Add ARRAY_SIZE macro, and use it where possible.
diff --git a/py/modarray.c b/py/modarray.c
index d8ff715..ff668f5 100644
--- a/py/modarray.c
+++ b/py/modarray.c
@@ -14,8 +14,8 @@
     .map = {
         .all_keys_are_qstrs = 1,
         .table_is_fixed_array = 1,
-        .used = sizeof(mp_module_array_globals_table) / sizeof(mp_map_elem_t),
-        .alloc = sizeof(mp_module_array_globals_table) / sizeof(mp_map_elem_t),
+        .used = ARRAY_SIZE(mp_module_array_globals_table),
+        .alloc = ARRAY_SIZE(mp_module_array_globals_table),
         .table = (mp_map_elem_t*)mp_module_array_globals_table,
     },
 };