This routine suspends execution of the calling thread until the
    specified target thread thread terminates.

    On return from a successful pthread_join() call with a non-
    NULL value_ptr argument, the value passed to pthread_exit()
    is returned in the location referenced by value_ptr, and the
    terminating thread is detached.

    If more than one thread attempts to join with the same thread,
    the results are unpredictable.

    A call to pthread_join() returns after the target thread
    terminates. The pthread_join() routine is a deferred cancelation
    point; the target thread will not be detached if the thread
    blocked in pthread_join() is canceled.

    If a thread calls this routine and specifies its own pthread_t, a
    deadlock can result.

    The pthread_join() (or pthread_detach())  routine should
    eventually be called for every thread that is created with the
    detachstate attribute of its thread object set to PTHREAD_CREATE_
    JOINABLE, so that storage associated with the thread can be
    reclaimed.

                                   NOTE

       For OpenVMS Alpha systems:
       The pthread_join() routine is defined to pthread_join64()
       if you compile using /pointer_size=long. If you do not
       specify /pointer_size, or if you specify /pointer_
       size=short, then pthread_join() is defined to be pthread_
       join32(). You can call pthread_join32() or pthread_join64()
       instead of pthread_join(). The pthread_join32() form
       returns a 32-bit void * value in the address to which
       value_ptr points. The pthread_join64() form returns a 64-
       bit void * value. You can call either, or you can call
       pthread_join(). Note that if you call pthread_join32() and
       the thread with which you join returns a 64-bit value, the
       high 32 bits of which are not 0 (zero), the Threads Library
       discards those high bits with no warning.