C library - feclearexcept() function

---

---

The C fenv library feclearexcept() function is used to clear the floating-point exceptions in the floating-point environment specified by the bitmask argument excepts. If the except is equal to '0' it returns 0.

The bitmask argument excepts is a bitwise OR combination of floating -point exception macros such as FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW, FE_UNDERFLOW, and FE_ALL_EXCEPT.

Syntax

Following is the C library syntax of feclearexcept() function −

int feclearexcept(int excepts);

Parameters

This function accepts a single parameter −

• excepts − It represent a bitmask listing of the exception flags to clear.

Return Value

This function returns '0' if all the exception cleared. Otherwise, non-zero if an error occurs.

Example 1

Following is the basic c program to demonstrate the use of feclearexcept() function.

#include <stdio.h>
#include <math.h>
#include <fenv.h>

int main() {
   // Clear all floating-point exceptions.
   feclearexcept(FE_ALL_EXCEPT);
   
   // floating-point operation.
   double result = sqrt(-1.0);
   printf("%lf \n", result);
   
   // If floating-point exceptions were raised.
   if (fetestexcept(FE_INVALID)) {
     // Handle the invalid operation exception.
     printf("Invalid floating-point operation occurred.\n");
   }
   else {
       printf("No Invalid floating-point operation occurred. \n");
   }
   return 0;
}

Output

We get the following output if the floating-point number is not valid −

-nan 
Invalid floating-point operation occurred.

Example 2

Pass the excepts value 0

In the following example, if we pass the except value 0 then feclearexcept() function returns 0.

#include <stdio.h>
#include <math.h>
#include <fenv.h>

int main() {
   // Clear all floating-point exceptions.
   feclearexcept(FE_ALL_EXCEPT);
   int excepts = 0;
   int res = feclearexcept(excepts);
   printf("%d", res);
}

Output

Following is the output −

0

Example 3

The program below performs a floating-point division operation and raises a divide by zero exception if we try to divide by 0.

#include <stdio.h>
#include <fenv.h>

int main() {
   // Clear following floating-point exceptions.
   feclearexcept(FE_DIVBYZERO | FE_OVERFLOW);

   //divide-by-zero exception.
   double result = 1.0 / 0.0;

   // Check if the divide-by-zero exception was raised.
   if (fetestexcept(FE_DIVBYZERO)) {
      printf("Divide-by-zero exception.\n");
   } else {
      printf("No divide-by-zero exception.\n");
   }

   // Check if the overflow exception was raised.
   if (fetestexcept(FE_OVERFLOW)) {
      printf("Overflow exception.\n");
   } else {
      printf("No overflow exception.\n");
   }

   return 0;
}

Output

Following is the output −

Divide-by-zero exception.
No overflow exception.