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gdb
!!!gdb
NAME
SYNOPSIS
DESCRIPTION
OPTIONS
SEE ALSO
COPYING
----
!!NAME


gdb - The GNU Debugger
!!SYNOPSIS


__gdb__


[[__-help__] [[__-nx__] [[__-q__] [[__-batch__]
[[__-cd=__''dir''] [[__-f__] [[__-b__ ''bps'']
[[__-tty=__''dev''] [[__-s__ ''symfile'']
[[__-e__ ''prog''] [[__-se__ ''prog''] [[__-c__
''core''] [[__-x__ ''cmds''] [[__-d__ ''dir'']
[[''prog''[[''core''|''procID]]''
!!DESCRIPTION


The purpose of a debugger such as GDB 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.


GDB can do four main kinds of things (plus other things in
support of these) to help you catch bugs in the
act:


Start your program, specifying anything that might affect
its behavior.


Make your program stop on specified conditions.


Examine what has happened, when your program has
stopped.


Change things in your program, so you can experiment with
correcting the effects of one bug and go on to learn about
another.


You can use GDB to debug programs written in C, C++, and
Modula-2. Fortran support will be added when a GNU Fortran
compiler is ready.


GDB is invoked with the shell command __gdb__. Once
started, it reads commands from the terminal until you tell
it to exit with the GDB command __quit__. You can get
online help from __gdb__ itself by using the command
__help__.


You can run __gdb__ with no arguments or options; but the
most usual way to start GDB is with one argument or two,
specifying an executable program as the
argument:


gdb program


You can also start with both an executable program and a
core file specified:


gdb program core


You can, instead, specify a process ID as a second argument,
if you want to debug a running process:


gdb program 1234


would attach GDB to process __1234__ (unless you also
have a file named `__1234__'; GDB does check for a core
file first).


Here are some of the most frequently needed GDB
commands:


__break__
[[''file''__:__]''function''


Set a breakpoint at ''function'' (in
''file'').


__run__ [[''arglist'']


Start your program (with ''arglist'', if
specified).


__bt__


Backtrace: display the program stack.


__print__ ''expr''


Display the value of an expression.


__c__


Continue running your program (after stopping, e.g. at a
breakpoint).


__next__


Execute next program line (after stopping); step ''over''
any function calls in the line.


__step__


Execute next program line (after stopping); step ''into''
any function calls in the line.


__help__ [[''name'']


Show information about GDB command ''name'', or general
information about using GDB.


__quit__


Exit from GDB.


For full details on GDB, see ''Using GDB: A Guide to the
GNU Source-Level Debugger'', by Richard M. Stallman and
Roland H. Pesch. The same text is available online as the
__gdb__ entry in the __info__ program.
!!OPTIONS


Any arguments other than options specify an executable file
and core file (or process ID); that is, the first argument
encountered with no associated option flag is equivalent to
a `__-se__' option, and the second, if any, is equivalent
to a `__-c__' option if it's the name of a file. 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
`__+__' rather than `__-__', though we illustrate the
more usual convention.)


All the options and command line arguments you give are
processed in sequential order. The order makes a difference
when the `__-x__' option is used.


__-help__


__-h__


List all options, with brief explanations.


__-symbols=__''file''


__-s__ ''file''


Read symbol table from file ''file''.


__-write__


Enable writing into executable and core files.


__-exec=__''file''


__-e__ ''file''


Use file ''file'' as the executable file to execute when
appropriate, and for examining pure data in conjunction with
a core dump.


__-se=__''file''


Read symbol table from file ''file'' and use it as the
executable file.


__-core=__''file''


__-c__ ''file''


Use file ''file'' as a core dump to examine.


__-command=__''file''


__-x__ ''file''


Execute GDB commands from file ''file''.


__-directory=__''directory''


__-d__ ''directory''


Add ''directory'' to the path to search for source
files.


__-nx__


__-n__


Do not execute commands from any `__.gdbinit__'
initialization files. Normally, the commands in these files
are executed after all the command options and arguments
have been processed.


__-quiet__


__-q__


``Quiet''. Do not print the introductory and copyright
messages. These messages are also suppressed in batch
mode.


__-batch__


Run in batch mode. Exit with status __0__ after
processing all the command files specified with `__-x__'
(and `__.gdbinit__', if not inhibited). Exit with nonzero
status if an error occurs in executing the GDB commands in
the command files.


Batch mode may be useful for running GDB as a filter, for
example to download and run a program on another computer;
in order to make this more useful, the message


Program exited normally.


(which is ordinarily issued whenever a program running under
GDB control terminates) is not issued when running in batch
mode.


__-cd=__''directory''


Run GDB using ''directory'' as its working directory,
instead of the current directory.


__-fullname__


__-f__


Emacs sets this option when it runs GDB as a subprocess. It
tells GDB 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 ` __32__' characters,
followed by the file name, line number and character
position separated by colons, and a newline. The
Emacs-to-GDB interface program uses the two ` __32__'
characters as a signal to display the source code for the
frame.


__-b__ ''bps''


Set the line speed (baud rate or bits per second) of any
serial interface used by GDB for remote
debugging.


__-tty=__''device''


Run using ''device'' for your program's standard input
and output.
!!SEE ALSO


`__gdb__' entry in __info__; ''Using GDB: A Guide to
the GNU Source-Level Debugger'', Richard M. Stallman and
Roland H. Pesch, July 1991.
!!COPYING


Copyright (c) 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 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 this
permission notice may be included in translations approved
by the Free Software Foundation instead of in the original
English.
----
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Last edited on Monday, June 3, 2002 6:50:15 pm by "perry"
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