[PATCH] Don't define uses-allocator variable templates in C++11

[Jonathan Wakely]

These variable templates give warnings in C++11 mode when
-Wsystem-headers is used:

In file included from /home/jwakely/gcc/7/include/c++/7.0.0/memory:77:0,
                 from vt.cc:1:
/home/jwakely/gcc/7/include/c++/7.0.0/bits/uses_allocator.h:130:20: warning: variable templates only available with -std=c++14 or -std=gnu++14
     constexpr bool __is_uses_allocator_constructible_v =
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/jwakely/gcc/7/include/c++/7.0.0/bits/uses_allocator.h:141:20: warning: variable templates only available with -std=c++14 or -std=gnu++14
     constexpr bool __is_nothrow_uses_allocator_constructible_v =
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We don't need them, so let's only define them for C++14 and up.

	* include/bits/uses_allocator.h (__is_uses_allocator_constructible_v)
	(__is_nothrow_uses_allocator_constructible_v): Only define for C++14
	and later.

Tested powerpc64le-linux, committed to trunk.

-------------- next part --------------
commit b19fd14727318d5d6f3a411a2a600f89d07ab28a
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Oct 18 12:31:11 2016 +0100

    Don't define uses-allocator variable templates in C++11
    
    	* include/bits/uses_allocator.h (__is_uses_allocator_constructible_v)
    	(__is_nothrow_uses_allocator_constructible_v): Only define for C++14
    	and later.

diff --git a/libstdc++-v3/include/bits/uses_allocator.h b/libstdc++-v3/include/bits/uses_allocator.h
index c7d14f3..612c53c 100644
--- a/libstdc++-v3/include/bits/uses_allocator.h
+++ b/libstdc++-v3/include/bits/uses_allocator.h
@@ -126,9 +126,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     : __is_uses_allocator_predicate<is_constructible, _Tp, _Alloc, _Args...>
     { };
 
+#if __cplusplus >= 201402L
   template<typename _Tp, typename _Alloc, typename... _Args>
     constexpr bool __is_uses_allocator_constructible_v =
       __is_uses_allocator_constructible<_Tp, _Alloc, _Args...>::value;
+#endif // C++14
 
   template<typename _Tp, typename _Alloc, typename... _Args>
     struct __is_nothrow_uses_allocator_constructible
@@ -137,9 +139,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     { };
 
 
+#if __cplusplus >= 201402L
   template<typename _Tp, typename _Alloc, typename... _Args>
     constexpr bool __is_nothrow_uses_allocator_constructible_v =
       __is_nothrow_uses_allocator_constructible<_Tp, _Alloc, _Args...>::value;
+#endif // C++14
 
   template<typename _Tp, typename... _Args>
     void __uses_allocator_construct_impl(__uses_alloc0 __a, _Tp* __ptr,