C++拷贝构造函数

#include <iostream>

using namespace std;

class Line {
   public:
      int getLength( void );
      Line( int len );             // simple constructor
      Line( const Line &obj);      // copy constructor
      ~Line();                     // destructor

   private:
      int *ptr;
};

// Member functions definitions including constructor
Line::Line(int len) {
   cout << Normal constructor allocating ptr << endl;

   // allocate memory for the pointer;
   ptr = new int;
   *ptr = len;
}

Line::Line(const Line &obj) {
   cout << Copy constructor allocating ptr. << endl;
   ptr = new int;
   *ptr = *obj.ptr;     // copy the value
}

Line::~Line(void) {
   cout << Freeing memory! << endl;
   delete ptr;
}

int Line::getLength( void ) {
   return *ptr;
}

void display(Line obj) {
   cout << Length of line :  << obj.getLength() <<endl;
}

// Main function for the program
int main() {
   Line line(10);

   display(line);

   return 0;
}