pub unsafe extern "C" fn coap_insert_optlist(
optlist_chain: *mut *mut coap_optlist_t,
optlist: *mut coap_optlist_t,
) -> c_intpub unsafe extern "C" fn coap_insert_optlist(
optlist_chain: *mut *mut coap_optlist_t,
optlist: *mut coap_optlist_t,
) -> c_int