Local Open Scope logic.
Hint Extern 2 (@data_at ?cs1 ?sh _ _ ?p |-- @data_at ?cs2 ?sh _ _ ?p) =>
(tryif constr_eq cs1 cs2 then fail
else simple apply change_compspecs_data_at_cancel;
[ reflexivity | reflexivity | apply JMeq_refl]) : cancel.

Lemma body_md_update: semax_body HmacDrbgVarSpecs HmacDrbgFunSpecs
f_mbedtls_md_hmac_update md_update_spec.