Thread: I made a graphing library in C

Link to Github site GitHub - FullNitrous/CGLib: Library for graphing in C.

My suggestions:

• Place the header inclusion guard at the very top of the header file. There's no point processing any further if the header has already been included, so this helps the compiler help you.
• It probably is not wise to define a macro constant named PI. One option is to use a library prefix, e.g., C_GRAPH_PI.
• Likewise, you really should prefix the struct and function names that form the interface of your library.
• It looks like your library interface only consists of 5 functions, despite defining quite a few structs. Is that intentional? It seems to me that you require users of your library to create the struct objects by hand, and then pass them to these functions. It is more typical for each struct object to come with initialisation functions and other functions. In fact, you might even choose to make the structs be opaque pointers instead, allowing you to change their layout at will without breaking your library interface compatibility between versions (as long as you don't introduce backward incompatibilities for the interface functions).
• If there are helper functions in source files that do not form part of your library interface, declare them static. This also means that they won't need a library prefix for their names since the internal linkage means there will be no name collision.
• Remember to do the simple though tedious things like checking the result of fopen. If you don't, your users will find debugging to be much harder since your functions will just mysteriously fail.