Function send_id 

pub unsafe fn send_id(
    recv: *mut c_void,
    s: *const c_void,
    a: *mut c_void,
) -> *mut c_void

Send a message with a specific, non-variadic signature.

Safety

recv must be a live Objective-C object that responds to s, and the declared argument and return types must match that selector’s. Nothing here checks either.