[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 #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Right. This can be worked around for any GCC releases except 5.5, 6.4 and 7.1,
but anything older can't be fixed.