C++中dynamic_cas操作符的工作原理

http://stackoverflow.com/questions/13783312/how-does-dynamic-cast-work

http://publib.boulder.ibm.com/infocenter/lnxpcomp/v8v101/index.jsp?topic=%2Fcom.ibm.xlcpp8l.doc%2Flanguage%2Fref%2Fkeyword_dynamic_cast.htm

http://www.codingunit.com/cplusplus-tutorial-typecasting-part-2-rtti-dynamic_cast-typeid-and-type_info

http://msdn.microsoft.com/en-us/library/cby9kycs(v=vs.80).aspx