__builtin_add_overflow  104 lib/intprops-internal.h #    define _GL_HAS_BUILTIN_ADD_OVERFLOW __has_builtin (__builtin_add_overflow)
__builtin_add_overflow  144 lib/intprops-internal.h #    define _GL_INT_ADD_WRAPV(a, b, r)      __builtin_add_overflow (a, b, r)