https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89464
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> --- alignas is a keyword in C++, it's not supposed to be a macro at all. GCC 8.3.0 now uses alignas in the standard library headers, which is OK because it's a C++ feature supported by the compiler. Stop defining a macro with the name of a keyword, that's undefined.
