On Alpha systems, unwinds the call stack. On Integrity server
    systems, do not use this service; use $GOTO_UNWIND_64 instead.
    Format
      SYS$GOTO_UNWIND  target_invo ,target_pc ,[new_r0] ,[new_r1]
    C Prototype
      int sys$goto_unwind  (void *target_invo, void *(*(target_pc)),
                           unsigned __int64 *new_r0, unsigned
                           __int64 *new_r1);
Additional Information:
explode
extract