> Hmm, perhaps it successfully gets you out and only misses frames.  I'm
> pretty sure I remember that when debugging a Windows build of GDB, the
> select helper threads live somewhere in NTDLL without a valid frame.

I am not sure about that particular thread. But for the other ones,
we are indeed counting on the fact that all we lose is skipping one
frame.

> I'd be curious to see it, at least, but I'm not sure what we can do.

Here it is. The diff is probably malformed, because I had to remove
a couple of patches we backported from head, but that should give
you the idea.

-- 
Joel