c++ - 请解释以下赋值语句的输出

Question

我有以下代码片段。

    #include <iostream>
    using namespace std;
    
    class A
    {
        int* ptr;
        int size;
        public:
            A(int n):ptr(new int[n]),size(n) 
            { 
                cout << "default constructfor class A object:0x" << hex << this << dec << endl; 
            }
            A(const A& obj): ptr (new int[obj.size]), size(obj.size) 
            { 
                memcpy (ptr, obj.ptr, obj.size); 
                cout << "copy constructfor class A object:0x" << hex << this << ", called with 0x" << &obj << dec << endl;
            }
            A operator=(const A& obj)
            {
                cout << "Normal assignment operator function called 0x" << hex << this << ", called with 0x" << &obj << dec << endl;
                delete[]ptr;
                ptr = new int[obj.size];
                s
ize = obj.size;
                memcpy(ptr, obj.ptr, obj.size);
                return *this;
            }
            A(A&& obj) : ptr(obj.ptr), size(obj.size) 
            { 
                obj.ptr = NULL; 
                obj.size = 0; 
                cout << "move constructfor class A object:0x" << hex << this << ", called with 0x"<< &obj << dec << endl; 
            }
            A& operator=(A&& obj)
            {
                cout << "move assignment operator function called 0x" << hex << this << ", called with 0x" << &obj << dec << endl;
                ptr = obj.ptr;
                size = obj.size;
                obj.ptr = NULL;
                obj.size = 0;
                return *this;
            }
            ~A() 
            { 
                cout << "destructor class A object:0x" << hex << this << dec << endl; 
            }
    };
    A f(A a) { return a; }
    int main()
    {
        A a1(8);
        A a2 = a1;
        A a3 = *(new A(7)); // This would be a memory leak. please ignore this.
        A a4 = f(a3);

        a1 = a2 = a4 = f(a3) = a3;

        cout << "Object a1 address - 0x" << hex << &a1 << dec << endl;
        cout << "Object a2 address - 0x" << hex << &a2 << dec << endl;
        cout << "Object a3 address - 0x" << hex << &a3 << dec << endl;
        cout << "Object a4 address - 0x" << hex << &a4 << dec << endl;

        return 0;
    }

我想了解以下赋值语句的输出。

a1 = a2 = a4 = f(a3) = a3;

我为此得到的输出如下。
-------------------------------------------------- --------------------------
A 类对象的复制构造：0x010FFB5C，使用 0x010FFCD4 调用
A 类对象的移动构造：0x010FFBC4，使用 0x010FFB5C 调用
析构函数类A 对象：0x010FFB5C
称为 0x010FFBC4 的普通赋值运算符函数，使用 0x010FFCD4 调用
A 类的复制构造 对象：0x010FFBB4，使用 0x010FFBC4 调用
移动赋值运算符函数，调用 0x010FFCC4，使用 0x010FFBB4 调用
普通赋值运算符函数称为 0x010FFCE4，使用 0x010FFCC4 调用
A 类对象的复制构造:0x010FFBA4，用 0x010FFCE4 调用
移动赋值运算符函数调用 0x010FFCF4，调用 0x010FFBA4
---------------------------------------- ------------------------------------
对象 a1 的
地址 - 0x010FFCF4 对象 a2 的地址 - 0x010FFCE4
的地址对象 a3 - 0x010FFCD4
对象 a4 的地址 - 0x010FFCC4

有人可以解释这段代码片段中赋值语句的输出吗？请耐心等待，因为我是移动和右值参考概念的新手。

标签： c++c++11rvalue-referencemove-assignment-operator