RFC: Frame cache s not always available.

[Daniel Berlin]

>>>>> "FN" == Fernando Nasser <fnasser@redhat.com> writes:

   FN> considered valid.  For some oversighting, or maybe because it is
   FN> gradually being implemented, gdb only tests for the return value of
   FN> get_current_frame() in one place and assumes in several places that
   FN> selected_frame is set.

   FN> I found two places that are more troublesome and created the attached
   FN> patch.  I did implement the frame invalid situation in the arm target
   FN> (on my sandbox only) and this two changes alone were enough.  We may
   FN> found a few others in the future, and the situation were we do not
   FN> have a current or selected frame are not checked in yet, but I believe
   FN> we should make the code more robust and check this patch in anyway.


I've found a few places in the code as well where the frame is invalid
because we switched threads.
I had to manually force gdb to reinit the frame cache, or else we wouldn't
have the right frames.

However, i believe this may be a side effect of the way the beos port is
done, so i have them #ifdef'd for BEOS.
Just wanted to throw this out in case someone was working with threads and
saw incorrect stack backtraces.
--Dan