Definition isGlobalBlock {F V : Type} (ge : Genv.t F V) :=
fun b => (fst (genv2blocksBool ge)) b || (snd (genv2blocksBool ge)) b.

Lemma replace_externs_meminj_preserves_globals:
forall {F V} (ge: Genv.t F V) nu
(PG: meminj_preserves_globals ge (extern_of nu) /\
(forall b, isGlobalBlock ge b = true -> frgnBlocksSrc nu b = true))
mu  fSrc fTgt (Hyp: mu = replace_externs nu fSrc fTgt)
(FRG: forall b, frgnBlocksSrc nu b = true -> fSrc b = true),
meminj_preserves_globals ge (extern_of mu) /\
(forall b, isGlobalBlock ge b = true -> frgnBlocksSrc mu b = true).