// It scans an object and visits its children.

  void scan_object(oop obj) {

  {- -------------------------------------------
  (1) (assert)
      ---------------------------------------- -}

        assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");

  {- -------------------------------------------
  (1) (トレース出力)
      ---------------------------------------- -}

        if (_cm->verbose_high())
          gclog_or_tty->print_cr("[%d] we're scanning object "PTR_FORMAT,
                                 _task_id, (void*) obj);

  {- -------------------------------------------
  (1) _words_scanned フィールドを増加させておく.
      ---------------------------------------- -}

        size_t obj_size = obj->size();
        _words_scanned += obj_size;

  {- -------------------------------------------
  (1) oop_iterate() を呼び出して, _cm_oop_closure を適用する.
      ---------------------------------------- -}

        obj->oop_iterate(_oop_closure);
        statsOnly( ++_objs_scanned );
        check_limits();
      }