#include <iostream>
#include <unistd.h>

using namespace std;

void Handler1(void) {
    cout << endl;
    cout << "A call to Handler 1" << endl;
    cout << endl;
    return;
}

void Handler2() {
    cout << endl;
    cout << "A call to Handler 2" << endl;
    cout << endl;
    return;
}

void Handler3(int code, void * ) {
    cout << endl;
    cout << "Handler 3 called  status= " << code  << endl;
    cout << endl;
    return;
}

void Handler4(int code, void * data) {
    cout << endl;
    cout << "Handler 4 called  status= " << code 
         << " data= " << reinterpret_cast<unsigned long>(data) << endl;
    cout << endl;
    return;
}

void Handler5(int code, void * data) {
    cout << endl;
    cout << "Handler 5 called  status= " << code 
         << " data= " << static_cast<int *> (data) 
         << " *data = " << *(static_cast<int*>(data)) << endl;
    cout << endl;
    return;
}

// I need this in the global space as the local variables 
// (on the stack, main's activation record)
// have gone out of scope when the exit function is called.

int value = 7;

int main() {

    // just to demo we can call a handler multiple times.
    atexit(Handler1);
    atexit(Handler1);
    atexit(Handler2);
    atexit(Handler1);

    // some permutations on on_exit
    on_exit(Handler3, static_cast<void *>(nullptr));
    on_exit(Handler4, reinterpret_cast<void *>(42));
    on_exit(Handler5, static_cast<void *> (&value));

    return 5;
}