(** ** Semantics of external functions. *)
(** For functions defined outside the program ([EF_external], [EF_builtin] and [EF_runtime]), we do not define their semantics, but only assume that it satisfies [extcall_properties]. *)
Parameter external_functions_sem: String.string -> signature -> extcall_sem.

(* Specifications: *)
Axiom external_functions_properties:
forall id sg, extcall_properties (external_functions_sem id sg) sg.