, until you see the problem -happen. - -@table @code -@item step -@kindex step -@kindex s -Continue running the program until control reaches a different source -line, then stop it and return control to the debugger. This command is -abbreviated @code{s}. - -You may use the @code{step} command when control is within a function -for which there is no debugging information. In that case, execution -will proceed until control reaches a different function, or is about to -return from this function. - -@item step @var{count} -Continue running as in @code{step}, but do so @var{count} times. If a -breakpoint is reached or a signal not related to stepping occurs before -@var{count} steps, stepping stops right away. - -@item next -@kindex next -@kindex n -Continue to the next source line in the current stack frame. Similar to -@code{step}, but any function calls appearing within the line of code -are executed without stopping. Execution stops when control reaches a -different line of code at the stack level which was executing when the -@code{next} command was given. This command is abbreviated @code{n}. - -An argument is a repeat count, as in @code{step}. - -@code{next} within a function that lacks debugging information acts like -@code{step}, but any function calls appearing within the code of the -function are executed without stopping. - -@item finish -@kindex finish -Continue running until just after the selected stack frame returns (or -until there is some other reason to stop, such as a fatal signal or a -breakpoint). Print the value returned by the selected stack frame (if -any). - -Contrast this with the @code{return} command (@pxref{Returning}). - -@item until -@kindex until -@item u -@kindex u -Continue running until a source line past the current line, in the -current stack frame, is reached. This command is used to avoid single -stepping through a loop more than once. It is like the @code{next} -command, except that when @code{until} encounters a jump, it -automatically continues execution until the program counter is greater -than the address of the jump. - -This means that when you reach the end of a loop after single stepping -though it, @code{until} will cause the program to continue execution -until the loop is exited. In contrast, a @code{next} command at the end -of a loop will simply step back to the beginning of the loop, which -would force you to step through the next iteration. - -@code{until} always stops the program if it attempts to exit the current -stack frame. - -@code{until} may produce somewhat counterintuitive results if the order -of the source lines does not match the actual order of execution. For -example, in the following excerpt from a debugging session, the @code{f} -(@code{frame}) command shows that execution is stopped at line -@code{206}; yet when we use @code{until}, we get to line @code{195}: - -@example -(_GDBP__) f -#0 main (argc=4, argv=0xf7fffae8) at m4.c:206 -206 expand_input(); -(_GDBP__) until -195 for ( ; argc > 0; NEXTARG) @{ -@end example - -In this case, (as for any C @code{for}-loop), the loop-step expression -(here, @samp{argc > 0}) is executed @emph{after} the statements in the -body of the loop, but is written before them. Therefore, the -@code{until} command appeared to step back to the beginning of the loop -when it advanced to this expression. However, it has not really gone to -an earlier statement---not in terms of the actual machine code. - -@code{until} with no argument works by means of single -instruction stepping, and hence is slower than @code{until} with an -argument. - -@item until @var{location} -@item u @var{location} -Continue running the program until either the specified location is -reached, or the current (innermost) stack frame returns. @var{location} -is any of the forms of argument acceptable to @code{break} (@pxref{Set -Breaks}). This form of the command uses breakpoints, and hence is -quicker than @code{until} without an argument. - -@item stepi -@itemx si -@kindex stepi -@kindex si -Execute one machine instruction, then stop and return to the debugger. - -It is often useful to do @samp{display/i $pc} when stepping by machine -instructions. This will cause the next instruction to be executed to -be displayed automatically at each stop. @xref{Auto Display}. - -An argument is a repeat count, as in @code{step}. - -@item nexti -@itemx ni -@kindex nexti -@kindex ni -Execute one machine instruction, but if it is a function call, -proceed until the function returns. - -An argument is a repeat count, as in @code{next}. -@end table - -The @code{continue} command can be used after stepping to resume execution -until the next breakpoint or signal. - -@node Continuing, Signals, Stepping, Stopping -@section Continuing - -After your program stops, most likely you will want it to run some more if -the bug you are looking for has not happened yet. - -@table @code -@item continue -@kindex continue -Continue running the program at the place where it stopped. -@end table - -If the program stopped at a breakpoint, the place to continue running -is the address of the breakpoint. You might expect that continuing would -just stop at the same breakpoint immediately. In fact, @code{continue} -takes special care to prevent that from happening. You do not need -to disable the breakpoint to proceed through it after stopping there. -You can, however, specify an ignore-count for the breakpoint that the -program stopped at, by means of an argument to the @code{continue} command. -@xref{Conditions}. - -If the program stopped because of a signal other than @code{SIGINT} or -@code{SIGTRAP}, continuing will cause the program to see that signal. -You may not want this to happen. For example, if the program stopped -due to some sort of memory reference error, you might store correct -values into the erroneous variables and continue, hoping to see more -execution; but the program would probably terminate immediately as -a result of the fatal signal once it sees the signal. To prevent this, -you can continue with @samp{signal 0}. @xref{Signaling}. You can -also act in advance to control what signals your program will see, using -the @code{handle} command (@pxref{Signals}). - -@node Signals, , Continuing, Stopping -@section Signals -@cindex signals - -A signal is an asynchronous event that can happen in a program. The -operating system defines the possible kinds of signals, and gives each -kind a name and a number. For example, in Unix @code{SIGINT} is the -signal a program gets when you type an interrupt (often @kbd{C-c}); -@code{SIGSEGV} is the signal a program gets from referencing a place in -memory far away from all the areas in use; @code{SIGALRM} occurs when -the alarm clock timer goes off (which happens only if the program has -requested an alarm). - -@cindex fatal signals -Some signals, including @code{SIGALRM}, are a normal part of the -functioning of the program. Others, such as @code{SIGSEGV}, indicate -errors; these signals are @dfn{fatal} (kill the program immediately) if the -program has not specified in advance some other way to handle the signal. -@code{SIGINT} does not indicate an error in the program, but it is normally -fatal so it can carry out the purpose of the interrupt: to kill the program. - -_GDBN__ has the ability to detect any occurrence of a signal in the program -running under _GDBN__'s control. You can tell _GDBN__ in advance what to do for -each kind of signal. - -@cindex handling signals -Normally, _GDBN__ is set up to ignore non-erroneous signals like @code{SIGALRM} -(so as not to interfere with their role in the functioning of the program) -but to stop the program immediately whenever an error signal happens. -You can change these settings with the @code{handle} command. - -@table @code -@item info signals -@kindex info signals -Print a table of all the kinds of signals and how _GDBN__ has been told to -handle each one. You can use this to see the signal numbers of all -the defined types of signals. - -@item handle @var{signal} @var{keywords}@dots{} -@kindex handle -Change the way _GDBN__ handles signal @var{signal}. @var{signal} can be the -number of a signal or its name (with or without the @samp{SIG} at the -beginning). The @var{keywords} say what change to make. -@end table - -@group -The keywords allowed by the @code{handle} command can be abbreviated. -Their full names are: - -@table @code -@item nostop -_GDBN__ should not stop the program when this signal happens. It may -still print a message telling you that the signal has come in. - -@item stop -_GDBN__ should stop the program when this signal happens. This implies -the @code{print} keyword as well. - -@item print -_GDBN__ should print a message when this signal happens. - -@item noprint -_GDBN__ should not mention the occurrence of the signal at all. This -implies the @code{nostop} keyword as well. - -@item pass -_GDBN__ should allow the program to see this signal; the program will be -able to handle the signal, or may be terminated if the signal is fatal -and not handled. - -@item nopass -_GDBN__ should not allow the program to see this signal. -@end table -@end group - -When a signal has been set to stop the program, the program cannot see the -signal until you continue. It will see the signal then, if @code{pass} is -in effect for the signal in question @i{at that time}. In other words, -after _GDBN__ reports a signal, you can use the @code{handle} command with -@code{pass} or @code{nopass} to control whether that signal will be seen by -the program when you later continue it. - -You can also use the @code{signal} command to prevent the program from -seeing a signal, or cause it to see a signal it normally would not see, -or to give it any signal at any time. @xref{Signaling}. - - -@node Stack, Source, Stopping, Top -@chapter Examining the Stack - -When your program has stopped, the first thing you need to know is where it -stopped and how it got there. - -@cindex call stack -Each time your program performs a function call, the information about -where in the program the call was made from is saved in a block of data -called a @dfn{stack frame}. The frame also contains the arguments of the -call and the local variables of the function that was called. All the -stack frames are allocated in a region of memory called the @dfn{call -stack}. - -When your program stops, the _GDBN__ commands for examining the stack allow you -to see all of this information. - -@cindex selected frame -One of the stack frames is @dfn{selected} by _GDBN__ and many _GDBN__ commands -refer implicitly to the selected frame. In particular, whenever you ask -_GDBN__ for the value of a variable in the program, the value is found in the -selected frame. There are special _GDBN__ commands to select whichever frame -you are interested in. - -When the program stops, _GDBN__ automatically selects the currently executing -frame and describes it briefly as the @code{frame} command does -(@pxref{Frame Info, Info}). - -@menu -* Frames:: Stack Frames -* Backtrace:: Backtraces -* Selection:: Selecting a Frame -* Frame Info:: Information on a Frame -@end menu - -@node Frames, Backtrace, Stack, Stack -@section Stack Frames - -@cindex frame -@cindex stack frame -The call stack is divided up into contiguous pieces called @dfn{stack -frames}, or @dfn{frames} for short; each frame is the data associated -with one call to one function. The frame contains the arguments given -to the function, the function's local variables, and the address at -which the function is executing. - -@cindex initial frame -@cindex outermost frame -@cindex innermost frame -When your program is started, the stack has only one frame, that of the -function @code{main}. This is called the @dfn{initial} frame or the -@dfn{outermost} frame. Each time a function is called, a new frame is -made. Each time a function returns, the frame for that function invocation -is eliminated. If a function is recursive, there can be many frames for -the same function. The frame for the function in which execution is -actually occurring is called the @dfn{innermost} frame. This is the most -recently created of all the stack frames that still exist. - -@cindex frame pointer -Inside your program, stack frames are identified by their addresses. A -stack frame consists of many bytes, each of which has its own address; each -kind of computer has a convention for choosing one of those bytes whose -address serves as the address of the frame. Usually this address is kept -in a register called the @dfn{frame pointer register} while execution is -going on in that frame. - -@cindex frame number -_GDBN__ assigns numbers to all existing stack frames, starting with -zero for the innermost frame, one for the frame that called it, -and so on upward. These numbers do not really exist in your program; -they are assigned by _GDBN__ to give you a way of designating stack -frames in _GDBN__ commands. - -@cindex frameless execution -Some compilers allow functions to be compiled so that they operate -without stack frames. (For example, the @code{_GCC__} option -@samp{-fomit-frame-pointer} will generate functions without a frame.) -This is occasionally done with heavily used library functions to save -the frame setup time. _GDBN__ has limited facilities for dealing with -these function invocations. If the innermost function invocation has no -stack frame, _GDBN__ will nevertheless regard it as though it had a -separate frame, which is numbered zero as usual, allowing correct -tracing of the function call chain. However, _GDBN__ has no provision -for frameless functions elsewhere in the stack. - -@node Backtrace, Selection, Frames, Stack -@section Backtraces - -A backtrace is a summary of how the program got where it is. It shows one -line per frame, for many frames, starting with the currently executing -frame (frame zero), followed by its caller (frame one), and on up the -stack. - -@table @code -@item backtrace -@itemx bt -@kindex backtrace -@kindex bt -Print a backtrace of the entire stack: one line per frame for all -frames in the stack. - -You can stop the backtrace at any time by typing the system interrupt -character, normally @kbd{Control-C}. - -@item backtrace @var{n} -@itemx bt @var{n} -Similar, but print only the innermost @var{n} frames. - -@item backtrace -@var{n} -@itemx bt -@var{n} -Similar, but print only the outermost @var{n} frames. -@end table - -@kindex where -@kindex info stack -@kindex info s -The names @code{where} and @code{info stack} (abbreviated @code{info s}) -are additional aliases for @code{backtrace}. - -Each line in the backtrace shows the frame number and the function name. -The program counter value is also shown---unless you use @code{set -print address off}. The backtrace also shows the source file name and -line number, as well as the arguments to the function. The program -counter value is omitted if it is at the beginning of the code for that -line number. - -Here is an example of a backtrace. It was made with the command -@samp{bt 3}, so it shows the innermost three frames. - -@smallexample -@group -#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8) at builtin.c:993 -#1 0x6e38 in expand_macro (sym=0x2b600) at macro.c:242 -#2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08) - at macro.c:71 -(More stack frames follow...) -@end group -@end smallexample - -@noindent -The display for frame zero doesn't begin with a program counter -value, indicating that the program has stopped at the beginning of the -code for line @code{993} of @code{builtin.c}. - -@node Selection, Frame Info, Backtrace, Stack -@section Selecting a Frame - -Most commands for examining the stack and other data in the program work on -whichever stack frame is selected at the moment. Here are the commands for -selecting a stack frame; all of them finish by printing a brief description -of the stack frame just selected. - -@table @code -@item frame @var{n} -@itemx f @var{n} -@kindex frame -@kindex f -Select frame number @var{n}. Recall that frame zero is the innermost -(currently executing) frame, frame one is the frame that called the -innermost one, and so on. The highest-numbered frame is @code{main}'s -frame. - -@item frame @var{addr} -@itemx f @var{addr} -Select the frame at address @var{addr}. This is useful mainly if the -chaining of stack frames has been damaged by a bug, making it -impossible for _GDBN__ to assign numbers properly to all frames. In -addition, this can be useful when the program has multiple stacks and -switches between them. - -_if_(_SPARC__) -On the SPARC architecture, @code{frame} needs two addresses to -select an arbitrary frame: a frame pointer and a stack pointer. -@c note to future updaters: this is conditioned on a flag -@c FRAME_SPECIFICATION_DYADIC in the tm-*.h files, currently only used -@c by SPARC, hence the specific attribution. Generalize or list all -@c possibilities if more supported machines start doing this. -_fi_(_SPARC__) - -@item up @var{n} -@kindex up -Move @var{n} frames up the stack. For positive numbers @var{n}, this -advances toward the outermost frame, to higher frame numbers, to frames -that have existed longer. @var{n} defaults to one. - -@item down @var{n} -@kindex down -@kindex do -Move @var{n} frames down the stack. For positive numbers @var{n}, this -advances toward the innermost frame, to lower frame numbers, to frames -that were created more recently. @var{n} defaults to one. You may -abbreviate @code{down} as @code{do}. -@end table - -All of these commands end by printing two lines of output describing the -frame. The first line shows the frame number, the function name, the -arguments, and the source file and line number of execution in that -frame. The second line shows the text of that source line. For -example: - -@smallexample -(_GDBP__) up -#1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc) at env.c:10 -10 read_input_file (argv[i]); -@end smallexample - -After such a printout, the @code{list} command with no arguments will print -ten lines centered on the point of execution in the frame. @xref{List}. - -@table @code -@item up-silently @var{n} -@itemx down-silently @var{n} -@kindex down-silently -@kindex up-silently -These two commands are variants of @code{up} and @code{down}, -respectively; they differ in that they do their work silently, without -causing display of the new frame. They are intended primarily for use -in _GDBN__ command scripts, where the output might be unnecessary and -distracting. - -@end table - -@node Frame Info, , Selection, Stack -@section Information About a Frame - -There are several other commands to print information about the selected -stack frame. - -@table @code -@item frame -@itemx f -When used without any argument, this command does not change which frame -is selected, but prints a brief description of the currently -selected stack frame. It can be abbreviated @code{f}. With an -argument, this command is used to select a stack frame (@pxref{Selection}). - -@item info frame -@kindex info frame -@itemx info f -@kindex info f -This command prints a verbose description of the selected stack frame, -including the address of the frame, the addresses of the next frame down -(called by this frame) and the next frame up (caller of this frame), -the address of the frame's arguments, the program counter saved in it -(the address of execution in the caller frame), and which registers -were saved in the frame. The verbose description is useful when -something has gone wrong that has made the stack format fail to fit -the usual conventions. - -@item info frame @var{addr} -@itemx info f @var{addr} -Print a verbose description of the frame at address @var{addr}, -without selecting that frame. The selected frame remains unchanged by -this command. - -@item info args -@kindex info args -Print the arguments of the selected frame, each on a separate line. - -@item info locals -@kindex info locals -Print the local variables of the selected frame, each on a separate -line. These are all variables declared static or automatic within all -program blocks that execution in this frame is currently inside of. - -@item info catch -@kindex info catch -@cindex catch exceptions -@cindex exception handlers -Print a list of all the exception handlers that are active in the -current stack frame at the current point of execution. To see other -exception handlers, visit the associated frame (using the @code{up}, -@code{down}, or @code{frame} commands); then type @code{info catch}. -@xref{Exception Handling}. -@end table - -@node Source, Data, Stack, Top -@chapter Examining Source Files - -_GDBN__ can print parts of your program's source, since the debugging -information recorded in your program tells _GDBN__ what source files -were used to built it. When your program stops, _GDBN__ spontaneously -prints the line where it stopped. Likewise, when you select a stack -frame (@pxref{Selection}), _GDBN__ prints the line where execution in -that frame has stopped. You can print other portions of source files by -explicit command. - -If you use _GDBN__ through its GNU Emacs interface, you may prefer to -use Emacs facilities to view source; @pxref{Emacs}. - -@menu -* List:: Printing Source Lines -* Search:: Searching Source Files -* Source Path:: Specifying Source Directories -* Machine Code:: Source and Machine Code -@end menu - -@node List, Search, Source, Source -@section Printing Source Lines - -@kindex list -@kindex l -To print lines from a source file, use the @code{list} command -(abbreviated @code{l}). There are several ways to specify what part -of the file you want to print. - -Here are the forms of the @code{list} command most commonly used: - -@table @code -@item list @var{linenum} -Print ten lines centered around line number @var{linenum} in the -current source file. - -@item list @var{function} -Print ten lines centered around the beginning of function -@var{function}. - -@item list -Print ten more lines. If the last lines printed were printed with a -@code{list} command, this prints ten lines following the last lines -printed; however, if the last line printed was a solitary line printed -as part of displaying a stack frame (@pxref{Stack}), this prints ten -lines centered around that line. - -@item list - -Print ten lines just before the lines last printed. -@end table - -Repeating a @code{list} command with @key{RET} discards the argument, -so it is equivalent to typing just @code{list}. This is more useful -than listing the same lines again. An exception is made for an -argument of @samp{-}; that argument is preserved in repetition so that -each repetition moves up in the source file. - -@cindex linespec -In general, the @code{list} command expects you to supply zero, one or two -@dfn{linespecs}. Linespecs specify source lines; there are several ways -of writing them but the effect is always to specify some source line. -Here is a complete description of the possible arguments for @code{list}: - -@table @code -@item list @var{linespec} -Print ten lines centered around the line specified by @var{linespec}. - -@item list @var{first},@var{last} -Print lines from @var{first} to @var{last}. Both arguments are -linespecs. - -@item list ,@var{last} -Print ten lines ending with @var{last}. - -@item list @var{first}, -Print ten lines starting with @var{first}. - -@item list + -Print ten lines just after the lines last printed. - -@item list - -Print ten lines just before the lines last printed. - -@item list -As described in the preceding table. -@end table - -Here are the ways of specifying a single source line---all the -kinds of linespec. - -@table @code -@item @var{number} -Specifies line @var{number} of the current source file. -When a @code{list} command has two linespecs, this refers to -the same source file as the first linespec. - -@item +@var{offset} -Specifies the line @var{offset} lines after the last line printed. -When used as the second linespec in a @code{list} command that has -two, this specifies the line @var{offset} lines down from the -first linespec. - -@item -@var{offset} -Specifies the line @var{offset} lines before the last line printed. - -@item @var{filename}:@var{number} -Specifies line @var{number} in the source file @var{filename}. - -@item @var{function} -@c FIXME: "of the open-brace" is C-centric. When we add other langs... -Specifies the line of the open-brace that begins the body of the -function @var{function}. - -@item @var{filename}:@var{function} -Specifies the line of the open-brace that begins the body of the -function @var{function} in the file @var{filename}. You only need the -file name with a function name to avoid ambiguity when there are -identically named functions in different source files. - -@item *@var{address} -Specifies the line containing the program address @var{address}. -@var{address} may be any expression. -@end table - -@node Search, Source Path, List, Source -@section Searching Source Files -@cindex searching -@kindex reverse-search - -There are two commands for searching through the current source file for a -regular expression. - -@table @code -@item forward-search @var{regexp} -@itemx search @var{regexp} -@kindex search -@kindex forward-search -The command @samp{forward-search @var{regexp}} checks each line, starting -with the one following the last line listed, for a match for @var{regexp}. -It lists the line that is found. You can abbreviate the command name -as @code{fo}. The synonym @samp{search @var{regexp}} is also supported. - -@item reverse-search @var{regexp} -The command @samp{reverse-search @var{regexp}} checks each line, starting -with the one before the last line listed and going backward, for a match -for @var{regexp}. It lists the line that is found. You can abbreviate -this command as @code{rev}. -@end table - -@node Source Path, Machine Code, Search, Source -@section Specifying Source Directories - -@cindex source path -@cindex directories for source files -Executable programs sometimes do not record the directories of the source -files from which they were compiled, just the names. Even when they do, -the directories could be moved between the compilation and your debugging -session. _GDBN__ has a list of directories to search for source files; -this is called the @dfn{source path}. Each time _GDBN__ wants a source file, -it tries all the directories in the list, in the order they are present -in the list, until it finds a file with the desired name. Note that -the executable search path is @emph{not} used for this purpose. Neither is -the current working directory, unless it happens to be in the source -path. - -If _GDBN__ can't find a source file in the source path, and the object -program records a directory, _GDBN__ tries that directory too. If the -source path is empty, and there is no record of the compilation -directory, _GDBN__ will, as a last resort, look in the current -directory. - -Whenever you reset or rearrange the source path, _GDBN__ will clear out -any information it has cached about where source files are found, where -each line is in the file, etc. - -@kindex directory -When you start _GDBN__, its source path is empty. -To add other directories, use the @code{directory} command. - -@table @code -@item directory @var{dirname} @dots{} -Add directory @var{dirname} to the front of the source path. Several -directory names may be given to this command, separated by @samp{:} or -whitespace. You may specify a directory that is already in the source -path; this moves it forward, so it will be searched sooner. You can use -the string @samp{$cdir} to refer to the compilation directory (if one is -recorded), and @samp{$cwd} to refer to the current working directory. -@footnote{@samp{$cwd} is not the same as @samp{.}---the former tracks -the current working directory as it changes during your _GDBN__ session, -while the latter is immediately expanded to the current directory at the -time you add an entry to the source path.} - -@item directory -Reset the source path to empty again. This requires confirmation. - -@c RET-repeat for @code{directory} is explicitly disabled, but since -@c repeating it would be a no-op we don't say that. (thanks to RMS) - -@item show directories -@kindex show directories -Print the source path: show which directories it contains. -@end table - -If your source path is cluttered with directories that are no longer of -interest, _GDBN__ may sometimes cause confusion by finding the wrong -versions of source. You can correct the situation as follows: - -@enumerate -@item -Use @code{directory} with no argument to reset the source path to empty. - -@item -Use @code{directory} with suitable arguments to reinstall the -directories you want in the source path. You can add all the -directories in one command. -@end enumerate - -@node Machine Code, , Source Path, Source -@section Source and Machine Code -You can use the command @code{info line} to map source lines to program -addresses (and viceversa), and the command @code{disassemble} to display -a range of addresses as machine instructions. - -@table @code -@item info line @var{linespec} -@kindex info line -Print the starting and ending addresses of the compiled code for -source line @var{linespec}. You can specify source lines in any of the -ways understood by the @code{list} command (@pxref{List}). -@end table - -For example, we can use @code{info line} to inquire on where the object -code for the first line of function @code{m4_changequote} lies: -@smallexample -(_GDBP__) info line m4_changecom -Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350. -@end smallexample - -@noindent -We can also inquire (using @code{*@var{addr}} as the form for -@var{linespec}) what source line covers a particular address: -@smallexample -(_GDBP__) info line *0x63ff -Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404. -@end smallexample - -@kindex $_ -After @code{info line}, the default address for the @code{x} -command is changed to the starting address of the line, so that -@samp{x/i} is sufficient to begin examining the machine code -(@pxref{Memory}). Also, this address is saved as the value of the -convenience variable @code{$_} (@pxref{Convenience Vars}). - -@table @code -@kindex disassemble -@item disassemble -This specialized command is provided to dump a range of memory as -machine instructions. The default memory range is the function -surrounding the program counter of the selected frame. A single -argument to this command is a program counter value; the function -surrounding this value will be dumped. Two arguments (separated by one -or more spaces) specify a range of addresses (first inclusive, second -exclusive) to be dumped. -@end table - -We can use @code{disassemble} to inspect the object code -range shown in the last @code{info line} example: - -@smallexample -(_GDBP__) disas 0x63e4 0x6404 -Dump of assembler code from 0x63e4 to 0x6404: -0x63e4 <builtin_init+5340>: ble 0x63f8 <builtin_init+5360> -0x63e8 <builtin_init+5344>: sethi %hi(0x4c00), %o0 -0x63ec <builtin_init+5348>: ld [%i1+4], %o0 -0x63f0 <builtin_init+5352>: b 0x63fc <builtin_init+5364> -0x63f4 <builtin_init+5356>: ld [%o0+4], %o0 -0x63f8 <builtin_init+5360>: or %o0, 0x1a4, %o0 -0x63fc <builtin_init+5364>: call 0x9288 <path_search> -0x6400 <builtin_init+5368>: nop -End of assembler dump. -(_GDBP__) - -@end smallexample - -@node Data, Symbols, Source, Top -@chapter Examining Data - -@cindex printing data -@cindex examining data -@kindex print -@kindex inspect -@c "inspect" isn't quite a synonym if you're using Epoch, which we don't -@c document because it's nonstandard... Under Epoch it displays in a -@c different window or something like that. -The usual way to examine data in your program is with the @code{print} -command (abbreviated @code{p}), or its synonym @code{inspect}. It -evaluates and prints the value of any valid expression of the language -the program is written in (for now, C or C++). You type - -@example -print @var{exp} -@end example - -@noindent -where @var{exp} is any valid expression (in the source language), and -the value of @var{exp} is printed in a format appropriate to its data -type. - -A more low-level way of examining data is with the @code{x} command. -It examines data in memory at a specified address and prints it in a -specified format. @xref{Memory}. - -@menu -* Expressions:: Expressions -* Variables:: Program Variables -* Arrays:: Artificial Arrays -* Output formats:: Output formats -* Memory:: Examining Memory -* Auto Display:: Automatic Display -* Print Settings:: Print Settings -* Value History:: Value History -* Convenience Vars:: Convenience Variables -* Registers:: Registers -* Floating Point Hardware:: Floating Point Hardware -@end menu - -@node Expressions, Variables, Data, Data -@section Expressions -@cindex expressions -@code{print} and many other _GDBN__ commands accept an expression and -compute its value. Any kind of constant, variable or operator defined -by the programming language you are using is legal in an expression in -_GDBN__. This includes conditional expressions, function calls, casts -and string constants. It unfortunately does not include symbols defined -by preprocessor @code{#define} commands, or C++ expressions involving -@samp{::}, the name resolution operator. -@c FIXME: actually C++ a::b works except in obscure circumstances where it -@c FIXME...can conflict with GDB's own name scope resolution. - -Casts are supported in all languages, not just in C, because it is so -useful to cast a number into a pointer so as to examine a structure -at that address in memory. - -_GDBN__ supports three kinds of operator in addition to those of programming -languages: - -@table @code -@item @@ -@samp{@@} is a binary operator for treating parts of memory as arrays. -@xref{Arrays}, for more information. - -@item :: -@samp{::} allows you to specify a variable in terms of the file or -function where it is defined. @xref{Variables}. - -@item @{@var{type}@} @var{addr} -Refers to an object of type @var{type} stored at address @var{addr} in -memory. @var{addr} may be any expression whose value is an integer or -pointer (but parentheses are required around binary operators, just as in -a cast). This construct is allowed regardless of what kind of data is -normally supposed to reside at @var{addr}.@refill -@end table - -@node Variables, Arrays, Expressions, Data -@section Program Variables - -The most common kind of expression to use is the name of a variable -in your program. - -Variables in expressions are understood in the selected stack frame -(@pxref{Selection}); they must either be global (or static) or be visible -according to the scope rules of the programming language from the point of -execution in that frame. This means that in the function - -@example -foo (a) - int a; -@{ - bar (a); - @{ - int b = test (); - bar (b); - @} -@} -@end example - -@noindent -the variable @code{a} is usable whenever the program is executing -within the function @code{foo}, but the variable @code{b} is visible -only while the program is executing inside the block in which @code{b} -is declared. - -@cindex variable name conflict -There is an exception: you can refer to a variable or function whose -scope is a single source file even if the current execution point is not -in this file. But it is possible to have more than one such variable or -function with the same name (in different source files). If that happens, -referring to that name has unpredictable effects. If you wish, you can -specify a variable in a particular file, using the colon-colon notation: - -@cindex colon-colon -@kindex :: -@example -@var{file}::@var{variable} -@end example - -@noindent -Here @var{file} is the name of the source file whose variable you want. - -@cindex C++ name resolution -This use of @samp{::} is very rarely in conflict with the very similar -use of the same notation in C++. _GDBN__ also supports use of the C++ -name resolution operator in _GDBN__ expressions. - -@node Arrays, Output formats, Variables, Data -@section Artificial Arrays - -@cindex artificial array -@kindex @@ -It is often useful to print out several successive objects of the -same type in memory; a section of an array, or an array of -dynamically determined size for which only a pointer exists in the -program. - -This can be done by constructing an @dfn{artificial array} with the -binary operator @samp{@@}. The left operand of @samp{@@} should be -the first element of the desired array, as an individual object. -The right operand should be the desired length of the array. The result is -an array value whose elements are all of the type of the left argument. -The first element is actually the left argument; the second element -comes from bytes of memory immediately following those that hold the -first element, and so on. Here is an example. If a program says - -@example -int *array = (int *) malloc (len * sizeof (int)); -@end example - -@noindent -you can print the contents of @code{array} with - -@example -p *array@@len -@end example - -The left operand of @samp{@@} must reside in memory. Array values made -with @samp{@@} in this way behave just like other arrays in terms of -subscripting, and are coerced to pointers when used in expressions. -Artificial arrays most often appear in expressions via the value history -(@pxref{Value History}), after printing one out.) - -@node Output formats, Memory, Arrays, Data -@section Output formats - -@cindex formatted output -@cindex output formats -By default, _GDBN__ prints a value according to its data type. Sometimes -this is not what you want. For example, you might want to print a number -in hex, or a pointer in decimal. Or you might want to view data in memory -at a certain address as a character string or as an instruction. To do -these things, specify an @dfn{output format} when you print a value. - -The simplest use of output formats is to say how to print a value -already computed. This is done by starting the arguments of the -@code{print} command with a slash and a format letter. The format -letters supported are: - -@table @code -@item x -Regard the bits of the value as an integer, and print the integer in -hexadecimal. - -@item d -Print as integer in signed decimal. - -@item u -Print as integer in unsigned decimal. - -@item o -Print as integer in octal. - -@item t -Print as integer in binary. The letter @samp{t} stands for ``two''. - -@item a -Print as an address, both absolute in hex and as an offset from the -nearest preceding symbol. This format can be used to discover where (in -what function) an unknown address is located: -@example -(_GDBP__) p/a 0x54320 -_0__$3 = 0x54320 <_initialize_vx+396>_1__ -@end example - - -@item c -Regard as an integer and print it as a character constant. - -@item f -Regard the bits of the value as a floating point number and print -using typical floating point syntax. -@end table - -For example, to print the program counter in hex (@pxref{Registers}), type - -@example -p/x $pc -@end example - -@noindent -Note that no space is required before the slash; this is because command -names in _GDBN__ cannot contain a slash. - -To reprint the last value in the value history with a different format, -you can use the @code{print} command with just a format and no -expression. For example, @samp{p/x} reprints the last value in hex. - -@node Memory, Auto Display, Output formats, Data -@section Examining Memory - -@cindex examining memory -@table @code -@kindex x -@item x/@var{nfu} @var{expr} -The command @code{x} (for `examine') can be used to examine memory -without being constrained by your program's data types. You can specify -the unit size @var{u} of memory to inspect, and a repeat count @var{n} of how -many of those units to display. @code{x} understands the formats -@var{f} used by @code{print}; two additional formats, @samp{s} (string) -and @samp{i} (machine instruction) can be used without specifying a unit -size. -@end table - -For example, @samp{x/3uh 0x54320} is a request to display three halfwords -(@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}), -starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four -words (@samp{w}) of memory above the stack pointer (here, @samp{$sp}; -@pxref{Registers}) in hexadecimal (@samp{x}). - -Since the letters indicating unit sizes are all distinct from the -letters specifying output formats, you don't have to remember whether -unit size or format comes first; either order will work. The output -specifications @samp{4xw} and @samp{4wx} mean exactly the same thing. - -After the format specification, you supply an expression for the address -where _GDBN__ is to begin reading from memory. The expression need not -have a pointer value (though it may); it is always interpreted as an -integer address of a byte of memory. @xref{Expressions} for more -information on expressions. - -These are the memory units @var{u} you can specify with the @code{x} -command: - -@table @code -@item b -Examine individual bytes. - -@item h -Examine halfwords (two bytes each). - -@item w -Examine words (four bytes each). - -@cindex word -Many assemblers and cpu designers still use `word' for a 16-bit quantity, -as a holdover from specific predecessor machines of the 1970's that really -did use two-byte words. But more generally the term `word' has always -referred to the size of quantity that a machine normally operates on and -stores in its registers. This is 32 bits for all the machines that _GDBN__ -runs on. - -@item g -Examine giant words (8 bytes). -@end table - -You can combine these unit specifications with any of the formats -described for @code{print}. @xref{Output formats}. - -@code{x} has two additional output specifications which derive the unit -size from the data inspected: - -@table @code -@item s -Print a null-terminated string of characters. Any explicitly specified -unit size is ignored; instead, the unit is however many bytes it takes -to reach a null character (including the null character). - -@item i -Print a machine instruction in assembler syntax (or nearly). Any -specified unit size is ignored; the number of bytes in an instruction -varies depending on the type of machine, the opcode and the addressing -modes used. The command @code{disassemble} gives an alternative way of -inspecting machine instructions. @xref{Machine Code}. -@end table - -If you omit either the format @var{f} or the unit size @var{u}, @code{x} -will use the same one that was used last. If you don't use any letters -or digits after the slash, you can omit the slash as well. - -You can also omit the address to examine. Then the address used is just -after the last unit examined. This is why string and instruction -formats actually compute a unit-size based on the data: so that the next -string or instruction examined will start in the right place. - -When the @code{print} command shows a value that resides in memory, -@code{print} also sets the default address for the @code{x} command. -@code{info line} also sets the default for @code{x}, to the address of -the start of the machine code for the specified line (@pxref{Machine -Code}), and @code{info breakpoints} sets it to the address of the last -breakpoint listed (@pxref{Set Breaks}). - -When you use @key{RET} to repeat an @code{x} command, the address -specified previously (if any) is ignored, so that the repeated command -examines the successive locations in memory rather than the same ones. - -You can examine several consecutive units of memory with one command by -writing a repeat-count after the slash (before the format letters, if -any). Omitting the repeat count @var{n} displays one unit of the -appropriate size. The repeat count must be a decimal integer. It has -the same effect as repeating the @code{x} command @var{n} times except -that the output may be more compact, with several units per line. For -example, - -@example -x/10i $pc -@end example - -@noindent -prints ten instructions starting with the one to be executed next in the -selected frame. After doing this, you could print a further seven -instructions with - -@example -x/7 -@end example - -@noindent ----where the format and address are allowed to default. - -@kindex $_ -@kindex $__ -The addresses and contents printed by the @code{x} command are not put -in the value history because there is often too much of them and they -would get in the way. Instead, _GDBN__ makes these values available for -subsequent use in expressions as values of the convenience variables -@code{$_} and @code{$__}. After an @code{x} command, the last address -examined is available for use in expressions in the convenience variable -@code{$_}. The contents of that address, as examined, are available in -the convenience variable @code{$__}. - -If the @code{x} command has a repeat count, the address and contents saved -are from the last memory unit printed; this is not the same as the last -address printed if several units were printed on the last line of output. - -@node Auto Display, Print Settings, Memory, Data -@section Automatic Display -@cindex automatic display -@cindex display of expressions - -If you find that you want to print the value of an expression frequently -(to see how it changes), you might want to add it to the @dfn{automatic -display list} so that _GDBN__ will print its value each time the program stops. -Each expression added to the list is given a number to identify it; -to remove an expression from the list, you specify that number. -The automatic display looks like this: - -@example -2: foo = 38 -3: bar[5] = (struct hack *) 0x3804 -@end example - -@noindent -showing item numbers, expressions and their current values. As with -displays you request manually using @code{x} or @code{print}, you can -specify the output format you prefer; in fact, @code{display} decides -whether to use @code{print} or @code{x} depending on how elaborate your -format specification is---it uses @code{x} if you specify a unit size, -or one of the two formats (@samp{i} and @samp{s}) that are only -supported by @code{x}; otherwise it uses @code{print}. - -@table @code -@item display @var{exp} -@kindex display -Add the expression @var{exp} to the list of expressions to display -each time the program stops. @xref{Expressions}. - -@code{display} will not repeat if you press @key{RET} again after using it. - -@item display/@var{fmt} @var{exp} -For @var{fmt} specifying only a display format and not a size or -count, add the expression @var{exp} to the auto-display list but -arranges to display it each time in the specified format @var{fmt}. -@xref{Output formats}. - -@item display/@var{fmt} @var{addr} -For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a -number of units, add the expression @var{addr} as a memory address to -be examined each time the program stops. Examining means in effect -doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory}. -@end table - -For example, @samp{display/i $pc} can be helpful, to see the machine -instruction about to be executed each time execution stops (@samp{$pc} -is a common name for the program counter; @pxref{Registers}). - -@table @code -@item undisplay @var{dnums}@dots{} -@itemx delete display @var{dnums}@dots{} -@kindex delete display -@kindex undisplay -Remove item numbers @var{dnums} from the list of expressions to display. - -@code{undisplay} will not repeat if you press @key{RET} after using it. -(Otherwise you would just get the error @samp{No display number dots{}}.) - -@item disable display @var{dnums}@dots{} -@kindex disable display -Disable the display of item numbers @var{dnums}. A disabled display -item is not printed automatically, but is not forgotten. It may be -enabled again later. - -@item enable display @var{dnums}@dots{} -@kindex enable display -Enable display of item numbers @var{dnums}. It becomes effective once -again in auto display of its expression, until you specify otherwise. - -@item display -Display the current values of the expressions on the list, just as is -done when the program stops. - -@item info display -@kindex info display -Print the list of expressions previously set up to display -automatically, each one with its item number, but without showing the -values. This includes disabled expressions, which are marked as such. -It also includes expressions which would not be displayed right now -because they refer to automatic variables not currently available. -@end table - -If a display expression refers to local variables, then it does not make -sense outside the lexical context for which it was set up. Such an -expression is disabled when execution enters a context where one of its -variables is not defined. For example, if you give the command -@code{display last_char} while inside a function with an argument -@code{last_char}, then this argument will be displayed while the program -continues to stop inside that function. When it stops elsewhere---where -there is no variable @code{last_char}---display is disabled. The next time -your program stops where @code{last_char} is meaningful, you can enable the -display expression once again. - -@node Print Settings, Value History, Auto Display, Data -@section Print Settings - -@cindex format options -@cindex print settings -_GDBN__ provides the following ways to control how arrays, structures, -and symbols are printed. - -@noindent -These settings are useful for debugging programs in any language: - -@table @code -@item set print address -@item set print address on -@kindex set print address -_GDBN__ will print memory addresses showing the location of stack -traces, structure values, pointer values, breakpoints, and so forth, -even when it also displays the contents of those addresses. The default -is on. For example, this is what a stack frame display looks like, with -@code{set print address on}: -@smallexample -(_GDBP__) f -#0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>") - at input.c:530 -530 if (lquote != def_lquote) -@end smallexample - -@item set print address off -Do not print addresses when displaying their contents. For example, -this is the same stack frame displayed with @code{set print address off}: -@example -(_GDBP__) set print addr off -(_GDBP__) f -#0 set_quotes (lq="<<", rq=">>") at input.c:530 -530 if (lquote != def_lquote) -@end example - -@item show print address -@kindex show print address -Show whether or not addresses are to be printed. - -@item set print array -@itemx set print array on -@kindex set print array -_GDBN__ will pretty print arrays. This format is more convenient to read, -but uses more space. The default is off. - -@item set print array off. -Return to compressed format for arrays. - -@item show print array -@kindex show print array -Show whether compressed or pretty format is selected for displaying -arrays. - -@item set print elements @var{number-of-elements} -@kindex set print elements -If _GDBN__ is printing a large array, it will stop printing after it has -printed the number of elements set by the @code{set print elements} command. -This limit also applies to the display of strings. - -@item show print elements -@kindex show print elements -Display the number of elements of a large array that _GDBN__ will print -before losing patience. - -@item set print pretty on -@kindex set print pretty -Cause _GDBN__ to print structures in an indented format with one member per -line, like this: - -@example -$1 = @{ - next = 0x0, - flags = @{ - sweet = 1, - sour = 1 - @}, - meat = 0x54 "Pork" -@} -@end example - -@item set print pretty off -Cause _GDBN__ to print structures in a compact format, like this: - -@smallexample -$1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, meat \ -= 0x54 "Pork"@} -@end smallexample - -@noindent -This is the default format. - -@item show print pretty -@kindex show print pretty -Show which format _GDBN__ will use to print structures. - -@item set print sevenbit-strings on -Print using only seven-bit characters; if this option is set, -_GDBN__ will display any eight-bit characters (in strings or character -values) using the notation @code{\}@var{nnn}. For example, @kbd{M-a} is -displayed as @code{\341}. - -@item set print sevenbit-strings off -Print using either seven-bit or eight-bit characters, as required. This -is the default. - -@item show print sevenbit-strings -Show whether or not _GDBN__ will print only seven-bit characters. - -@item set print union on -@kindex set print union -Tell _GDBN__ to print unions which are contained in structures. This is the -default setting. - -@item set print union off -Tell _GDBN__ not to print unions which are contained in structures. - -@item show print union -@kindex show print union -Ask _GDBN__ whether or not it will print unions which are contained in -structures. - -For example, given the declarations - -@smallexample -typedef enum @{Tree, Bug@} Species; -typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms; -typedef enum @{Caterpillar, Cocoon, Butterfly@} Bug_forms; - -struct thing @{ - Species it; - union @{ - Tree_forms tree; - Bug_forms bug; - @} form; -@}; - -struct thing foo = @{Tree, @{Acorn@}@}; -@end smallexample - -@noindent -with @code{set print union on} in effect @samp{p foo} would print - -@smallexample -$1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@} -@end smallexample - -@noindent -and with @code{set print union off} in effect it would print - -@smallexample -$1 = @{it = Tree, form = @{...@}@} -@end smallexample -@end table - -@noindent -These settings are of interest when debugging C++ programs: - -@table @code -@item set print demangle -@itemx set print demangle on -@kindex set print demangle -Print C++ names in their source form rather than in the mangled form -in which they are passed to the assembler and linker for type-safe linkage. -The default is on. - -@item show print demangle -@kindex show print demangle -Show whether C++ names will be printed in mangled or demangled form. - -@item set print asm-demangle -@itemx set print asm-demangle on -@kindex set print asm-demangle -Print C++ names in their source form rather than their mangled form, even -in assembler code printouts such as instruction disassemblies. -The default is off. - -@item show print asm-demangle -@kindex show print asm-demangle -Show whether C++ names in assembly listings will be printed in mangled -or demangled form. - -@item set print object -@itemx set print object on -@kindex set print object -When displaying a pointer to an object, identify the @emph{actual} -(derived) type of the object rather than the @emph{declared} type, using -the virtual function table. - -@item set print object off -Display only the declared type of objects, without reference to the -virtual function table. This is the default setting. - -@item show print object -@kindex show print object -Show whether actual, or declared, object types will be displayed. - -@item set print vtbl -@itemx set print vtbl on -@kindex set print vtbl -Pretty print C++ virtual function tables. The default is off. - -@item set print vtbl off -Do not pretty print C++ virtual function tables. - -@item show print vtbl -@kindex show print vtbl -Show whether C++ virtual function tables are pretty printed, or not. - -@end table - -@node Value History, Convenience Vars, Print Settings, Data -@section Value History - -@cindex value history -Values printed by the @code{print} command are saved in _GDBN__'s @dfn{value -history} so that you can refer to them in other expressions. Values are -kept until the symbol table is re-read or discarded (for example with -the @code{file} or @code{symbol-file} commands). When the symbol table -changes, the value history is discarded, since the values may contain -pointers back to the types defined in the symbol table. - -@cindex @code{$} -@cindex @code{$$} -@cindex history number -The values printed are given @dfn{history numbers} for you to refer to them -by. These are successive integers starting with one. @code{print} shows you -the history number assigned to a value by printing @samp{$@var{num} = } -before the value; here @var{num} is the history number. - -To refer to any previous value, use @samp{$} followed by the value's -history number. The way @code{print} labels its output is designed to -remind you of this. Just @code{$} refers to the most recent value in -the history, and @code{$$} refers to the value before that. -@code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2} -is the value just prior to @code{$$}, @code{$$1} is equivalent to -@code{$$}, and @code{$$0} is equivalent to @code{$}. - -For example, suppose you have just printed a pointer to a structure and -want to see the contents of the structure. It suffices to type - -@example -p *$ -@end example - -If you have a chain of structures where the component @code{next} points -to the next one, you can print the contents of the next one with this: - -@example -p *$.next -@end example - -@noindent -You can print successive links in the chain by repeating this -command---which you can do by just typing @key{RET}. - -Note that the history records values, not expressions. If the value of -@code{x} is 4 and you type these commands: - -@example -print x -set x=5 -@end example - -@noindent -then the value recorded in the value history by the @code{print} command -remains 4 even though the value of @code{x} has changed. - -@table @code -@kindex show values -@item show values -Print the last ten values in the value history, with their item numbers. -This is like @samp{p@ $$9} repeated ten times, except that @code{show -values} does not change the history. - -@item show values @var{n} -Print ten history values centered on history item number @var{n}. - -@item show values + -Print ten history values just after the values last printed. If no more -values are available, produces no display. -@end table - -Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the -same effect as @samp{show values +}. - -@node Convenience Vars, Registers, Value History, Data -@section Convenience Variables - -@cindex convenience variables -_GDBN__ provides @dfn{convenience variables} that you can use within -_GDBN__ to hold on to a value and refer to it later. These variables -exist entirely within _GDBN__; they are not part of your program, and -setting a convenience variable has no direct effect on further execution -of your program. That's why you can use them freely. - -Convenience variables are prefixed with @samp{$}. Any name preceded by -@samp{$} can be used for a convenience variable, unless it is one of -the predefined machine-specific register names (@pxref{Registers}). -(Value history references, in contrast, are @emph{numbers} preceded -by @samp{$}. @xref{Value History}.) - -You can save a value in a convenience variable with an assignment -expression, just as you would set a variable in your program. Example: - -@example -set $foo = *object_ptr -@end example - -@noindent -would save in @code{$foo} the value contained in the object pointed to by -@code{object_ptr}. - -Using a convenience variable for the first time creates it; but its value -is @code{void} until you assign a new value. You can alter the value with -another assignment at any time. - -Convenience variables have no fixed types. You can assign a convenience -variable any type of value, including structures and arrays, even if -that variable already has a value of a different type. The convenience -variable, when used as an expression, has the type of its current value. - -@table @code -@item show convenience -@kindex show convenience -Print a list of convenience variables used so far, and their values. -Abbreviated @code{show con}. -@end table - -One of the ways to use a convenience variable is as a counter to be -incremented or a pointer to be advanced. For example, to print -a field from successive elements of an array of structures: - -_0__@example -set $i = 0 -print bar[$i++]->contents -@i{@dots{} repeat that command by typing @key{RET}.} -_1__@end example - -Some convenience variables are created automatically by _GDBN__ and given -values likely to be useful. - -@table @code -@item $_ -The variable @code{$_} is automatically set by the @code{x} command to -the last address examined (@pxref{Memory}). Other commands which -provide a default address for @code{x} to examine also set @code{$_} -to that address; these commands include @code{info line} and @code{info -breakpoint}. - -@item $__ -The variable @code{$__} is automatically set by the @code{x} command -to the value found in the last address examined. -@end table - -@node Registers, Floating Point Hardware, Convenience Vars, Data -@section Registers - -@cindex registers -Machine register contents can be referred to in expressions as variables -with names starting with @samp{$}. The names of registers are different -for each machine; use @code{info registers} to see the names used on -your machine. - -@table @code -@item info registers -@kindex info registers -Print the names and values of all registers (in the selected stack frame). - -@item info registers @var{regname} -Print the relativized value of register @var{regname}. @var{regname} -may be any register name valid on the machine you are using, with -or without the initial @samp{$}. -@end table - -The register names @code{$pc} and @code{$sp} are used on most machines -for the program counter register and the stack pointer. For example, -you could print the program counter in hex with -@example -p/x $pc -@end example - -@noindent -or print the instruction to be executed next with -@example -x/i $pc -@end example - -@noindent -or add four to the stack pointer with -@example -set $sp += 4 -@end example - -@noindent -The last is a way of removing one word from the stack, on machines where -stacks grow downward in memory (most machines, nowadays). This assumes -that the innermost stack frame is selected; setting @code{$sp} is -not allowed when other stack frames are selected. (To pop entire frames -off the stack, regardless of machine architecture, use @code{return}; -@pxref{Returning}.) - -Often @code{$fp} is used for a register that contains a pointer to the -current stack frame, and @code{$ps} is sometimes used for a register -that contains the processor status. These standard register names may -be available on your machine even though the @code{info registers} -command shows other names. For example, on the SPARC, @code{info -registers} displays the processor status register as @code{$psr} but you -can also refer to it as @code{$ps}. - -_GDBN__ always considers the contents of an ordinary register as an -integer when the register is examined in this way. Some machines have -special registers which can hold nothing but floating point; these -registers are considered to have floating point values. There is no way -to refer to the contents of an ordinary register as floating point value -(although you can @emph{print} it as a floating point value with -@samp{print/f $@var{regname}}). - -Some registers have distinct ``raw'' and ``virtual'' data formats. This -means that the data format in which the register contents are saved by -the operating system is not the same one that your program normally -sees. For example, the registers of the 68881 floating point -coprocessor are always saved in ``extended'' (raw) format, but all C -programs expect to work with ``double'' (virtual) format. In such -cases, _GDBN__ normally works with the virtual format only (the format that -makes sense for your program), but the @code{info registers} command -prints the data in both formats. - -Normally, register values are relative to the selected stack frame -(@pxref{Selection}). This means that you get the value that the -register would contain if all stack frames farther in were exited and -their saved registers restored. In order to see the true contents of -hardware registers, you must select the innermost frame (with -@samp{frame 0}). - -However, _GDBN__ must deduce where registers are saved, from the machine -code generated by your compiler. If some registers are not saved, or if -_GDBN__ is unable to locate the saved registers, the selected stack -frame will make no difference. - -@node Floating Point Hardware, , Registers, Data -@section Floating Point Hardware -@cindex floating point -Depending on the host machine architecture, _GDBN__ may be able to give -you more information about the status of the floating point hardware. - -@table @code -@item info float -@kindex info float -If available, provides hardware-dependent information about the floating -point unit. The exact contents and layout vary depending on the -floating point chip. -@end table -@c FIXME: this is a cop-out. Try to get examples, explanations. Only -@c FIXME...supported currently on arm's and 386's. Mark properly with -@c FIXME... m4 macros to isolate general statements from hardware-dep, -@c FIXME... at that point. - -@node Symbols, Altering, Data, Top -@chapter Examining the Symbol Table - -The commands described in this section allow you to inquire about the -symbols (names of variables, functions and types) defined in your -program. This information is inherent in the text of your program and -does not change as the program executes. _GDBN__ finds it in your -program's symbol table, in the file indicated when you started _GDBN__ -(@pxref{File Options}), or by one of the file-management commands -(@pxref{Files}). - -@table @code -@item info address @var{symbol} -@kindex info address -Describe where the data for @var{symbol} is stored. For a register -variable, this says which register it is kept in. For a non-register -local variable, this prints the stack-frame offset at which the variable -is always stored. - -Note the contrast with @samp{print &@var{symbol}}, which does not work -at all for a register variables, and for a stack local variable prints -the exact address of the current instantiation of the variable. - -@item whatis @var{exp} -@kindex whatis -Print the data type of expression @var{exp}. @var{exp} is not -actually evaluated, and any side-effecting operations (such as -assignments or function calls) inside it do not take place. -@xref{Expressions}. - -@item whatis -Print the data type of @code{$}, the last value in the value history. - -@item ptype @var{typename} -@kindex ptype -Print a description of data type @var{typename}. @var{typename} may be -the name of a type, or for C code it may have the form -@samp{struct @var{struct-tag}}, @samp{union @var{union-tag}} or -@samp{enum @var{enum-tag}}.@refill - -@item ptype @var{exp} -Print a description of the type of expression @var{exp}. @code{ptype} -differs from @code{whatis} by printing a detailed description, instead of just -the name of the type. For example, if your program declares a variable -as -@example -struct complex {double real; double imag;} v; -@end example -@noindent -compare the output of the two commands: -@example -(_GDBP__) whatis v -type = struct complex -(_GDBP__) ptype v -type = struct complex { - double real; - double imag; -} -@end example - -@item info types @var{regexp} -@itemx info types -@kindex info types -Print a brief description of all types whose name matches @var{regexp} -(or all types in your program, if you supply no argument). Each -complete typename is matched as though it were a complete line; thus, -@samp{i type value} gives information on all types in your program whose -name includes the string @code{value}, but @samp{i type ^value$} gives -information only on types whose complete name is @code{value}. - -This command differs from @code{ptype} in two ways: first, like -@code{whatis}, it does not print a detailed description; second, it -lists all source files where a type is defined. - -@item info source -@kindex info source -Show the name of the current source file---that is, the source file for -the function containing the current point of execution. - -@item info sources -@kindex info sources -Print the names of all source files in the program for which there is -debugging information, organized into two lists: those for which symbols -have been read in, and those for which symbols will be read in on -demand. -@c FIXME: above passive AND awkward! - -@item info functions -@kindex info functions -Print the names and data types of all defined functions. - -@item info functions @var{regexp} -Print the names and data types of all defined functions -whose names contain a match for regular expression @var{regexp}. -Thus, @samp{info fun step} finds all functions whose names -include @code{step}; @samp{info fun ^step} finds those whose names -start with @code{step}. - -@item info variables -@kindex info variables -Print the names and data types of all variables that are declared -outside of functions (i.e., excluding local variables). - -@item info variables @var{regexp} -Print the names and data types of all variables (except for local -variables) whose names contain a match for regular expression -@var{regexp}. - - -@ignore -This was never implemented. -@item info methods -@itemx info methods @var{regexp} -@kindex info methods -The @code{info methods} command permits the user to examine all defined -methods within C++ program, or (with the @var{regexp} argument) a -specific set of methods found in the various C++ classes. Many -C++ classes provide a large number of methods. Thus, the output -from the @code{ptype} command can be overwhelming and hard to use. The -@code{info-methods} command filters the methods, printing only those -which match the regular-expression @var{regexp}. -@end ignore - -@item printsyms @var{filename} -@kindex printsyms -Write a complete dump of the debugger's symbol data into the -file @var{filename}. -@end table - -@node Altering, _GDBN__ Files, Symbols, Top -@chapter Altering Execution - -Once you think you have found an error in the program, you might want to -find out for certain whether correcting the apparent error would lead to -correct results in the rest of the run. You can find the answer by -experiment, using the _GDBN__ features for altering execution of the -program. - -For example, you can store new values into variables or memory -locations, give the program a signal, restart it at a different address, -or even return prematurely from a function to its caller. - -@menu -* Assignment:: Assignment to Variables -* Jumping:: Continuing at a Different Address -* Signaling:: Giving the Program a Signal -* Returning:: Returning from a Function -* Calling:: Calling your Program's Functions -@end menu - -@node Assignment, Jumping, Altering, Altering -@section Assignment to Variables - -@cindex assignment -@cindex setting variables -To alter the value of a variable, evaluate an assignment expression. -@xref{Expressions}. For example, - -@example -print x=4 -@end example - -@noindent -would store the value 4 into the variable @code{x}, and then print the -value of the assignment expression (which is 4). All the assignment -operators of C are supported, including the increment operators -@samp{++} and @samp{--}, and combining assignments such as @samp{+=} and -_0__@samp{<<=}_1__. - -@kindex set -@kindex set variable -@cindex variables, setting -If you are not interested in seeing the value of the assignment, use the -@code{set} command instead of the @code{print} command. @code{set} is -really the same as @code{print} except that the expression's value is not -printed and is not put in the value history (@pxref{Value History}). The -expression is evaluated only for its effects. - -If the beginning of the argument string of the @code{set} command -appears identical to a @code{set} subcommand, use the @code{set -variable} command instead of just @code{set}. This command is identical -to @code{set} except for its lack of subcommands. For example, a -program might well have a variable @code{width}---which leads to -an error if we try to set a new value with just @samp{set width=13}, as -we might if @code{set width} didn't happen to be a _GDBN__ command: -@example -(_GDBP__) whatis width -type = double -(_GDBP__) p width -$4 = 13 -(_GDBP__) set width=47 -Invalid syntax in expression. -@end example -@noindent -The invalid expression, of course, is @samp{=47}. What we can do in -order to actually set our program's variable @code{width} is -@example -(_GDBP__) set var width=47 -@end example - -_GDBN__ allows more implicit conversions in assignments than C does; you can -freely store an integer value into a pointer variable or vice versa, and -any structure can be converted to any other structure that is the same -length or shorter. -@comment FIXME: how do structs align/pad in these conversions? -@comment /pesch@cygnus.com 18dec1990 - -To store values into arbitrary places in memory, use the @samp{@{@dots{}@}} -construct to generate a value of specified type at a specified address -(@pxref{Expressions}). For example, @code{@{int@}0x83040} refers -to memory location @code{0x83040} as an integer (which implies a certain size -and representation in memory), and - -@example -set @{int@}0x83040 = 4 -@end example - -@noindent -stores the value 4 into that memory location. - -@node Jumping, Signaling, Assignment, Altering -@section Continuing at a Different Address - -Ordinarily, when you continue the program, you do so at the place where -it stopped, with the @code{continue} command. You can instead continue at -an address of your own choosing, with the following commands: - -@table @code -@item jump @var{linespec} -@kindex jump -Resume execution at line @var{linespec}. Execution will stop -immediately if there is a breakpoint there. @xref{List} for a -description of the different forms of @var{linespec}. - -The @code{jump} command does not change the current stack frame, or -the stack pointer, or the contents of any memory location or any -register other than the program counter. If line @var{linespec} is in -a different function from the one currently executing, the results may -be bizarre if the two functions expect different patterns of arguments or -of local variables. For this reason, the @code{jump} command requests -confirmation if the specified line is not in the function currently -executing. However, even bizarre results are predictable if you are -well acquainted with the machine-language code of the program. - -@item jump *@var{address} -Resume execution at the instruction at address @var{address}. -@end table - -You can get much the same effect as the @code{jump} command by storing a -new value into the register @code{$pc}. The difference is that this -does not start the program running; it only changes the address where it -@emph{will} run when it is continued. For example, - -@example -set $pc = 0x485 -@end example - -@noindent -causes the next @code{continue} command or stepping command to execute at -address 0x485, rather than at the address where the program stopped. -@xref{Stepping}. - -The most common occasion to use the @code{jump} command is to back up, -perhaps with more breakpoints set, over a portion of a program that has -already executed, in order to examine its execution in more detail. - -@group -@node Signaling, Returning, Jumping, Altering -@section Giving the Program a Signal - -@table @code -@item signal @var{signalnum} -@kindex signal -Resume execution where the program stopped, but give it immediately the -signal number @var{signalnum}. - -Alternatively, if @var{signalnum} is zero, continue execution without -giving a signal. This is useful when the program stopped on account of -a signal and would ordinary see the signal when resumed with the -@code{continue} command; @samp{signal 0} causes it to resume without a -signal. - -@code{signal} does not repeat when you press @key{RET} a second time -after executing the command. -@end table -@end group - -@node Returning, Calling, Signaling, Altering -@section Returning from a Function - -@table @code -@item return -@itemx return @var{expression} -@cindex returning from a function -@kindex return -You can cancel execution of a function call with the @code{return} -command. If you give an -@var{expression} argument, its value is used as the function's return -value. -@end table - -When you use @code{return}, _GDBN__ discards the selected stack frame -(and all frames within it). You can think of this as making the -discarded frame return prematurely. If you wish to specify a value to -be returned, give that value as the argument to @code{return}. - -This pops the selected stack frame (@pxref{Selection}), and any other -frames inside of it, leaving its caller as the innermost remaining -frame. That frame becomes selected. The specified value is stored in -the registers used for returning values of functions. - -The @code{return} command does not resume execution; it leaves the -program stopped in the state that would exist if the function had just -returned. In contrast, the @code{finish} command (@pxref{Stepping}) -resumes execution until the selected stack frame returns naturally. - -@node Calling, , Returning, Altering -@section Calling your Program's Functions - -@cindex calling functions -@kindex call -@table @code -@item call @var{expr} -Evaluate the expression @var{expr} without displaying @code{void} -returned values. -@end table - -You can use this variant of the @code{print} command if you want to -execute a function from your program, but without cluttering the output -with @code{void} returned values. The result is printed and saved in -the value history, if it is not void. - -@node _GDBN__ Files, Targets, Altering, Top -@chapter _GDBN__'s Files - -@menu -* Files:: Commands to Specify Files -* Symbol Errors:: Errors Reading Symbol Files -@end menu - -@node Files, Symbol Errors, _GDBN__ Files, _GDBN__ Files -@section Commands to Specify Files -@cindex core dump file -@cindex symbol table -_GDBN__ needs to know the file name of the program to be debugged, both in -order to read its symbol table and in order to start the program. To -debug a core dump of a previous run, _GDBN__ must be told the file name of -the core dump. - -The usual way to specify the executable and core dump file names is with -the command arguments given when you start _GDBN__, as discussed in -@pxref{Invocation}. - -Occasionally it is necessary to change to a different file during a -_GDBN__ session. Or you may run _GDBN__ and forget to specify the files you -want to use. In these situations the _GDBN__ commands to specify new files -are useful. - -@table @code -@item file @var{filename} -@cindex executable file -@kindex file -Use @var{filename} as the program to be debugged. It is read for its -symbols and for the contents of pure memory. It is also the program -executed when you use the @code{run} command. If you do not specify a -directory and the file is not found in _GDBN__'s working directory, - -_GDBN__ uses the environment variable @code{PATH} as a list of -directories to search, just as the shell does when looking for a program -to run. You can change the value of this variable, for both _GDBN__ and -your program, using the @code{path} command. - -@code{file} with no argument makes _GDBN__ discard any information it -has on both executable file and the symbol table. - -@item exec-file @var{filename} -@kindex exec-file -Specify that the program to be run (but not the symbol table) is found -in @var{filename}. _GDBN__ will search the environment variable @code{PATH} -if necessary to locate the program. - -@item symbol-file @var{filename} -@kindex symbol-file -Read symbol table information from file @var{filename}. @code{PATH} is -searched when necessary. Use the @code{file} command to get both symbol -table and program to run from the same file. - -@code{symbol-file} with no argument clears out _GDBN__'s information on your -program's symbol table. - -The @code{symbol-file} command causes _GDBN__ to forget the contents of its -convenience variables, the value history, and all breakpoints and -auto-display expressions. This is because they may contain pointers to -the internal data recording symbols and data types, which are part of -the old symbol table data being discarded inside _GDBN__. - -@code{symbol-file} will not repeat if you press @key{RET} again after -executing it once. - -On some kinds of object files, the @code{symbol-file} command does not -actually read the symbol table in full right away. Instead, it scans -the symbol table quickly to find which source files and which symbols -are present. The details are read later, one source file at a time, -when they are needed. - -The purpose of this two-stage reading strategy is to make _GDBN__ start up -faster. For the most part, it is invisible except for occasional pauses -while the symbol table details for a particular source file are being -read. (The @code{set verbose} command can turn these pauses into -messages if desired. @xref{Messages/Warnings}). - -When the symbol table is stored in COFF format, @code{symbol-file} does -read the symbol table data in full right away. We haven't implemented -the two-stage strategy for COFF yet. - -When _GDBN__ is configured for a particular environment, it will -understand debugging information in whatever format is the standard -generated for that environment; you may use either a GNU compiler, or -other compilers that adhere to the local conventions. Best results are -usually obtained from GNU compilers; for example, using @code{_GCC__} -you can generate debugging information for optimized code. - -@item core-file @var{filename} -@itemx core @var{filename} -@kindex core -@kindex core-file -Specify the whereabouts of a core dump file to be used as the ``contents -of memory''. Traditionally, core files contain only some parts of the -address space of the process that generated them; _GDBN__ can access the -executable file itself for other parts. - -@code{core-file} with no argument specifies that no core file is -to be used. - -Note that the core file is ignored when your program is actually running -under _GDBN__. So, if you have been running the program and you wish to -debug a core file instead, you must kill the subprocess in which the -program is running. To do this, use the @code{kill} command -(@pxref{Kill Process}). - -@item load @var{filename} -@kindex load -_if__(_GENERIC__) -Depending on what remote debugging facilities are configured into -_GDBN__, the @code{load} command may be available. Where it exists, it -is meant to make @var{filename} (an executable) available for debugging -on the remote system---by downloading, or dynamic linking, for example. -@code{load} also records @var{filename}'s symbol table in _GDBN__, like -the @code{add-symbol-file} command. - -If @code{load} is not available on your _GDBN__, attempting to execute -it gets the error message ``@code{You can't do that when your target is -@dots{}}'' -_fi__(_GENERIC__) - -_if__(_VXWORKS__) -On VxWorks, @code{load} will dynamically link @var{filename} on the -current target system as well as adding its symbols in _GDBN__. -_fi__(_VXWORKS__) - -_if__(_I960__) -@cindex download to Nindy-960 -With the Nindy interface to an Intel 960 board, @code{load} will -download @var{filename} to the 960 as well as adding its symbols in -_GDBN__. -_fi__(_I960__) - -@code{load} will not repeat if you press @key{RET} again after using it. - -@item add-symbol-file @var{filename} @var{address} -@kindex add-symbol-file -@cindex dynamic linking -The @code{add-symbol-file} command reads additional symbol table information -from the file @var{filename}. You would use this command when that file -has been dynamically loaded (by some other means) into the program that -is running. @var{address} should be the memory address at which the -file has been loaded; _GDBN__ cannot figure this out for itself. - -The symbol table of the file @var{filename} is added to the symbol table -originally read with the @code{symbol-file} command. You can use the -@code{add-symbol-file} command any number of times; the new symbol data thus -read keeps adding to the old. To discard all old symbol data instead, -use the @code{symbol-file} command. - -@code{add-symbol-file} will not repeat if you press @key{RET} after using it. - -@item info files -@itemx info target -@kindex info files -@kindex info target -@code{info files} and @code{info target} are synonymous; both print the -current targets (@pxref{Targets}), including the names of the executable -and core dump files currently in use by _GDBN__, and the files from -which symbols were loaded. The command @code{help targets} lists all -possible targets rather than current ones. - -@end table - -All file-specifying commands allow both absolute and relative file names -as arguments. _GDBN__ always converts the file name to an absolute path -name and remembers it that way. - -@kindex sharedlibrary -@kindex share -@cindex shared libraries - -_GDBN__ supports the SunOS shared library format. Symbols from a shared -library cannot be referenced before the shared library has been linked -with the program. (That is to say, until after you type @code{run} and -the function @code{main} has been entered; or when examining core -files.) Once the shared library has been linked in, you can use the -following commands: - -@table @code -@item sharedlibrary @var{regex} -@itemx share @var{regex} -Load shared object library symbols for files matching a UNIX regular -expression. - -@item share -@itemx sharedlibrary -Load symbols for all shared libraries. - -@item info share -@itemx info sharedlibrary -@kindex info sharedlibrary -@kindex info share -Print the names of the shared libraries which you have loaded with the -@code{sharedlibrary} command. -@end table - -@code{sharedlibrary} does not repeat automatically when you press -@key{RET} after using it once. - -@node Symbol Errors, , Files, _GDBN__ Files -@section Errors Reading Symbol Files -While a symbol file is being read, _GDBN__ will occasionally encounter -problems, such as symbol types it does not recognize, or known bugs in -compiler output. By default, it prints one message about each such -type of problem, no matter how many times the problem occurs. You can -ask it to print more messages, to see how many times the problems occur, -or can shut the messages off entirely, with the @code{set -complaints} command (@xref{Messages/Warnings}). - -The messages currently printed, and their meanings, are: - -@table @code -@item inner block not inside outer block in @var{symbol} - -The symbol information shows where symbol scopes begin and end -(such as at the start of a function or a block of statements). This -error indicates that an inner scope block is not fully contained -in its outer scope blocks. - -_GDBN__ circumvents the problem by treating the inner block as if it had -the same scope as the outer block. In the error message, @var{symbol} -may be shown as ``@code{(don't know)}'' if the outer block is not a -function. - -@item block at @var{address} out of order - -The symbol information for symbol scope blocks should occur in -order of increasing addresses. This error indicates that it does not -do so. - -_GDBN__ does not circumvent this problem, and will have trouble locating -symbols in the source file whose symbols being read. (You can often -determine what source file is affected by specifying @code{set verbose -on}. @xref{Messages/Warnings}.) - -@item bad block start address patched - -The symbol information for a symbol scope block has a start address -smaller than the address of the preceding source line. This is known -to occur in the SunOS 4.1.1 (and earlier) C compiler. - -_GDBN__ circumvents the problem by treating the symbol scope block as -starting on the previous source line. - -@c @item{encountered DBX-style class variable debugging information. -@c You seem to have compiled your program with "g++ -g0" instead of "g++ -g". -@c Therefore _GDBN__ will not know about your class variables} -@c -@c This error indicates that the symbol information produced for a C++ -@c program includes zero-size fields, which indicated static fields in -@c a previous release of the G++ compiler. This message is probably -@c obsolete. -@c -@item bad string table offset in symbol @var{n} - -@cindex foo -Symbol number @var{n} contains a pointer into the string table which is -larger than the size of the string table. - -_GDBN__ circumvents the problem by considering the symbol to have the -name @code{foo}, which may cause other problems if many symbols end up -with this name. - -@item unknown symbol type @code{0x@var{nn}} - -The symbol information contains new data types that _GDBN__ does not yet -know how to read. @code{0x@var{nn}} is the symbol type of the misunderstood -information, in hexadecimal. - -_GDBN__ circumvents the error by ignoring this symbol information. This -will usually allow the program to be debugged, though certain symbols -will not be accessible. If you encounter such a problem and feel like -debugging it, you can debug @code{_GDBP__} with itself, breakpoint on -@code{complain}, then go up to the function @code{read_dbx_symtab} and -examine @code{*bufp} to see the symbol. - -@item stub type has NULL name -_GDBN__ could not find the full definition for a struct or class. - -@ignore -@c this is #if 0'd in dbxread.c as of (at least!) 17 may 1991 -@item const/volatile indicator missing, got '@var{X}' - -The symbol information for a C++ member function is missing some -information that the compiler should have output for it. -@end ignore - -@item C++ type mismatch between compiler and debugger - -The debugger could not parse a type specification output by the compiler -for some C++ object. - -@end table - -@node Targets, Controlling _GDBN__, _GDBN__ Files, Top -@chapter Specifying a Debugging Target -@cindex debugging target -@kindex target -A @dfn{target} is an interface between the debugger and a particular -kind of file or process. - -Often, you will be able to run _GDBN__ in the same host environment as the -program you are debugging; in that case, the debugging target can just be -specified as a side effect of the @code{file} or @code{core} commands. -When you need more flexibility---for example, running _GDBN__ on a -physically separate host, controlling standalone systems over a -serial port, or realtime systems over a TCP/IP connection---you can use -the @code{target} command. - -@menu -* Active Targets:: Active Targets -* Target Commands:: Commands for Managing Targets -* Remote:: Remote Debugging -@end menu - -@node Active Targets, Target Commands, Targets, Targets -@section Active Targets -@cindex stacking targets -@cindex active targets -@cindex multiple targets - -Targets are managed in three @dfn{strata} that correspond to different -classes of target: processes, core files, and executable files. This -allows you to (for example) start a process and inspect its activity -without abandoning your work on a core file. - -More than one target can potentially respond to a request. In -particular, when you access memory _GDBN__ will examine the three strata of -targets until it finds a target that can handle that particular address. -Strata are always examined in a fixed order: first a process if there is -one, then a core file if there is one, and finally an executable file if -there is one of those. - -When you specify a new target in a given stratum, it replaces any target -previously in that stratum. - -To get rid of a target without replacing it, use the @code{detach} -command. The related command @code{attach} provides you with a way of -choosing a particular running process as a new target. @xref{Attach}. - -@node Target Commands, Remote, Active Targets, Targets -@section Commands for Managing Targets - -@table @code -@item target @var{type} @var{parameters} -Connects the _GDBN__ host environment to a target machine or process. A -target is typically a protocol for talking to debugging facilities. You -use the argument @var{type} to specify the type or protocol of the -target machine. - -Further @var{parameters} are interpreted by the target protocol, but -typically include things like device names or host names to connect -with, process numbers, and baud rates. - -The @code{target} command will not repeat if you press @key{RET} again -after executing the command. - -@item help target -@kindex help target -Displays the names of all targets available. To display targets -currently selected, use either @code{info target} or @code{info files} -(@pxref{Files}). - -@item help target @var{name} -Describe a particular target, including any parameters necessary to -select it. -@end table - -Here are some common targets (available, or not, depending on the _GDBN__ -configuration): - -@table @code -@item target exec @var{prog} -@kindex target exec -An executable file. @samp{target exec @var{prog}} is the same as -@samp{exec-file @var{prog}}. - -@item target core @var{filename} -@kindex target core -A core dump file. @samp{target core @var{filename}} is the same as -@samp{core-file @var{filename}}. - -@item target remote @var{dev} -@kindex target remote -Remote serial target in _GDBN__-specific protocol. The argument @var{dev} -specifies what serial device to use for the connection (e.g. -@file{/dev/ttya}). @xref{Remote}. - -_if__(_AMD29K__) -@item target amd-eb @var{dev} @var{speed} @var{PROG} -@kindex target amd-eb -@cindex AMD EB29K -Remote PC-resident AMD EB29K board, attached over serial lines. -@var{dev} is the serial device, as for @code{target remote}; -@var{speed} allows you to specify the linespeed; and @var{PROG} is the -name of the program to be debugged, as it appears to DOS on the PC. -@xref{EB29K Remote}. - -_fi__(_AMD29K__) -_if__(_I960__) -@item target nindy @var{devicename} -@kindex target nindy -An Intel 960 board controlled by a Nindy Monitor. @var{devicename} is -the name of the serial device to use for the connection, e.g. -@file{/dev/ttya}. @xref{i960-Nindy Remote}. - -_fi__(_I960__) -_if__(_VXWORKS__) -@item target vxworks @var{machinename} -@kindex target vxworks -A VxWorks system, attached via TCP/IP. The argument @var{machinename} -is the target system's machine name or IP address. -@xref{VxWorks Remote}. -_fi__(_VXWORKS__) -@end table - -_if__(_GENERIC__) -Different targets are available on different configurations of _GDBN__; your -configuration may have more or fewer targets. -_fi__(_GENERIC__) - -@node Remote, , Target Commands, Targets -@section Remote Debugging -@cindex remote debugging - -_if__(_GENERIC__) -@menu -_undivert__(1) -@end menu -_fi__(_GENERIC__) - -If you are trying to debug a program running on a machine that can't run -_GDBN__ in the usual way, it is often useful to use remote debugging. For -example, you might use remote debugging on an operating system kernel, or on -a small system which does not have a general purpose operating system -powerful enough to run a full-featured debugger. - -Some configurations of _GDBN__ have special serial or TCP/IP interfaces -to make this work with particular debugging targets. In addition, -_GDBN__ comes with a generic serial protocol (specific to _GDBN__, but -not specific to any particular target system) which you can use if you -write the remote stubs---the code that will run on the remote system to -communicate with _GDBN__. - -To use the _GDBN__ remote serial protocol, the program to be debugged on -the remote machine needs to contain a debugging stub which talks to -_GDBN__ over the serial line. Several working remote stubs are -distributed with _GDBN__; see the @file{README} file in the _GDBN__ -distribution for more information. - -For details of this communication protocol, see the comments in the -_GDBN__ source file @file{remote.c}. - -To start remote debugging, first run _GDBN__ and specify as an executable file -the program that is running in the remote machine. This tells _GDBN__ how -to find the program's symbols and the contents of its pure text. Then -establish communication using the @code{target remote} command with a device -name as an argument. For example: - -@example -target remote /dev/ttyb -@end example - -@noindent -if the serial line is connected to the device named @file{/dev/ttyb}. This -will stop the remote machine if it is not already stopped. - -Now you can use all the usual commands to examine and change data and to -step and continue the remote program. - -To resume the remote program and stop debugging it, use the @code{detach} -command. - -Other remote targets may be available in your -configuration of _GDBN__; use @code{help targets} to list them. - -_if__(_GENERIC__) -_undivert__(2) -@c Text on starting up GDB in various specific cases; it goes up front -@c in manuals configured for any of those particular situations, here -@c otherwise. -_fi__(_GENERIC__) - -@node Controlling _GDBN__, Sequences, Targets, Top -@chapter Controlling _GDBN__ - -You can alter many aspects of _GDBN__'s interaction with you by using -the @code{set} command. For commands controlling how _GDBN__ displays -data, @pxref{Print Settings}; other settings are described here. - -@menu -* Prompt:: Prompt -* Editing:: Command Editing -* History:: Command History -* Screen Size:: Screen Size -* Numbers:: Numbers -* Messages/Warnings:: Optional Warnings and Messages -@end menu - -@node Prompt, Editing, Controlling _GDBN__, Controlling _GDBN__ -@section Prompt -@cindex prompt -_GDBN__ indicates its readiness to read a command by printing a string -called the @dfn{prompt}. This string is normally @samp{(_GDBP__)}. You -can change the prompt string with the @code{set prompt} command. For -instance, when debugging _GDBN__ with _GDBN__, it is useful to change -the prompt in one of the _GDBN__<>s so that you can always tell which -one you are talking to. - -@table @code -@item set prompt @var{newprompt} -@kindex set prompt -Directs _GDBN__ to use @var{newprompt} as its prompt string henceforth. -@kindex show prompt -@item show prompt -Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}} -@end table - -@node Editing, History, Prompt, Controlling _GDBN__ -@section Command Editing -@cindex readline -@cindex command line editing -_GDBN__ reads its input commands via the @dfn{readline} interface. This -GNU library provides consistent behavior for programs which provide a -command line interface to the user. Advantages are @code{emacs}-style -or @code{vi}-style inline editing of commands, @code{csh}-like history -substitution, and a storage and recall of command history across -debugging sessions. - -You may control the behavior of command line editing in _GDBN__ with the -command @code{set}. - -@table @code -@kindex set editing -@cindex editing -@item set editing -@itemx set editing on -Enable command line editing (enabled by default). - -@item set editing off -Disable command line editing. - -@kindex show editing -@item show editing -Show whether command line editing is enabled. - -@node History, Screen Size, Editing, Controlling _GDBN__ -@section Command History -@cindex history substitution -@cindex history file -@kindex set history filename -@item set history filename @var{fname} -Set the name of the _GDBN__ command history file to @var{fname}. This is -the file from which _GDBN__ will read an initial command history -list or to which it will write this list when it exits. This list is -accessed through history expansion or through the history -command editing characters listed below. This file defaults to the -value of the environment variable @code{GDBHISTFILE}, or to -@file{./.gdb_history} if this variable is not set. - -@cindex history save -@kindex set history save -@item set history save -@itemx set history save on -Record command history in a file, whose name may be specified with the -@code{set history filename} command. By default, this option is disabled. - -@item set history save off -Stop recording command history in a file. - -@cindex history size -@kindex set history size -@item set history size @var{size} -Set the number of commands which _GDBN__ will keep in its history list. -This defaults to the value of the environment variable -@code{HISTSIZE}, or to 256 if this variable is not set. -@end table - -@cindex history expansion -History expansion assigns special meaning to the character @kbd{!}. -@iftex -(@xref{Event Designators}.) -@end iftex -Since @kbd{!} is also the logical not operator in C, history expansion -is off by default. If you decide to enable history expansion with the -@code{set history expansion on} command, you may sometimes need to -follow @kbd{!} (when it is used as logical not, in an expression) with -a space or a tab to prevent it from being expanded. The readline -history facilities will not attempt substitution on the strings -@kbd{!=} and @kbd{!(}, even when history expansion is enabled. - -The commands to control history expansion are: - -@table @code - -@kindex set history expansion -@item set history expansion on -@itemx set history expansion -Enable history expansion. History expansion is off by default. - -@item set history expansion off -Disable history expansion. - -The readline code comes with more complete documentation of -editing and history expansion features. Users unfamiliar with @code{emacs} -or @code{vi} may wish to read it. -@iftex -@xref{Command Line Editing}. -@end iftex - -@group -@kindex show history -@item show history -@itemx show history filename -@itemx show history save -@itemx show history size -@itemx show history expansion -These commands display the state of the _GDBN__ history parameters. -@code{show history} by itself displays all four states. -@end group - -@end table - -@table @code -@kindex show commands -@item show commands -Display the last ten commands in the command history. - -@item show commands @var{n} -Print ten commands centered on command number @var{n}. - -@item show commands + -Print ten commands just after the commands last printed. - -@end table - -@node Screen Size, Numbers, History, Controlling _GDBN__ -@section Screen Size -@cindex size of screen -@cindex pauses in output -Certain commands to _GDBN__ may produce large amounts of information -output to the screen. To help you read all of it, _GDBN__ pauses and -asks you for input at the end of each page of output. Type @key{RET} -when you want to continue the output. _GDBN__ also uses the screen -width setting to determine when to wrap lines of output. Depending on -what is being printed, it tries to break the line at a readable place, -rather than simply letting it overflow onto the following line. - -Normally _GDBN__ knows the size of the screen from the termcap data base -together with the value of the @code{TERM} environment variable and the -@code{stty rows} and @code{stty cols} settings. If this is not correct, -you can override it with the @code{set height} and @code{set -width} commands: - -@table @code -@item set height @var{lpp} -@itemx show height -@itemx set width @var{cpl} -@itemx show width -@kindex set height -@kindex set width -@kindex show width -@kindex show height -These @code{set} commands specify a screen height of @var{lpp} lines and -a screen width of @var{cpl} characters. The associated @code{show} -commands display the current settings. - -If you specify a height of zero lines, _GDBN__ will not pause during output -no matter how long the output is. This is useful if output is to a file -or to an editor buffer. -@end table - -@node Numbers, Messages/Warnings, Screen Size, Controlling _GDBN__ -@section Numbers -@cindex number representation -@cindex entering numbers -You can always enter numbers in octal, decimal, or hexadecimal in _GDBN__ by -the usual conventions: octal numbers begin with @samp{0}, decimal -numbers end with @samp{.}, and hexadecimal numbers begin with @samp{0x}. -Numbers that begin with none of these are, by default, entered in base -10; likewise, the default display for numbers---when no particular -format is specified---is base 10. You can change the default base for -both input and output with the @code{set radix} command. - -@table @code -@kindex set radix -@item set radix @var{base} -Set the default base for numeric input and display. Supported choices -for @var{base} are decimal 8, 10, 16. @var{base} must itself be -specified either unambiguously or using the current default radix; for -example, any of - -@example -set radix 012 -set radix 10. -set radix 0xa -@end example - -@noindent -will set the base to decimal. On the other hand, @samp{set radix 10} -will leave the radix unchanged no matter what it was. - -@kindex show radix -@item show radix -Display the current default base for numeric input and display. - -@end table - -@node Messages/Warnings, , Numbers, Controlling _GDBN__ -@section Optional Warnings and Messages -By default, _GDBN__ is silent about its inner workings. If you are running -on a slow machine, you may want to use the @code{set verbose} command. -It will make _GDBN__ tell you when it does a lengthy internal operation, so -you won't think it has crashed. - -Currently, the messages controlled by @code{set verbose} are those which -announce that the symbol table for a source file is being read -(@pxref{Files}, in the description of the command -@code{symbol-file}). -@c The following is the right way to do it, but emacs 18.55 doesn't support -@c @ref, and neither the emacs lisp manual version of texinfmt or makeinfo -@c is released. -@ignore -see @code{symbol-file} in @ref{Files}). -@end ignore - -@table @code -@kindex set verbose -@item set verbose on -Enables _GDBN__'s output of certain informational messages. - -@item set verbose off -Disables _GDBN__'s output of certain informational messages. - -@kindex show verbose -@item show verbose -Displays whether @code{set verbose} is on or off. -@end table - -By default, if _GDBN__ encounters bugs in the symbol table of an object file, -it prints a single message about each type of problem it finds, then -shuts up (@pxref{Symbol Errors}). You can suppress these messages, or allow more than one such -message to be printed if you want to see how frequent the problems are. - -@table @code -@kindex set complaints -@item set complaints @var{limit} -Permits _GDBN__ to output @var{limit} complaints about each type of unusual -symbols before becoming silent about the problem. Set @var{limit} to -zero to suppress all complaints; set it to a large number to prevent -complaints from being suppressed. - -@kindex show complaints -@item show complaints -Displays how many symbol complaints _GDBN__ is permitted to produce. -@end table - -By default, _GDBN__ is cautious, and asks what sometimes seem to be a -lot of stupid questions to confirm certain commands. For example, if -you try to run a program which is already running: -@example -(_GDBP__) run -The program being debugged has been started already. -Start it from the beginning? (y or n) -@end example - -If you're willing to unflinchingly face the consequences of your own -commands, you can disable this ``feature'': - -@table @code -@kindex set confirm -@cindex flinching -@cindex confirmation -@cindex stupid questions -@item set confirm off -Disables confirmation requests. - -@item set confirm on -Enables confirmation requests (the default). - -@item show confirm -@kindex show confirm -Displays state of confirmation requests. -@end table - -@node Sequences, Emacs, Controlling _GDBN__, Top -@chapter Canned Sequences of Commands - -Aside from breakpoint commands (@pxref{Break Commands}), _GDBN__ provides two -ways to store sequences of commands for execution as a unit: -user-defined commands and command files. - -@menu -* Define:: User-Defined Commands -* Command Files:: Command Files -* Output:: Commands for Controlled Output -@end menu - -@node Define, Command Files, Sequences, Sequences -@section User-Defined Commands - -@cindex user-defined command -A @dfn{user-defined command} is a sequence of _GDBN__ commands to which you -assign a new name as a command. This is done with the @code{define} -command. - -@table @code -@item define @var{commandname} -@kindex define -Define a command named @var{commandname}. If there is already a command -by that name, you are asked to confirm that you want to redefine it. - -The definition of the command is made up of other _GDBN__ command lines, -which are given following the @code{define} command. The end of these -commands is marked by a line containing @code{end}. - -@item document @var{commandname} -@kindex document -Give documentation to the user-defined command @var{commandname}. The -command @var{commandname} must already be defined. This command reads -lines of documentation just as @code{define} reads the lines of the -command definition, ending with @code{end}. After the @code{document} -command is finished, @code{help} on command @var{commandname} will print -the documentation you have specified. - -You may use the @code{document} command again to change the -documentation of a command. Redefining the command with @code{define} -does not change the documentation. - -@item help user-defined -@kindex help user-defined -List all user-defined commands, with the first line of the documentation -(if any) for each. - -@item info user -@itemx info user @var{commandname} -@kindex info user -Display the _GDBN__ commands used to define @var{commandname} (but not its -documentation). If no @var{commandname} is given, display the -definitions for all user-defined commands. -@end table - -User-defined commands do not take arguments. When they are executed, the -commands of the definition are not printed. An error in any command -stops execution of the user-defined command. - -Commands that would ask for confirmation if used interactively proceed -without asking when used inside a user-defined command. Many _GDBN__ commands -that normally print messages to say what they are doing omit the messages -when used in a user-defined command. - -@node Command Files, Output, Define, Sequences -@section Command Files - -@cindex command files -A command file for _GDBN__ is a file of lines that are _GDBN__ commands. Comments -(lines starting with @kbd{#}) may also be included. An empty line in a -command file does nothing; it does not mean to repeat the last command, as -it would from the terminal. - -@cindex init file -@cindex @file{_GDBINIT__} -When you start _GDBN__, it automatically executes commands from its -@dfn{init files}. These are files named @file{_GDBINIT__}. _GDBN__ -reads the init file (if any) in your home directory and then the init -file (if any) in the current working directory. (The init files are not -executed if you use the @samp{-nx} option; @pxref{Mode Options}.) You -can also request the execution of a command file with the @code{source} -command: - -@table @code -@item source @var{filename} -@kindex source -Execute the command file @var{filename}. -@end table - -The lines in a command file are executed sequentially. They are not -printed as they are executed. An error in any command terminates execution -of the command file. - -Commands that would ask for confirmation if used interactively proceed -without asking when used in a command file. Many _GDBN__ commands that -normally print messages to say what they are doing omit the messages -when called from command files. - -@node Output, , Command Files, Sequences -@section Commands for Controlled Output - -During the execution of a command file or a user-defined command, normal -_GDBN__ output is suppressed; the only output that appears is what is -explicitly printed by the commands in the definition. This section -describes three commands useful for generating exactly the output you -want. - -@table @code -@item echo @var{text} -@kindex echo -@c I don't consider backslash-space a standard C escape sequence -@c because it's not in ANSI. -Print @var{text}. Nonprinting characters can be included in @var{text} -using C escape sequences, such as @samp{\n} to print a newline. @b{No -newline will be printed unless you specify one.} In addition to the -standard C escape sequences, a backslash followed by a space stands for a -space. This is useful for outputting a string with spaces at the -beginning or the end, since leading and trailing spaces are otherwise -trimmed from all arguments. Thus, to print @samp{@ and foo =@ }, use the -command @samp{echo \@ and foo = \@ }. -@c FIXME: verify hard copy actually issues enspaces for '@ '! Will this -@c confuse texinfo? - -A backslash at the end of @var{text} can be used, as in C, to continue -the command onto subsequent lines. For example, - -@example -echo This is some text\n\ -which is continued\n\ -onto several lines.\n -@end example - -produces the same output as - -@example -echo This is some text\n -echo which is continued\n -echo onto several lines.\n -@end example - -@item output @var{expression} -@kindex output -Print the value of @var{expression} and nothing but that value: no -newlines, no @samp{$@var{nn} = }. The value is not entered in the -value history either. @xref{Expressions} for more information on -expressions. - -@item output/@var{fmt} @var{expression} -Print the value of @var{expression} in format @var{fmt}. You can use -the same formats as for @code{print}; @pxref{Output formats}, for more -information. - -@item printf @var{string}, @var{expressions}@dots{} -@kindex printf -Print the values of the @var{expressions} under the control of -@var{string}. The @var{expressions} are separated by commas and may -be either numbers or pointers. Their values are printed as specified -by @var{string}, exactly as if the program were to execute - -@example -printf (@var{string}, @var{expressions}@dots{}); -@end example - -For example, you can print two values in hex like this: - -@example -printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo -@end example - -The only backslash-escape sequences that you can use in the format -string are the simple ones that consist of backslash followed by a -letter. -@end table - -@node Emacs, _GDBN__ Bugs, Sequences, Top -@chapter Using _GDBN__ under GNU Emacs - -@cindex emacs -A special interface allows you to use GNU Emacs to view (and -edit) the source files for the program you are debugging with -_GDBN__. - -To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the -executable file you want to debug as an argument. This command starts -_GDBN__ as a subprocess of Emacs, with input and output through a newly -created Emacs buffer. - -Using _GDBN__ under Emacs is just like using _GDBN__ normally except for two -things: - -@itemize @bullet -@item -All ``terminal'' input and output goes through the Emacs buffer. -@end itemize - -This applies both to _GDBN__ commands and their output, and to the input -and output done by the program you are debugging. - -This is useful because it means that you can copy the text of previous -commands and input them again; you can even use parts of the output -in this way. - -All the facilities of Emacs' Shell mode are available for this purpose. - -@itemize @bullet -@item -_GDBN__ displays source code through Emacs. -@end itemize - -Each time _GDBN__ displays a stack frame, Emacs automatically finds the -source file for that frame and puts an arrow (_0__@samp{=>}_1__) at the -left margin of the current line. Emacs uses a separate buffer for -source display, and splits the window to show both your _GDBN__ session -and the source. - -Explicit _GDBN__ @code{list} or search commands still produce output as -usual, but you probably will have no reason to use them. - -@quotation -@emph{Warning:} If the directory where your program resides is not your -current directory, it can be easy to confuse Emacs about the location of -the source files, in which case the auxiliary display buffer will not -appear to show your source. _GDBN__ can find programs by searching your -environment's @code{PATH} variable, so the _GDBN__ input and output -session will proceed normally; but Emacs doesn't get enough information -back from _GDBN__ to locate the source files in this situation. To -avoid this problem, either start _GDBN__ mode from the directory where -your program resides, or specify a full path name when prompted for the -@kbd{M-x gdb} argument. - -A similar confusion can result if you use the _GDBN__ @code{file} command to -switch to debugging a program in some other location, from an existing -_GDBN__ buffer in Emacs. -@end quotation - -By default, @kbd{M-x gdb} calls the program called @file{gdb}. If -you need to call _GDBN__ by a different name (for example, if you keep -several configurations around, with different names) you can set the -Emacs variable @code{gdb-command-name}; for example, -@example -(setq gdb-command-name "mygdb") -@end example -@noindent -(preceded by @kbd{ESC ESC}, or typed in the @code{*scratch*} buffer, or -in your @file{.emacs} file) will make Emacs call the program named -``@code{mygdb}'' instead. - -In the _GDBN__ I/O buffer, you can use these special Emacs commands in -addition to the standard Shell mode commands: - -@table @kbd -@item C-h m -Describe the features of Emacs' _GDBN__ Mode. - -@item M-s -Execute to another source line, like the _GDBN__ @code{step} command; also -update the display window to show the current file and location. - -@item M-n -Execute to next source line in this function, skipping all function -calls, like the _GDBN__ @code{next} command. Then update the display window -to show the current file and location. - -@item M-i -Execute one instruction, like the _GDBN__ @code{stepi} command; update -display window accordingly. - -@item M-x gdb-nexti -Execute to next instruction, using the _GDBN__ @code{nexti} command; update -display window accordingly. - -@item C-c C-f -Execute until exit from the selected stack frame, like the _GDBN__ -@code{finish} command. - -@item M-c -Continue execution of the program, like the _GDBN__ @code{continue} -command. @emph{Warning:} In Emacs v19, this command is @kbd{C-c C-p}. - -@item M-u -Go up the number of frames indicated by the numeric argument -(@pxref{Arguments, , Numeric Arguments, emacs, The GNU Emacs Manual}), -like the _GDBN__ @code{up} command. @emph{Warning:} In Emacs v19, this -command is @kbd{C-c C-u}.@refill - -@item M-d -Go down the number of frames indicated by the numeric argument, like the -_GDBN__ @code{down} command. @emph{Warning:} In Emacs v19, this command -is @kbd{C-c C-d}. - -@item C-x & -Read the number where the cursor is positioned, and insert it at the end -of the _GDBN__ I/O buffer. For example, if you wish to disassemble code -around an address that was displayed earlier, type @kbd{disassemble}; -then move the cursor to the address display, and pick up the -argument for @code{disassemble} by typing @kbd{C-x &}. - -You can customize this further on the fly by defining elements of the list -@code{gdb-print-command}; once it is defined, you can format or -otherwise process numbers picked up by @kbd{C-x &} before they are -inserted. A numeric argument to @kbd{C-x &} will both flag that you -wish special formatting, and act as an index to pick an element of the -list. If the list element is a string, the number to be inserted is -formatted using the Emacs function @code{format}; otherwise the number -is passed as an argument to the corresponding list element. - -@end table - -In any source file, the Emacs command @kbd{C-x SPC} (@code{gdb-break}) -tells _GDBN__ to set a breakpoint on the source line point is on. - -If you accidentally delete the source-display buffer, an easy way to get -it back is to type the command @code{f} in the _GDBN__ buffer, to -request a frame display; when you run under Emacs, this will recreate -the source buffer if necessary to show you the context of the current -frame. - -The source files displayed in Emacs are in ordinary Emacs buffers -which are visiting the source files in the usual way. You can edit -the files with these buffers if you wish; but keep in mind that _GDBN__ -communicates with Emacs in terms of line numbers. If you add or -delete lines from the text, the line numbers that _GDBN__ knows will cease -to correspond properly to the code. - -@c The following dropped because Epoch is nonstandard. Reactivate -@c if/when v19 does something similar. ---pesch@cygnus.com 19dec1990 -@ignore -@kindex emacs epoch environment -@kindex epoch -@kindex inspect - -Version 18 of Emacs has a built-in window system called the @code{epoch} -environment. Users of this environment can use a new command, -@code{inspect} which performs identically to @code{print} except that -each value is printed in its own window. -@end ignore - -@node _GDBN__ Bugs, Renamed Commands, Emacs, Top -@c node-name, next, previous, up -@chapter Reporting Bugs in _GDBN__ -@cindex Bugs in _GDBN__ -@cindex Reporting Bugs in _GDBN__ - -Your bug reports play an essential role in making _GDBN__ reliable. - -Reporting a bug may help you by bringing a solution to your problem, or it -may not. But in any case the principal function of a bug report is to help -the entire community by making the next version of _GDBN__ work better. Bug -reports are your contribution to the maintenance of _GDBN__. - -In order for a bug report to serve its purpose, you must include the -information that enables us to fix the bug. - -@menu -* Bug Criteria:: Have You Found a Bug? -* Bug Reporting:: How to Report Bugs -@end menu - -@node Bug Criteria, Bug Reporting, _GDBN__ Bugs, _GDBN__ Bugs -@section Have You Found a Bug? -@cindex Bug Criteria - -If you are not sure whether you have found a bug, here are some guidelines: - -@itemize @bullet -@item -@cindex Fatal Signal -@cindex Core Dump -If the debugger gets a fatal signal, for any input whatever, that is a -_GDBN__ bug. Reliable debuggers never crash. - -@item -@cindex error on Valid Input -If _GDBN__ produces an error message for valid input, that is a bug. - -@item -@cindex Invalid Input -If _GDBN__ does not produce an error message for invalid input, -that is a bug. However, you should note that your idea of -``invalid input'' might be our idea of ``an extension'' or ``support -for traditional practice''. - -@item -If you are an experienced user of debugging tools, your suggestions -for improvement of _GDBN__ are welcome in any case. -@end itemize - -@node Bug Reporting, , Bug Criteria, _GDBN__ Bugs -@section How to Report Bugs -@cindex Bug Reports -@cindex Compiler Bugs, Reporting - -A number of companies and individuals offer support for GNU products. -If you obtained _GDBN__ from a support organization, we recommend you -contact that organization first. - -Contact information for many support companies and individuals is -available in the file @file{etc/SERVICE} in the GNU Emacs distribution. - -In any event, we also recommend that you send bug reports for _GDBN__ to one -of these addresses: - -@example -bug-gdb@@prep.ai.mit.edu -@{ucbvax|mit-eddie|uunet@}!prep.ai.mit.edu!bug-gdb -@end example - -@strong{Do not send bug reports to @samp{info-gdb}, or to -@samp{help-gdb}, or to any newsgroups.} Most users of _GDBN__ do not want to -receive bug reports. Those that do, have arranged to receive @samp{bug-gdb}. - -The mailing list @samp{bug-gdb} has a newsgroup which serves as a -repeater. The mailing list and the newsgroup carry exactly the same -messages. Often people think of posting bug reports to the newsgroup -instead of mailing them. This appears to work, but it has one problem -which can be crucial: a newsgroup posting often lacks a mail path -back to the sender. Thus, if we need to ask for more information, we -may be unable to reach you. For this reason, it is better to send bug -reports to the mailing list. - -As a last resort, send bug reports on paper to: - -@example -GNU Debugger Bugs -545 Tech Square -Cambridge, MA 02139 -@end example - -The fundamental principle of reporting bugs usefully is this: -@strong{report all the facts}. If you are not sure whether to state a -fact or leave it out, state it! - -Often people omit facts because they think they know what causes the -problem and assume that some details don't matter. Thus, you might -assume that the name of the variable you use in an example does not matter. -Well, probably it doesn't, but one cannot be sure. Perhaps the bug is a -stray memory reference which happens to fetch from the location where that -name is stored in memory; perhaps, if the name were different, the contents -of that location would fool the debugger into doing the right thing despite -the bug. Play it safe and give a specific, complete example. That is the -easiest thing for you to do, and the most helpful. - -Keep in mind that the purpose of a bug report is to enable us to fix -the bug if it is new to us. It isn't as important what happens if -the bug is already known. Therefore, always write your bug reports on -the assumption that the bug has not been reported previously. - -Sometimes people give a few sketchy facts and ask, ``Does this ring a -bell?'' Those bug reports are useless, and we urge everyone to -@emph{refuse to respond to them} except to chide the sender to report -bugs properly. - -To enable us to fix the bug, you should include all these things: - -@itemize @bullet -@item -The version of _GDBN__. _GDBN__ announces it if you start with no -arguments; you can also print it at any time using @code{show version}. - -Without this, we won't know whether there is any point in looking for -the bug in the current version of _GDBN__. - -@item -A complete input script, and all necessary source files, that will -reproduce the bug. - -@item -What compiler (and its version) was used to compile _GDBN__---e.g. -``_GCC__-1.37.1''. - -@item -The command arguments you gave the compiler to compile your example and -observe the bug. For example, did you use @samp{-O}? To guarantee -you won't omit something important, list them all. - -If we were to try to guess the arguments, we would probably guess wrong -and then we might not encounter the bug. - -@item -The type of machine you are using, and the operating system name and -version number. - -@item -A description of what behavior you observe that you believe is -incorrect. For example, ``It gets a fatal signal.'' - -Of course, if the bug is that _GDBN__ gets a fatal signal, then we will -certainly notice it. But if the bug is incorrect output, we might not -notice unless it is glaringly wrong. We are human, after all. You -might as well not give us a chance to make a mistake. - -Even if the problem you experience is a fatal signal, you should still -say so explicitly. Suppose something strange is going on, such as, -your copy of _GDBN__ is out of synch, or you have encountered a -bug in the C library on your system. (This has happened!) Your copy -might crash and ours would not. If you told us to expect a crash, -then when ours fails to crash, we would know that the bug was not -happening for us. If you had not told us to expect a crash, then we -would not be able to draw any conclusion from our observations. - -@item -If you wish to suggest changes to the _GDBN__ source, send us context -diffs. If you even discuss something in the _GDBN__ source, refer to -it by context, not by line number. - -The line numbers in our development sources won't match those in your -sources. Your line numbers would convey no useful information to us. - -@end itemize - -Here are some things that are not necessary: - -@itemize @bullet -@item -A description of the envelope of the bug. - -Often people who encounter a bug spend a lot of time investigating -which changes to the input file will make the bug go away and which -changes will not affect it. - -This is often time consuming and not very useful, because the way we -will find the bug is by running a single example under the debugger -with breakpoints, not by pure deduction from a series of examples. -We recommend that you save your time for something else. - -Of course, if you can find a simpler example to report @emph{instead} -of the original one, that is a convenience for us. Errors in the -output will be easier to spot, running under the debugger will take -less time, etc. - -However, simplification is not vital; if you don't want to do this, -report the bug anyway and send us the entire test case you used. - -@item -A patch for the bug. - -A patch for the bug does help us if it is a good one. But don't omit -the necessary information, such as the test case, on the assumption that -a patch is all we need. We might see problems with your patch and decide -to fix the problem another way, or we might not understand it at all. - -Sometimes with a program as complicated as _GDBN__ it is very hard to -construct an example that will make the program follow a certain path -through the code. If you don't send us the example, we won't be able -to construct one, so we won't be able to verify that the bug is fixed. - -And if we can't understand what bug you are trying to fix, or why your -patch should be an improvement, we won't install it. A test case will -help us to understand. - -@item -A guess about what the bug is or what it depends on. - -Such guesses are usually wrong. Even we can't guess right about such -things without first using the debugger to find the facts. -@end itemize - -@iftex -@include rdl-apps.texinfo -@end iftex - -@node Renamed Commands, Installing _GDBN__, _GDBN__ Bugs, Top -@appendix Commands Renamed in 4.0 - -The following commands were renamed in _GDBN__ 4.0, in order to make the -command set as a whole more consistent and easier to use and remember: - -@kindex add-syms -@kindex delete environment -@kindex info copying -@kindex info convenience -@kindex info directories -@kindex info editing -@kindex info history -@kindex info targets -@kindex info values -@kindex info version -@kindex info warranty -@kindex set addressprint -@kindex set arrayprint -@kindex set prettyprint -@kindex set screen-height -@kindex set screen-width -@kindex set unionprint -@kindex set vtblprint -@kindex set demangle -@kindex set asm-demangle -@kindex set sevenbit-strings -@kindex set array-max -@kindex set caution -@kindex set history write -@kindex show addressprint -@kindex show arrayprint -@kindex show prettyprint -@kindex show screen-height -@kindex show screen-width -@kindex show unionprint -@kindex show vtblprint -@kindex show demangle -@kindex show asm-demangle -@kindex show sevenbit-strings -@kindex show array-max -@kindex show caution -@kindex show history write -@kindex unset - -@ifinfo -OLD COMMAND NEW COMMAND ---------------- ---------------------------------- -add-syms add-symbol-file -delete environment unset environment -info convenience show convenience -info copying show copying -info directories show directories -info editing show commands -info history show values -info targets help target -info values show values -info version show version -info warranty show warranty -set/show addressprint set/show print address -set/show array-max set/show print elements -set/show arrayprint set/show print array -set/show asm-demangle set/show print asm-demangle -set/show caution set/show confirm -set/show demangle set/show print demangle -set/show history write set/show history save -set/show prettyprint set/show print pretty -set/show screen-height set/show height -set/show screen-width set/show width -set/show sevenbit-strings set/show print sevenbit-strings -set/show unionprint set/show print union -set/show vtblprint set/show print vtbl - -unset [ No longer an alias for delete ] -@end ifinfo - -@tex -\vskip \parskip\vskip \baselineskip -\halign{\tt #\hfil &\qquad#&\tt #\hfil\cr -{\bf Old Command} &&{\bf New Command}\cr -add-syms &&add-symbol-file\cr -delete environment &&unset environment\cr -info convenience &&show convenience\cr -info copying &&show copying\cr -info directories &&show directories \cr -info editing &&show commands\cr -info history &&show values\cr -info targets &&help target\cr -info values &&show values\cr -info version &&show version\cr -info warranty &&show warranty\cr -set{\rm / }show addressprint &&set{\rm / }show print address\cr -set{\rm / }show array-max &&set{\rm / }show print elements\cr -set{\rm / }show arrayprint &&set{\rm / }show print array\cr -set{\rm / }show asm-demangle &&set{\rm / }show print asm-demangle\cr -set{\rm / }show caution &&set{\rm / }show confirm\cr -set{\rm / }show demangle &&set{\rm / }show print demangle\cr -set{\rm / }show history write &&set{\rm / }show history save\cr -set{\rm / }show prettyprint &&set{\rm / }show print pretty\cr -set{\rm / }show screen-height &&set{\rm / }show height\cr -set{\rm / }show screen-width &&set{\rm / }show width\cr -set{\rm / }show sevenbit-strings &&set{\rm / }show print sevenbit-strings\cr -set{\rm / }show unionprint &&set{\rm / }show print union\cr -set{\rm / }show vtblprint &&set{\rm / }show print vtbl\cr -\cr -unset &&\rm(No longer an alias for delete)\cr -} -@end tex - -@node Installing _GDBN__, Copying, Renamed Commands, Top -@appendix Installing _GDBN__ -@cindex configuring _GDBN__ -@cindex installation - -The script @code{config.gdb} automates the process of preparing _GDBN__ -for installation; you can then use @code{make} to actually build it. -The best way to build _GDBN__ is in a subdirectory that records the -configuration options used; this gives you a clean way of building -_GDBN__ binaries with several different configuration options. -@code{config.gdb} doesn't depend on this---it's just a good habit. For -example, assuming the _GDBN__ source is in a directory called -``@code{gdb-4.0}'': - -@example -cd gdb-4.0 -mkdir =sun3os4 -cd =sun3os4 -../config.gdb sun3os4 -make -@end example - -@noindent -will install _GDBN__ on a Sun 3 running SunOS 4. - -@table @code -@kindex config.gdb -@item config.gdb @var{machine} -@itemx config.gdb -srcdir=@var{dir} @var{machine} -This is the most usual way of configuring _GDBN__; to debug programs running -on the same machine as _GDBN__ itself. If you wish to build the _GDBN__ binaries -in a completely different directory from the sources, specify a path to -the source directory using the @samp{-srcdir} option. - -@item config.gdb -host -@cindex host environments -Display a list of supported host environments for _GDBN__. - -@item config.gdb @var{host} @var{target} -@itemx config.gdb -srcdir=@var{dir} @var{host} @var{target} -@cindex cross-debugging -_GDBN__ can also be used as a cross-debugger, running on a machine of one -type while debugging a program running on a machine of another type. -You configure it this way by specifying first the @var{host}, then the -@var{target} environment on the @code{config.gdb} argument list; the -@var{host} is where _GDBN__ runs, and the @var{target} is where your program -runs. @xref{Remote}. Again, you can use @samp{-srcdir} to specify a -path to the _GDBN__ source. - -@item config.gdb -target -@cindex target environments -Display a list of supported target environments for _GDBN__. -@end table - -@node Copying, Index, Installing _GDBN__, Top -@appendix Copying GDB -@c this is an attempt to kluge around what may be a bug in texinfo; -@c @xrefs to this node came out pointing several pages further down when -@c the @node was immediately followed by @unnumbered. -@c While we're at it, might as well give an Appendix heading that -@c matches RMS' preferred nodename "Copying". - -@unnumbered GNU GENERAL PUBLIC LICENSE -@center Version 1, February 1989 - -@display -Copyright @copyright{} 1989 Free Software Foundation, Inc. -675 Mass Ave, Cambridge, MA 02139, USA - -Everyone is permitted to copy and distribute verbatim copies -of this license document, but changing it is not allowed. -@end display - -@unnumberedsec Preamble - - The license agreements of most software companies try to keep users -at the mercy of those companies. By contrast, our General Public -License is intended to guarantee your freedom to share and change free -software---to make sure the software is free for all its users. The -General Public License applies to the Free Software Foundation's -software and to any other program whose authors commit to using it. -You can use it for your programs, too. - - When we speak of free software, we are referring to freedom, not -price. Specifically, the General Public License is designed to make -sure that you have the freedom to give away or sell copies of free -software, that you receive source code or can get it if you want it, -that you can change the software or use pieces of it in new free -programs; and that you know you can do these things. - - To protect your rights, we need to make restrictions that forbid -anyone to deny you these rights or to ask you to surrender the rights. -These restrictions translate to certain responsibilities for you if you -distribute copies of the software, or if you modify it. - - For example, if you distribute copies of a such a program, whether -gratis or for a fee, you must give the recipients all the rights that -you have. You must make sure that they, too, receive or can get the -source code. And you must tell them their rights. - - We protect your rights with two steps: (1) copyright the software, and -(2) offer you this license which gives you legal permission to copy, -distribute and/or modify the software. - - Also, for each author's protection and ours, we want to make certain -that everyone understands that there is no warranty for this free -software. If the software is modified by someone else and passed on, we -want its recipients to know that what they have is not the original, so -that any problems introduced by others will not reflect on the original -authors' reputations. - - The precise terms and conditions for copying, distribution and -modification follow. - -@iftex -@unnumberedsec TERMS AND CONDITIONS -@end iftex -@ifinfo -@center TERMS AND CONDITIONS -@end ifinfo - -@enumerate -@item -This License Agreement applies to any program or other work which -contains a notice placed by the copyright holder saying it may be -distributed under the terms of this General Public License. The -``Program'', below, refers to any such program or work, and a ``work based -on the Program'' means either the Program or any work containing the -Program or a portion of it, either verbatim or with modifications. Each -licensee is addressed as ``you''. - -@item -You may copy and distribute verbatim copies of the Program's source -code as you receive it, in any medium, provided that you conspicuously and -appropriately publish on each copy an appropriate copyright notice and -disclaimer of warranty; keep intact all the notices that refer to this -General Public License and to the absence of any warranty; and give any -other recipients of the Program a copy of this General Public License -along with the Program. You may charge a fee for the physical act of -transferring a copy. - -@item -You may modify your copy or copies of the Program or any portion of -it, and copy and distribute such modifications under the terms of Paragraph -1 above, provided that you also do the following: - -@itemize @bullet -@item -cause the modified files to carry prominent notices stating that -you changed the files and the date of any change; and - -@item -cause the whole of any work that you distribute or publish, that -in whole or in part contains the Program or any part thereof, either -with or without modifications, to be licensed at no charge to all -third parties under the terms of this General Public License (except -that you may choose to grant warranty protection to some or all -third parties, at your option). - -@item -If the modified program normally reads commands interactively when -run, you must cause it, when started running for such interactive use -in the simplest and most usual way, to print or display an -announcement including an appropriate copyright notice and a notice -that there is no warranty (or else, saying that you provide a -warranty) and that users may redistribute the program under these -conditions, and telling the user how to view a copy of this General -Public License. - -@item -You may charge a fee for the physical act of transferring a -copy, and you may at your option offer warranty protection in -exchange for a fee. -@end itemize - -Mere aggregation of another independent work with the Program (or its -derivative) on a volume of a storage or distribution medium does not bring -the other work under the scope of these terms. - -@item -You may copy and distribute the Program (or a portion or derivative of -it, under Paragraph 2) in object code or executable form under the terms of -Paragraphs 1 and 2 above provided that you also do one of the following: - -@itemize @bullet -@item -accompany it with the complete corresponding machine-readable -source code, which must be distributed under the terms of -Paragraphs 1 and 2 above; or, - -@item -accompany it with a written offer, valid for at least three -years, to give any third party free (except for a nominal charge -for the cost of distribution) a complete machine-readable copy of the -corresponding source code, to be distributed under the terms of -Paragraphs 1 and 2 above; or, - -@item -accompany it with the information you received as to where the -corresponding source code may be obtained. (This alternative is -allowed only for noncommercial distribution and only if you -received the program in object code or executable form alone.) -@end itemize - -Source code for a work means the preferred form of the work for making -modifications to it. For an executable file, complete source code means -all the source code for all modules it contains; but, as a special -exception, it need not include source code for modules which are standard -libraries that accompany the operating system on which the executable -file runs, or for standard header files or definitions files that -accompany that operating system. - -@item -You may not copy, modify, sublicense, distribute or transfer the -Program except as expressly provided under this General Public License. -Any attempt otherwise to copy, modify, sublicense, distribute or transfer -the Program is void, and will automatically terminate your rights to use -the Program under this License. However, parties who have received -copies, or rights to use copies, from you under this General Public -License will not have their licenses terminated so long as such parties -remain in full compliance. - -@item -By copying, distributing or modifying the Program (or any work based -on the Program) you indicate your acceptance of this license to do so, -and all its terms and conditions. - -@item -Each time you redistribute the Program (or any work based on the -Program), the recipient automatically receives a license from the original -licensor to copy, distribute or modify the Program subject to these -terms and conditions. You may not impose any further restrictions on the -recipients' exercise of the rights granted herein. - -@item -The Free Software Foundation may publish revised and/or new versions -of the General Public License from time to time. Such new versions will -be similar in spirit to the present version, but may differ in detail to -address new problems or concerns. - -Each version is given a distinguishing version number. If the Program -specifies a version number of the license which applies to it and ``any -later version'', you have the option of following the terms and conditions -either of that version or of any later version published by the Free -Software Foundation. If the Program does not specify a version number of -the license, you may choose any version ever published by the Free Software -Foundation. - -@item -If you wish to incorporate parts of the Program into other free -programs whose distribution conditions are different, write to the author -to ask for permission. For software which is copyrighted by the Free -Software Foundation, write to the Free Software Foundation; we sometimes -make exceptions for this. Our decision will be guided by the two goals -of preserving the free status of all derivatives of our free software and -of promoting the sharing and reuse of software generally. - -@iftex -@heading NO WARRANTY -@end iftex -@ifinfo -@center NO WARRANTY -@end ifinfo - -@item -BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY -FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN -OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES -PROVIDE THE PROGRAM ``AS IS'' WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED -OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF -MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS -TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE -PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, -REPAIR OR CORRECTION. - -@item -IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL -ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR -REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, -INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES -ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT -LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES -SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE -WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN -ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. -@end enumerate - -@iftex -@heading END OF TERMS AND CONDITIONS -@end iftex -@ifinfo -@center END OF TERMS AND CONDITIONS -@end ifinfo - -@page -@unnumberedsec Applying These Terms to Your New Programs - - If you develop a new program, and you want it to be of the greatest -possible use to humanity, the best way to achieve this is to make it -free software which everyone can redistribute and change under these -terms. - - To do so, attach the following notices to the program. It is safest to -attach them to the start of each source file to most effectively convey -the exclusion of warranty; and each file should have at least the -``copyright'' line and a pointer to where the full notice is found. - -@smallexample -@var{one line to give the program's name and a brief idea of what it does.} -Copyright (C) 19@var{yy} @var{name of author} - -This program is free software; you can redistribute it and/or modify -it under the terms of the GNU General Public License as published by -the Free Software Foundation; either version 1, or (at your option) -any later version. - -This program is distributed in the hope that it will be useful, -but WITHOUT ANY WARRANTY; without even the implied warranty of -MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the -GNU General Public License for more details. - -You should have received a copy of the GNU General Public License -along with this program; if not, write to the Free Software -Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. -@end smallexample - -Also add information on how to contact you by electronic and paper mail. - -If the program is interactive, make it output a short notice like this -when it starts in an interactive mode: - -@smallexample -Gnomovision version 69, Copyright (C) 19@var{yy} @var{name of author} -Gnomovision comes with ABSOLUTELY NO WARRANTY; for details type `show w'. -This is free software, and you are welcome to redistribute it -under certain conditions; type `show c' for details. -@end smallexample - -The hypothetical commands `show w' and `show c' should show the -appropriate parts of the General Public License. Of course, the -commands you use may be called something other than `show w' and `show -c'; they could even be mouse-clicks or menu items---whatever suits your -program. - -You should also get your employer (if you work as a programmer) or your -school, if any, to sign a ``copyright disclaimer'' for the program, if -necessary. Here is a sample; alter the names: - -@smallexample -Yoyodyne, Inc., hereby disclaims all copyright interest in the -program `Gnomovision' (a program to direct compilers to make passes -at assemblers) written by James Hacker. - -@var{signature of Ty Coon}, 1 April 1989 -Ty Coon, President of Vice -@end smallexample - -That's all there is to it! +_fi__(0) +_include__(gdb.top-m4) +_include__(gdb.sample-m4) +_include__(gdb.invoc-m4) +_include__(gdb.cmds-m4) +_include__(gdb.run-m4) +_include__(gdb.stop-m4) +_include__(gdb.stack-m4) +_include__(gdb.src-m4) +_include__(gdb.data-m4) +_include__(gdb.symb-m4) +_include__(gdb.alter-m4) +_include__(gdb.files-m4) +_include__(gdb.tgts-m4) +_include__(gdb.ctl-m4) +_include__(gdb.canned-m4) +_include__(gdb.emacs-m4) +_include__(gdb.bugs-m4) +_include__(gdb.rdln-m4) +_include__(gdb.rename-m4) +_include__(gdb.install-m4) +_include__(gdb.gpl-m4) @node Index, , Copying, Top @unnumbered Index |