C++为什么要调用这个析构函数,它来自何处

Question

我正在学习析构函数,复制和克隆,因此我编写了这段代码.一切都很清楚,但一行.它是第5行中的析构函数Destructor myClass1 0x28fec0.它来自哪里,为什么叫它？

控制台输出:

Constructor myClass1 0x28fe98
Constructor myClass2 0x28fe88
Constructor myClass3 0x28fe78
operator=
Destructor myClass1 0x28fec0
clone
Constructor clone 0x28fed0
operator=
Destructor clone 0x28fed0
Destructor myClass3 0x28fe78
Destructor myClass2 0x28fe88
Destructor myClass1 0x28fe98

main.cpp中:

#include <iostream>
#include "MyClass.h"

int main(){
    MyClass myClass1("myClass1"), myClass2("myClass2"), myClass3("myClass3");
    myClass2 = myClass1;
    myClass3 = myClass1.clone();
    return 0;
}

MyClass.h:

#ifndef MYCLASS_H
#define MYCLASS_H

#include <iostream>
#include <string>

class MyClass{
private:
    int *values;
    int size;
    int *copies;
    std::string name;
public:
    MyClass();
    MyClass(std::string name);
    ~MyClass();
    void operator=(MyClass myClass);
    MyClass clone();
};

#endif

MyClass.cpp:

#include "MyClass.h"

MyClass::MyClass(){
    std::cout << "Constructor" << this << std::endl;
    name = "None";
    size = 1;
    values = new int[1];
    values[0] = 0;
    copies = new int;
    *copies = 1;
    count++;
}

MyClass::MyClass(std::string name){
    std::cout << "Constructor " << name << " " << this << std::endl;
    size = 1;
    values = new int[1];
    values[0] = 0;
    copies = new int;
    *copies = 1;
    count++;
    this->name = name;
}

MyClass::~MyClass(){
    std::cout << "Destructor " << name << " " << this << std::endl;
    if(*copies == 1){
        delete [] values;
        values = 0;
        delete copies;
        copies = 0;
    }
    count--;
}

void MyClass::operator=(MyClass myClass){
    std::cout << "operator=" << std::endl;
    if(*copies == 1){
        delete copies;
        copies = 0;
        delete [] values;
        values = 0;
    }
    size = myClass.size;
    values = myClass.values;
    copies = myClass.copies;
    (*copies)++;
}

MyClass MyClass::clone(){
    std::cout << "clone" << std::endl;
    MyClass myClass("clone");
    myClass.size = size;
    delete [] myClass.values;

    myClass.values = new int[size];
    for(int i = 0; i < size; i++){
        myClass.values[i] = values[i];
    }
    return myClass;
}

Answer 1

因为你把这个论点operator=作为副本.

因此它MyClass在内部创建一个对象operator=,在operator=返回时会被破坏.