[PATCH] PR libstdc++/92267 fix ABI change in deque iterators

[Jonathan Wakely]

Defaulting the copy constructor on its first declaration made it change
from user-provided (and non-trivial) to implicitly-defined (and
trivial). This caused an ABI incompatibility between GCC 8 and GCC 9,
where functions taking a deque iterator disagree on the argument passing
convention.

        PR libstdc++/92267
        * include/bits/stl_deque.h (_Deque_iterator(const _Deque_iterator&)):
        Do not define as defaulted.
        * testsuite/23_containers/deque/types/92267.cc: New test.

Tested powerpc64le-linux, committed to trunk.

Backport to gcc-9-branch to follow shortly.


commit 04994f2e4e26ccc4308207735fb8393cb8e89bef
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Tue Oct 29 16:44:01 2019 +0000

    PR libstdc++/92267 fix ABI change in deque iterators
    
    Defaulting the copy constructor on its first declaration made it change
    from user-provided (and non-trivial) to implicitly-defined (and
    trivial). This caused an ABI incompatibility between GCC 8 and GCC 9,
    where functions taking a deque iterator disagree on the argument passing
    convention.
    
            PR libstdc++/92267
            * include/bits/stl_deque.h (_Deque_iterator(const 
_Deque_iterator&)):
            Do not define as defaulted.
            * testsuite/23_containers/deque/types/92267.cc: New test.

diff --git a/libstdc++-v3/include/bits/stl_deque.h 
b/libstdc++-v3/include/bits/stl_deque.h
index 50491e76ff5..676768c0159 100644
--- a/libstdc++-v3/include/bits/stl_deque.h
+++ b/libstdc++-v3/include/bits/stl_deque.h
@@ -156,13 +156,16 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 #else
       // Conversion from iterator to const_iterator.
       template<typename _Iter,
-             typename = _Require<is_same<_Self, const_iterator>,
-                                 is_same<_Iter, iterator>>>
+              typename = _Require<is_same<_Self, const_iterator>,
+                                  is_same<_Iter, iterator>>>
        _Deque_iterator(const _Iter& __x) noexcept
        : _M_cur(__x._M_cur), _M_first(__x._M_first),
         _M_last(__x._M_last), _M_node(__x._M_node) { }
 
-      _Deque_iterator(const _Deque_iterator&) = default;
+      _Deque_iterator(const _Deque_iterator& __x) noexcept
+       : _M_cur(__x._M_cur), _M_first(__x._M_first),
+        _M_last(__x._M_last), _M_node(__x._M_node) { }
+
       _Deque_iterator& operator=(const _Deque_iterator&) = default;
 #endif
 
diff --git a/libstdc++-v3/testsuite/23_containers/deque/types/92267.cc 
b/libstdc++-v3/testsuite/23_containers/deque/types/92267.cc
new file mode 100644
index 00000000000..cab8d25f0db
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/deque/types/92267.cc
@@ -0,0 +1,27 @@
+// Copyright (C) 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-do compile { target c++11 } }
+
+#include <deque>
+
+using std::deque;
+using std::is_trivially_copy_constructible;
+
+// PR libstdc++/92267
+static_assert(!is_trivially_copy_constructible<deque<int>::iterator>::value);
+static_assert(!is_trivially_copy_constructible<deque<int>::const_iterator>::value);