Proof with eauto with wd.
intros.
inversion Harg; subst;
eapply extcall_arg_valid in H; eauto.
eapply extcall_arg_valid in H0; eauto...
Qed.

Lemma free_wd_domain :
forall (m m' : mem) b lo hi (f : memren),
domain_memren f m ->
Mem.free m b lo hi = Some m' ->
valid_mem m ->
valid_mem m' /\ domain_memren f m'.