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# FE_DFL_ENV

From cppreference.com
< cpp‎ | numeric‎ | fenv

Defined in header `<cfenv>` |  |
#define FE_DFL_ENV /*implementation defined*/ |  | (since C++11)

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.

Additional macros that begin with `FE_` followed by uppercase letters, and have the type const std::fenv_t*, may be supported by an implementation.

### [edit] Example

Run this code

    #include <iostream>
    #include <cfenv>

    #pragma STDC FENV_ACCESS ON

    void show_env()
    {
        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";
        int r = std::fegetround();
        switch(r)
        {
            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();
    }

Output:

    On startup:
    rounding to nearest

    Before restoration:
    underflow is raised
    overflow is raised
    rounding up

    After reset to default:
    rounding to nearest

### [edit] See also

fegetenv fesetenv (C++11) | saves or restores the current floating point environment (function) [edit]
feupdateenv (C++11) | restores the floating-point environment and raises the previously raise exceptions (function) [edit]

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