From 2d82342cf299220e0e7f84d464b205231fd41e8f Mon Sep 17 00:00:00 2001
From: nobu <nobu@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Fri, 28 Mar 2014 02:27:14 +0000
Subject: [PATCH] string.c: unset $~ if unmatch

* string.c (rb_pat_search): unset $~ if the last match failed.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45458 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 string.c                 | 11 ++++++++---
 test/ruby/test_string.rb |  8 ++++++++
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/string.c b/string.c
index 6e316426af..2b0c69c6fc 100644
--- a/string.c
+++ b/string.c
@@ -3893,9 +3893,14 @@ rb_pat_search(VALUE pat, VALUE str, long pos, int set_backref_str)
 {
     if (BUILTIN_TYPE(pat) == T_STRING) {
 	pos = rb_str_index(str, pat, pos);
-	if (pos >= 0 && set_backref_str) {
-	    str = rb_str_new_frozen(str);
-	    rb_backref_set_string(str, pos, RSTRING_LEN(pat));
+	if (set_backref_str) {
+	    if (pos >= 0) {
+		str = rb_str_new_frozen(str);
+		rb_backref_set_string(str, pos, RSTRING_LEN(pat));
+	    }
+	    else {
+		rb_backref_set(Qnil);
+	    }
 	}
 	return pos;
     }
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index 5c8c4184a0..62402353a7 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -1147,6 +1147,14 @@ class TestString < Test::Unit::TestCase
     res = []
     a.scan(/./) { |w| res << w }
     assert_predicate(res[0], :tainted?, '[ruby-core:33338] #4087')
+
+    /h/ =~ a
+    a.scan(/x/)
+    assert_nil($~)
+
+    /h/ =~ a
+    a.scan('x')
+    assert_nil($~)
   end
 
   def test_size