C library - fesetexceptflag() function

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The C fenv library fesetexceptflag() function is used to set the state of specified floating-point exception flags through the 'excepts' argument. This argument is a bitwise OR combination of the floating-point exception macros, such as FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW, and FE_UNDERFLOW.

Syntax

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

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

Parameters

This function accepts a following parameters −

• flagp − It represent a pointer to an 'fexcept_t' object where the flags will be stored or read from.

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

Return Value

This function returns 0 if it successfully get the state of the specified exception, non-zero otherwise.

Example 1

Following is the basic C example demonstrating the use of fesetexceptflag() to set a single floating-point exception flag.

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

int main() {
   // Declare a variable to hold the exception flag
   fexcept_t flag;

   // Set the FE_OVERFLOW exception flag
   if (fesetexceptflag(&flag, FE_OVERFLOW) != 0) {
      printf("Failed to set the FE_OVERFLOW exception flag.\n");
      return 1;
   } else {
      printf("Successfully set the FE_OVERFLOW exception flag.\n");
   }
   return 0;
}

Output

Following is the output −

Successfully set the FE_OVERFLOW exception flag.

Example 2

The following C program uses the fesetexceptflag() to set the FE_INVALID exception flag.

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

int main() {
    // Declare a variable to hold the exception flag
    fexcept_t flag;

    // Set the FE_OVERFLOW exception flag
    if (fesetexceptflag(&flag, FE_INVALID) != 0) {
        printf("Failed to set the FE_INVALID exception flag.\n");
        return 1;
    } else {
        printf("Successfully set the FE_INVALID exception flag.\n");
    }
    return 0;
}

Output

Following is the output −

Successfully set the FE_INVALID exception flag.

Example 3

Here is the another example that sets the FE_INVALID exception flag and then checks if it was successfully set.

#include <stdio.h>
#include <fenv.h>
int main() {
   fexcept_t flag;

   // Set the FE_INVALID exception flag
   if (fesetexceptflag(&flag, FE_INVALID) != 0) {
      printf("Failed to set the FE_INVALID exception flag.\n");
      return 1;
   } else {
      printf("Successfully set the FE_INVALID exception flag.\n");
   }

   // Perform an invalid floating-point operation to trigger FE_INVALID
   double result = 1.0 / 0.0;

   // Check if FE_INVALID is raised
   if (fetestexcept(FE_INVALID)) {
      printf("FE_INVALID exception is raised due to division by zero.\n");
   } else {
      printf("FE_INVALID exception is not raised.\n");
   }
   return 0;
}

Output

Following is the output −

Successfully set the FE_INVALID exception flag.
FE_INVALID exception is not raised.