根据《effective C++》第7章所述，new的一个子类对象赋值给基类指针delete的时候为了防止子类的析构函数没有调用要在基类的析构函数加上virtual 关键字：

#include <stdint.h>
#include <iostream>
#include <iomanip>
#include <vector>

class A
{
public:
    A() : a(0)
    {
    }
    virtual  ~A()
    {
        std::cout << "delete A" << std::endl;
    }

private:
    int a;
};

class B : public A
{
public:
    B() : A(), b(1), c(2) {}
    ~B()
    {
        std::cout << "delete B" << std::endl;
    }

private:
    int b;
    int c;
    // members
};
int main()
{
    A *a1 = new B;
    delete a1; 
}

成功析构！

然而根据《more effective C++》第三章所说，用一个数组存放基类的指针指向子类的对象，使用delete []来释放子类的对象会出现内存泄漏（crash）：

#include <stdint.h>
#include <iostream>
#include <iomanip>
#include <vector>

class A
{
public:
    A() : a(0)
    {
    }
    virtual ~A()
    {
        std::cout << "delete A" << std::endl;
    }

private:
    int a;
};

class B : public A
{
public:
    B() : A(), b(1), c(2) {}
    ~B()
    {
        std::cout << "delete B" << std::endl;
    }

private:
    int b;
    int c;
    // members
};
int main()
{
    A *a1 = new B[2];
    delete[] a1;
}

结果是什么也没有输出。

一个朴素的解决办法是不要使用new一个指针数组，改用vector或array来存放指针：

#include <stdint.h>
#include <iostream>
#include <iomanip>
#include <vector>

class A
{
public:
    A() : a(0)
    {
    }
    virtual ~A()
    {
        std::cout << "delete A" << std::endl;
    }

private:
    int a;
};

class B : public A
{
public:
    B() : A(), b(1), c(2) {}
    ~B()
    {
        std::cout << "delete B" << std::endl;
    }

private:
    int b;
    int c;
    // members
};
int main()
{

    std::vector<A *> v;
    v.push_back(new B);
    v.push_back(new B);
    for (int i = 0; i < v.size(); ++i)
        delete v[i]; 
}

这样即使用一个基类指针指向子类指针也能正确地析构