FE_DFL_ENV
Defined in header <fenv.h> |
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(since C99) |
The macro constant FE_DFL_ENV expands to an expression of type const 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 fenv_t*, may be supported by an implementation.
Example
#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();
}Output:
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_TONEARESTReferences
- C11 standard (ISO/IEC 9899:2011):
- 7.6/9 Floating-point environment <fenv.h> (p: 208)
- C99 standard (ISO/IEC 9899:1999):
- 7.6/8 Floating-point environment <fenv.h> (p: 188-189)
See also
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(C99)
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saves or restores the current floating-point environment (function) |
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(C99)
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restores the floating-point environment and raises the previously raise exceptions (function) |
C++ documentation for FE_DFL_ENV |
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