signbit
#define signbit(__x) __fpmacro_unary_floating(signbit, __x)
#undef signbit
#define signbit(x) (__builtin_signbit(x))
#undef signbit
#define signbit(x) (__builtin_signbitf(x))
#undef signbit
#define signbit(x) (__builtin_signbitl(x))