#define FE_DIVBYZERO /*implementation defined power of 2*/
(since C99)#define FE_INEXACT /*implementation defined power of 2*/
(since C99)#define FE_INVALID /*implementation defined power of 2*/
(since C99)#define FE_OVERFLOW /*implementation defined power of 2*/
(since C99)#define FE_UNDERFLOW /*implementation defined power of 2*/
(since C99) #define FE_ALL_EXCEPT FE_DIVBYZERO | FE_INEXACT | \ FE_INVALID | FE_OVERFLOW | \
All these macro constants (except FE_ALL_EXCEPT) expand to integer constant expressions that are distinct powers of 2, which uniquely identify all supported floating-point exceptions. Each macro is only defined if it is supported.
The macro constant FE_ALL_EXCEPT, which expands to the bitwise OR of all other FE_*, is always defined and is zero if floating-point exceptions are not supported by the implementation.
FE_DIVBYZERO pole error occurred in an earlier floating-point operation FE_INEXACT inexact result: rounding was necessary to store the result of an earlier floating-point operation FE_INVALID domain error occurred in an earlier floating-point operation FE_OVERFLOW the result of an earlier floating-point operation was too large to be representable FE_UNDERFLOW the result of an earlier floating-point operation was subnormal with a loss of precision FE_ALL_EXCEPT bitwise OR of all supported floating-point exceptions
The implementation may define additional macro constants in <fenv.h> to identify additional floating-point exceptions. All such constants begin with FE_ followed by at least one uppercase letter.
See math_errhandling for further details.
[edit] Example#include <stdio.h>
#include <math.h>
#include <float.h>
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
void show_fe_exceptions(void)
{
printf("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");
feclearexcept(FE_ALL_EXCEPT);
printf("\n");
}
int main(void)
{
printf("MATH_ERREXCEPT is %s\n",
math_errhandling & MATH_ERREXCEPT ? "set" : "not set");
printf("0.0/0.0 = %f\n", 0.0/0.0);
show_fe_exceptions();
printf("1.0/0.0 = %f\n", 1.0/0.0);
show_fe_exceptions();
printf("1.0/10.0 = %f\n", 1.0/10.0);
show_fe_exceptions();
printf("sqrt(-1) = %f\n", sqrt(-1));
show_fe_exceptions();
printf("DBL_MAX*2.0 = %f\n", DBL_MAX*2.0);
show_fe_exceptions();
printf("nextafter(DBL_MIN/pow(2.0,52),0.0) = %.1f\n",
nextafter(DBL_MIN/pow(2.0,52),0.0));
show_fe_exceptions();
}
Possible output:
MATH_ERREXCEPT is set 0.0/0.0 = nan exceptions raised: FE_INVALID 1.0/0.0 = inf exceptions raised: FE_DIVBYZERO 1.0/10.0 = 0.100000 exceptions raised: FE_INEXACT sqrt(-1) = -nan exceptions raised: FE_INVALID DBL_MAX*2.0 = inf exceptions raised: FE_INEXACT FE_OVERFLOW nextafter(DBL_MIN/pow(2.0,52),0.0) = 0.0 exceptions raised: FE_INEXACT FE_UNDERFLOW[edit] References
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