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 (see Getting In and Out of GDB: Invocation.).

   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 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 GDB and your program, using the `path' command.

     On systems with memory-mapped files, an auxiliary file
     `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.

     When GDB 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 `gcc' you can generate debugging information for
     optimized code.

     On some kinds of object files, the `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 GDB
     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.  *Note Optional warnings
     and messages: Messages/Warnings.)

     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.

`symbol-file FILENAME [ -readnow ] [ -mapped ]'
`file FILENAME [ -readnow ] [ -mapped ]'
     You can override the GDB two-stage strategy for reading symbol
     tables by using the `-readnow' option with any of the commands that
     load symbol table information, if you want to be sure GDB has the
     entire symbol table available.

     If memory-mapped files are available on your system through the
     `mmap' system call, you can use another option, `-mapped', to
     cause GDB to write the symbols for your program into a reusable
     file.  Future GDB 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 GDB 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), GDB 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
     GDB.  It holds an exact image of the internal GDB symbol table.
     It cannot be shared across multiple host platforms.

`core-file [ FILENAME ]'
     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; GDB
     can access the executable file itself for other parts.

     `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 GDB.  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 Killing the child process: Kill Process.).

`load FILENAME'
     Depending on what remote debugging facilities are configured into
     GDB, the `load' command may be available.  Where it exists, it is
     meant to make FILENAME (an executable) available for debugging on
     the remote system--by downloading, or dynamic linking, for example.
     `load' also records the FILENAME symbol table in GDB, like the
     `add-symbol-file' command.

     If your GDB does not have a `load' command, attempting to execute
     it gets the error message "`You can't do that when your target is
     ...'"

     The file is loaded at whatever address is specified in the
     executable.  For some object file formats, you can specify the
     load address when you link the program; for other formats, like
     a.out, the object file format specifies a fixed address.

     On VxWorks, `load' links FILENAME dynamically on the current
     target system as well as adding its symbols in GDB.

     With the Nindy interface to an Intel 960 board, `load' downloads
     FILENAME to the 960 as well as adding its symbols in GDB.

     When you select remote debugging to a Hitachi SH, H8/300, or
     H8/500 board (see GDB and Hitachi Microprocessors: Hitachi Remote.), the `load' command downloads your program to the Hitachi
     board and also opens it as the current executable target for GDB
     on your host (like the `file' command).

     `load' does not repeat if you press <RET> again after using it.

`add-symbol-file FILENAME ADDRESS'
`add-symbol-file FILENAME ADDRESS [ -readnow ] [ -mapped ]'
     The `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; GDB cannot figure this
     out for itself.  You can specify 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.

     `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 GDB manages the symbol table
     information for FILENAME.

`add-shared-symbol-file'
     The `add-shared-symbol-file' command can be used only under
     Harris' CXUX operating system for the Motorola 88k.  GDB
     automatically looks for shared libraries, however if GDB does not
     find yours, you can run `add-shared-symbol-file'.  It takes no
     arguments.

`section'
     The `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
     lists all the sections and their addresses.

`info files'
`info target'
     `info files' and `info target' are synonymous; both print the
     current target (see Specifying a Debugging Target: Targets.),
     including the names of the executable and core dump files
     currently in use by GDB, 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.  GDB always converts the file name to an absolute
file name and remembers it that way.

   GDB supports SunOS, SVr4, Irix 5, and IBM RS/6000 shared libraries.
GDB 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, GDB does not understand references to a
function in a shared library, however--unless you are debugging a core
file).

`info share'
`info sharedlibrary'
     Print the names of the shared libraries which are currently loaded.

`sharedlibrary REGEX'
`share REGEX'
     Load shared object library symbols for files matching a Unix
     regular expression.  As with files loaded automatically, it only
     loads shared libraries required by your program for a core file or
     after typing `run'.  If REGEX is omitted all shared libraries
     required by your program are loaded.