useful link

http://blog.csdn.net/crystal_avast/article/details/7678704   C++虚继承的概念


http://www.cnblogs.com/chio/archive/2007/06/21/792431.html  虚函数的真相（VC编译器如何实现“virtual ”规则）
http://blog.csdn.net/apemancsdn/article/details/82606  C++虚函数调用的反汇编解析
http://www.cnblogs.com/cornflower/archive/2010/02/21/1670156.html 跳槽
http://blog.csdn.net/coomon2000/article/details/1888290