如何写C++基类析构函数?

#include <iostream>

class Base
{
public:
    Base() {
        std::cout << "Base Constructor()" << std::endl;
    }
    ~Base() {
        std::cout << "Base Destructor()" << std::endl;
    }
};

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

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

$ g++ a.cpp && ./a.out
Base Constructor()
Derived Constructor()
Base Destructor()

可以看到，派生类的析构函数没有被调到。
解决方法是，在基类的析构函数前加virtual。

#include <iostream>

class Base
{
public:
    Base() {
        std::cout << "Base Constructor()" << std::endl;
    }
    virtual ~Base() {
        std::cout << "Base Destructor()" << std::endl;
    }
};

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

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

$ g++ a.cpp && ./a.out
Base Constructor()
Derived Constructor()
Derived Destructor()
Base Destructor()