How pkcs11 is solving the issue of ctypes Carray lifetimes

reachable.ml

module Reachable_ptr : sig
  type 'a t
  val typ : 'a Ctypes_static.typ -> 'a t Ctypes_static.typ
  val setf : ('b, 'c) Ctypes.structured ->
    ('a t, ('b, 'c) Ctypes.structured) Ctypes.field -> 'a Ctypes.ptr -> unit
  val getf : ('b, 'c) Ctypes.structured ->
    ('a t, ('b, 'c) Ctypes.structured) Ctypes.field -> 'a Ctypes.ptr
end = struct


  type 'a t = 'a ptr


  let typ = Ctypes.ptr


  (** Add a GC dependency from one object to another:
      while [from] is reachable, [to_] is reachable too. *)
  let add_gc_link ~from ~to_ =
    let r = ref (Some (Obj.repr to_)) in
    let finaliser _ = r := None in
    Gc.finalise finaliser from


  let setf s f v =
    add_gc_link ~from:s ~to_:v;
    Ctypes.setf s f v


  let getf = Ctypes.getf


end