https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86306
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- _Atomic is a C keyword, it is not part of C++. Clang++ accepts it as a non-standard extension. GCC ddoes not accept it, because it's not part of C++. If you don't understand what this means, stop filing bugs.
