虚析构函数

#include
using namespace std;

class base
{
public:
      base();
       ~base();
};
base::base()
{
   cout<<"base construct"<}
base::~base()
{
   cout<<"base deconstruct"<}

class child:public base
{
public:
       child();
       ~child();
};
child::child()
{
   cout<<"child construct"<}
child::~child()
{
   cout<<"child deconstruct"<}

void main()
{
   base *ptr=new child();
   delete ptr;
   ptr=NULL;
}

结果：

base construct

child construct

base deconstruct

child deconstruct

 

如果没有virtual的话，结果是：

base construct

child construct

base deconstruct