foo.c

#include <stdio.h>

struct {
    int first;
    int second;
}typedef myStruct;

int getFirst (myStruct* a) { return (*a).first; }
int getSecond (myStruct* a) { return (*a).second; }

int sum(myStruct* a, myStruct* b, int (*pt2Func)(myStruct*)) {
    int result = pt2Func(a) + pt2Func(b);
    return result;
}

void main() {
    myStruct sOne = {1,2};
    myStruct sTwo = {10,100};
    printf("Sum First: %d\n", sum(&sOne, &sTwo, &getFirst));
    printf("Sum Second: %d\n", sum(&sOne, &sTwo, &getSecond));
}