MATH_ERRNO, MATH_ERREXCEPT, math_errhandling

The macro constant math_errhandling expands to an expression of type int that is either equal to MATH_ERRNO , or equal to MATH_ERREXCEPT , or equal to their bitwise OR ( MATH_ERRNO | MATH_ERREXCEPT ).

The value of math_errhandling indicates the type of error handling that is performed by the floating-point operators and functions :

If the implementation supports IEEE floating-point arithmetic (IEC 60559), math_errhandling & MATH_ERREXCEPT is required to be non-zero.

The following floating-point error conditions are recognized:

Notes

Whether FE_INEXACT is raised by the mathematical library functions is unspecified in general, but may be explicitly specified in the description of the function (e.g. rint vs nearbyint ).

Before C99, floating-point exceptions were not specified, EDOM was required for any domain error, ERANGE was required for overflows and implementation-defined for underflows.

Example

#include <stdio.h>
#include <fenv.h>
#include <math.h>
#include <errno.h>
#pragma STDC FENV_ACCESS ON
int main(void)
{
    printf("MATH_ERRNO is %s\n", math_errhandling & MATH_ERRNO ? "set" : "not set");
    printf("MATH_ERREXCEPT is %s\n",
           math_errhandling & MATH_ERREXCEPT ? "set" : "not set");
    feclearexcept(FE_ALL_EXCEPT);
    errno = 0;
    printf("log(0) = %f\n", log(0));
    if(errno == ERANGE)
        perror("errno == ERANGE");
    if(fetestexcept(FE_DIVBYZERO))
        puts("FE_DIVBYZERO (pole error) reported");
}

MATH_ERRNO is set
MATH_ERREXCEPT is set
log(0) = -inf
errno = ERANGE: Numerical result out of range
FE_DIVBYZERO (pole error) reported

References

See also