[Bug libstdc++/78968] conflict between gnu's __cxa_thread_atexit and LLVM's/FreeBSD's implementation

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78968

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to h2+bugs from comment #0)
> This is a bug in gcc.  The libsupc++ configuration assumes that there are
> exactly two possibilities: either libc is glibc and implements
> __cxa_thread_atexit() using __cxa_thread_atexit_impl(), or libsupc++ must
> provide an implementation on its own.

Although this isn't quite right, there's no assumption of glibc.

The two possibilities are that only __cxa_thread_atexit_impl exists, or that
neither __cxa_thread_atexit_impl nor __cxa_thread_atexit exists.

There's no assumption about the provenance of __cxa_thread_atexit_impl.