Method operator()

cpp/src/arrow/util/task_group_test.cc:221–229

  Status final_status_;

  Status operator()() {
    if (!barrier_->load()) {
      SleepFor(1e-5);
      // Note the TaskGroup should be kept alive by the fact this task
      // is still running...
      weak_group_ptr_.lock()->Append(*this);
    }
    return final_status_;
  }
};

// Try to replicate subtle lifetime issues when destroying a TaskGroup