Function t_unserialize_ex 

pub unsafe extern "C-unwind" fn t_unserialize_ex<T: Altrep>(
    class: SEXP,
    state: SEXP,
    attr: SEXP,
    objf: c_int,
    levs: c_int,
) -> SEXP

Trampoline for UnserializeEX method (extended unserialization with attributes).

Safety

class, state, and attr must be valid SEXPs from R.