[v3] Fix std::function to cope with volatile-qualified pointers to members

[Jonathan Wakely]

(N.B. not pointers to volatile member functions!)

        * include/std/functional (__callable_functor): Overload for
        volatile-qualified pointers.
        * testsuite/20_util/function/10.cc: New.

Tested x86_64-linux, committed to trunk.  I think the problem is
obscure enough that the fix doesn't need to go on older branches.

commit fb1df22f59d2ac8f60b9ec1b90f5ce062dbfdaab
Author: Jonathan Wakely <jwakely....@gmail.com>
Date:   Tue Mar 27 22:18:00 2012 +0100

        * include/std/functional (__callable_functor): Overload for
        volatile-qualified pointers.
        * testsuite/20_util/function/10.cc: New.

diff --git a/libstdc++-v3/include/std/functional 
b/libstdc++-v3/include/std/functional
index 14785dd..980c6ab 100644
--- a/libstdc++-v3/include/std/functional
+++ b/libstdc++-v3/include/std/functional
@@ -1716,6 +1716,16 @@ _GLIBCXX_HAS_NESTED_TYPE(result_type)
     __callable_functor(_Member _Class::* const &__p)
     { return std::mem_fn(__p); }
 
+  template<typename _Member, typename _Class>
+    inline _Mem_fn<_Member _Class::*>
+    __callable_functor(_Member _Class::* volatile &__p)
+    { return std::mem_fn(__p); }
+
+  template<typename _Member, typename _Class>
+    inline _Mem_fn<_Member _Class::*>
+    __callable_functor(_Member _Class::* const volatile &__p)
+    { return std::mem_fn(__p); }
+
   template<typename _Signature>
     class function;
 
diff --git a/libstdc++-v3/testsuite/20_util/function/10.cc 
b/libstdc++-v3/testsuite/20_util/function/10.cc
new file mode 100644
index 0000000..3776f39
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/function/10.cc
@@ -0,0 +1,37 @@
+// { dg-options "-std=gnu++0x" }
+// { dg-do compile }
+//
+// Copyright (C) 2012 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/>.
+
+// 20.8.11 polymorphic function object wrapper
+
+#include <functional>
+
+struct X { void f() { } };
+
+void (X::*p)() = &X::f;
+void (X::* volatile& vp)() = p;
+
+typedef std::function<void(X&)> function_type;
+
+void test01()
+{
+  function_type f( vp );
+  function_type f2( std::ref(vp) );
+  function_type f3( std::cref(vp) );
+}