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[PATCH 2/2] libstdc++: Add std::aligned_union.


C++11: [meta.trans.other]

* libstdc++-v3/testsuite/20_util/aligned_union/1.cc: New file.
* libstdc++-v3/include/std/type_traits (__strictest_alignment): New
  helper struct.
  (aligned_union): New struct (C++11).
  (aligned_union_t): New type alias (C++14).
---
 libstdc++-v3/include/std/type_traits              | 43 ++++++++++++++
 libstdc++-v3/testsuite/20_util/aligned_union/1.cc | 72 
+++++++++++++++++++++++
 2 files changed, 115 insertions(+)
 create mode 100644 libstdc++-v3/testsuite/20_util/aligned_union/1.cc

diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-
v3/include/std/type_traits
index 4b434a6..2b75345 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -1837,6 +1837,46 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       };
     };
 
+  template <typename... _Types>
+    struct __strictest_alignment
+    {
+      static const size_t _M_alignment = 0;
+      static const size_t _M_size = 0;
+    };
+
+  template <typename _T, typename... _Types>
+    struct __strictest_alignment<_T, _Types...>
+    {
+      static const size_t _M_alignment =
+        alignof(_T) > __strictest_alignment<_Types...>::_M_alignment ?
+        alignof(_T) : __strictest_alignment<_Types...>::_M_alignment;
+      static const size_t _M_size =
+        sizeof(_T) > __strictest_alignment<_Types...>::_M_size ?
+        sizeof(_T) : __strictest_alignment<_Types...>::_M_size;
+    };
+
+  /**
+   *  @brief Provide aligned storage for types.
+   *
+   *  [meta.trans.other]
+   *
+   *  Provides aligned storage for any of the provided types of at
+   *  least size _Len.
+   *
+   *  @see aligned_storage
+   */
+  template <size_t _Len, typename... _Types>
+    struct aligned_union
+    {
+      /// The value of the strictest alignment of _Types.
+      static const size_t alignment_value =
+        __strictest_alignment<_Types...>::_M_alignment;
+      static const size_t _M_len =
+        _Len > __strictest_alignment<_Types...>::_M_size ?
+        _Len : __strictest_alignment<_Types...>::_M_size;
+      /// The storage.
+      typedef typename aligned_storage<_M_len, alignment_value>::type type;
+    };
 
   // Decay trait for arrays and functions, used for perfect forwarding
   // in make_pair, make_tuple, etc.
@@ -2173,6 +2213,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	    __alignof__(typename __aligned_storage_msa<_Len>::__type)>
     using aligned_storage_t = typename aligned_storage<_Len, _Align>::type;
 
+  template <size_t Len, class... Types>
+    using aligned_union_t = typename aligned_union<Len,Types...>::type;
+
   /// Alias template for decay
   template<typename _Tp>
     using decay_t = typename decay<_Tp>::type;
diff --git a/libstdc++-v3/testsuite/20_util/aligned_union/1.cc b/libstdc++-
v3/testsuite/20_util/aligned_union/1.cc
new file mode 100644
index 0000000..c01ecc0
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/aligned_union/1.cc
@@ -0,0 +1,72 @@
+// { dg-options " -std=gnu++11 " }
+
+// 2014-04-16 RÃÂdiger Sonderfeld  <ruediger@c-plusplus.de>
+
+// Copyright (C) 2014 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/>.
+
+// C++11 [meta.trans.other] 20.9.7.6: aligned_union
+
+#include <type_traits>
+#include <initializer_list>
+#include <testsuite_tr1.h>
+
+struct MSAlignType { } __attribute__((__aligned__));
+
+template<typename...T>
+  struct mymax
+  {
+    static const std::size_t alignment = 0;
+    static const std::size_t size = 0;
+  };
+
+template<typename L,  typename...T>
+  struct mymax<L, T...>
+  {
+    static const std::size_t alignment = alignof(L) > mymax<T...>::alignment
+      ? alignof(L) : mymax<T...>::alignment;
+    static const std::size_t size = sizeof(L) > mymax<T...>::size
+      ? sizeof(L) : mymax<T...>::size;
+  };
+
+void test01()
+{
+  using std::aligned_union;
+  using std::alignment_of;
+  using std::size_t;
+  using namespace __gnu_test;
+
+  const size_t max_a = mymax<char, short, int, double, int[4],
+                             ClassType, MSAlignType>::alignment;
+  const size_t max_s = mymax<char, short, int, double, int[4],
+                             ClassType, MSAlignType>::size;
+
+  typedef aligned_union<0, char, short, int, double, int[4],
+                        ClassType, MSAlignType> au_type;
+  static_assert(au_type::alignment_value == max_a, "Alignment value");
+  static_assert(sizeof(au_type::type) >= max_s, "Storage size");
+
+  typedef aligned_union<max_s+100, char, short, int, double, int[4],
+                        ClassType, MSAlignType> au_type2;
+  static_assert(sizeof(au_type2::type) >= max_s+100,
+                "Storage size (at least len)");
+}
+
+int main()
+{
+  test01();
+}
-- 
1.9.2


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