libstdc++: Restore __gnu_debug::array [PR100682]

As the PR points out, we removed the debug version of std::array without
any period of deprecation. Although std::array contains all the actual
debug checks now, removing the <debug/arrray> header breaks any code
that was using that explicitly. The manual still lists doing that as
supported.

This restores the <debug/array> header, but simply defines
__gnu_debug::array as an alias for std::array, and declares the alias
with the deprecated attribute. The docs are updated to match.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	PR libstdc++/100682
	* doc/xml/manual/debug_mode.xml: Update documentation about
	debug capability of std::array.
	* doc/html/*: Regenerate.
	* include/debug/array: New file.

1 files changed, 45 insertions, 0 deletions

diff --git a/libstdc++-v3/include/debug/array b/libstdc++-v3/include/debug/array
new file mode 100644
index 00000000000..5cb51dfe8b5
--- /dev/null
+++ b/libstdc++-v3/include/debug/array
@@ -0,0 +1,45 @@
+// Redeclaration of std::array in debug namespace -*- C++ -*-
+
+// Copyright (C) 2021 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.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+// <http://www.gnu.org/licenses/>.
+
+/** @file debug/array
+ *  This file is a GNU debug extension to the Standard C++ Library.
+ */
+
+#ifndef _GLIBCXX_DEBUG_ARRAY
+#define _GLIBCXX_DEBUG_ARRAY 1
+
+#pragma GCC system_header
+
+#include <array>
+
+namespace __gnu_debug
+{
+  template<typename _Tp, std::size_t _Nm>
+    using array _GLIBCXX_DEPRECATED_SUGGEST("std::array")
+      = std::array<_Tp, _Nm>;
+
+  using std::get;
+  using std::swap;
+}
+#endif // _GLIBCXX_DEBUG_ARRAY