So far I haven't managed to reproduce the issue with the trace, I tried with
32-bit and 64-bit drivers, with and without sb, also I tried to build mesa with
your configure parameters (though I had to adjust them a bit to make it work
for me) - I haven't seen any segfaults with the trace, valgrind doesn't provide
any hints either.

I suspect it may be something specific to your configuration, compiler version,
etc.