https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89864
--- Comment #41 from Iain Sandoe <iains at gcc dot gnu.org> --- inconclusive so far, it's agreed that _Atomic is not a C++ keyword, but not clear what is best solution to the SDK use. If you filed a radar, please copy the number here (no-one else can see it, but at least we can point the Apple devs to it - so they can look internally).