ThreadCritical::~ThreadCritical() {

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

      assert(tc_owner == pthread_self(), "must have correct owner");
      assert(tc_count > 0, "must have correct count");

  {- -------------------------------------------
  (1) ロックの再帰確保数をデクリメントする.
      もし確保数が 0 になったら, pthread_mutex_unlock() でロックを解放する.
      ---------------------------------------- -}

      tc_count--;
      if (tc_count == 0) {
        tc_owner = 0;
        int ret = pthread_mutex_unlock(&tc_mutex);
        guarantee(ret == 0, "fatal error with pthread_mutex_unlock()");
      }
    }