risky callback

risky_callback.cpp

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

class bar{
public:
    bar(){}
    ~bar(){}
    void setPointer(void* pointer){
        std::cout << "setPointer called" << std::endl;
        _pointer = pointer;
    }
    void onFinish(){
        if(_pointer) {
            std::cout << "pointer is alive" << std::endl;
        }else
            std::cout << "pointer is dead" << std::endl;
    }
private:
    void* _pointer;
};

class foo{
public:
    foo(){}
    ~foo(){}
    void setBadPointer(bar& bar){
        bar.setPointer(this);
    }
};

int main(){
    bar _bar;
    foo* _foo = new foo;
    _foo->setBadPointer(_bar);
    delete _foo;
    _foo = nullptr;

    _bar.onFinish();
    // prints "pointer is alive"
    return 0;
}