different behavior under gdb - how to track this down?

[Skip Montanaro]

I am trying to debug a segmentation violation in a complex system
(Python, Gtk+, PyGtk, all from current CVS).  All code is running on a
Mandrake 8.0 system built with gcc 2.96.  Unfortunately, if I run the
Python script under gdb (20011010-gdb+dejagnu), the program clearly
behaves differently than when it is run standalone.  For example,
various Gtk warnings are displayed when it's run under gdb, but not
when run standalone.  If I set a breakpoint in g_log, then pop up one
stack frame, I find execution at



    g_return_val_if_fail (default_value >= minimum &&

                          default_value <= maximum, NULL);



When I examine default_value, minimum and maximum, they all have
acceptable values (0.5, 0.0 and 1.0, respectively), so g_log shouldn't
be called.



With all the (apparently) spurious Gtk warnings, the program never
gets to the place where the segmentation violation occurs.  I can get
a backtrace from the core file, but obviously can't step my way into
the problem, only examine it after the fact.



Any idea how to debug this problem?



Thx,



--

Skip Montanaro

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