AdjoiningVirtualSpaces::AdjoiningVirtualSpaces(ReservedSpace rs,
                                               size_t min_low_byte_size,
                                               size_t min_high_byte_size,
                                               size_t alignment) :

  {- -------------------------------------------
  (1) 各フィールドに引数を初期値として設定するだけ
      ---------------------------------------- -}

      _reserved_space(rs), _min_low_byte_size(min_low_byte_size),
      _min_high_byte_size(min_high_byte_size), _low(0), _high(0),
      _alignment(alignment) {}