FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW, FE_UNDERFLOW, FE_ALL_EXCEPT

Since C++11

Header: <cfenv>

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 defined only if it is supported.

# Declarations

#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)

# Example

#include <cfenv>
#include <cmath>
#include <iostream>
 
// #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 << "division 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";
}

# See also