(*****************The following variant is used in the linker***********)
Definition gvars_included {V1 V2} (gv1:option (globvar V1)) (gv2: option (globvar V2)): Prop :=
  match gv1, gv2 with
   None, None => True
 | None, Some x2 => True
 | Some x1, None => False
 | Some x1, Some x2 => gvar_init x1 = gvar_init x2 /\
                       gvar_readonly x1 = gvar_readonly x2 /\
                       gvar_volatile x1 = gvar_volatile x2
 end.

Lemma gvars_cohereD {F1 V1 F2 V2} (ge1:Genv.t F1 V1) (ge2:Genv.t F2 V2) (HG: forall b, gvars_included (Genv.find_var_info ge1 b) (Genv.find_var_info ge2 b)) b gv1 (GV: Genv.find_var_info ge1 b = Some gv1): exists gv2, Genv.find_var_info ge2 b = Some gv2 /\ gvar_init gv1 = gvar_init gv2 /\ gvar_readonly gv1 = gvar_readonly gv2 /\ gvar_volatile gv1 = gvar_volatile gv2.