The move / swap members were not correctly taking all of the possible states of the basic_stringbuf into account. Just rewrote these members. Test included. This fixes http://llvm.org/bugs/show_bug.cgi?id=15659.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@178690 91177308-0d34-0410-b5e6-96231b3b80d8

test/input.output/string.streams/stringstream.cons/move2.pass.cpp

@@ -0,0 +1,37 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <sstream>
+
+// template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> >
+// class basic_stringstream
+
+// basic_stringstream(basic_stringstream&& rhs);
+
+#include <sstream>
+#include <vector>
+#include <string>
+#include <cassert>
+
+int main()
+{
+#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+    std::vector<std::istringstream> vecis;
+    vecis.push_back(std::istringstream());
+    vecis.back().str("hub started at [00 6b 8b 45 69]");
+    vecis.push_back(std::istringstream());
+    vecis.back().str("hub started at [00 6b 8b 45 69]");
+    for (int n = 0; n < vecis.size(); n++)
+    {
+        assert(vecis[n].str().size() == 31);
+        vecis[n].seekg(0, std::ios_base::beg);
+        assert(vecis[n].str().size() == 31);
+    }
+#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+}