c++中的继承:构造顺序

Question

#include<iostream>
using namespace std;
class Parent
{
    public:
        Parent ( )
        {
            cout << "P";
        }
};
class Child : public Parent
{
    public:
        Child ( )
        {
            cout << "C";
        }
};
int main ( )
{
    Child obj1;
    Child obj2 ( obj1 );
    return 0;
}

程序如下:

=> An object of the class 'Child' named 'obj1' is created
=> Call to the constructor of the 'Child' class is made
=> Call to the constructor of the 'Parent' class is made
=> "P" is printed
=> Control transferred back to 'Child ( )'
=> "C" is printed
=> An object 'obj2' of the class 'Child' is created as a copy of 'obj1'
=> Call to the copy constructor of the 'Child' class is made
=> Call to the copy constructor of the 'Parent' class is made

下一个什么?复制发生在哪里——父节点的复制构造函数还是子节点的复制构造函数?在返回到main()之前，所有的控制都在哪里?

Answer 1

由于没有定义任何自定义复制构造函数，编译器提供了一个默认的。

默认复制构造函数调用基类的复制构造函数，然后按成员复制。

因为你的类没有数据成员，所以没有成员复制代码被调用。

为了更好地研究和理解代码执行的流程，你可能想要定义带有cout跟踪的自定义复制构造函数，例如:

class Parent 
{
public:
    ...
    Parent(const Parent& source)
    {
        std::cout << "Parent copy constructor" << std::endl;
    }
};
// ...similar for Child