variable.c: use `size_t` to avoid integer type mismatch.
@@ -486,7 +486,7 @@ mrb_value
mrb_obj_iv_inspect(mrb_state *mrb, struct RObject *obj)
{
iv_tbl *t = obj->iv;
- int len = iv_size(mrb, t);
+ size_t len = iv_size(mrb, t);
if (len > 0) {
const char *cn = mrb_obj_classname(mrb, mrb_obj_value(obj));
