C++ 对虚拟析构函数的解释：
By making the Base class Destructor virtual, both the destructors will be called in order. The order of execution of destructor in an inherited class during a clean up is like this. 1. Derived class destructor 2. Base class destructor 要点：
- 多层继承的时候，只要基类的析构是virtual的。每层 析构都会被调用
-
如果基层不是 virtual, 那么继承类的析构函数就不会被调用,这可能导致内存泄露
- 如果基层的析构函数不是 virtual，而 其它层是 virtual， 可能会导致异常。
对3的解释：不同编译器对这个的做法是不同的，当然，不管怎么说，这种情况应该避免。在VC 2005中，非基层的虚拟析构函数，将在基层的非虚拟析构函数之后被调用，但是由于基层的析构函数已经被调用，类已经被释放，因此会导致一个异常,个人感觉是vc的bug。
一个简单的例子：
#include <iostream>
using namespace std;
class Base
{
public:
Base(){ cout<<"Constructor: Base"<<endl;}
/*virtual*/ ~Base(){ cout<<"Destructor : Base"<<endl;}
};
class Sec : public Base
{
public:
Sec(){ cout << "Constructor: Sec"<< endl;}
/*virtual*/~Sec(){ cout << "Destructor: Sec"<< endl;}
};
class Derived: public Sec
{
//Doing a lot of jobs by extending the functionality
public:
Derived(){ cout<<"Constructor: Derived"<<endl;}
/*virtual*/~Derived(){ cout<<"Destructor : Derived"<<endl;}
};
void main()
{
Base *Var = new Derived();
delete Var;
int i;
cin >> i;
}
