C++默认拷贝构造

class Person
{
public:
   Person()
   {   
      std::cout << "Person()构造" << std::endl;
   }   

   ~Person()
   {   
      std::cout << "~Person()析构" << std::endl;
   }   

   int age_get()
   {   
      return m_age;
   }   

   void age_set(int age)
   {   
      m_age = age;
   }   

private:
   int m_age;
};

int main()
{
   Person p1; 
   p1.age_set(12);
   Person p2 = p1; 
   std::cout << p2.age_get() << std::endl;

   Person p3(p1);
   std::cout << p3.age_get() << std::endl;

   return 0;
} 

$ ./a.out     
Person()构造
12
12
~Person()析构
~Person()析构
~Person()析构