/sys$common/syshlp/helplib.hlb POSIX Threads, PTHREAD routines, pthread_exit, Arguments  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 value_ptr

    Value copied and returned to the caller of pthread_join(). Note
    that void * is used as a universal datatype, not as a pointer.
    The Threads Library treats the value_ptr as a value and stores it
    to be returned by pthread_join().