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copied!<p>Answering your first question, I recommend to encapsulate your structures using opaque pointers (a.k.a Handles).</p> <p>For example, you may declare a handle to a linked list (here MS-like naming):</p> <pre><code>typedef struct linked_list_t* HLINKEDLIST; </code></pre> <p>We assume that linked_list_t is a generic one (composed of void pointers).</p> <p>This way you can hide what a "handle" to a linked list is, or in what form is implemented (information hiding):</p> <pre><code>HLINKEDLIST LinkedListCreate(); LinkedListAdd(LLELEMENT v); LinkedListCopy(HLINKEDLIST dst, const HLINKEDLIST src); </code></pre> <p>Handle subtypes are also commonly defined, such as PHLINKEDLIST (pointer to a linked list handle). </p> <p>Related types can also be defined for convenience (and to use the limited information hiding available in C). e.g: the linked list element type can be defined as </p> <pre><code>typedef void* LLELEMENT; </code></pre> <p>There are good books on Data Structures in C to check. This is good: <a href="http://rads.stackoverflow.com/amzn/click/0201498413" rel="nofollow noreferrer">http://www.amazon.com/Interfaces-Implementations-Techniques-Creating-Reusable/dp/0201498413</a></p> <p>Also note that LLELEMENT is actually compatible with void* so if you are defining other type def as:</p> <pre><code>typedef void* SYSTEMDATA; </code></pre> <p>SYSTEMDATA is compatible with LLELEMENT, so the compiler won't complain on:</p> <pre><code>int QuerySystemData(SYSTEMDATA* sd); </code></pre> <p>and calling:</p> <pre><code>QuerySystemData(lle); </code></pre> <p>where lle is of type LLELEMENT.</p> <p>This type checking can be enforced encapsulating simple members in structs. If I don't remember bad, declaring STRICT in a program using windows.h causes handles to be type-safer (incompatible between). Definitions like the following are common:</p> <pre><code>typedef struct __HWND { int __handle; } __HWND; typedef __HWND* HWND; </code></pre> <p>If the simpler definitions were:</p> <pre><code>typedef int HWND; typedef int HBITMAP; </code></pre> <p>The two handles would be type compatible and interchangeable on functions expecting to work with windows and functions expecting to work with bitmaps (potential horrible bugs).</p>

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