[PATCH] PR libstdc++/80478 make std::mem_fn work with noexcept functions

[Jonathan Wakely]

We need partial specializations of _Mem_fn for member function types
that are noexcept(true). Rather than relying on deducing the
exception-specification (which is not supported by Clang yet) I've
just added some more uses of the macro that generates the partial
specializations.

        PR libstdc++/80478
        * include/std/functional (_Mem_fn_traits_base): Add specializations
        for noexcept member function types.
        * testsuite/20_util/function_objects/mem_fn/80478.cc: New test.

Tested powerpc64le-linux, committed to trunk. Backport to gcc-7-branch
coming shortly.



commit 17f840633e1681c2c27468b190c250c9c9960b51
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Thu May 18 17:49:05 2017 +0100

    PR libstdc++/80478 make std::mem_fn work with noexcept functions
    
        PR libstdc++/80478
        * include/std/functional (_Mem_fn_traits_base): Add specializations
        for noexcept member function types.
        * testsuite/20_util/function_objects/mem_fn/80478.cc: New test.

diff --git a/libstdc++-v3/include/std/functional 
b/libstdc++-v3/include/std/functional
index e4a82ee..465b3ec 100644
--- a/libstdc++-v3/include/std/functional
+++ b/libstdc++-v3/include/std/functional
@@ -135,6 +135,12 @@ _GLIBCXX_MEM_FN_TRAITS( , true_type, true_type)
 _GLIBCXX_MEM_FN_TRAITS(&, true_type, false_type)
 _GLIBCXX_MEM_FN_TRAITS(&&, false_type, true_type)
 
+#if __cplusplus > 201402L
+_GLIBCXX_MEM_FN_TRAITS(noexcept, true_type, true_type)
+_GLIBCXX_MEM_FN_TRAITS(& noexcept, true_type, false_type)
+_GLIBCXX_MEM_FN_TRAITS(&& noexcept, false_type, true_type)
+#endif
+
 #undef _GLIBCXX_MEM_FN_TRAITS
 #undef _GLIBCXX_MEM_FN_TRAITS2
 
diff --git a/libstdc++-v3/testsuite/20_util/function_objects/mem_fn/80478.cc 
b/libstdc++-v3/testsuite/20_util/function_objects/mem_fn/80478.cc
new file mode 100644
index 0000000..f49fcaa
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/function_objects/mem_fn/80478.cc
@@ -0,0 +1,27 @@
+// 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-options "-std=gnu++17" }
+// { dg-do compile { target c++1z } }
+
+#include <functional>
+
+struct X {
+  void f() noexcept { }
+};
+
+auto f = std::mem_fn(&X::f);