std::fetestexcept (3) - Linux Manuals

std::fetestexcept: std::fetestexcept

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