dangling reference

A dangling reference is a reference to an object that no longer exists. 
```
#include <iostream>
using namespace std;

int& bar() {
    int n = 10;
    return n;  // warning: reference to local variable ‘n’ returned 
}

int main() {
    int& i = bar();
    cout<<i<<endl;
    return 0;
}
```