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

    #include <tis.h>

    int
    tis_once (
          pthread_once_t   *once_control,
          void   (*init_routine) (void));