Definition mem_respects_readonly {F V} (ge : Genv.t F V) m :=
    forall b gv, Genv.find_var_info ge b = Some gv ->
                 gvar_readonly gv && negb (gvar_volatile gv) = true ->
           Genv.load_store_init_data ge m b 0 (gvar_init gv) /\
           Mem.valid_block m b /\ (forall ofs : Z, ~ Mem.perm m b ofs Max Writable).

Lemma free_contents: forall m b lo hi m' b' ofs, Mem.free m b lo hi = Some m' -> ~adr_range (b,lo) (hi-lo) (b',ofs) -> ZMap.get ofs (PMap.get b' (Mem.mem_contents m)) = ZMap.get ofs (PMap.get b' (Mem.mem_contents m')).