`sig
type t
external repr : 'a -> Obj.t = "%identity"
external obj : Obj.t -> 'a = "%identity"
external magic : 'a -> 'b = "%identity"
val is_block : Obj.t -> bool
external is_int : Obj.t -> bool = "%obj_is_int"
external tag : Obj.t -> int = "caml_obj_tag"
external size : Obj.t -> int = "%obj_size"
external reachable_words : Obj.t -> int = "caml_obj_reachable_words"
external field : Obj.t -> int -> Obj.t = "%obj_field"
external set_field : Obj.t -> int -> Obj.t -> unit = "%obj_set_field"
external set_tag : Obj.t -> int -> unit = "caml_obj_set_tag"
val double_field : Obj.t -> int -> float
val set_double_field : Obj.t -> int -> float -> unit
external new_block : int -> int -> Obj.t = "caml_obj_block"
external dup : Obj.t -> Obj.t = "caml_obj_dup"
external truncate : Obj.t -> int -> unit = "caml_obj_truncate"
external add_offset : Obj.t -> Int32.t -> Obj.t = "caml_obj_add_offset"
val first_non_constant_constructor_tag : int
val last_non_constant_constructor_tag : int
val lazy_tag : int
val closure_tag : int
val object_tag : int
val infix_tag : int
val forward_tag : int
val no_scan_tag : int
val abstract_tag : int
val string_tag : int
val double_tag : int
val double_array_tag : int
val custom_tag : int
val final_tag : int
val int_tag : int
val out_of_heap_tag : int
val unaligned_tag : int
val extension_constructor : 'a -> extension_constructor
val extension_name : extension_constructor -> string
val extension_id : extension_constructor -> int
val marshal : Obj.t -> bytes
val unmarshal : bytes -> int -> Obj.t * int
module Ephemeron :
sig
type obj_t = Obj.t
type t
val create : int -> Obj.Ephemeron.t
val length : Obj.Ephemeron.t -> int
val get_key : Obj.Ephemeron.t -> int -> Obj.Ephemeron.obj_t option
val get_key_copy : Obj.Ephemeron.t -> int -> Obj.Ephemeron.obj_t option
val set_key : Obj.Ephemeron.t -> int -> Obj.Ephemeron.obj_t -> unit
val unset_key : Obj.Ephemeron.t -> int -> unit
val check_key : Obj.Ephemeron.t -> int -> bool
val blit_key :
Obj.Ephemeron.t -> int -> Obj.Ephemeron.t -> int -> int -> unit
val get_data : Obj.Ephemeron.t -> Obj.Ephemeron.obj_t option
val get_data_copy : Obj.Ephemeron.t -> Obj.Ephemeron.obj_t option
val set_data : Obj.Ephemeron.t -> Obj.Ephemeron.obj_t -> unit
val unset_data : Obj.Ephemeron.t -> unit
val check_data : Obj.Ephemeron.t -> bool
val blit_data : Obj.Ephemeron.t -> Obj.Ephemeron.t -> unit
end
end`