Add size check to Store.

stepper.py

@@ -65,6 +65,8 @@ def step(insns, terminator, blocks, stack_frames, ssa_env, global_env, heap,
         TODO('Load')
     elif isinstance(next_insn, ll.Store):
         ty = next_insn.ty
+        base_ty = ty2base_ty(ty, tdecs)
+        size = base_ty2size(base_ty)
         value = next_insn.value
         location = next_insn.location
 
@@ -75,7 +77,12 @@ def step(insns, terminator, blocks, stack_frames, ssa_env, global_env, heap,
         print('heap[{}] <- {}'
               .format(location_v, value_v))
 
-        heap[location_v] = value_v
+        if size == 1:
+            heap[location_v] = value_v
+        else:
+            err(('This emulator cannot store objects larger than 1 cell.'
+                 ' Current size is {}')
+                .format(size))
     elif isinstance(next_insn, ll.Icmp):
         cnd = next_insn.cnd
         left = next_insn.left