SNANBIT
# define DBL_SNANBIT (SNANBIT*__BIT(DBL_MANT_DIG - 2))
(SNANBIT*__BIT(LDBL_MANT_DIG - 2 - EXT_FRACLBITS))
# define FLT_SNANBIT (SNANBIT*__BIT(FLT_MANT_DIG - 2))