Add Printable.Failwith for Analyses.control_spec_c initial value

src/domains/printable.ml

@@ -567,6 +567,31 @@ struct
 end
 
 
+module type FailwithMessage =
+sig
+  val message: string
+end
+
+module Failwith (Message: FailwithMessage): S =
+struct
+  type t = |
+
+  let name () = "failwith"
+  let equal _ _ = failwith Message.message
+  let compare _ _ = failwith Message.message
+  let hash _ = failwith Message.message
+  let tag _ = failwith Message.message
+
+  let show _ = failwith Message.message
+  let pretty _ _ = failwith Message.message
+  let printXml _ _ = failwith Message.message
+  let to_yojson _ = failwith Message.message
+
+  let arbitrary _ = failwith Message.message
+  let relift _ = failwith Message.message
+end
+
+
 (** Concatenates a list of strings that
     fit in the given character constraint *)
 let get_short_list begin_str end_str list =

src/framework/analyses.ml

@@ -269,8 +269,15 @@ struct
 end
 
 
-let control_spec_c: (module Printable.S) ref = ref (module Printable.Unit: Printable.S) (* TODO: some failing printable instead *)
 (** Reference to top-level Control Spec context first-class module. *)
+let control_spec_c: (module Printable.S) ref =
+  let module Failwith = Printable.Failwith (
+    struct
+      let message = "uninitialized control_spec_c"
+    end
+    )
+  in
+  ref (module Failwith: Printable.S)
 
 (** Top-level Control Spec context as static module, which delegates to {!control_spec_c}.
     This allows using top-level context values inside individual analyses. *)