Safer timeout computation.

src/cry.ml

@@ -25,7 +25,12 @@ let poll r w timeout =
     match timeout with
       | x when x < 0. -> Poll.Timeout.never
       | 0. -> Poll.Timeout.immediate
-      | x -> Poll.Timeout.after (Int64.of_float (x *. 1_000_000_000.))
+      | x ->
+          let frac, int = modf x in
+          let int = Int64.mul (Int64.of_float int) 1_000_000_000L in
+          let frac = Int64.of_float (frac *. 1_000_000_000.) in
+          let timeout = Int64.add int frac in
+          Poll.Timeout.after timeout
   in
   let poll = Poll.create () in
   List.iter (fun fd -> Poll.set poll fd Poll.Event.read) r;