pub type CK_C_GetFunctionList = Option<unsafe extern "C" fn(ppFunctionList: CK_FUNCTION_LIST_PTR_PTR) -> CK_RV>;
enum CK_C_GetFunctionList { None, Some(unsafe extern "C" fn(_: *mut *mut CK_FUNCTION_LIST) -> u32), }
No value.
Some value of type T.
T