FE_DFL_ENV

#include <stdio.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()
{
 printf ("On startup:\n");
 show_fe_environment();
 
 // Change environment
 fesetround (FE_DOWNWARD ); // change rounding mode
 feraiseexcept (FE_INVALID ); // raise exception
 printf ("\nBefore restoration:\n");
 show_fe_environment();
 
 fesetenv (FE_DFL_ENV); // restore
 printf ("\nAfter restoring default environment:\n");
 show_fe_environment();
}

On startup:
current exceptions raised: none
current rounding method: FE_TONEAREST
 
Before restoration:
current exceptions raised: FE_INVALID
current rounding method: FE_DOWNWARD
 
After restoring default environment:
current exceptions raised: none
current rounding method: FE_TONEAREST