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

 1 struct A
 2 {
 3     virtual void f() {tcout << _T("A::f()\n");}
 4 };
 5 
 6 struct B : public A
 7 {
 8     void f() {tcout << _T("B::f()\n");}
 9 };
10 
11 struct C : public B
12 {
13     void f() {tcout << _T("C::f()\n");}
14 };
15 
16 struct D : public C
17 {
18     void f() {tcout << _T("D::f()\n");}
19 };
20 
21 
22 int _tmain(int argc, TCHAR * argv[], TCHAR * envp[])
23 {
24     A * pA = new D;
25     pA->f();
26 
27     return 0;
28 }