Where Function pointers are stored ?

[2001goran]

Hi

Where function are stored in memory?


In the following example , where function pointer fp stored ?

#include <math.h>
#include <stdio.h>
 
// Function taking a function pointer as an argument
double compute_sum(double (*funcp)(double), double lo, double hi)
{
double  sum = 0.0;
 
    // Add values returned by the pointed-to function '*funcp'
    for (int i = 0;  i <= 100;  i++)
        {
double  x, y;
 
        // Use the function pointer 'funcp' to invoke the function
        x = i/100.0 * (hi - lo) + lo;
        y = (*funcp)(x);
        sum += y;
        }
return sum;
}
 
int main(void)
{
double  (*fp)(double);      // Function pointer
    double  sum;
 
    // Use 'sin()' as the pointed-to function
    fp = &sin;
    sum = compute_sum(fp, 0.0, 1.0);
    printf("sum(sin): %f\n", sum);
 
    // Use 'cos()' as the pointed-to function
    sum = compute_sum(&cos, 0.0, 1.0);
    printf("sum(cos): %f\n", sum);
   

    return 0;
}

[anduril462]

It depends on where you declare it. In the code above, it is stored on the stack, just like sum or any other local variables, like if you had a char * or int * variable. You could dynamically allocate space for a function pointer, and have it be stored on the heap, or declare it as a global or static local, and have it be stored with the other global and static local variables, but that is less common.

Remember, a function pointer is just a pointer, so all it contains is the address. It doesn't store the function itself (i.e. no code or variables).