【C/C++】虚析构函数

直接从代码看结果

// demo 1
class Base {
public:
    Base() {
        cout << "Base Constructor" << endl;
    }

    ~Base() {
        cout << "Base Destructor" << endl;
    }
};

class Derived : public Base {
public:
    Derived() {
        cout << "Derived Constructor" << endl;
    }

    ~Derived() {
        cout << "Derived Destructor" << endl;
    }
};

int main() {
    Base *obj = new Derived();
    delete obj;
}

输出：
Base Constructor
Derived Constructor
Base Destructor

// demo 2, 更改Base析构函数的定义，其他不变
class Base {
public:
    Base() {
        cout << "Base Constructor" << endl;
    }

    virtual ~Base() {
        cout << "Base Destructor" << endl;
    }
};

输出：
Base Constructor
Derived Constructor
Derived Destructor
Base Destructor

// demo 3, 更改Base析构函数的定义，定义为纯虚函数
class Base {
public:
    Base() {
        cout << "Base Constructor" << endl;
    }

    virtual ~Base() = 0;
};

编译出错：
undefined reference to `Base::~Base()’

// demo 4, 定义Base的析构函数为纯虚函数，并且实现
class Base {
public:
    Base() {
        cout << "Base Constructor" << endl;
    }

    virtual ~Base() = 0;
};

Base::~Base() {

}

输出：
Base Constructor
Derived Constructor
Derived Destructor

继承关系下的析构函数定义为虚函数

构造函数不能为虚函数

纯虚函数可以有其实现