For the record, at the top of this thread I said I thought it was
fine, too. I've run into these often enough due to deliberate
attempts by runtimes to terminate the stack that I think it outweighs
the (minor, to my mind) value of seeing a 0x00000000 frame that
indicates an actual error.
GDB should be honest with the user about what it finds, but I don't
think we can be a multi-platform debugger and be that picky about
confining each bit of logic to exactly the platforms that promise to
uphold it.