SNMALLOC_SLOW_PATH decltype()

in src/mem/corealloc.h [480:526]
37 lines of code
3 McCabe index (conditional complexity)

    SNMALLOC_SLOW_PATH decltype(auto)
    handle_message_queue_inner(Action action, Args... args)
    {
      bool need_post = false;
      auto local_state = backend_state_ptr();
      auto domesticate =
        [local_state](freelist::QueuePtr p) SNMALLOC_FAST_PATH_LAMBDA {
          return capptr_domesticate<SharedStateHandle>(local_state, p);
        };
      auto cb = [this, local_state, &need_post](freelist::HeadPtr msg)
                  SNMALLOC_FAST_PATH_LAMBDA {
#ifdef SNMALLOC_TRACING
                    std::cout << "Handling remote" << std::endl;
#endif

                    auto& entry = SharedStateHandle::Pagemap::get_metaentry(
                      local_state, snmalloc::address_cast(msg));

                    handle_dealloc_remote(entry, msg.as_void(), need_post);

                    return true;
                  };

      if constexpr (SharedStateHandle::Options.QueueHeadsAreTame)
      {
        /*
         * The front of the queue has already been validated; just change the
         * annotating type.
         */
        auto domesticate_first = [](freelist::QueuePtr p)
                                   SNMALLOC_FAST_PATH_LAMBDA {
                                     return freelist::HeadPtr(p.unsafe_ptr());
                                   };
        message_queue().dequeue(key_global, domesticate_first, domesticate, cb);
      }
      else
      {
        message_queue().dequeue(key_global, domesticate, domesticate, cb);
      }

      if (need_post)
      {
        post();
      }

      return action(args...);
    }