Function wcsxfrm 

#[unsafe(no_mangle)]
pub extern "C" fn wcsxfrm(
    ws1: *mut wchar_t,
    ws2: *const wchar_t,
    n: size_t,
) -> size_t

See https://pubs.opengroup.org/onlinepubs/9799919799/functions/wcsxfrm.html.