[cfe-dev] _Unwind_Exception use by libcxxabi on linux

[Rafael Ávila de Espíndola]

> Is the right fix to copy _Unwind_Exception from darwin's unwind.h into
> clang's unwind.h? Provide it from libcxxabi? Something else?

I think it is to define it on our unwind.h. The rationale for that
header is that unwind.h is an system header on OS X, but a gcc header on
linux.

We aim to provide a drop in replacement for gcc, so we should provide a
unwind.h too on systems where it is provided by gcc.

> Jeffrey

Cheers,
Rafael