Value.t is the OCaml type corresponding to Emacs's universal type of values. It is
represented as an OCaml custom block (emacs_value_ops in ecaml_stubs.c) wrapped
around the emacs_value pointer type defined by the Emacs native-code module
interface, emacs-module.h, available in Emacs 25 and beyond. This module has
low-level functions for working with Emacs values, OCaml wrappers that call the C
functions specified in emacs-module.h. All other calls from OCaml to Emacs are
built on top of this module.
module type Make_subtype_arg : sig ... endmodule type Funcall : sig ... endmodule type Subtype : sig ... endmodule type Value : sig ... end