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
    endnetent
    fattach
    fmtmsg
    getdate
    getdate_err
    gethostent
    getmsg
    getnetbyaddr
    getnetbyname
    getnetent
    getpmsg
    isastream
    lio_listio
    mlockall
    munlockall
    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
    timer_getoverrun
    ulimit
    waitid