Am I correct to assume one cannot forward-declare a library's opaque pointer type?

Question

There are a lot of questions out there about forward declarations and opaque types, but most seem to be from the perspective of the library author, or people trying to use i

Answer 1

The library should define FOO for you, either opaquely or transparently, as it's own source refers to FOO.

#include should get you the prototypes to the functions the library provides, and also the types needed to interact with them.

If you create your own FOO type, you'll almost certainly get a compile error indicating multiple definition of 'FOO' when you include the function prototypes from the library.