From 622f3f14b6928ee4fe3afa96db0250eb9da32e7a Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Mon, 26 Jan 2015 02:37:51 +0000
Subject: [PATCH] string.c: terminate when embedded

* string.c (str_make_independent_expand): terminate String when
  moved from heap to embedded.  [Fix GH-821].

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49405 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 ChangeLog                      | 5 +++++
 string.c                       | 1 +
 test/-ext-/string/test_cstr.rb | 9 +++++++++
 3 files changed, 15 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index 9dc983a8cb..3ac6ab493f 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Mon Jan 26 11:37:49 2015  Dave Stevens  <dave@crowdlab.com>
+
+	* string.c (str_make_independent_expand): terminate String when
+	  moved from heap to embedded.  [Fix GH-821].
+
 Sun Jan 25 12:04:12 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* array.c (flatten): no need to call to_ary method on elements
diff --git a/string.c b/string.c
index c8707c62a6..ffe2e6233a 100644
--- a/string.c
+++ b/string.c
@@ -1593,6 +1593,7 @@ str_make_independent_expand(VALUE str, long expand)
 	ptr = RSTRING(str)->as.heap.ptr;
 	STR_SET_EMBED(str);
 	memcpy(RSTRING(str)->as.ary, ptr, len);
+	RSTRING(str)->as.ary[len] = '\0'; /* Ensure string is terminated */
 	STR_SET_EMBED_LEN(str, len);
 	return;
     }
diff --git a/test/-ext-/string/test_cstr.rb b/test/-ext-/string/test_cstr.rb
index 6f2fdef3d4..72a9dd6dfa 100644
--- a/test/-ext-/string/test_cstr.rb
+++ b/test/-ext-/string/test_cstr.rb
@@ -86,6 +86,15 @@ class Test_StringCStr < Test::Unit::TestCase
     }
   end
 
+  def test_embedded_from_heap
+    gh821 = "[GH-821]"
+    embedded_string = "abcdefghi"
+    string = embedded_string.gsub("efg", "123")
+    {}[string] = 1
+    non_terminated = "#{string}#{nil}"
+    assert_nil(Bug::String.cstr_term_char(non_terminated), gh821)
+  end
+
   def assert_wchars_term_char(str)
     result = {}
     WCHARS.map do |enc|