From e04046515389ba4d019a13db33de198b85480b00 Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Sat, 15 Sep 2018 16:27:06 +0000
Subject: [PATCH] encoding.c: check external encoding

* encoding.c (rb_enc_get_index): external encoding may not be Data
  object.  [ruby-core:89016] [Bug #15122]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64753 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 encoding.c           | 2 +-
 test/ruby/test_io.rb | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/encoding.c b/encoding.c
index d130eb2612..10a0ab0371 100644
--- a/encoding.c
+++ b/encoding.c
@@ -803,7 +803,7 @@ rb_enc_get_index(VALUE obj)
 	if (NIL_P(tmp)) {
 	    tmp = rb_funcallv(obj, rb_intern("external_encoding"), 0, 0);
 	}
-	if (is_data_encoding(tmp)) {
+	if (is_obj_encoding(tmp)) {
 	    i = enc_check_encoding(tmp);
 	}
 	break;
diff --git a/test/ruby/test_io.rb b/test/ruby/test_io.rb
index 27077b425b..eeda96c9ef 100644
--- a/test/ruby/test_io.rb
+++ b/test/ruby/test_io.rb
@@ -3855,4 +3855,11 @@ __END__
       th.join
     end;
   end
+
+  def test_external_encoding_index
+    IO.pipe {|r, w|
+      assert_raise(TypeError) {Marshal.dump(r)}
+      assert_raise(TypeError) {Marshal.dump(w)}
+    }
+  end
 end