Linked list is a very important data structure. In C++, with the support of templating, we can implement a template linked likst class and use it for any data type we want. However, in C, there is no such thing like templating. How can we implement a generic linked list? It is tedious to re-implement functions like list_add and list_remove for every data type that needs to be linked. Besides, it is hard to make one node in two lists simultaneously.