GDB Script predefined variables

GDB Script predefined variables

[Rob Quill]

Hi,

I was wondering what predefined variables, if any, there are in GDB,
that can be used when writing a GDB script. Specifically, I want the
script to be able to test when the program has finished executing, but
any other predefined variables would also be useful, if there is a
list somewhere or someone knows them all.

Thanks for your time.

Rob

Re: GDB Script predefined variables

[Andrew STUBBS]

Rob Quill wrote:
> I was wondering what predefined variables, if any, there are in GDB,
> that can be used when writing a GDB script. Specifically, I want the
> script to be able to test when the program has finished executing, but
> any other predefined variables would also be useful, if there is a
> list somewhere or someone knows them all.

To show all GDB variables, predefined or otherwise:

(gdb) show conv

For your specific needs, there is a variable '$_exitcode' defined after 
the program exits (it does not exist before).

If you try to test a GDB convenience variable before it exists,  GDB 
will create it for you, but it does not initialise it (the value will be 
'void'). I'm not sure it is an official feature, but the following 
comparison works:

if $_exitcode == (void)0
   echo program not finished\n
end

The value of the void is not significant - it is just to make the 
expression valid.

HTH

Andrew