Definition memory_block (sh: share) (n: Z) (v: val) : mpred :=
match v with
| Vptr b ofs => (!!(Ptrofs.unsigned ofs + n < Ptrofs.modulus)) && memory_block' sh (nat_of_Z n) b (Ptrofs.unsigned ofs)
| _ => FF
end.

Lemma mapsto_conflict:
forall sh t v v2 v3,
nonunit sh ->
mapsto sh t v v2 * mapsto sh t v v3 |-- FF.