Definition bmatch (m: mem) (b: block) (ab: ablock) : Prop :=
  smatch m b ab.(ab_summary) /\
  forall chunk ofs v, Mem.load chunk m b ofs = Some v -> vmatch v (ablock_load chunk ab ofs).

Lemma bmatch_ext: forall m b ab m', bmatch m b ab -> (forall ofs n bytes, Mem.loadbytes m' b ofs n = Some bytes -> n >= 0 -> Mem.loadbytes m b ofs n = Some bytes) -> bmatch m' b ab.