FP_ZERO
__x_c == (__typeof(__x_c)) 0 ? FP_ZERO : \
FP_SUBNORMAL, FP_ZERO, x)
if (classify(0.0) != FP_ZERO)
#define classify(X) __builtin_fpclassify(FP_NAN,FP_INF,FP_NOR,FP_SUB,FP_ZERO,X)