子类拷贝构造函数会调用父类拷贝构造函数吗？

一. 编译器提供的默认子类拷贝构造函数会调用父类拷贝构造函数。

cpp 复制代码

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

class Parent {
public:
    Parent(string home_address = "中国") : m_home_address(home_address) {
        cout << "调用父类构造函数" << endl;
    }
    Parent(const Parent &other) {
        m_home_address = other.m_home_address;
        cout << "调用父类拷贝构造函数" << endl;
    }
    string get_home_address() {return m_home_address;}
private:
    string m_home_address;
};

class Child : public Parent {
public:
    Child(string home_address = "") : Parent(home_address) {
        cout << "调用子类构造函数" << endl;
    }
private:
};

int main(int argc, char *argv[]) {
    Child c1("广州");
    cout << "c1 home_address = " << c1.get_home_address() << endl << endl;

    Child c2 = c1; // 调用了子类的默认拷贝构造函数
    cout << "c2 home_address = " << c2.get_home_address() << endl;
    return 0;
}

从打印的信息中，我们可以知道：

创建一个对象 c1 时，先调用父类构造函数，后调用子类构造函数。
创建 c2 对象时，执行了编译器提供的默认子类拷贝构造函数，具体构造顺序为：先调用父类拷贝构造函数，后调用编译器提供的默认子类拷贝构造函数。从而打印出 c2 home_address = 广州

二. 重写的子类拷贝构造函数默认不会调用父类的拷贝构造函数，而是调用父类默认构造函数。

cpp 复制代码

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

class Parent {
public:
    Parent(string home_address = "中国") : m_home_address(home_address) {
        cout << "调用父类构造函数" << endl;
    }
    Parent(const Parent &other) {
        m_home_address = other.m_home_address;
        cout << "调用父类拷贝构造函数" << endl;
    }
    string get_home_address() {return m_home_address;}
private:
    string m_home_address;
};

class Child : public Parent {
public:
    Child(string home_address = "") : Parent(home_address) {
        cout << "调用子类构造函数" << endl;
    }
    Child(const Child &other) {
        cout << "调用子类拷贝构造函数" << endl;
    }
private:
};

int main(int argc, char *argv[]) {
    Child c1("广州");
    cout << "c1 home_address = " << c1.get_home_address() << endl << endl;

    Child c2 = c1; // 调用了子类的默认拷贝构造函数
    cout << "c2 home_address = " << c2.get_home_address() << endl;
    return 0;
}

从打印的信息中，我们可以知道：

创建 c2 对象时，执行了子类拷贝构造函数，具体构造顺序为：先调用父类默认构造函数，后调用子类拷贝构造函数。从而打印出 c2 home_address = 中国

三. 重写的子类拷贝构造函数时应当显式的告诉编译器去调用父类的拷贝构造函数去构造父类，从而避免调用子类拷贝构造函数去创建一个对象时，导致子类中包含父类的那部分数据丢失的情况发生。具体做法为：Child(const Child &other) : Parent(other);

cpp 复制代码

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

class Parent {
public:
    Parent(string home_address = "中国") : m_home_address(home_address) {
        cout << "调用父类构造函数" << endl;
    }
    Parent(const Parent &other) {
        m_home_address = other.m_home_address;
        cout << "调用父类拷贝构造函数" << endl;
    }
    string get_home_address() {return m_home_address;}
private:
    string m_home_address;
};

class Child : public Parent {
public:
    Child(string home_address = "") : Parent(home_address) {
        cout << "调用子类构造函数" << endl;
    }
    Child(const Child &other) : Parent(other) {
        cout << "调用子类拷贝构造函数" << endl;
    }
private:
};

int main(int argc, char *argv[]) {
    Child c1("广州");
    cout << "c1 home_address = " << c1.get_home_address() << endl << endl;

    Child c2 = c1; // 调用了子类的默认拷贝构造函数
    cout << "c2 home_address = " << c2.get_home_address() << endl;
    return 0;
}

从打印的信息中，我们可以知道：

创建 c2 对象时，执行了子类拷贝构造函数，具体构造顺序为：先调用父类拷贝构造函数，后调用子类拷贝构造函数。从而打印出 c2 home_address = 广州