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Re: Fully automating GDB (aka how to make canned command strings see the exit status)


Daniel Jacobowitz wrote:
On Thu, Mar 16, 2006 at 05:11:21PM +0000, Alex Bennee wrote:
Hi,

I've got a program I'm trying to debug that crashes on a very
intermittent basis. I suspect the core dumps I'm getting are incomplete
so I would like to try and catch the the crash live in gdb.

I figure a canned script to run the program is the answer. However how
do I tell if the program has exited successfully (in which case I can
run again) to hitting the SEG and staying put for when I come back in
the morning?

There's lots of ways you can do this. There's nothing in the GDB command line scripting language that will work, but you can drive GDB using something like "expect" instead; have the expect script stop when it sees a SIGSEGV in the output.

Actually, if $_exitcode is not set (or is void) then no program has exited properly. Otherwise, $_exitcode is what it says on the tin.


Of course, there's no direct way to test for undefined variables (and anyway as soon as you look as them they are no longer undefined as such), and there is no way to compare void, but there is an indirect way. Use init-if-undefined to set $_exitcode to some unlikely value (999999 perhaps) and then check that.

The script might be

  run
  init-if-undefined $_exitcode = 999999
  if $_exitcode != 999999
    quit
  endif

That's untested, and GDB 6.4 only.

HTH

Andrew


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