warning: `extern` fn uses type `Modes`, which is not FFI-safe
 --> src/main.rs:5:33
  |
5 | pub extern "C" fn get_mode() -> mylib::Modes {
  |                                 ^^^^^^^^^^^^ not FFI-safe
  |
  = note: this enum is non-exhaustive
  = note: `#[warn(improper_ctypes_definitions)]` on by default