C++: Class member reference validity?

Question

Class A
    {
     A(int& foo) : m_foo(foo) {}

     int& m_foo;
    };


int main(void)
{
 A* bar = 0;
 {
   int var = 5;
   bar = new A(var);
 }
 std::cout << "Is m_foo still valid?:" << bar.m_foo << std::endl;
}

"m_foo" is a reference and "var" is a local variable which is given to the constructor. "var" gets out of the scope before printing the value so does it make m_foo also invalid?

If m_foo is a pointer, then it would be invalid but does it work the same way with references?

Answer 1

m_foo is not valid when int var falls out of scope. The thing to which it refers has gone away.

Answer 2

Yes, a reference member becomes invalid if referenced object gets de-allocated. Same as with pointers. If you intend to keep references, make sure the lifetimes nest. Or use something like boost::weak_ptr.