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

On modern operating systems, each process has its own address space and addresses are only valid within a process. If you want to execute code in some other process, you either have to inject a shared library or attach your program as a debugger.

Once you are in the other program's address space, this code invokes a function at an arbitrary address:

typedef int func(void);
func* f = (func*)0xdeadbeef;
int i = f();