libstdc++: Implementing P0767 - deprecate POD

This adds the deprecated attribute to std::is_pod and std::is_pod_v for
C++20.

2019-12-05  JeanHeyd "ThePhD" Meneide  <phdofthehouse@gmail.com>

	* include/bits/c++config (_GLIBCXX20_DEPRECATED): Add new macro.
	* include/std/type_traits (is_pod, is_pod_v): Deprecate for C++20.
	* testuite/20_util/is_pod/deprecated-2a.cc: New test.

From-SVN: r280065

4 files changed, 44 insertions, 2 deletions

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index c4a98f8..5725771 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,9 @@
+2020-01-09  JeanHeyd "ThePhD" Meneide  <phdofthehouse@gmail.com>
+
+	* include/bits/c++config (_GLIBCXX20_DEPRECATED): Add new macro.
+	* include/std/type_traits (is_pod, is_pod_v): Deprecate for C++20.
+	* testuite/20_util/is_pod/deprecated-2a.cc: New test.
+
 2020-01-09  Jonathan Wakely  <jwakely@redhat.com>
 
 	PR libstdc++/93205
diff --git a/libstdc++-v3/include/bits/c++config b/libstdc++-v3/include/bits/c++config
index f983743..875a5e7 100644
--- a/libstdc++-v3/include/bits/c++config
+++ b/libstdc++-v3/include/bits/c++config
@@ -78,6 +78,7 @@
 //   _GLIBCXX_USE_DEPRECATED
 //   _GLIBCXX_DEPRECATED
 //   _GLIBCXX17_DEPRECATED
+//   _GLIBCXX20_DEPRECATED( string-literal )
 #ifndef _GLIBCXX_USE_DEPRECATED
 # define _GLIBCXX_USE_DEPRECATED 1
 #endif
@@ -94,6 +95,12 @@
 # define _GLIBCXX17_DEPRECATED
 #endif
 
+#if defined(__DEPRECATED) && (__cplusplus > 201703L)
+# define _GLIBCXX20_DEPRECATED(MSG) [[deprecated(MSG)]]
+#else
+# define _GLIBCXX20_DEPRECATED(MSG)
+#endif
+
 // Macros for ABI tag attributes.
 #ifndef _GLIBCXX_ABI_TAG_CXX11
 # define _GLIBCXX_ABI_TAG_CXX11 __attribute ((__abi_tag__ ("cxx11")))
diff --git a/libstdc++-v3/include/std/type_traits b/libstdc++-v3/include/std/type_traits
index 061835b..c69867c 100644
--- a/libstdc++-v3/include/std/type_traits
+++ b/libstdc++-v3/include/std/type_traits
@@ -685,10 +685,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	"template argument must be a complete class or an unbounded array");
     };
 
-  /// is_pod
+  /// is_pod (deprecated in C++20)
   // Could use is_standard_layout && is_trivial instead of the builtin.
   template<typename _Tp>
-    struct is_pod
+    struct
+    _GLIBCXX20_DEPRECATED("use is_standard_layout && is_trivial instead")
+    is_pod
     : public integral_constant<bool, __is_pod(_Tp)>
     {
       static_assert(std::__is_complete_or_unbounded(__type_identity<_Tp>{}),
@@ -3078,6 +3080,7 @@ template <typename _Tp>
 template <typename _Tp>
   inline constexpr bool is_standard_layout_v = is_standard_layout<_Tp>::value;
 template <typename _Tp>
+  _GLIBCXX20_DEPRECATED("use is_standard_layout_v && is_trivial_v instead")
   inline constexpr bool is_pod_v = is_pod<_Tp>::value;
 template <typename _Tp>
   inline constexpr bool is_literal_type_v = is_literal_type<_Tp>::value;
diff --git a/libstdc++-v3/testsuite/20_util/is_pod/deprecated-2a.cc b/libstdc++-v3/testsuite/20_util/is_pod/deprecated-2a.cc
new file mode 100644
index 0000000..848baf7
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/is_pod/deprecated-2a.cc
@@ -0,0 +1,26 @@
+// Copyright (C) 2020 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 compile { target c++2a } }
+
+#include <type_traits>
+
+static_assert(std::is_pod<int>::value); // { dg-warning "is deprecated" }
+static_assert(std::is_pod_v<int>); // { dg-warning "is deprecated" }
+
+// { dg-prune-output "declared here" }