V1.Callbacktype 'a t = 'a callbackval create_v : (unit -> unit) -> (unit -> unit) tval free_v : (unit -> unit) t -> unitval create_pscob_field :
(unit -> CobField.t cptr) ->
(unit -> CobField.t cptr) tval free_pscob_field : (unit -> CobField.t cptr) t -> unit