Returning lvalue from function

Question

Why the result of returning lvalue from function is that that object std::vector<int> v in main() function has same memory address as returned object std::vector<int> vec in a get_vec() function, even though these objects exist in a different stack frame ?

Why there is not called move constructor ?

#include <iostream>
#include <vector>


std::vector<int> get_vec()
{
    std::vector<int> vec = { 1, 2, 3, 4, 5 }; 
    std::cout << "get_vec():\n" << &vec << '\n' << vec.data() << "\n\n";   
    return vec;
}

int main()
{
    std::vector<int> v = get_vec();
    std::cout << "main():\n" << &v << '\n' << v.data() << "\n\n";   
  
    return 0;
}

OUTPUT:
get_vec():
0x7a07ee93baa0
0x226b290

main():
0x7a07ee93baa0
0x226b290

Answer 1

vec is either moved (automatically, because you're returning a local variable), or, if the compiler is smart enough, is the same object as v (this is called NRVO).

In both cases .data() is going to stay the same. When moved, the new vector takes ownership of the other vector's heap memory.

&vec,&v are going to be the same only if the compiler performs NRVO.