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# FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW, FE_UNDERFLOW, FE_ALL_EXCEPT

From cppreference.com
< cpp‎ | numeric‎ | fenv

Defined in header `<cfenv>` |  |
#define FE_DIVBYZERO /*implementation defined power of 2*/ |  | (since C++11)
#define FE_INEXACT /*implementation defined power of 2*/ |  | (since C++11)
#define FE_INVALID /*implementation defined power of 2*/ |  | (since C++11)
#define FE_OVERFLOW /*implementation defined power of 2*/ |  | (since C++11)
#define FE_UNDERFLOW /*implementation defined power of 2*/ |  | (since C++11)
#define FE_ALL_EXCEPT FE_DIVBYZERO | FE_INEXACT | \ FE_INVALID | FE_OVERFLOW | \ FE_UNDERFLOW |  | (since C++11)

All these macro constants (except FE_ALL_EXCEPT) expand to integer constant expressions that are distinct powers of 2, which uniquely identify all supported floating-point exceptions. Each macro is only defined if it is supported.

The macro constant FE_ALL_EXCEPT, which expands to the bitwise OR of all other `FE_*`, is always defined and is zero if floating-point exceptions are not supported by the implementation.

Constant | Explanation
`FE_DIVBYZERO` | division by zero occurred during the earlier floating-point operation
`FE_INEXACT` | inexact result: rounding was necessary to store the result of the earlier floating-point operation
`FE_INVALID` | invalid operation: the earlier floating-point operation could not performed
`FE_OVERFLOW` | the result of the earlier floating-point operation was too large to be representable
`FE_UNDERFLOW` | the result of the earlier floating-point operation was subnormal
`FE_ALL_EXCEPT` | bitwise OR of all supported floating-point exceptions

The implementation may define additional macro constants in `<cfenv>` to identify additional floating-point exceptions. All such constants begin with `FE_` followed by at least one uppercase letter.

### [edit] Example

[edit]
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

### [edit] See also

math_errhandling MATH_ERRNO MATH_ERREXCEPT (C++11)(C++11)(C++11) | defines the error handling mechanism used by the common mathematical functions (macro constant) [edit]

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