How to implement the inheritance and polymorphism in C

C++ 有许多features（ abstract class， virtual deconstuctor，RTTI， virtual inheritance）完全用C 去模拟一个C++ 其实是很难。

下面列一个表，如何用C 去模拟C++的一些主要功能：

Feature in C++	Implemented in C
Class	structure
data member	data member
static_ data member	global member and link
membor function	function point
constructor function	global access entry
destructor  function	x
access decorator	x
Inheritance	Composit
Ploymorphism	Overwite the function point
RTTI	OK

下面一个例子来自于 codeproject：

http://www.codeproject.com/KB/cpp/InheritancePolymorphismC.aspx