Definition field_address t gfs p :=
  if (field_compatible_dec t gfs p)
  then offset_val (nested_field_offset t gfs) p
  else Vundef.Definition field_address0 t gfs p :=
  if (field_compatible0_dec t gfs p)
  then offset_val (nested_field_offset t gfs) p
  else Vundef.

Lemma lvar_size_compatible: forall {cs: compspecs} id t v rho, locald_denote (lvar id t v) rho -> sizeof t < Ptrofs.modulus -> size_compatible t v.