Instance CompSpecs : compspecs. make_compspecs prog. Defined.
Definition Vprog : varspecs. mk_varspecs prog. Defined.
Definition putchar_spec := DECLARE _putchar putchar_spec.
Definition getchar_spec := DECLARE _getchar getchar_spec.
Definition getchar_blocking_spec :=
DECLARE _getchar_blocking
WITH k : byte -> IO_itree
PRE [ ]
PROP ()
LOCAL ()
SEP (ITREE (r <- read stdin;; k r))
POST [ tint ]
EX i : byte,
PROP ()
LOCAL (temp ret_temp (Vubyte i))
SEP (ITREE (k i)).
Definition putchar_blocking_spec :=
DECLARE _putchar_blocking
WITH c : byte, k : IO_itree
PRE [ _c OF tint ]
PROP ()
LOCAL (temp _c (Vubyte c))
SEP (ITREE (r <- write stdout c ;; k))
POST [ tint ]
PROP ()
LOCAL (temp ret_temp (Vubyte c))
SEP (ITREE k).
Program Fixpoint chars_of_Z (n : Z) { measure (Z.to_nat n) } : list byte :=
let n' := n / 10 in
match n' <=? 0 with true => [Byte.repr (n + char0)] | false => chars_of_Z n' ++ [Byte.repr (n mod 10 + char0)] end.
Next Obligation.
Opaque Nat.div Nat.modulo.
Definition ext_link := ext_link_prog prog.
Instance Espec : OracleKind := IO_Espec ext_link.
Definition init_mem := proj1_sig init_mem_exists.
Definition main_block_exists : {b | Genv.find_symbol (Genv.globalenv prog) (prog_main prog) = Some b}.
Definition main_block := proj1_sig main_block_exists.

Theorem prog_ext_correct : exists q,
semantics.initial_core (Clight_core.cl_core_sem (globalenv prog)) 0 init_mem q init_mem (Vptr main_block Ptrofs.zero) [] /\
forall n, @step_lemmas.dry_safeN _ _ _ _ semax.genv_symb_injective (Clight_core.cl_core_sem (globalenv prog))
(io_dry_spec ext_link) (Genv.globalenv prog) n
main_itree q init_mem.