Red Hat ENTERPRISE LINUX 4 - DEVELOPER TOOLS GUIDE, Manual

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Chapter 17.
gdb Files
gdb 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 your program. To debug a core dump of a previous run, you must also tell gdb the
name of the core dump file.
17.1. Commands to specify files
You may want to specify executable and core dump file names. The usual way to do this is at start-up
time, using the arguments to gdb’s start-up commands (refer to Chapter 4 Getting In and Out of gdb ).
Occasionally it is necessary to change to a different file during a gdb session. Or you may run gdb and
forget to specify a file you want to use. In these situations the gdb commands to specify new files are
useful.
file
filename
Use
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
run
command. If you do not
specify a directory and the file is not found in the gdb working directory, gdb uses the environ-
ment variable
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 gdb and your program, using
the
path
command.
On systems with memory-mapped files, an auxiliary file named
filename
.syms
may
hold symbol table information for
filename
. If so, gdb maps in the symbol table from
filename
.syms
, starting up more quickly. See the descriptions of the file options
-mapped
and
-readnow
(available on the command line, and with the commands
file
,
symbol-file
, or
add-symbol-file
, described below), for more information.
file
file
with no argument makes gdb discard any information it has on both executable file and the
symbol table.
exec-file [
filename
]
Specify that the program to be run (but not the symbol table) is found in
filename
. gdb searches
the environment variable
PATH
if necessary to locate your program. Omitting
filename
means
to discard information on the executable file.
symbol-file [
filename
]
Read symbol table information from file
filename
.
PATH
is searched when necessary. Use the
file
command to get both symbol table and program to run from the same file.
symbol-file
with no argument clears out gdb information on your program’s symbol table.
The
symbol-file
command causes gdb 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 gdb.
symbol-file
does not repeat if you press [RET] again after executing it once.