NAME¶

std::fetestexcept - std::fetestexcept

Synopsis¶

Defined in header <cfenv>
int fetestexcept( int excepts ); (since C++11)

Determines which of the specified subset of the floating point exceptions are
currently set. The argument excepts is a bitwise OR of the floating point exception
macros.

Parameters¶

excepts - bitmask listing the exception flags to test

Return value¶

Bitwise OR of the floating-point exception macros that are both included in excepts
and correspond to floating-point exceptions currently set.

Example¶

// Run this code

#include <iostream>
#include <cfenv>
#include <cmath>

#pragma STDC FENV_ACCESS ON

volatile double zero = 0.0; // volatile not needed where FENV_ACCESS is supported
volatile double one = 1.0; // volatile not needed where FENV_ACCESS is supported

int main()
{
std::feclearexcept(FE_ALL_EXCEPT);
std::cout << "1.0/0.0 = " << 1.0 / zero << '\n';
if(std::fetestexcept(FE_DIVBYZERO)) {
std::cout << "division by zero reported\n";
} else {
std::cout << "divsion by zero not reported\n";
}

std::feclearexcept(FE_ALL_EXCEPT);
std::cout << "1.0/10 = " << one/10 << '\n';
if(std::fetestexcept(FE_INEXACT)) {
std::cout << "inexact result reported\n";
} else {
std::cout << "inexact result not reported\n";
}

std::feclearexcept(FE_ALL_EXCEPT);
std::cout << "sqrt(-1) = " << std::sqrt(-1) << '\n';
if(std::fetestexcept(FE_INVALID)) {
std::cout << "invalid result reported\n";
} else {
std::cout << "invalid result not reported\n";
}
}

Output:¶

1.0/0.0 = inf
division by zero reported
1.0/10 = 0.1
inexact result reported
sqrt(-1) = -nan
invalid result reported

See also¶

feclearexcept clears the specified floating-point status flags
(C++11) (function)