Hi
Here is the patch to implement the always equal alloc optimization
for forward_list. With this version there is no abi issue.
I also prefer to implement the _Fwd_list_node_base move operator
for consistency with the move constructor and used it where applicable.
* include/bits/forward_list.h
(_Fwd_list_node_base& operator=(_Fwd_list_node_base&&)): Implement.
(_Fwd_list_impl(_Fwd_list_impl&&, _Node_alloc_type&&)): New.
(_Fwd_list_base(_Fwd_list_base&&, _Node_alloc_type&&, std::true_type)):
New, use latter.
(forward_list(forward_list&&, _Node_alloc_type&&, std::false_type)):
New.
(forward_list(forward_list&&, _Node_alloc_type&&, std::true_type)):
New.
(forward_list(forward_list&&, const _Alloc&)): Adapt to use latters.
* include/bits/forward_list.tcc
(_Fwd_list_base(_Fwd_list_base&&, _Node_alloc_type&&)): Adapt to use
_M_impl._M_head move assignment.
(forward_list<>::merge(forward_list<>&&, _Comp)): Likewise.
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 9ddbcb2..dec91ea 100644
--- a/libstdc++-v3/include/bits/forward_list.h
+++ b/libstdc++-v3/include/bits/forward_list.h
@@ -60,7 +60,14 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_Fwd_list_node_base(const _Fwd_list_node_base&) = delete;
_Fwd_list_node_base& operator=(const _Fwd_list_node_base&) = delete;
- _Fwd_list_node_base& operator=(_Fwd_list_node_base&&) = delete;
+
+ _Fwd_list_node_base&
+ operator=(_Fwd_list_node_base&& __x)
+ {
+ _M_next = __x._M_next;
+ __x._M_next = nullptr;
+ return *this;
+ }
_Fwd_list_node_base* _M_next = nullptr;
@@ -75,7 +82,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
__end->_M_next = _M_next;
}
else
- __begin->_M_next = 0;
+ __begin->_M_next = nullptr;
_M_next = __keep;
return __end;
}
@@ -180,7 +187,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
if (_M_node)
return _Fwd_list_iterator(_M_node->_M_next);
else
- return _Fwd_list_iterator(0);
+ return _Fwd_list_iterator(nullptr);
}
_Fwd_list_node_base* _M_node;
@@ -251,7 +258,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
if (this->_M_node)
return _Fwd_list_const_iterator(_M_node->_M_next);
else
- return _Fwd_list_const_iterator(0);
+ return _Fwd_list_const_iterator(nullptr);
}
const _Fwd_list_node_base* _M_node;
@@ -298,6 +305,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_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))
{ }
@@ -323,15 +334,21 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
_Fwd_list_base(_Node_alloc_type&& __a)
: _M_impl(std::move(__a)) { }
+ // When allocators are always equal.
+ _Fwd_list_base(_Fwd_list_base&& __lst, _Node_alloc_type&& __a,
+ std::true_type)
+ : _M_impl(std::move(__lst._M_impl), std::move(__a))
+ { }
+
+ // When allocators are not always equal.
_Fwd_list_base(_Fwd_list_base&& __lst, _Node_alloc_type&& __a);
_Fwd_list_base(_Fwd_list_base&&) = default;
~_Fwd_list_base()
- { _M_erase_after(&_M_impl._M_head, 0); }
+ { _M_erase_after(&_M_impl._M_head, nullptr); }
protected:
-
_Node*
_M_get_node()
{
@@ -448,7 +465,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
: _Base(_Node_alloc_type(__al))
{ }
-
/**
* @brief Copy constructor with allocator argument.
* @param __list Input list to copy.
@@ -458,14 +474,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
: _Base(_Node_alloc_type(__al))
{ _M_range_initialize(__list.begin(), __list.end()); }
- /**
- * @brief Move constructor with allocator argument.
- * @param __list Input list to move.
- * @param __al An allocator object.
- */
- forward_list(forward_list&& __list, const _Alloc& __al)
- noexcept(_Node_alloc_traits::_S_always_equal())
- : _Base(std::move(__list), _Node_alloc_type(__al))
+ private:
+ forward_list(forward_list&& __list, _Node_alloc_type&& __al,
+ std::false_type)
+ : _Base(std::move(__list), std::move(__al))
{
// If __list is not empty it means its allocator is not equal to __a,
// so we need to move from each element individually.
@@ -474,6 +486,24 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
std::__make_move_if_noexcept_iterator(__list.end()));
}
+ forward_list(forward_list&& __list, _Node_alloc_type&& __al,
+ std::true_type)
+ noexcept
+ : _Base(std::move(__list), _Node_alloc_type(__al), std::true_type{})
+ { }
+
+ public:
+ /**
+ * @brief Move constructor with allocator argument.
+ * @param __list Input list to move.
+ * @param __al An allocator object.
+ */
+ forward_list(forward_list&& __list, const _Alloc& __al)
+ noexcept(_Node_alloc_traits::_S_always_equal())
+ : forward_list(std::move(__list), _Node_alloc_type(__al),
+ typename _Node_alloc_traits::is_always_equal{})
+ { }
+
/**
* @brief Creates a %forward_list with default constructed elements.
* @param __n The number of elements to initially create.
@@ -702,7 +732,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
*/
iterator
end() noexcept
- { return iterator(0); }
+ { return iterator(nullptr); }
/**
* Returns a read-only iterator that points one past the last
@@ -711,7 +741,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
*/
const_iterator
end() const noexcept
- { return const_iterator(0); }
+ { return const_iterator(nullptr); }
/**
* Returns a read-only (constant) iterator that points to the
@@ -738,7 +768,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
*/
const_iterator
cend() const noexcept
- { return const_iterator(0); }
+ { return const_iterator(nullptr); }
/**
* Returns true if the %forward_list is empty. (Thus begin() would
@@ -746,7 +776,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
*/
bool
empty() const noexcept
- { return this->_M_impl._M_head._M_next == 0; }
+ { return this->_M_impl._M_head._M_next == nullptr; }
/**
* Returns the largest possible number of elements of %forward_list.
@@ -1051,7 +1081,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
*/
void
clear() noexcept
- { this->_M_erase_after(&this->_M_impl._M_head, 0); }
+ { this->_M_erase_after(&this->_M_impl._M_head, nullptr); }
// 23.3.4.6 forward_list operations:
diff --git a/libstdc++-v3/include/bits/forward_list.tcc b/libstdc++-v3/include/bits/forward_list.tcc
index b7c906e..f13e959 100644
--- a/libstdc++-v3/include/bits/forward_list.tcc
+++ b/libstdc++-v3/include/bits/forward_list.tcc
@@ -41,10 +41,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
: _M_impl(std::move(__a))
{
if (__lst._M_get_Node_allocator() == _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;
- }
+ this->_M_impl._M_head = std::move(__lst._M_impl._M_head);
}
template<typename _Tp, typename _Alloc>
@@ -362,11 +359,9 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
__list._M_impl._M_head._M_next);
__node = __node->_M_next;
}
+
if (__list._M_impl._M_head._M_next)
- {
- __node->_M_next = __list._M_impl._M_head._M_next;
- __list._M_impl._M_head._M_next = 0;
- }
+ *__node = std::move(__list._M_impl._M_head);
}
template<typename _Tp, typename _Alloc>
@@ -397,7 +392,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
forward_list<_Tp, _Alloc>::
sort(_Comp __comp)
{
- // If `next' is 0, return immediately.
+ // If `next' is nullptr, return immediately.
_Node* __list = static_cast<_Node*>(this->_M_impl._M_head._M_next);
if (!__list)
return;
@@ -407,8 +402,8 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
while (1)
{
_Node* __p = __list;
- __list = 0;
- _Node* __tail = 0;
+ __list = nullptr;
+ _Node* __tail = nullptr;
// Count number of merges we do in this pass.
unsigned long __nmerges = 0;
@@ -476,7 +471,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
// Now p has stepped `insize' places along, and q has too.
__p = __q;
}
- __tail->_M_next = 0;
+ __tail->_M_next = nullptr;
// If we have done only one merge, we're finished.
// Allow for nmerges == 0, the empty list case.
