Most of the users find it hard to use.
You may have issues with how you set up your compiler. For instance, even if you include the correct header files for all of your functions, you still need to provide your linker with the correct path to the library that has the actual implementation. Otherwise, you will get "undefined function" error messages. Be careful that your compiler doesn't actually support these functions at all (this could happen if you include your own declaration of a function to get around a compile-time error).