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Starting your program
Use the `run' command to start your program under GDB. You must
first specify the program name (except on VxWorks) with an
argument to GDB (*note Getting In and Out of GDB: Invocation.), or
by using the `file' or `exec-file' command (*note Commands to
specify files: Files.).
If you are running your program in an execution environment that
supports processes, `run' creates an inferior process and makes that
process run your program. (In environments without processes, `run'
jumps to the start of your program.)
The execution of a program is affected by certain information it
receives from its superior. GDB provides ways to specify this
information, which you must do _before_ starting your program. (You
can change it after starting your program, but such changes only affect
your program the next time you start it.) This information may be
divided into four categories:
Specify the arguments to give your program as the arguments of the
`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 `SHELL' environment variable. *Note
Your program's arguments: Arguments.
Your program normally inherits its environment from GDB, but you
can use the GDB commands `set environment' and `unset environment'
to change parts of the environment that affect your program.
*Note Your program's environment: Environment.
The _working directory._
Your program inherits its working directory from GDB. You can set
the GDB working directory with the `cd' command in GDB. *Note
Your program's working directory: Working Directory.
The _standard input and output._
Your program normally uses the same device for standard input and
standard output as GDB is using. You can redirect input and output
in the `run' command line, or you can use the `tty' command to set
a different device for your program. *Note Your program's input
and output: Input/Output.
_Warning:_ While input and output redirection work, you cannot use
pipes to pass the output of the program you are debugging to
another program; if you attempt this, GDB is likely to wind up
debugging the wrong program.
When you issue the `run' command, your program begins to execute
immediately. *Note Stopping and continuing: Stopping, for discussion
of how to arrange for your program to stop. Once your program has
stopped, you may call functions in your program, using the `print' or
`call' commands. *Note Examining Data: Data.
If the modification time of your symbol file has changed since the
last time GDB read its symbols, GDB discards its symbol table, and
reads it again. When it does this, GDB tries to retain your current
The name of the main procedure can vary from language to language.
With C or C++, the main procedure name is always `main', but other
languages such as Ada do not require a specific name for their
main procedure. The debugger provides a convenient way to start
the execution of the program and to stop at the beginning of the
main procedure, depending on the language used.
The `start' command does the equivalent of setting a temporary
breakpoint at the beginning of the main procedure and then invoking
the `run' command.
Some programs contain an elaboration phase where some startup code
is executed before the main program is called. This depends on the
languages used to write your program. In C++ for instance,
constructors for static and global objects are executed before
`main' is called. It is therefore possible that the debugger stops
before reaching the main procedure. However, the temporary
breakpoint will remain to halt execution.
Specify the arguments to give to your program as arguments to the
`start' command. These arguments will be given verbatim to the
underlying `run' command. Note that the same arguments will be
reused if no argument is provided during subsequent calls to
`start' or `run'.
It is sometimes necessary to debug the program during elaboration.
In these cases, using the `start' command would stop the
execution of your program too late, as the program would have
already completed the elaboration phase. Under these
circumstances, insert breakpoints in your elaboration code before
running your program.
Created Mon Nov 8 17:42:36 2004 on tillpc with info_to_html version 0.9.6.