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# fegetenv, fesetenv

From cppreference.com
< c‎ | numeric‎ | fenv

Defined in header `<fenv.h>` |  |
int fegetenv( fenv_t* envp ); | (1) | (since C99)
int fesetenv( const fenv_t* envp ); | (2) | (since C99)

1) Attempts to store the status of the floating-point environment in the object pointed to by `envp`.

2) Attempts to establish the floating-point environment from the object pointed to by `envp`. The value of that object must be previously obtained by a call to feholdexcept or `fegetenv` or be a floating-point macro constant. If any of the floating-point status flags are set in `envp`, they become set in the environment (and are then testable with fetestexcept), but the corresponding floating-point exceptions are not raised (execution continues uninterrupted)

### [edit] Parameters

envp | - | pointer to the object of type fenv_t which holds the status of the floating-point environment

### [edit] Return value

​0​ on success, non-zero otherwise.

### [edit] Example

Run this code

    #include <stdio.h>
    #include <math.h>
    #include <fenv.h>

    #pragma STDC FENV_ACCESS ON

    void show_fe_exceptions(void)
    {
        printf("current exceptions raised: ");
        if(fetestexcept(FE_DIVBYZERO))     printf(" FE_DIVBYZERO");
        if(fetestexcept(FE_INEXACT))       printf(" FE_INEXACT");
        if(fetestexcept(FE_INVALID))       printf(" FE_INVALID");
        if(fetestexcept(FE_OVERFLOW))      printf(" FE_OVERFLOW");
        if(fetestexcept(FE_UNDERFLOW))     printf(" FE_UNDERFLOW");
        if(fetestexcept(FE_ALL_EXCEPT)==0) printf(" none");
        printf("\n");
    }

    void show_fe_rounding_method(void)
    {
        printf("current rounding method:    ");
        switch (fegetround()) {
               case FE_TONEAREST:  printf ("FE_TONEAREST");  break;
               case FE_DOWNWARD:   printf ("FE_DOWNWARD");   break;
               case FE_UPWARD:     printf ("FE_UPWARD");     break;
               case FE_TOWARDZERO: printf ("FE_TOWARDZERO"); break;
               default:            printf ("unknown");
        };
        printf("\n");
    }

    void show_fe_environment(void)
    {
        show_fe_exceptions();
        show_fe_rounding_method();
    }

    int main(void)
    {
        fenv_t curr_env;
        int rtn;

        /* Show default environment. */
        show_fe_environment();
        printf("\n");

        /* Perform some computation under default environment. */
        printf("+11.5 -> %+4.1f\n", rint(+11.5)); /* midway between two integers */
        printf("+12.5 -> %+4.1f\n", rint(+12.5)); /* midway between two integers */
        show_fe_environment();
        printf("\n");

        /* Save current environment. */
        rtn = fegetenv(&curr_env);

        /* Perform some computation with new rounding method. */
        feclearexcept(FE_ALL_EXCEPT);
        fesetround(FE_DOWNWARD);
        printf("1.0/0.0 = %f\n", 1.0/0.0);
        printf("+11.5 -> %+4.1f\n", rint(+11.5));
        printf("+12.5 -> %+4.1f\n", rint(+12.5));
        show_fe_environment();
        printf("\n");

        /* Restore previous environment. */
        rtn = fesetenv(&curr_env);
        show_fe_environment();

        return 0;
    }

Output:

    current exceptions raised: none
    current rounding method:   FE_TONEAREST

    +11.5 -> +12.0
    +12.5 -> +12.0
    current exceptions raised: FE_INEXACT
    current rounding method:   FE_TONEAREST

    1.0/0.0 = inf
    +11.5 -> +11.0
    +12.5 -> +12.0
    current exceptions raised: FE_DIVBYZERO FE_INEXACT
    current rounding method:   FE_DOWNWARD

    current exceptions raised: FE_INEXACT
    current rounding method:   FE_TONEAREST

### [edit] References

- C11 standard (ISO/IEC 9899:2011):

  - 7.6.4.1 The fegetenv function (p: 213)

  - 7.6.4.3 The fesetenv function (p: 214)

- C99 standard (ISO/IEC 9899:1999):

  - 7.6.4.1 The fegetenv function (p: 194)

  - 7.6.4.3 The fesetenv function (p: 195)

### [edit] See also

feholdexcept (C99) | saves the environment, clears all status flags and ignores all future errors (function) [edit]
feupdateenv (C99) | restores the floating-point environment and raises the previously raise exceptions (function) [edit]
FE_DFL_ENV (C99) | default floating-point environment (macro constant) [edit]
C++ documentation for fegetenv, fesetenv

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