Hi
Here is the patch to default the default and move constructors on
the std::forward_list. Putting a move constructor on _Fwd_list_node_base
helped limiting the code impact of this patch. It doesn't have any side
effect as iterator types using this base type are not defining any move
semantic.
I also took the time to optimize the move constructor with
allocator when allocator is always equal. It avoids initializing an
empty forward list for nothing.
I think it is fine but could we have an abi issue because of the
change in forward_list.tcc ?
* include/bits/forward_list.h
(_Fwd_list_node_base(_Fwd_list_node_base&&)): New.
(_Fwd_list_impl()): Add noexcept qualification.
(_Fwd_list_impl(_Fwd_list_impl&&)): New, default.
(_Fwd_list_impl(_Fwd_list_impl&&, _Node_alloc_type&&)): New.
(_Fwd_list_base()): Default.
(_Fwd_list_base(_Fwd_list_base&&, _Node_alloc_type&&, true_type)): New.
(_Fwd_list_base(_Fwd_list_base&&, _Node_alloc_type&&, false_type)):
New.
(_Fwd_list_base(_Fwd_list_base&& __lst, _Node_alloc_type&& __a)): Use
latter.
(_Fwd_list_base(_Fwd_list_base&&)): Default.
(forward_list<>()): Default.
(forward_list<>(forward_list&&)): Default.
* include/bits/forward_list.tcc
(_Fwd_list_base(_Fwd_list_base&&, _Node_alloc_type&&, false_type)):
New.
* testsuite/23_containers/forward_list/allocator/default_init.cc: New.
Tested under Linux x86_64, ok to commit ?
François
diff --git a/libstdc++-v3/include/bits/forward_list.h b/libstdc++-v3/include/bits/forward_list.h
index f319b7f..312cd9e 100644
--- a/libstdc++-v3/include/bits/forward_list.h
+++ b/libstdc++-v3/include/bits/forward_list.h
@@ -53,6 +53,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
struct _Fwd_list_node_base
{
_Fwd_list_node_base() = default;
+ _Fwd_list_node_base(_Fwd_list_node_base&& __x) noexcept
+ : _M_next(__x._M_next)
+ { __x._M_next = nullptr; }
_Fwd_list_node_base* _M_next = nullptr;
@@ -284,15 +287,22 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_Fwd_list_node_base _M_head;
_Fwd_list_impl()
- : _Node_alloc_type(), _M_head()
+ noexcept( noexcept(_Node_alloc_type()) )
+ : _Node_alloc_type()
{ }
_Fwd_list_impl(const _Node_alloc_type& __a)
- : _Node_alloc_type(__a), _M_head()
+ : _Node_alloc_type(__a)
+ { }
+
+ _Fwd_list_impl(_Fwd_list_impl&&) = default;
+
+ _Fwd_list_impl(_Fwd_list_impl&& __fl, _Node_alloc_type&& __a)
+ : _Node_alloc_type(std::move(__a)), _M_head(std::move(__fl._M_head))
{ }
_Fwd_list_impl(_Node_alloc_type&& __a)
- : _Node_alloc_type(std::move(__a)), _M_head()
+ : _Node_alloc_type(std::move(__a))
{ }
};
@@ -311,20 +321,25 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_M_get_Node_allocator() const noexcept
{ return this->_M_impl; }
- _Fwd_list_base()
- : _M_impl() { }
+ private:
+ _Fwd_list_base(_Fwd_list_base&& __lst, _Node_alloc_type&& __a, std::true_type)
+ : _M_impl(std::move(__lst._M_impl), std::move(__a))
+ { }
+
+ _Fwd_list_base(_Fwd_list_base&&, _Node_alloc_type&&, std::false_type);
+
+ public:
+ _Fwd_list_base() = default;
_Fwd_list_base(_Node_alloc_type&& __a)
: _M_impl(std::move(__a)) { }
- _Fwd_list_base(_Fwd_list_base&& __lst, _Node_alloc_type&& __a);
+ _Fwd_list_base(_Fwd_list_base&& __lst, _Node_alloc_type&& __a)
+ : _Fwd_list_base(std::move(__lst), std::move(__a),
+ typename _Node_alloc_traits::is_always_equal{})
+ { }
- _Fwd_list_base(_Fwd_list_base&& __lst)
- : _M_impl(std::move(__lst._M_get_Node_allocator()))
- {
- this->_M_impl._M_head._M_next = __lst._M_impl._M_head._M_next;
- __lst._M_impl._M_head._M_next = 0;
- }
+ _Fwd_list_base(_Fwd_list_base&&) = default;
~_Fwd_list_base()
{ _M_erase_after(&_M_impl._M_head, 0); }
@@ -436,10 +451,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
/**
* @brief Creates a %forward_list with no elements.
*/
- forward_list()
- noexcept(is_nothrow_default_constructible<_Node_alloc_type>::value)
- : _Base()
- { }
+ forward_list() = default;
/**
* @brief Creates a %forward_list with no elements.
@@ -532,15 +544,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
/**
* @brief The %forward_list move constructor.
- * @param __list A %forward_list of identical element and allocator
- * types.
+ * @param A %forward_list of identical element and allocator types.
*
- * The newly-created %forward_list contains the exact contents of @a
- * __list. The contents of @a __list are a valid, but unspecified
- * %forward_list.
+ * The newly-created %forward_list contains the exact contents of the
+ * moved instance. The content of the moved instance is valid, but
+ * unspecified %forward_list.
*/
- forward_list(forward_list&& __list) noexcept
- : _Base(std::move(__list)) { }
+ forward_list(forward_list&&) = default;
/**
* @brief Builds a %forward_list from an initializer_list
diff --git a/libstdc++-v3/include/bits/forward_list.tcc b/libstdc++-v3/include/bits/forward_list.tcc
index b823b09..95db8a6 100644
--- a/libstdc++-v3/include/bits/forward_list.tcc
+++ b/libstdc++-v3/include/bits/forward_list.tcc
@@ -36,7 +36,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
template<typename _Tp, typename _Alloc>
_Fwd_list_base<_Tp, _Alloc>::
- _Fwd_list_base(_Fwd_list_base&& __lst, _Node_alloc_type&& __a)
+ _Fwd_list_base(_Fwd_list_base&& __lst, _Node_alloc_type&& __a,
+ std::false_type)
: _M_impl(std::move(__a))
{
if (__lst._M_get_Node_allocator() == _M_get_Node_allocator())
diff --git a/libstdc++-v3/testsuite/23_containers/forward_list/allocator/default_init.cc b/libstdc++-v3/testsuite/23_containers/forward_list/allocator/default_init.cc
new file mode 100644
index 0000000..b56c9cc
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/forward_list/allocator/default_init.cc
@@ -0,0 +1,67 @@
+// Copyright (C) 2017 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 run { target c++11 } }
+// { dg-options "-O0" }
+// { dg-xfail-run-if "PR c++/65816" { *-*-* } }
+
+#include <forward_list>
+#include <testsuite_hooks.h>
+#include <testsuite_allocator.h>
+
+#include <ext/aligned_buffer.h>
+
+using T = int;
+
+using __gnu_test::default_init_allocator;
+
+void test01()
+{
+ typedef default_init_allocator<T> alloc_type;
+ typedef std::forward_list<T, alloc_type> test_type;
+
+ __gnu_cxx::__aligned_buffer<test_type> buf;
+ __builtin_memset(buf._M_addr(), ~0, sizeof(test_type));
+
+ test_type *tmp = ::new(buf._M_addr()) test_type;
+
+ VERIFY( tmp->get_allocator().state == 0 );
+
+ tmp->~test_type();
+}
+
+void test02()
+{
+ typedef default_init_allocator<T> alloc_type;
+ typedef std::forward_list<T, alloc_type> test_type;
+
+ __gnu_cxx::__aligned_buffer<test_type> buf;
+ __builtin_memset(buf._M_addr(), ~0, sizeof(test_type));
+
+ test_type *tmp = ::new(buf._M_addr()) test_type();
+
+ VERIFY( tmp->get_allocator().state == 0 );
+
+ tmp->~test_type();
+}
+
+int main()
+{
+ test01();
+ test02();
+ return 0;
+}
