c++ 基类已经存在virtual修饰的同名成员函数，派生类加不加无所谓，都是virtual的

struct A
{
virtual void f() {tcout << _T("A::f()\n");}
};

struct B : public A
{
void f() {tcout << _T("B::f()\n");}
};

struct C : public B
{
void f() {tcout << _T("C::f()\n");}
};

struct D : public C
{
void f() {tcout << _T("D::f()\n");}
};

int _tmain(int argc, TCHAR * argv[], TCHAR * envp[])
{
A * pA = new D;
pA->f();

return 0;
}