exception performance in modern gcc

[Brendan Miller <catphive at catphive dot net>]

Various places online indicate that throwing exceptions has fairly
poor perforamnce on older versions of G++; however, I'm having a hard
time finding benchmarks for modern 4.x G++. Does anyone have
experience with this? Are there any good benchmarks on modern GCC?

I understand that exceptions aren't meant to be thrown often, so it
doesn't usually matter if exceptions are a little slow, but I'd like
to understand the performance a little better. If anyone knows where I
can find notes on how the exception propagation mechanism works at a
fairly low level that would also be helpful. I'm trying to get a
picture of where the costs come from, aside from calling destructors
as the stack unwinds.