Set Bullet Behavior "Strict Subproofs".
(* Variables to be instantiated once the program is known. *)
Definition _f := 1%positive.      (* alpha-convertible *)
Definition _args := 2%positive.   (* alpha-convertible *)
Definition _lock := 1%positive.   (* alpha-convertible *)
Definition _cond := 2%positive.   (* alpha-convertible *)
(*Definition _lock_t := 2%positive. (* 2 (* or sometimes 3 -WM *) is the number given by clightgen when threads.h is included first *)*)
Definition voidstar_funtype := Tfunction (Tcons (tptr tvoid) Tnil) (tptr tvoid) cc_default.
(* Definition tlock := Tstruct _lock_t noattr. *)
Definition tlock := (Tarray (Tpointer Tvoid noattr) 2 noattr).
(* Notation tlock := tuint (only parsing). *)
Goal forall (cenv: composite_env), @sizeof cenv tlock = LKSIZE.
(* In fact we need locks to two resources: 1) the resource invariant, for passing the resources 2) the join resource invariant, for returning all resources, including itself for this we need to define them in a mutually recursive fashion: *)
Definition res_invariants_fun Q sh1 p1 sh2 p2 : (bool -> mpred) -> (bool -> mpred) :=
fun R b =>
if b then
(Q * lock_inv sh2 p2 (|> R false))%logic
else
(Q * lock_inv sh1 p1 (|> R true) * lock_inv sh2 p2 (|> R false))%logic.
Definition res_invariants Q sh1 p1 sh2 p2 : bool -> mpred := HORec (res_invariants_fun Q sh1 p1 sh2 p2).
Definition res_invariant Q sh1 p1 sh2 p2 : mpred := res_invariants Q sh1 p1 sh2 p2 true.
Definition join_res_invariant Q sh1 p1 sh2 p2 : mpred := res_invariants Q sh1 p1 sh2 p2 false.

Lemma res_invariant_eq Q sh1 p1 sh2 p2 :
res_invariant Q sh1 p1 sh2 p2 =
(Q *
lock_inv sh2 p2 (|> join_res_invariant Q sh1 p1 sh2 p2))%logic.