commit 0df80f6d05625f80e1e3e05a46e355728881b38a
Author: Anil Madhavapeddy <anil@recoil.org>
Date:   Sat Aug 3 20:20:55 2013 +0100

    OCaml 4.01.0dev has a Unix.O_CLOEXEC flag, so add this to Lwt_unix too.
    
    This was added quite recently in ocaml/ocaml@2207c45056e69d1ea5

diff --git a/src/unix/lwt_unix.ml b/src/unix/lwt_unix.ml
index 5115ffe..4222f7b 100644
--- a/src/unix/lwt_unix.ml
+++ b/src/unix/lwt_unix.ml
@@ -596,6 +596,9 @@ type open_flag =
 #if ocaml_version >= (3, 13)
   | O_SHARE_DELETE
 #endif
+#if ocaml_version >= (4, 01)
+  | O_CLOEXEC
+#endif
 
 #if windows
 
diff --git a/src/unix/lwt_unix.mli b/src/unix/lwt_unix.mli
index cc9df59..f85df52 100644
--- a/src/unix/lwt_unix.mli
+++ b/src/unix/lwt_unix.mli
@@ -315,6 +315,9 @@ type open_flag =
 #if ocaml_version >= (3, 13)
   | O_SHARE_DELETE
 #endif
+#if ocaml_version >= (4, 01)
+  | O_CLOEXEC
+#endif
 
 val openfile : string -> open_flag list -> file_perm -> file_descr Lwt.t
   (** Wrapper for [Unix.openfile]. *)