NOT implemented system interfaces from the Single Unix Specification, Volume 4:

    aio_cancel
    aio_error
    aio_fsync
    aio_read
    aio_return
    aio_suspend
    aio_write
    duplocale
    endnetent
    fattach
    fmtmsg
    freelocale
    getdate
    getdate_err
    gethostent
    getmsg
    getnetbyaddr
    getnetbyname
    getnetent
    getpmsg
    isalnum_l
    isalpha_l
    isastream
    isblank_l
    iscntrl_l
    isdigit_l
    isgraph_l
    islower_l
    isprint_l
    ispunct_l
    isspace_l
    isupper_l
    iswalnum_l
    iswalpha_l
    iswblank_l
    iswcntrl_l
    iswdigit_l
    iswgraph_l
    iswlower_l
    iswprint_l
    iswpunct_l
    iswspace_l
    iswupper_l
    iswxdigit_l
    isxdigit_l
    lio_listio
    mlockall
    munlockall
    newlocale
    posix_mem_offset
    posix_trace[...]
    posix_typed_[...]
    pthread_mutexattr_getrobust
    pthread_mutexattr_setrobust
    pthread_mutex_consistent
    pthread_mutex_timedlock
    pthread_rwlock_timedrdlock
    pthread_rwlock_timedwrlock
    putmsg
    setnetent
    sigtimedwait
    strcasecmp_l
    strcoll_l
    strfmon_l
    strncasecmp_l
    strxfrm_l
    timer_getoverrun
    tolower_l
    toupper_l
    towctrans_l
    ulimit
    uselocale
    waitid
    wcscasecmp_l
    wcsncasecmp_l
    wcsxfrm_l
    wctrans_l
    wctype_l