virtual继承出来的类实例出现delete异常

本题的代码：

#include <iostream>

using namespace std;

class Base

{

public:

Base() { cout<<"Base"<<endl; }

~Base() { cout<<"~Base"<<endl; }

};

class Derive : virtual public Base

{

public:

Derive() { cout<<" Derive"<<endl; }

~Derive() { cout<<" ~Derive"<<endl; }

};

int main(int argc, char* argv[])

{

Base * b = new Derive();

delete b;

return 0;

}

上面的delete将引发访存异常（VC6.0）。如果主函数里代码改为：

Derive * b = new Derive();

delete b;

return 0;

将不会有什么异常出现。