sig
  type t
  external repr : 'a -> Obj.t = "%identity"
  external obj : Obj.t -> 'a = "%identity"
  external magic : 'a -> 'b = "%identity"
  external is_block : Obj.t -> bool = "obj_is_block"
  external is_int : Obj.t -> bool = "%obj_is_int"
  external tag : Obj.t -> int = "obj_tag"
  external size : Obj.t -> int = "%obj_size"
  external field : Obj.t -> int -> Obj.t = "%obj_field"
  external set_field : Obj.t -> int -> Obj.t -> unit = "%obj_set_field"
  external new_block : int -> len:int -> Obj.t = "obj_block"
  external dup : Obj.t -> Obj.t = "obj_dup"
  external truncate : Obj.t -> len:int -> unit = "obj_truncate"
  val no_scan_tag : int
  val closure_tag : int
  val infix_tag : int
  val object_tag : int
  val abstract_tag : int
  val string_tag : int
  val double_tag : int
  val double_array_tag : int
  val final_tag : int
  val marshal : Obj.t -> string
  val unmarshal : string -> int -> Obj.t * int
end