Behaviour of pass by reference and its scope

In the below code the variable 'a' is passed to the constructor by reference and the reference of the parameter of the constructor receiving the address of a 'x' is passed as reference to attribute.The attribute is then initialized with value 3. The program is outputing the value 3 when running;

MY QUESTION

Shouldn't the program crash or show 2 because after the constructor is called x should go out of scope and be released and its address should be freed right. and trying to write to it should give a memory access violation. However in this case the x is still in program control holding the address of 'a'

Is this valid c++ behavior or am i missing something?

#include <iostream>
#include <conio.h>

using namespace std;

class myclass {

public:
    int& attribute;
    myclass(int& x):attribute(x) {

    }

    void func() {
        attribute = 3;
    }
};

int main() {
    int a = 2;
    myclass obj(a);
    obj.func();
    std::cout << a;
    _getch();
}