Description

   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.