拷贝构造函数

浅拷贝(bitwise copy)&深拷贝(memberwise copy)

没有virtual函数

#include <iostream>
#include <string>
using namespace std;

class A {
public:
    A(): n_(0) {
        ptr_ = new char[5];
        for (int i = 0; i < 5; ++ i) ptr_[i] = i + '0';
        s_ = "12345";
    }
    int n_;
    char* ptr_; // bitwise copy
    string s_; // memberwise copy, because string has a copy construct function
};
  
  
int main() {
  A a;
  A b = a;
  for (int i = 0; i < 5; ++ i) b.ptr_[i] = i + 'a';
  b.s_ = "abcde";

  cout << a.ptr_[0] << " " << b.ptr_[0] << endl;
  cout << a.s_ << " " << b.s_ << endl;

  return 0;
}

output:
a a
12345 abcde

类A没有拷贝构造函数，当发生赋值时，编译器必须为其添加一个拷贝构造。对于常规变量，例如int，char是浅拷贝；然而string是深拷贝，因为string类存在拷贝构造函数。*

存在virtual函数

#include <iostream>
class Animal {
  public:
    virtual void Run() {...}
};

class Tiger: public Animal {
  public:
    virtual void Run() {...}
};

int main() {
  Tiger tiger;
  // 发生截断
  // 并且，animal的虚指针vptr指向类Animal
  Animal animal = tiger; // memberwise copy
  animal.Run(); // 调用的Animal的Run()
}