进入f()函数后

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　　再看<<Thinking in C++>>中的一段代码，更为清晰的讲解了拷贝构造函数的机制：

//: HowMany_2.cpp
#include <string>
#include <iostream>

using namespace std;

class HowMany {
  string name;
  static int objectCount;
 
public:
  HowMany(const string& id = "") {
    name = id;
    ++objectCount;
    print("HowMany()");
  }
  ~HowMany() {
    --objectCount;
    print("~HowMany()");
  }
  HowMany(const HowMany& h) {
    name = h.name + "copy";
    ++objectCount;
    print("HowMany(const HowMany&)");
  }
 
  void print(const string& msg = "") {
    if (msg.length() != 0) {
      cout << msg << endl;
    }
    cout << ' ' << name << ": "
   << "objectCount = " << objectCount << endl;
  
    return ;
  }
};

int HowMany::objectCount = 0;

HowMany f(HowMany x) {
  x.print("x argument inside f()");
  cout << "Return From f()" << endl;
  return x;
}

int main() {
  {
    HowMany h("h");
    cout << "Entering f()" << endl;
    HowMany h2 = f(h);
    cout << "Call f()， no return value" << endl;
    f(h);
    cout << "After call to f()" << endl;
  }
  // getchar();
  return 0;
} ///:~