[求助]虚构函数

#include <iostream.h>

class Base1
{
public :
Base1()
{
cout<<"class Base1"<<endl;
}
};
class Base2
{
public:
Base2()
{
cout<<"class Base2"<<endl;
}
};
class Level1:public Base2,virtual public Base1
{
public :
Level1()
{
cout<<"class Level1"<<endl;
}
};
class Level2: public Base2,virtual public Base1
{
public :
Level2()
{
cout<<"class Level2"<<endl;
}};
class Toplevel:public Level1,virtual public Level2
{
public :
Toplevel()
{
cout<<"class Toplevel"<<endl;
}
};
void main ()
{
Toplevel obj;
}

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