This tip has been extracted from the main void pointer article.
When you don’t know the type of the object whose address is held by a pointer, or a pointer has to be able to reference several objects with different types, the referenced type of that pointer can be set to void, as in void *. Void pointers are intended to be used as temporary storage for addresses, most often as function parameters or for function return values.
You should never write code that manipulates void pointers. In particular, you should never attempt to perform pointer arithmetic (addition or subtraction) on void pointers as the results are undefined.
As soon as possible and before they are used, your code should convert the values held by void pointers to pointers with an appropriate referenced type, either by assigning them to a regular object pointers, or casting them to the required type.