};

  static pthread_key_t CreateKey() {
    pthread_key_t key;
    // When a thread exits, DeleteThreadLocalValue() will be called on
    // the object managed for that thread.
    GTEST_CHECK_POSIX_SUCCESS_(
        pthread_key_create(&key, &DeleteThreadLocalValue));
    return key;
  }

  T* GetOrCreateValue() const {
    ThreadLocalValueHolderBase* const holder =