Function wcsrtombs 

#[unsafe(no_mangle)]
pub unsafe extern "C" fn wcsrtombs(
    s: *mut c_char,
    ws: *mut *const wchar_t,
    n: size_t,
    st: *mut mbstate_t,
) -> size_t

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