Benchmark function pointer versus direct call.

bench-function-pointer.c

#include <stdio.h>

#define MAX 100000000

int calculate() {
    int sum = 0;
    for (int i = 0; i < 10; i++) {
        sum += i;
    }
    return sum;
}

long direct() {
    long total = 0;
    for (int i = 0; i < MAX ; i++) {
        total += calculate();
    }
    return total;
}

long pointer(int (*sum)()) {
    long total = 0;
    for (int i = 0; i < MAX; i++) {
        total += sum();
    }
    return total;
}

int main() {
    printf("total: %ld\n", direct());
    printf("total: %ld\n", pointer(calculate));
    return 0;
}