gdb 6.8, Qt 4.2.3, MinGW environment

I'm getting an Assert failure in qbytearray.h (becausing somewhere I'm doing a .at() with an invalid index). I'm trying to catch it in console based gdb to be able to look at the stack trace to see from whence it has come. The gdb manual recommends breaking on __raise_exception for gnu c++, but gdb couldn't find that symbol; breaking on 'throw' also doesn't work.

Any suggestions on how to break on throwing an Assert error in Qt files?

Thanks, Doug