Need a C++ expert: libstdc++/9756

[Phil Edwards]

Would somebody more familiar with the exceptions/unwinding mechanism than I
am -- that'd be just about all of ya -- please take a look at this new PR?
All I can tell is that __cxa_rethrow's call to _Unwind_*_RaiseException is
erroneously returning, which leads to a call to terminate(), which results
in an infinite loop.

-- 
I would therefore like to posit that computing's central challenge, viz. "How
not to make a mess of it," has /not/ been met.
                                                 - Edsger Dijkstra, 1930-2002