What is fesetexceptflag() in C?

The fesetexceptflag function is a C library function that resets the floating-point environment’s exception status flags.

To use the fesetexceptflag function, we need to import the fenv.h header file, as shown below:

#include <fenv.h>

Example

The fesetexceptflag resets the flags to a state that the fegetexceptflag function saved.

First, we enable the pragma FENV_ACCESS so that the program can call the functions.
We set the floating-point exception macros in the set_execptions function defined in the program. The fetestexcept function sets the exceptions.
We call the set_exceptions function, which successfully sets all the flags defined in the function.
To save this floating-point exception state, we call the fegetexceptflag function.
To test the fesetexceptflag function, we raise two exceptions using the feraiseexcept function and set the state.
The final step is calling the fesetexceptflag function, which reinstates the previously saved state, as shown in the code below:

#include <stdio.h>
#include <fenv.h>
 
#pragma STDC FENV_ACCESS ON
//Set the floating-point exception macros
void set_exceptions()
{
    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()
{
    //Declare fexcept_t object
    fexcept_t excepts;
 
    //Set the current execption flags 
    feraiseexcept(FE_UNDERFLOW);
    set_exceptions();
 
    //Save the flags by calling fegetexecptflag 
    fegetexceptflag(&excepts,FE_ALL_EXCEPT);
 
    //Raise two exceptions 
    feclearexcept(FE_ALL_EXCEPT);
    feraiseexcept(FE_OVERFLOW | (FE_DIVBYZERO));
    set_exceptions();
 
    // Restore the flags by calling fesetexecptflag 
    fesetexceptflag(&excepts,FE_ALL_EXCEPT);
    set_exceptions();
 
    return 0;
}

What is fesetexceptflag() in C?

Syntax

Parameters

Return value

Example