pub type ddsrt_avl_compare_t = Option<unsafe extern "C" fn(a: *const c_void, b: *const c_void) -> c_int>;
enum ddsrt_avl_compare_t { None, Some(unsafe extern "C" fn(_: *const c_void, _: *const c_void) -> i32), }
No value.
Some value of type T.
T