https://gcc.gnu.org/g:ca24f585fc3b7bf5e145cf3ee3f6f83ad8a4f2dd
commit r15-5907-gca24f585fc3b7bf5e145cf3ee3f6f83ad8a4f2dd
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Tue Nov 12 15:36:17 2024 +0000
libstdc++: Refactor std::list::size() for cxx11 ABI
Remove some preprocessor conditionals by moving the _M_size member for
the cxx11 ABI into a new base class, which is empty for the gcc4-compat
ABI.
Move some unused members that are only retained for ABI compatibility to
the end of _List_base and add an explanatory comment. Stop using
list::_M_node_count and list::_D_distance and then move them to the end
of std::list with a comment too.
libstdc++-v3/ChangeLog:
* include/bits/stl_list.h (_List_size): New struct.
(_List_node_header): Replace _M_size member with _List_size base
class.
(_List_node_header(_List_node_header&&)): Replace explicit uses
of _M_size with initializing the base.
(_List_node_header::_M_init): Likewise.
(_List_base::_S_distance, _List_base::_M_distance)
(_List_base::_M_node_count): Move to end of class body and add
comment.
(list::_S_distance, list::_M_node_count): Likewise.
(list::size): Inline _M_node_count effects to here.
(list::splice(iterator, list&, iterator, iterator)): Use #if and
call std::distance instead of _S_distance.
Diff:
---
libstdc++-v3/include/bits/stl_list.h | 179 +++++++++++++++++++----------------
1 file changed, 97 insertions(+), 82 deletions(-)
diff --git a/libstdc++-v3/include/bits/stl_list.h
b/libstdc++-v3/include/bits/stl_list.h
index cf3d05fcae95..dfdab6e511a9 100644
--- a/libstdc++-v3/include/bits/stl_list.h
+++ b/libstdc++-v3/include/bits/stl_list.h
@@ -105,22 +105,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_unhook() _GLIBCXX_USE_NOEXCEPT;
};
- /// The %list node header.
- struct _List_node_header : public _List_node_base
+ struct _List_size
{
#if _GLIBCXX_USE_CXX11_ABI
- std::size_t _M_size;
+ // Store the size here so that std::list::size() is fast.
+ size_t _M_size;
#endif
+ };
+
+ /// The %list node header.
+ struct _List_node_header : public _List_node_base, _List_size
+ {
_List_node_header() _GLIBCXX_NOEXCEPT
{ _M_init(); }
#if __cplusplus >= 201103L
_List_node_header(_List_node_header&& __x) noexcept
- : _List_node_base{ __x._M_next, __x._M_prev }
-# if _GLIBCXX_USE_CXX11_ABI
- , _M_size(__x._M_size)
-# endif
+ : _List_node_base(__x), _List_size(__x)
{
if (__x._M_base()->_M_next == __x._M_base())
this->_M_next = this->_M_prev = this;
@@ -143,9 +145,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__node->_M_next = __xnode->_M_next;
__node->_M_prev = __xnode->_M_prev;
__node->_M_next->_M_prev = __node->_M_prev->_M_next = __node;
-# if _GLIBCXX_USE_CXX11_ABI
- _M_size = __x._M_size;
-# endif
+ _List_size::operator=(__x);
__x._M_init();
}
}
@@ -155,9 +155,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_M_init() _GLIBCXX_NOEXCEPT
{
this->_M_next = this->_M_prev = this;
-#if _GLIBCXX_USE_CXX11_ABI
- this->_M_size = 0;
-#endif
+ _List_size::operator=(_List_size());
}
private:
@@ -437,21 +435,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
rebind<_List_node<_Tp> >::other _Node_alloc_type;
typedef __gnu_cxx::__alloc_traits<_Node_alloc_type> _Node_alloc_traits;
-#if !_GLIBCXX_INLINE_VERSION
- static size_t
- _S_distance(const __detail::_List_node_base* __first,
- const __detail::_List_node_base* __last)
- {
- size_t __n = 0;
- while (__first != __last)
- {
- __first = __first->_M_next;
- ++__n;
- }
- return __n;
- }
-#endif
-
struct _List_impl
: public _Node_alloc_type
{
@@ -489,33 +472,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
void _M_inc_size(size_t __n) { _M_impl._M_node._M_size += __n; }
void _M_dec_size(size_t __n) { _M_impl._M_node._M_size -= __n; }
-
-# if !_GLIBCXX_INLINE_VERSION
- size_t
- _M_distance(const __detail::_List_node_base* __first,
- const __detail::_List_node_base* __last) const
- { return _S_distance(__first, __last); }
-
- // return the stored size
- size_t _M_node_count() const { return _M_get_size(); }
-# endif
#else
// dummy implementations used when the size is not stored
size_t _M_get_size() const { return 0; }
void _M_set_size(size_t) { }
void _M_inc_size(size_t) { }
void _M_dec_size(size_t) { }
-
-# if !_GLIBCXX_INLINE_VERSION
- size_t _M_distance(const void*, const void*) const { return 0; }
-
- // count the number of nodes
- size_t _M_node_count() const
- {
- return _S_distance(_M_impl._M_node._M_next,
- std::__addressof(_M_impl._M_node));
- }
-# endif
#endif
typename _Node_alloc_traits::pointer
@@ -550,16 +512,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
#if __cplusplus >= 201103L
_List_base(_List_base&&) = default;
-# if !_GLIBCXX_INLINE_VERSION
- _List_base(_List_base&& __x, _Node_alloc_type&& __a)
- : _M_impl(std::move(__a))
- {
- if (__x._M_get_Node_allocator() == _M_get_Node_allocator())
- _M_move_nodes(std::move(__x));
- // else caller must move individual elements.
- }
-# endif
-
// Used when allocator is_always_equal.
_List_base(_Node_alloc_type&& __a, _List_base&& __x)
: _M_impl(std::move(__a), std::move(__x._M_impl))
@@ -585,6 +537,57 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
void
_M_init() _GLIBCXX_NOEXCEPT
{ this->_M_impl._M_node._M_init(); }
+
+#if !_GLIBCXX_INLINE_VERSION
+ // XXX GLIBCXX_ABI Deprecated
+ // These members are unused by std::list now, but we keep them here
+ // so that an explicit instantiation of std::list will define them.
+ // This ensures that explicit instantiations still define these symbols,
+ // so that explicit instantiation declarations of std::list that were
+ // compiled with old versions of GCC can still find these old symbols.
+
+# if __cplusplus >= 201103L
+ _List_base(_List_base&& __x, _Node_alloc_type&& __a)
+ : _M_impl(std::move(__a))
+ {
+ if (__x._M_get_Node_allocator() == _M_get_Node_allocator())
+ _M_move_nodes(std::move(__x));
+ // else caller must move individual elements.
+ }
+# endif
+
+ static size_t
+ _S_distance(const __detail::_List_node_base* __first,
+ const __detail::_List_node_base* __last)
+ {
+ size_t __n = 0;
+ while (__first != __last)
+ {
+ __first = __first->_M_next;
+ ++__n;
+ }
+ return __n;
+ }
+
+#if _GLIBCXX_USE_CXX11_ABI
+ size_t
+ _M_distance(const __detail::_List_node_base* __first,
+ const __detail::_List_node_base* __last) const
+ { return _S_distance(__first, __last); }
+
+ // return the stored size
+ size_t _M_node_count() const { return _M_get_size(); }
+#else
+ size_t _M_distance(const void*, const void*) const { return 0; }
+
+ // count the number of nodes
+ size_t _M_node_count() const
+ {
+ return _S_distance(_M_impl._M_node._M_next,
+ std::__addressof(_M_impl._M_node));
+ }
+#endif
+#endif // ! INLINE_VERSION
};
/**
@@ -722,27 +725,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
}
#endif
-#if _GLIBCXX_USE_CXX11_ABI
- static size_t
- _S_distance(const_iterator __first, const_iterator __last)
- { return std::distance(__first, __last); }
-
- // return the stored size
- size_t
- _M_node_count() const
- { return this->_M_get_size(); }
-#else
- // dummy implementations used when the size is not stored
- static size_t
- _S_distance(const_iterator, const_iterator)
- { return 0; }
-
- // count the number of nodes
- size_t
- _M_node_count() const
- { return std::distance(begin(), end()); }
-#endif
-
public:
// [23.2.2.1] construct/copy/destroy
// (assign() and get_allocator() are also listed in this section)
@@ -1216,7 +1198,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
_GLIBCXX_NODISCARD
size_type
size() const _GLIBCXX_NOEXCEPT
- { return _M_node_count(); }
+ {
+#if _GLIBCXX_USE_CXX11_ABI
+ return this->_M_get_size(); // return the stored size
+#else
+ return std::distance(begin(), end()); // count the number of nodes
+#endif
+ }
/** Returns the size() of the largest possible %list. */
_GLIBCXX_NODISCARD
@@ -1810,9 +1798,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
if (this != std::__addressof(__x))
_M_check_equal_allocators(__x);
- size_t __n = _S_distance(__first, __last);
+#if _GLIBCXX_USE_CXX11_ABI
+ size_t __n = std::distance(__first, __last);
this->_M_inc_size(__n);
__x._M_dec_size(__n);
+#endif
this->_M_transfer(__position._M_const_cast(),
__first._M_const_cast(),
@@ -2175,6 +2165,31 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11
{ explicit _Finalize_merge(list&, list&, const iterator&) { } };
#endif
+#if !_GLIBCXX_INLINE_VERSION
+ // XXX GLIBCXX_ABI Deprecated
+ // These members are unused by std::list now, but we keep them here
+ // so that an explicit instantiation of std::list will define them.
+ // This ensures that any objects or libraries compiled against old
+ // versions of GCC will still be able to use the symbols.
+
+#if _GLIBCXX_USE_CXX11_ABI
+ static size_t
+ _S_distance(const_iterator __first, const_iterator __last)
+ { return std::distance(__first, __last); }
+
+ size_t
+ _M_node_count() const
+ { return this->_M_get_size(); }
+#else
+ static size_t
+ _S_distance(const_iterator, const_iterator)
+ { return 0; }
+
+ size_t
+ _M_node_count() const
+ { return std::distance(begin(), end()); }
+#endif
+#endif // ! INLINE_VERSION
};
#if __cpp_deduction_guides >= 201606
