基类和派生类析构函数执行顺序

转载一片博客：

http://www.cnblogs.com/dongling/p/5864295.html

下面是自己实验结果：

没有声明虚函数时:

#include <iostream>
using namespace std;

class Base
{
public:
    Base()
    {
        cout<<"Base contruction"<<endl;
    }
     ~Base()
    {
        cout<<"Base deconstruction"<<endl;
    }

};

class Derived: public Base
{
public:
    Derived(int i)
    {
        num = i;
        cout<<"Derived contruction "<<num<<endl;
    }
     ~Derived()
    {
        cout<<"Derived deconstruction"<<num<<endl;
    }

};

int main()
{
    Derived derived(1);

    Base* basePtr;
    Derived* derevedPtr;
    
    basePtr = new Derived(2);
    
    delete basePtr;
    
    


}

输出：

Base contruction
Derived contruction 1
Base contruction
Derived contruction 2
Base deconstruction
Derived deconstruction1
Base deconstruction
跟上面博文实验结果一致

总结：
由上面的实验结果可以看出，当 new CDerive() 时，会先运行基类的构造函数，然后再运行派生类的构造函数；
而当 delete pointer 时，编译器只考虑 pointer 指针本身的类型而不关心 pointer 实际指向的类型，即：若 pointer 为基类指针，则只调用基类的析构函数(不管 pointer 实际指向的是基类还是派生类)；若 pointer 是派生类指针，则先调用派生类的析构函数，再调用基类的析构函数，调用顺序与调用构造函数的顺序相反。

在声明虚函数之后：

#include <iostream>
using namespace std;

class Base
{
public:
    Base()
    {
        cout<<"Base contruction"<<endl;
    }
    virtual ~Base()
    {
        cout<<"Base deconstruction"<<endl;
    }

};

class Derived: public Base
{
public:
    Derived(int i)
    {
        num = i;
        cout<<"Derived contruction "<<num<<endl;
    }
    virtual ~Derived()
    {
        cout<<"Derived deconstruction"<<num<<endl;
    }

};

int main()
{
    Derived derived(1);

    Base* basePtr;
    Derived* derevedPtr;
    
    basePtr = new Derived(2);
    
    delete basePtr;
    
    


}

输出：

Base contruction
Derived contruction 1
Base contruction
Derived contruction 2
Derived deconstruction2
Base deconstruction
Derived deconstruction1
Base deconstruction