Pass by Value Copies, Pass by Reference Does Not

1#include <iostream>
2#include <string>
3using namespace std;
4 
5class Tag {
6    string m_name;
7public:
8    Tag(const string& name) : m_name(name) { cout << "ctor " << m_name << endl; }
9    Tag(const Tag& other) : m_name(other.m_name) { cout << "copy " << m_name << endl; }
10    ~Tag() { cout << "dtor " << m_name << endl; }
11};
12 
13void byValue(Tag t) {
14    cout << "in byValue" << endl;
15}
16 
17void byRef(const Tag& t) {
18    cout << "in byRef" << endl;
19}
20 
21int main() {
22    Tag a("a");
23    byValue(a);
24    byRef(a);
25    cout << "end of main" << endl;
26    return 0;
27}