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 the name of the core dump file.
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 's start-up commands (see section Getting In and Out of).
Occasionally it is necessary to change to a different file during a session. Or you may run and forget to specify a file you want to use. In these situations the commands to specify new files are useful.
file filename
run command. If you do not specify a
directory and the file is not found in the working directory,
uses the environment 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
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, 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 discard any information it
has on both executable file and the symbol table.
exec-file [ filename ]
PATH
if necessary to locate your program. Omitting filename means to
discard information on the executable file.
symbol-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 information on your
program's symbol table.
The symbol-file command causes 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 .
symbol-file does not repeat if you press RET again after
executing it once.
When is configured for a particular environment, it
understands 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 symbol-file command does not normally 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, as they are needed.
The purpose of this two-stage reading strategy is to make
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 set verbose command can turn these
pauses into messages if desired. See section Optional warnings and messages.)
We have not implemented the two-stage strategy for COFF yet. When the
symbol table is stored in COFF format, symbol-file reads the
symbol table data in full right away. Note that "stabs-in-COFF"
still does the two-stage strategy, since the debug info is actually
in stabs format.
symbol-file filename [ -readnow ] [ -mapped ]
file filename [ -readnow ] [ -mapped ]
mmap system call, you can use another option, `-mapped', to
cause to write the symbols for your program into a reusable
file. Future debugging sessions map in symbol information
from this auxiliary symbol file (if the program has not changed), rather
than spending time reading the symbol table from the executable
program. Using the `-mapped' option has the same effect as
starting with the `-mapped' command-line option.
You can use both options together, to make sure the auxiliary symbol
file has all the symbol information for your program.
The auxiliary symbol file for a program called myprog is called
`myprog.syms'. Once this file exists (so long as it is newer
than the corresponding executable), always attempts to use
it when you debug myprog; no special options or commands are
needed.
The `.syms' file is specific to the host machine where you run
. It holds an exact image of the internal
symbol table. It cannot be shared across multiple host platforms.
core-file [ filename ]
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 . So, if you have been running your 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 kill command
(see section Killing the child process).
add-symbol-file filename address
add-symbol-file filename address [ -readnow ] [ -mapped ]
add-symbol-file filename -ssection address
add-symbol-file command reads additional symbol table
information from the file filename. You would use this command
when filename has been dynamically loaded (by some other means)
into the program that is running. address should be the memory
address at which the file has been loaded; cannot figure
this out for itself. You can additionally specify an arbitrary number
of `-ssection address' pairs, to give an explicit
section name and base address for that section. You can specify any
address as an expression.
The symbol table of the file filename is added to the symbol table
originally read with the symbol-file command. You can use the
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 symbol-file command without any arguments.
add-symbol-file does not repeat if you press RET after using it.
You can use the `-mapped' and `-readnow' options just as with
the symbol-file command, to change how manages the symbol
table information for filename.
add-shared-symbol-file
add-shared-symbol-file command can be used only under Harris' CXUX
operating system for the Motorola 88k. automatically looks for
shared libraries, however if does not find yours, you can run
add-shared-symbol-file. It takes no arguments.
section
section command changes the base address of section SECTION of
the exec file to ADDR. This can be used if the exec file does not contain
section addresses, (such as in the a.out format), or when the addresses
specified in the file itself are wrong. Each section must be changed
separately. The info files command, described below, lists all
the sections and their addresses.
info files
info target
info files and info target are synonymous; both print the
current target (see section Specifying a Debugging Target),
including the names of the executable and core dump files currently in
use by , and the files from which symbols were loaded. The
command help target lists all possible targets rather than
current ones.
All file-specifying commands allow both absolute and relative file names as arguments. always converts the file name to an absolute file name and remembers it that way.
supports HP-UX, SunOS, SVr4, Irix 5, and IBM RS/6000 shared libraries.
automatically loads symbol definitions from shared libraries
when you use the run command, or when you examine a core file.
(Before you issue the run command, does not understand
references to a function in a shared library, however--unless you are
debugging a core file).
On HP-UX, if the program loads a library explicitly,
automatically loads the symbols at the time of the shl_load call.
info share
info sharedlibrary
sharedlibrary regex
share regex
run. If
regex is omitted all shared libraries required by your program are
loaded.
On HP-UX systems, detects the loading of a shared library and automatically reads in symbols from the newly loaded library, up to a threshold that is initially set but that you can modify if you wish.
Beyond that threshold, symbols from shared libraries must be explicitly
loaded. To load these symbols, use the command sharedlibrary
filename. The base address of the shared library is determined
automatically by and need not be specified.
To display or set the threshold, use the commands:
set auto-solib-add threshold
sharedlibrary command. The default threshold is 100 megabytes.
show auto-solib-add
While reading a symbol file, occasionally encounters problems,
such as symbol types it does not recognize, or known bugs in compiler
output. By default, does not notify you of such problems, since
they are relatively common and primarily of interest to people
debugging compilers. If you are interested in seeing information
about ill-constructed symbol tables, you can either ask to print
only one message about each such type of problem, no matter how many
times the problem occurs; or you can ask to print more messages,
to see how many times the problems occur, with the set
complaints command (see section Optional warnings and messages).
The messages currently printed, and their meanings, include:
inner block not inside outer block in symbol
(don't know)" if the outer block is not a
function.
block at address out of order
set verbose on. See section Optional warnings and messages.)
bad block start address patched
bad string table offset in symbol n
foo, which may cause other problems if many symbols end up
with this name.
unknown symbol type 0xnn
0xnn is the symbol type of the
uncomprehended information, in hexadecimal.
circumvents the error by ignoring this symbol information.
This usually allows you to debug your program, though certain symbols
are not accessible. If you encounter such a problem and feel like
debugging it, you can debug complain, then go up to the function read_dbx_symtab
and examine *bufp to see the symbol.
stub type has NULL name
const/volatile indicator missing (ok if using g++ v1.x), got...
info mismatch between compiler and debugger
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