libstdc++: Implement P1413R3 'deprecate aligned_storage and aligned_u…

…nion'

These two patches implement P1413 (deprecate std::aligned_storage and
std::aligned_union) for C++23. Tested on x86_64-linux.

-- >8 --

Adds deprecated attributes for C++23, and makes use of it for
std::aligned_storage, std::aligned_storage_t, std::aligned_union, and
std::aligned_union_t.

libstdc++-v3/ChangeLog:

	* doc/doxygen/user.cfg.in (PREDEFINED): Add new macros.
	* include/bits/c++config (_GLIBCXX23_DEPRECATED)
        (_GLIBCXX23_DEPRECATED_SUGGEST): New macros.
	* include/std/type_traits (aligned_storage, aligned_union)
        (aligned_storage_t, aligned_union_t): Deprecate for C++23.
	* testsuite/20_util/aligned_storage/deprecated-2b.cc: New test.
	* testsuite/20_util/aligned_union/deprecated-2b.cc: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>

libstdc++-v3/doc/doxygen/user.cfg.in

@@ -2396,6 +2396,8 @@ PREDEFINED             = __cplusplus=202002L \
                          "_GLIBCXX17_DEPRECATED_SUGGEST(E)= " \
                          "_GLIBCXX20_DEPRECATED= " \
                          "_GLIBCXX20_DEPRECATED_SUGGEST(E)= " \
+                         "_GLIBCXX23_DEPRECATED= " \
+                         "_GLIBCXX23_DEPRECATED_SUGGEST(E)= " \
                          _GLIBCXX17_INLINE=inline \
                          _GLIBCXX_CHRONO_INT64_T=int64_t \
                          _GLIBCXX_DEFAULT_ABI_TAG \

libstdc++-v3/include/bits/c++config

@@ -86,6 +86,8 @@
 //   _GLIBCXX17_DEPRECATED_SUGGEST( string-literal )
 //   _GLIBCXX20_DEPRECATED
 //   _GLIBCXX20_DEPRECATED_SUGGEST( string-literal )
+//   _GLIBCXX23_DEPRECATED
+//   _GLIBCXX23_DEPRECATED_SUGGEST( string-literal )
 #ifndef _GLIBCXX_USE_DEPRECATED
 # define _GLIBCXX_USE_DEPRECATED 1
 #endif
@@ -131,6 +133,14 @@
 # define _GLIBCXX20_DEPRECATED_SUGGEST(ALT)
 #endif
 
+#if defined(__DEPRECATED) && (__cplusplus >= 202100L)
+# define _GLIBCXX23_DEPRECATED [[__deprecated__]]
+# define _GLIBCXX23_DEPRECATED_SUGGEST(ALT) _GLIBCXX_DEPRECATED_SUGGEST(ALT)
+#else
+# define _GLIBCXX23_DEPRECATED
+# define _GLIBCXX23_DEPRECATED_SUGGEST(ALT)
+#endif
+
 // Macros for ABI tag attributes.
 #ifndef _GLIBCXX_ABI_TAG_CXX11
 # define _GLIBCXX_ABI_TAG_CXX11 __attribute ((__abi_tag__ ("cxx11")))

libstdc++-v3/include/std/type_traits

@@ -2088,10 +2088,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  type shall be a POD type suitable for use as uninitialized
    *  storage for any object whose size is at most _Len and whose
    *  alignment is a divisor of _Align.
+   *
+   *  @deprecated Deprecated in C++23. Uses can be replaced by an
+   *  array std::byte[_Len] declared with alignas(_Align).
   */
   template<std::size_t _Len, std::size_t _Align =
 	   __alignof__(typename __aligned_storage_msa<_Len>::__type)>
-    struct aligned_storage
+    struct
+    _GLIBCXX23_DEPRECATED
+    aligned_storage
     {
       union type
       {
@@ -2127,9 +2132,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
    *  least size _Len.
    *
    *  @see aligned_storage
+   *
+   *  @deprecated Deprecated in C++23.
    */
   template <size_t _Len, typename... _Types>
-    struct aligned_union
+    struct
+    _GLIBCXX23_DEPRECATED
+    aligned_union
     {
     private:
       static_assert(sizeof...(_Types) != 0, "At least one type is required");
@@ -2580,10 +2589,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   /// Alias template for aligned_storage
   template<size_t _Len, size_t _Align =
 	    __alignof__(typename __aligned_storage_msa<_Len>::__type)>
-    using aligned_storage_t = typename aligned_storage<_Len, _Align>::type;
+    using aligned_storage_t _GLIBCXX23_DEPRECATED = typename aligned_storage<_Len, _Align>::type;
 
   template <size_t _Len, typename... _Types>
-    using aligned_union_t = typename aligned_union<_Len, _Types...>::type;
+    using aligned_union_t _GLIBCXX23_DEPRECATED = typename aligned_union<_Len, _Types...>::type;
 
   /// Alias template for decay
   template<typename _Tp>

libstdc++-v3/testsuite/20_util/aligned_storage/deprecated-2b.cc

@@ -0,0 +1,26 @@
+// Copyright (C) 2022 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++23" }
+// { dg-do compile { target c++23 } }
+
+#include <type_traits>
+
+std::aligned_storage<1, 1>::type x; // { dg-warning "is deprecated" }
+std::aligned_storage_t<1, 1> y; // { dg-warning "is deprecated" }
+
+// { dg-prune-output "declared here" }

libstdc++-v3/testsuite/20_util/aligned_union/deprecated-2b.cc

@@ -0,0 +1,26 @@
+// Copyright (C) 2022 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++23" }
+// { dg-do compile { target c++23 } }
+
+#include <type_traits>
+
+std::aligned_union<4, int>::type x; // { dg-warning "is deprecated" }
+std::aligned_union_t<4, int> y; // { dg-warning "is deprecated" }
+
+// { dg-prune-output "declared here" }