Calling a function through its address in memory in c / c++

Question

Given knowledge of the prototype of a function and its address in memory, is it possible to call this function from another process or some piece of code that knows nothing

Answer 1

In most OP, every process has its own memory, so you can't.

Sample code: a.c:

#include 

int r() {return 2;}
int main() {
    printf("%p\n",r);
    while(1);
}

b.c:

#include 

int main() {
int a,(*b)();
scanf("%p",&b);
a=b();
printf("%d\n",a);
return 0;
}

this get segmentation fault.