std::fetestexcept (3) Linux Manual Page

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
              (function)
(C++11)