C++2a Utility functions to implement uses-allocator construction (P0591R4)

	* include/std/memory (uses_allocator_construction_args): New set of
	overloaded functions.
	(make_obj_using_allocator, uninitialized_construct_using_allocator):
	New functions.
	* include/std/memory_resource (polymorphic_allocator::construct)
	[__cplusplus > 201703l]: Replace all overloads with a single function
	using uses_allocator_construction_args.
	* testsuite/20_util/polymorphic_allocator/construct_c++2a.cc: New
	test.
	* testsuite/20_util/uses_allocator/make_obj.cc: New test.

From-SVN: r269311

libstdc++-v3/ChangeLog

+2019-03-01  Jonathan Wakely  <jwakely@redhat.com>
+
+	* include/std/memory (uses_allocator_construction_args): New set of
+	overloaded functions.
+	(make_obj_using_allocator, uninitialized_construct_using_allocator):
+	New functions.
+	* include/std/memory_resource (polymorphic_allocator::construct)
+	[__cplusplus > 201703l]: Replace all overloads with a single function
+	using uses_allocator_construction_args.
+	* testsuite/20_util/polymorphic_allocator/construct_c++2a.cc: New
+	test.
+	* testsuite/20_util/uses_allocator/make_obj.cc: New test.
+
 2019-02-27  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/89466

libstdc++-v3/include/std/memory

@@ -91,6 +91,8 @@
 #include <cstdint>
 #if __cplusplus > 201703L
 # include <bit>			// for ispow2
+# include <new>			// for placement operator new
+# include <tuple>		// for tuple, make_tuple, make_from_tuple
 #endif
 namespace std _GLIBCXX_VISIBILITY(default)
 {
@@ -166,6 +168,197 @@ get_pointer_safety() noexcept { return pointer_safety::relaxed; }
     }
 #endif // C++2a
 
+#if __cplusplus > 201703L
+  template<typename _Tp>
+    struct __is_pair : false_type { };
+  template<typename _Tp, typename _Up>
+    struct __is_pair<pair<_Tp, _Up>> : true_type { };
+  template<typename _Tp, typename _Up>
+    struct __is_pair<const pair<_Tp, _Up>> : true_type { };
+
+  template<typename _Tp, typename __ = _Require<__not_<__is_pair<_Tp>>>,
+	   typename _Alloc, typename... _Args>
+    constexpr auto
+    __uses_alloc_args(const _Alloc& __a, _Args&&... __args) noexcept
+    {
+      if constexpr (uses_allocator_v<remove_cv_t<_Tp>, _Alloc>)
+	{
+	  if constexpr (is_constructible_v<_Tp, allocator_arg_t,
+					   const _Alloc&, _Args...>)
+	    {
+	      return tuple<allocator_arg_t, const _Alloc&, _Args&&...>(
+		  allocator_arg, __a, std::forward<_Args>(__args)...);
+	    }
+	  else
+	    {
+	      static_assert(is_constructible_v<_Tp, _Args..., const _Alloc&>);
+
+	      return tuple<_Args&&..., const _Alloc&>(
+		  std::forward<_Args>(__args)..., __a);
+	    }
+	}
+      else
+	{
+	  static_assert(is_constructible_v<_Tp, _Args...>);
+
+	  return tuple<_Args&&...>(std::forward<_Args>(__args)...);
+	}
+    }
+
+#if __cpp_concepts
+  template<typename _Tp>
+    concept bool _Std_pair = __is_pair<_Tp>::value;
+#endif
+
+// This is a temporary workaround until -fconcepts is implied by -std=gnu++2a
+#if __cpp_concepts
+# define _GLIBCXX_STD_PAIR_CONSTRAINT(T) _Std_pair T
+# define _GLIBCXX_STD_PAIR_CONSTRAINT_(T) _Std_pair T
+#else
+# define _GLIBCXX_STD_PAIR_CONSTRAINT(T) \
+      typename T, typename __ = _Require<__is_pair<T>>
+# define _GLIBCXX_STD_PAIR_CONSTRAINT_(T) typename T, typename
+#endif
+
+  template<typename _Tp,
+#if ! __cpp_concepts
+	   typename __ = _Require<__not_<__is_pair<_Tp>>>,
+#endif
+	   typename _Alloc, typename... _Args>
+    constexpr auto
+    uses_allocator_construction_args(const _Alloc& __a,
+				     _Args&&... __args) noexcept
+#if __cpp_concepts
+    requires ! _Std_pair<_Tp>
+#endif
+    {
+      return std::__uses_alloc_args<_Tp>(__a, std::forward<_Args>(__args)...);
+    }
+
+  template<_GLIBCXX_STD_PAIR_CONSTRAINT(_Tp), typename _Alloc,
+	   typename _Tuple1, typename _Tuple2>
+    constexpr auto
+    uses_allocator_construction_args(const _Alloc& __a, piecewise_construct_t,
+				     _Tuple1&& __x, _Tuple2&& __y) noexcept;
+
+  template<_GLIBCXX_STD_PAIR_CONSTRAINT(_Tp), typename _Alloc>
+    constexpr auto
+    uses_allocator_construction_args(const _Alloc&) noexcept;
+
+  template<_GLIBCXX_STD_PAIR_CONSTRAINT(_Tp), typename _Alloc,
+	   typename _Up, typename _Vp>
+    constexpr auto
+    uses_allocator_construction_args(const _Alloc&, _Up&&, _Vp&&) noexcept;
+
+  template<_GLIBCXX_STD_PAIR_CONSTRAINT(_Tp), typename _Alloc,
+	   typename _Up, typename _Vp>
+    constexpr auto
+    uses_allocator_construction_args(const _Alloc&,
+				     const pair<_Up, _Vp>&) noexcept;
+
+  template<_GLIBCXX_STD_PAIR_CONSTRAINT(_Tp), typename _Alloc,
+	   typename _Up, typename _Vp>
+    constexpr auto
+    uses_allocator_construction_args(const _Alloc&, pair<_Up, _Vp>&&) noexcept;
+
+  template<_GLIBCXX_STD_PAIR_CONSTRAINT_(_Tp), typename _Alloc,
+	   typename _Tuple1, typename _Tuple2>
+    constexpr auto
+    uses_allocator_construction_args(const _Alloc& __a, piecewise_construct_t,
+				     _Tuple1&& __x, _Tuple2&& __y) noexcept
+    {
+      using _Tp1 = typename _Tp::first_type;
+      using _Tp2 = typename _Tp::second_type;
+
+      return std::make_tuple(piecewise_construct,
+	  std::apply([&__a](auto&&... __args1) {
+	      return std::uses_allocator_construction_args<_Tp1>(
+		  __a, std::forward<decltype(__args1)>(__args1)...);
+	  }, std::forward<_Tuple1>(__x)),
+	  std::apply([&__a](auto&&... __args2) {
+	      return std::uses_allocator_construction_args<_Tp2>(
+		  __a, std::forward<decltype(__args2)>(__args2)...);
+	  }, std::forward<_Tuple2>(__y)));
+    }
+
+  template<_GLIBCXX_STD_PAIR_CONSTRAINT_(_Tp), typename _Alloc>
+    constexpr auto
+    uses_allocator_construction_args(const _Alloc& __a) noexcept
+    {
+      using _Tp1 = typename _Tp::first_type;
+      using _Tp2 = typename _Tp::second_type;
+
+      return std::make_tuple(piecewise_construct,
+	  std::uses_allocator_construction_args<_Tp1>(__a),
+	  std::uses_allocator_construction_args<_Tp2>(__a));
+    }
+
+  template<_GLIBCXX_STD_PAIR_CONSTRAINT_(_Tp), typename _Alloc,
+	   typename _Up, typename _Vp>
+    constexpr auto
+    uses_allocator_construction_args(const _Alloc& __a, _Up&& __u, _Vp&& __v)
+      noexcept
+    {
+      using _Tp1 = typename _Tp::first_type;
+      using _Tp2 = typename _Tp::second_type;
+
+      return std::make_tuple(piecewise_construct,
+	  std::uses_allocator_construction_args<_Tp1>(__a,
+	    std::forward<_Up>(__u)),
+	  std::uses_allocator_construction_args<_Tp2>(__a,
+	    std::forward<_Vp>(__v)));
+    }
+
+  template<_GLIBCXX_STD_PAIR_CONSTRAINT_(_Tp), typename _Alloc,
+	   typename _Up, typename _Vp>
+    constexpr auto
+    uses_allocator_construction_args(const _Alloc& __a,
+				     const pair<_Up, _Vp>& __pr) noexcept
+    {
+      using _Tp1 = typename _Tp::first_type;
+      using _Tp2 = typename _Tp::second_type;
+
+      return std::make_tuple(piecewise_construct,
+	  std::uses_allocator_construction_args<_Tp1>(__a, __pr.first),
+	  std::uses_allocator_construction_args<_Tp2>(__a, __pr.second));
+    }
+
+  template<_GLIBCXX_STD_PAIR_CONSTRAINT_(_Tp), typename _Alloc,
+	   typename _Up, typename _Vp>
+    constexpr auto
+    uses_allocator_construction_args(const _Alloc& __a,
+				     pair<_Up, _Vp>&& __pr) noexcept
+    {
+      using _Tp1 = typename _Tp::first_type;
+      using _Tp2 = typename _Tp::second_type;
+
+      return std::make_tuple(piecewise_construct,
+	  std::uses_allocator_construction_args<_Tp1>(__a,
+	    std::move(__pr).first),
+	  std::uses_allocator_construction_args<_Tp2>(__a,
+	    std::move(__pr).second));
+    }
+
+  template<typename _Tp, typename _Alloc, typename... _Args>
+    inline _Tp
+    make_obj_using_allocator(const _Alloc& __a, _Args&&... __args)
+    {
+      return std::make_from_tuple<_Tp>(uses_allocator_construction_args<_Tp>(
+	    __a, std::forward<_Args>(__args)...));
+    }
+
+  template<typename _Tp, typename _Alloc, typename... _Args>
+    inline _Tp*
+    uninitialized_construct_using_allocator(_Tp* __p, const _Alloc& __a,
+					    _Args&&... __args)
+    {
+      void* __vp = const_cast<void*>(static_cast<const volatile void*>(__p));
+      return ::new(__vp) _Tp(std::make_obj_using_allocator<_Tp>(__a,
+	    std::forward<_Args>(__args)...));
+    }
+
+#endif // C++2a
+
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
 #endif // C++11

libstdc++-v3/include/std/memory_resource

@@ -170,6 +170,7 @@ namespace pmr
       __attribute__((__nonnull__))
       { _M_resource->deallocate(__p, __n * sizeof(_Tp), alignof(_Tp)); }
 
+#if __cplusplus <= 201703L
       template<typename _Tp1, typename... _Args>
 	__attribute__((__nonnull__))
 	typename __not_pair<_Tp1>::type
@@ -242,6 +243,16 @@ namespace pmr
 			  forward_as_tuple(std::forward<_Up>(__pr.first)),
 			  forward_as_tuple(std::forward<_Vp>(__pr.second)));
 	}
+#else
+      template<typename _Tp1, typename... _Args>
+	__attribute__((__nonnull__))
+	void
+	construct(_Tp1* __p, _Args&&... __args)
+	{
+	  std::uninitialized_construct_using_allocator(__p, *this,
+	      std::forward<_Args>(__args)...);
+	}
+#endif
 
       template<typename _Up>
 	__attribute__((__nonnull__))

libstdc++-v3/testsuite/20_util/polymorphic_allocator/construct_c++2a.cc

+// Copyright (C) 2016-2019 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++2a" }
+// { dg-do run { target c++2a } }
+
+#include <memory_resource>
+#include <utility>
+#include <tuple>
+
+struct do_not_copy {
+  do_not_copy() = default;
+  do_not_copy(const do_not_copy&) { throw 1; }
+};
+
+void
+test01()
+{
+  struct X {
+    X(do_not_copy&&) { }
+  };
+
+  using pair = std::pair<X, int>;
+  std::pmr::polymorphic_allocator<pair> a;
+  auto ptr = a.allocate(1);
+  a.construct(ptr, std::piecewise_construct,
+      std::tuple<do_not_copy>{}, std::make_tuple(1));
+  a.deallocate(ptr, 1);
+}
+
+void
+test02()
+{
+  struct X {
+    using allocator_type = std::pmr::polymorphic_allocator<int>;
+    X(do_not_copy&&, const allocator_type&) { }
+  };
+
+  using pair = std::pair<X, int>;
+  std::pmr::polymorphic_allocator<pair> a;
+  auto ptr = a.allocate(1);
+  a.construct(ptr, std::piecewise_construct,
+      std::tuple<do_not_copy>{}, std::make_tuple(1));
+  a.deallocate(ptr, 1);
+}
+
+void
+test03()
+{
+  struct X {
+    using allocator_type = std::pmr::polymorphic_allocator<int>;
+    X(std::allocator_arg_t, const allocator_type&, do_not_copy&&) { }
+  };
+
+  using pair = std::pair<X, int>;
+  std::pmr::polymorphic_allocator<pair> a;
+  auto ptr = a.allocate(1);
+  a.construct(ptr, std::piecewise_construct,
+      std::tuple<do_not_copy>{}, std::make_tuple(1));
+  a.deallocate(ptr, 1);
+}
+
+void
+test04()
+{
+  struct X
+  {
+    using allocator_type = std::pmr::polymorphic_allocator<int>;
+    X() = default;
+    X(const X&) { throw 1; }
+    X(const X&, const allocator_type&) { }
+  };
+
+  struct Y
+  {
+    using allocator_type = std::pmr::polymorphic_allocator<int>;
+    Y() = default;
+    Y(const Y&) = delete;
+    Y(std::allocator_arg_t, const allocator_type&, const Y&) { }
+  };
+
+  using pair_type = std::pair<X, Y>;
+  std::pmr::polymorphic_allocator<pair_type> a;
+  auto ptr = a.allocate(1);
+  /* not const */ pair_type p;
+  a.construct(ptr, p); // LWG 2975
+  a.deallocate(ptr, 1);
+}
+
+void
+test05()
+{
+  struct X {
+    using allocator_type = std::pmr::polymorphic_allocator<char>;
+    X(int);
+    X(int, const allocator_type&) { }
+  };
+  std::pmr::polymorphic_allocator<X> a;
+  auto ptr = a.allocate(1);
+  a.construct(ptr, 1);
+  a.deallocate(ptr, 1);
+}
+
+int main()
+{
+  test01();
+  test02();
+  test03();
+  test04();
+  test05();
+}