Fix typo in std::wbuffer_convert

	* include/bits/locale_conv.h (wbuffer_convert::_M_conv_get): Fix typo.
	* testsuite/22_locale/conversions/buffer/3.cc: New test.

From-SVN: r254735

libstdc++-v3/ChangeLog

+2017-11-14  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/bits/locale_conv.h (wbuffer_convert::_M_conv_get): Fix typo.
+	* testsuite/22_locale/conversions/buffer/3.cc: New test.
+
 2017-11-10  Jonathan Wakely  <jwakely@redhat.com>
 
 	* testsuite/util/testsuite_tr1.h (ThrowMoveConsClass): Use noexcept.

libstdc++-v3/include/bits/locale_conv.h

@@ -431,7 +431,7 @@ _GLIBCXX_END_NAMESPACE_CXX11
 	streamsize __nbytes = sizeof(_M_get_buf) - _M_unconv;
 	__nbytes = std::min(__nbytes, _M_buf->in_avail());
 	if (__nbytes < 1)
-	  __nbytes == 1;
+	  __nbytes = 1;
 	__nbytes = _M_buf->sgetn(_M_get_buf + _M_unconv, __nbytes);
 	if (__nbytes < 1)
 	  return false;

libstdc++-v3/testsuite/22_locale/conversions/buffer/3.cc

+// Copyright (C) 2017 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-do run { target c++11 } }
+
+#include <locale>
+#include <streambuf>
+#include <testsuite_hooks.h>
+
+struct streambuf : std::streambuf
+{
+  int_type underflow() override
+  {
+    if (c != '\0')
+    {
+      this->setg(&c, &c, &c + 1);
+      return *this->gptr();
+    }
+    c = '\0';
+    return traits_type::eof();
+  }
+
+private:
+  char c = 'a';
+};
+
+struct codecvt : std::codecvt<wchar_t, char, std::mbstate_t> { };
+
+void
+test01()
+{
+  // https://gcc.gnu.org/ml/libstdc++/2017-11/msg00022.html
+  streambuf sb;
+  std::wbuffer_convert<codecvt> conv(&sb);
+  VERIFY( sb.in_avail() == 0 );
+  wchar_t c = conv.sgetc();
+  VERIFY( c == L'a' );
+}
+
+int
+main()
+{
+  test01();
+}