From 761562b65f33f47a18eae2c5db26ec48818498fc Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby-lang.org>
Date: Mon, 12 Dec 2016 01:00:24 +0900
Subject: freeze instance variables; ref #3340

---
 src/variable.c | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'src/variable.c')

diff --git a/src/variable.c b/src/variable.c
index 45dc055af..390da5455 100644
--- a/src/variable.c
+++ b/src/variable.c
@@ -489,6 +489,9 @@ mrb_obj_iv_set(mrb_state *mrb, struct RObject *obj, mrb_sym sym, mrb_value v)
 {
   iv_tbl *t = obj->iv;
 
+  if (MRB_FROZEN_P(obj)) {
+    mrb_raisef(mrb, E_RUNTIME_ERROR, "can't modify frozen %S", mrb_obj_value(obj));
+  }
   if (!t) {
     t = obj->iv = iv_new(mrb);
   }
-- 
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