return reference in cpp function returns a copy

Question

I am trying to return the reference of the argument in the function test, but when I assign another value to the returned reference, the original doesn't change:

#include <iostream>

using namespace std;

int& test(int& n) {
    return n;
}

int main() {
    int n = 1;
    int m = test(n);
    m = 2;
    cout << n << endl; // n = 1
    return 0;
}

How can I return this reference as I expect?

This testing is just for studying purposes.

Answer 1

Make m an lvalue reference:

 int& m = test(n);

You can also bind to temporaries like this:

int test(int& n) { // return by value
    return n;
}

int main() {
    int n = 1;
    int&& m = test(n); // rvalue reference binding to a copy of `n`
    m = 2;
    std::cout << n << std::endl;
    return 0;
}

Although the above code is not recommended.

Or even this:

int&& test( int& n ) // return by rvalue reference
{
    return std::move( n ); // cast `n` from lvalue to xvalue
}

int main( )
{
    int n = 1;
    int&& m = test(n);
    m = 2;
    std::cout << n << std::endl;
}

This one is also not recommended. Instead of rvalue reference, you should return by value.