event/PollBackend: add Item constructor

src/event/PollBackend.cxx

@@ -36,10 +36,9 @@ PollBackend::Add(int fd, unsigned events, void *obj) noexcept
 	e.events = events;
 	e.revents = 0;
 
-	auto i = items.emplace(fd, Item{}).first;
-	auto &item = i->second;
-	item.index = index;
-	item.obj = obj;
+	items.emplace(std::piecewise_construct,
+		      std::forward_as_tuple(fd),
+		      std::forward_as_tuple(index, obj));
 	return true;
 }
 

src/event/PollBackend.hxx

@@ -34,6 +34,12 @@ class PollBackend
 	{
 		std::size_t index;
 		void *obj;
+
+		constexpr Item(std::size_t _index, void *_obj) noexcept
+			:index(_index), obj(_obj) {}
+
+		Item(const Item &) = delete;
+		Item &operator=(const Item &) = delete;
 	};
 
 	std::vector<pollfd> poll_events;