FE_DFL_ENV

Since C++11

Header: <cfenv>

The macro constant FE_DFL_ENV expands to an expression of type const std::fenv_t*, which points to a full copy of the default floating-point environment, that is, the environment as loaded at program startup.

# Declarations

#define FE_DFL_ENV /*implementation defined*/

(since C++11)

# Example

#include <cfenv>
#include <iostream>
// #pragma STDC FENV_ACCESS ON
 
void show_env()
{
    const int e = std::fetestexcept(FE_ALL_EXCEPT);
    if (e & FE_DIVBYZERO)
        std::cout << "division by zero is raised\n";
    if (e & FE_INEXACT)
        std::cout << "inexact is raised\n";
    if (e & FE_INVALID)
        std::cout << "invalid is raised\n";
    if (e & FE_UNDERFLOW)
        std::cout << "underflow is raised\n";
    if (e & FE_OVERFLOW)
        std::cout << "overflow is raised\n";
 
    switch (std::fegetround())
    {  
        case FE_DOWNWARD:
            std::cout << "rounding down\n";
            break;
        case FE_TONEAREST:
            std::cout << "rounding to nearest\n";
            break;
        case FE_TOWARDZERO:
            std::cout << "rounding to zero\n";
            break;
        case FE_UPWARD:
            std::cout << "rounding up\n";
            break;
    }
}
 
int main()
{
    std::cout << "On startup:\n";
    show_env();
 
    std::feraiseexcept(FE_UNDERFLOW | FE_OVERFLOW);
    std::fesetround(FE_UPWARD);
 
    std::cout << "\nBefore restoration:\n";
    show_env();
 
    std::fesetenv(FE_DFL_ENV);
 
    std::cout << "\nAfter reset to default:\n";
    show_env();
}

# See also