Question

Possible Duplicate:
Returning the address of local or temporary variable
Can a local variable's memory be accessed outside its scope?
return reference to local variable

Is it an undefined behavior when you return a ref. to a local variable ?

http://ideone.com/Kz381

int & func(){

        int x = 10;
        return x;

}

int main() {

        int &y = func();
        cout << y << endl;

}

Answer 1

Yes it is. The variable is no longer available when the function ends.

You’re unlucky that it appears to work. The thing is, that memory isn’t cleared so the 10 is still there, but it can be reclaimed at any time, so it’s definitely not safe.