Imported Upstream version 8.5~beta1+dfsg

1 files changed, 26 insertions, 0 deletions

diff --git a/lib/canary.ml b/lib/canary.ml
new file mode 100644
index 00000000..23d7bd21
--- /dev/null
+++ b/lib/canary.ml
@@ -0,0 +1,26 @@
+(************************************************************************)
+(*  v      *   The Coq Proof Assistant  /  The Coq Development Team     *)
+(* <O___,, *   INRIA - CNRS - LIX - LRI - PPS - Copyright 1999-2015     *)
+(*   \VV/  **************************************************************)
+(*    //   *      This file is distributed under the terms of the       *)
+(*         *       GNU Lesser General Public License Version 2.1        *)
+(************************************************************************)
+
+type t = Obj.t
+
+let obj = Obj.new_block Obj.closure_tag 0
+  (** This is an empty closure block. In the current implementation, it is
+      sufficient to allow marshalling but forbid equality. Sadly still allows
+      hash. *)
+  (** FIXME : use custom blocks somehow. *)
+
+module type Obj = sig type t end
+
+module Make(M : Obj) =
+struct
+  type canary = t
+  type t = (canary * M.t)
+
+  let prj (_, x) = x
+  let inj x = (obj, x)
+end