Merge to upstream r225300.

Change-Id: I2b23715db9ac129ff80aa78ad5824db0a4d6fbb3

test/std/input.output/iostreams.base/ios/basic.ios.members/rdbuf.pass.cpp

@@ -0,0 +1,31 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <ios>
+
+// template <class charT, class traits> class basic_ios
+
+// basic_streambuf<charT,traits>* rdbuf() const;
+
+#include <ios>
+#include <streambuf>
+#include <cassert>
+
+int main()
+{
+    {
+        const std::ios ios(0);
+        assert(ios.rdbuf() == 0);
+    }
+    {
+        std::streambuf* sb = (std::streambuf*)1;
+        const std::ios ios(sb);
+        assert(ios.rdbuf() == sb);
+    }
+}