# std::fetestexcept

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< cpp‎ | numeric‎ | fenv

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

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