[Article] C++20 Practical Coroutines - main_task

main_task.cc

struct main_task {
  struct main_promise {
    using handle_t = std::coroutine_handle<main_promise>;
    main_task get_return_object() {
      return main_task{handle_t::from_promise(*this)};
    }
    std::suspend_never initial_suspend() noexcept { return {}; }
    std::suspend_always final_suspend() noexcept { return {}; }
    void unhandled_exception() { std::terminate(); }
    void return_value(int ret) { ret_ = ret; }

  private:
    int ret_;
    friend main_task;
  };
  using promise_type = main_promise;
  main_task(promise_type::handle_t handle) : handle_(handle) {}
  ~main_task() {
    if (handle_)
      handle_.destroy();
  }

  operator int() { return handle_.promise().ret_; }

private:
  promise_type::handle_t handle_;
};