Definition extract_exists_pre:
  forall {CS: compspecs} {Espec: OracleKind},
  forall (A : Type) (P : A -> environ->mpred) c (Delta: tycontext) (R: ret_assert),
  (forall x, @semax CS Espec Delta (P x) c R) ->
   @semax CS Espec Delta (EX x:A, P x) c R
  := @semax_extract_exists.

Lemma co_alignof_pos: forall co, (co_alignof co > 0)%Z.