complex (complex::real, [...]): Add const.

	* include/std/complex (complex::real, complex::imag): Add const.
	* testsuite/26_numerics/complex/value_operations/constexpr2.cc: New.

From-SVN: r216258

libstdc++-v3/ChangeLog

+2014-10-15  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/std/complex (complex::real, complex::imag): Add const.
+	* testsuite/26_numerics/complex/value_operations/constexpr2.cc: New.
+
 2014-10-15  Paolo Carlini  <paolo.carlini@oracle.com>
 
 	* include/std/limits: Remove stray semicolon.

libstdc++-v3/include/std/complex

@@ -144,11 +144,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       // DR 387. std::complex over-encapsulated.
       _GLIBCXX_ABI_TAG_CXX11
       constexpr _Tp 
-      real() { return _M_real; }
+      real() const { return _M_real; }
 
       _GLIBCXX_ABI_TAG_CXX11
       constexpr _Tp 
-      imag() { return _M_imag; }
+      imag() const { return _M_imag; }
 #else
       ///  Return real part of complex number.
       _Tp& 

libstdc++-v3/testsuite/26_numerics/complex/value_operations/constexpr2.cc

+// { dg-do compile }
+// { dg-options "-std=gnu++14" }
+
+// Copyright (C) 2014 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/>.
+
+#include <complex>
+
+int main()
+{
+  constexpr std::complex<int> c{};
+  constexpr auto r __attribute__((unused)) = real(c);
+  constexpr auto i __attribute__((unused)) = imag(c);
+}