fegetexceptflag, fesetexceptflag

int fegetexceptflag( fexcept_t* flagp, int excepts );

int fesetexceptflag( const fexcept_t* flagp, int excepts );

1) Attempts to obtain the full contents of the floating-point exception flags that are listed in the bitmask argument excepts, which is a bitwise OR of the floating point exception macros.

2) Attempts to copy the full contents of the floating-point exception flags that are listed in excepts from flagp into the floating-point environment. Does not raise any exceptions, only modifies the flags.

The full contents of a floating-point exception flag is not necessarily a boolean value indicating whether the exception is raised or cleared. For example, it may be a struct which includes the boolean status and the address of the code that triggered the exception. These functions obtain all such content and obtain/store it in flagp in implementation-defined format.

Parameters

Return value

​0​ on success, non-zero otherwise.

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");
}
 
int main(void)
{
    fexcept_t excepts;
 
    /* Setup a "current" set of exception flags. */
    feraiseexcept(FE_INVALID);
    show_fe_exceptions();
 
    /* Save current exception flags. */
    fegetexceptflag(&excepts,FE_ALL_EXCEPT);
 
    /* Temporarily raise two other exceptions. */
    feclearexcept(FE_ALL_EXCEPT);
    feraiseexcept(FE_OVERFLOW | FE_INEXACT);
    show_fe_exceptions();
 
    /* Restore previous exception flags. */
    fesetexceptflag(&excepts,FE_ALL_EXCEPT);
    show_fe_exceptions();
 
    return 0;
}

current exceptions raised: FE_INVALID
current exceptions raised: FE_INEXACT FE_OVERFLOW
current exceptions raised: FE_INVALID

References

• C11 standard (ISO/IEC 9899:2011):
• 7.6.2.2 The fegetexceptflag function (p: 210)
• 7.6.2.4 The fesetexceptflag function (p: 211)
• C99 standard (ISO/IEC 9899:1999):
• 7.6.2.2 The fegetexceptflag function (p: 191)
• 7.6.2.4 The fesetexceptflag function (p: 192)

See also