VMS Help POSIX Threads, PTHREAD routines, pthread_getspecific, Return Values  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    No errors are returned. This routine returns the thread-specific
    data value associated with the specified key argument. If no
    thread-specific data value is associated with key, or if key is
    not defined, then this routine returns a NULL value.