Definition bound_int (v : val) (b : Z) :=
match v with
| Vint i => -b < (Int.signed i) < b
| _ => False
end.
Definition product a b := map (fun vp => Val.mul (fst vp) (snd vp)) (combine a b).
Definition product_spec :=
DECLARE _product
WITH b0 : val, sh : share, orig_a : list val, orig_b : list val, out0 : val, a0 : val
PRE [_out OF (tptr tlong), _a OF (tptr tint), _b OF (tptr tint)]
PROP (writable_share sh;
length orig_a = 10%nat;
length orig_b = 10%nat;
forall i, 0 <= i < 10 -> is_long (Znth i orig_a Vundef);
forall i, 0 <= i < 10 -> is_long (Znth i orig_b Vundef);
forall i, 0 <= i < 10 -> bound_int (Znth i orig_a Vundef) 134217728;
forall i, 0 <= i < 10 -> bound_int (Znth i orig_b Vundef) 134217728)
LOCAL (temp _out out0;
temp _a a0;
temp _b b0;
`isptr (eval_id _out);
`isptr (eval_id _a);
`isptr (eval_id _b))
SEP (`(data_at sh (tarray tlong 10) orig_a a0);
`(data_at sh (tarray tlong 10) orig_b b0);
`(data_at_ sh (tarray tlong 10) out0))
POST [ tvoid ]
PROP ()
LOCAL ()
SEP (`(data_at sh (tarray tlong 10) orig_a a0);
`(data_at sh (tarray tlong 10) orig_b b0);
`(data_at sh (tarray tlong 10) (product orig_a orig_b) out0)).
Local Open Scope logic.
Definition Vprog : varspecs := nil.
Definition Gprog : funspecs :=   ltac:(with_library prog [product_spec]).

Lemma product_sumarray : semax_body Vprog Gprog f_product product_spec.