Definition StoreEffect (tv:val)(vl : list memval) (b:Values.block) (z:Z):bool :=
match tv with Vptr bb ofs => eq_block bb b &&
zle (Ptrofs.unsigned ofs) z && zlt z (Ptrofs.unsigned ofs + Z.of_nat (length vl))
| _ => false
end.

Lemma free_curWR m sp lo hi m' (FR: Mem.free m sp lo hi = Some m')
b z (EFF: FreeEffect m lo hi sp b z = true):
Mem.perm m b z Cur Writable.