#include <string>
#include <iostream>
 
class A
{
public:
	A(std::string& s) : s_(s)
	{ std::cout << "A::ctor" << std::endl; }
 
	A(const A& rhs) : s_(rhs.s_)
	{ std::cout << "A::copy" << std::endl; }
 
	~A()
	{ std::cout << "A::dtor" << std::endl; }
 
	A& operator=(const A& rhs)
	{ std::cout << "A::copyassign" << std::endl; }
 
private:
	std::string& s_;    
};
 
std::string s("hello world");
 
int main()
{
	A a(s);    // a.s_ references the global s.
	A b(a);    // b.s_ references the a.s_ that references the global s.
 
	return 0;
}

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