类能报告对象的创建、销毁、赋值以及每个对象一个识别号（代码来源于C++沉思录）

#include <iostream>class Test{
public:Test();Test(const Test&);Test& operator=(const Test&);~Test();
private:static int count;int id;
};int Test::count = 0;
Test::Test(){id = ++count;std::cout << "Test " << id<< " default constructor\n"; 
}
Test::Test(const Test& t){id = ++count;std:: cout << "Test " << id<< " copied from " << t.id << std::endl;
}
Test& Test:: operator=(const Test& t){std:: cout << "Test " << id<< " assigned from " << t.id << std::endl;
}
Test::~Test(){std::cout << "Test " << id << " destroyed" << std::endl;
}int main()
{Test s;Test t(s);s = t;return 0;
}