IEEE_TRAP_ENABLE_UNF
#define FP_EX_UNDERFLOW IEEE_TRAP_ENABLE_UNF
fp |= (~sw & (IEEE_TRAP_ENABLE_UNF | IEEE_TRAP_ENABLE_INE)) << 57;
sw |= (~fp >> 57) & (IEEE_TRAP_ENABLE_UNF | IEEE_TRAP_ENABLE_INE);
IEEE_TRAP_ENABLE_OVF | IEEE_TRAP_ENABLE_UNF |\
if (fex & IEEE_TRAP_ENABLE_UNF) si_code = FPE_FLTUND;
if (_fex & IEEE_TRAP_ENABLE_UNF) si_code = FPE_FLTUND;