构造函数、析构函数、复制构造函数的调用

#include <iostream>
using namespace std;

class A {
public:
    A() {
        cout << "构造函数调用" << endl;
    }

    A(const A &a) {//不加const会报错
        cout << "复制构造函数调用" << endl;
    }

    A& operator=(const A&a) {//不加const会报错
        cout << "重载的复制构造函数调用" << endl;
        return *this;
    }

    ~A() {
        cout << "析构函数调用" << endl;
    }

};

A function() {
    A x;
    return x;
}

int main()
{
    system("color fc");//调控制台背景色
    A b = function();
    cout << "----------" << endl;
    return 0;
}

image.png

#include <iostream>
using namespace std;

class A {
public:
    A() {
        cout << "构造函数调用" << endl;
    }

    A(const A &a) {//不加const会报错
        cout << "复制构造函数调用" << endl;
    }

    A& operator=(const A&a) {
        cout << "重载的复制构造函数调用" << endl;
        return *this;
    }

    ~A() {
        cout << "析构函数调用" << endl;
    }
};

A function() {
    return A();
}

int main()
{
    system("color fc");//调控制台背景色
    A b = function();
    cout << "----------" << endl;
    return 0;
}

image.png

#include <iostream>
using namespace std;

class A {
public:
    A() {
        cout << "构造函数调用" << endl;
    }

    A(const A &a) {
        cout << "复制构造函数调用" << endl;
    }

    A& operator=(const A&a) {
        cout << "重载的复制构造函数调用" << endl;
        return *this;
    }

    ~A() {
        cout << "析构函数调用" << endl;
    }

};

A function(A x) {
    return x;
}

int main()
{
    system("color fc");//调控制台背景色
    A b = function(A());
    cout << "----------" << endl;
    return 0;
}

image.png

#include <iostream>
using namespace std;

class A {
public:
    A() {
        cout << "构造函数调用" << endl;
    }

    A(A &a) {
        cout << "复制构造函数调用" << endl;
    }

    A& operator=(const A&a) {
        cout << "重载的复制构造函数调用" << endl;
        return *this;
    }

    ~A() {
        cout << "析构函数调用" << endl;
    }

};

A function_1(A x) {
    return x;
}

A function_2() {
    A x;
    return x;
}

int main()
{
    system("color fc");//调控制台背景色
    A a;
    cout << "----------" << endl;
    function_1(a);
    cout << "----------" << endl;
    A b;
    b = function_2();
    cout << "----------" << endl;
    function_2();
    cout << "----------" << endl;
    return 0;
}

image.png

#include <iostream>
using namespace std;

class A {
public:
    A() {
        cout << "构造函数调用" << endl;
    }

    A(A &a) {
        cout << "复制构造函数调用" << endl;
    }

    A& operator=(const A&a) {
        cout << "重载的复制构造函数调用" << endl;
        return *this;
    }

    ~A() {
        cout << "析构函数调用" << endl;
    }

};

A function_3(A y) {
    A x;
    return x;
}

int main()
{
    system("color fc");//调控制台背景色
    A c;
    A d;
    c = function_3(d);
    cout << "----------" << endl;
    return 0;
}

image.png