(** ** Proof that related states take related steps*)

Lemma symb_val_obs:
forall f fg g id ofs
(Hfg: forall b1 b2, fg b1 = Some b2 -> b1 = b2)
(Hge_wd: ge_wd fg g)
(Hincr: ren_incr fg f),
val_obs f (Senv.symbol_address g id ofs) (Senv.symbol_address g id ofs).