{"id":2226281,"url":"http://patchwork.ozlabs.org/api/patches/2226281/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/bmm.hhubjjpeho.gcc.gcc-TEST.redi.25.1.1@forge-stage.sourceware.org/","project":{"id":17,"url":"http://patchwork.ozlabs.org/api/projects/17/?format=json","name":"GNU Compiler Collection","link_name":"gcc","list_id":"gcc-patches.gcc.gnu.org","list_email":"gcc-patches@gcc.gnu.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"","list_archive_url":null,"date":"2026-04-22T10:36:18","name":"[v1,1/4] libstdc++: Refactor std::list::size() for cxx11 ABI","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"ac48d44ad93246b5e9d32c3ffba519fe5dc809c5","submitter":{"id":93210,"url":"http://patchwork.ozlabs.org/api/people/93210/?format=json","name":"Jonathan Wakely via Sourceware Forge","email":"forge-bot+redi@forge-stage.sourceware.org"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/gcc/patch/bmm.hhubjjpeho.gcc.gcc-TEST.redi.25.1.1@forge-stage.sourceware.org/mbox/","series":[{"id":500985,"url":"http://patchwork.ozlabs.org/api/series/500985/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=500985","date":"2026-04-22T10:36:19","name":"libstdc++: Add fancy pointer support to std::list and std::forward_list [PR57272]","version":1,"mbox":"http://patchwork.ozlabs.org/series/500985/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2226281/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2226281/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":["incoming@patchwork.ozlabs.org","gcc-patches@gcc.gnu.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","gcc-patches@gcc.gnu.org"],"Authentication-Results":["legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=gcc.gnu.org\n (client-ip=38.145.34.32; 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server2.sourceware.org","From":"Jonathan Wakely via Sourceware Forge\n ","Date":"Wed, 22 Apr 2026 10:36:18 +0000","Subject":"[PATCH v1 1/4] libstdc++: Refactor std::list::size() for cxx11 ABI","To":"gcc-patches mailing list ","Message-ID":"\n ","X-Mailer":"batrachomyomachia","X-Pull-Request-Organization":"gcc","X-Pull-Request-Repository":"gcc-TEST","X-Pull-Request":"https://forge.sourceware.org/gcc/gcc-TEST/pulls/25","References":"\n ","In-Reply-To":"\n ","X-Patch-URL":"\n https://forge.sourceware.org/redi/gcc/commit/28297cd9bf31930678ccc5ea03688ee6e2551b15","X-BeenThere":"gcc-patches@gcc.gnu.org","X-Mailman-Version":"2.1.30","Precedence":"list","List-Id":"Gcc-patches mailing list ","List-Unsubscribe":",\n ","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n ","Reply-To":"gcc-patches mailing list , redi@gcc.gnu.org","Errors-To":"gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org"},"content":"From: Jonathan Wakely \n\nRemove some preprocessor conditionals by moving the _M_size member for\nthe cxx11 ABI into a new base class, which is empty for the gcc4-compat\nABI.\n\nMove some unused members that are only retained for ABI compatibility to\nthe end of _List_base and add an explanatory comment. Stop using\nlist::_M_node_count and list::_D_distance and then move them to the end\nof std::list with a comment too.\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/bits/stl_list.h (_List_size): New struct.\n\t(_List_node_header): Replace _M_size member with _List_size base\n\tclass.\n\t(_List_node_header(_List_node_header&&)): Replace explicit uses\n\tof _M_size with initializing the base.\n\t(_List_node_header::_M_init): Likewise.\n\t(_List_base::_S_distance, _List_base::_M_distance)\n\t(_List_base::_M_node_count): Move to end of class body and add\n\tcomment.\n\t(list::_S_distance, list::_M_node_count): Likewise.\n\t(list::size): Inline _M_node_count effects to here.\n\t(list::splice(iterator, list&, iterator, iterator)): Use #if and\n\tcall std::distance instead of _S_distance.\n---\n libstdc++-v3/include/bits/stl_list.h | 179 +++++++++++++++------------\n 1 file changed, 97 insertions(+), 82 deletions(-)","diff":"diff --git a/libstdc++-v3/include/bits/stl_list.h b/libstdc++-v3/include/bits/stl_list.h\nindex 7deb04b4bfe4..d51fde90e2b8 100644\n--- a/libstdc++-v3/include/bits/stl_list.h\n+++ b/libstdc++-v3/include/bits/stl_list.h\n@@ -104,22 +104,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n _M_unhook() _GLIBCXX_USE_NOEXCEPT;\n };\n \n- /// The %list node header.\n- struct _List_node_header : public _List_node_base\n+ struct _List_size\n {\n #if _GLIBCXX_USE_CXX11_ABI\n- std::size_t _M_size;\n+ // Store the size here so that std::list::size() is fast.\n+ size_t _M_size;\n #endif\n+ };\n+\n \n+ /// The %list node header.\n+ struct _List_node_header : public _List_node_base, _List_size\n+ {\n _List_node_header() _GLIBCXX_NOEXCEPT\n { _M_init(); }\n \n #if __cplusplus >= 201103L\n _List_node_header(_List_node_header&& __x) noexcept\n- : _List_node_base{ __x._M_next, __x._M_prev }\n-# if _GLIBCXX_USE_CXX11_ABI\n- , _M_size(__x._M_size)\n-# endif\n+ : _List_node_base(__x), _List_size(__x)\n {\n \tif (__x._M_base()->_M_next == __x._M_base())\n \t this->_M_next = this->_M_prev = this;\n@@ -142,9 +144,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n \t __node->_M_next = __xnode->_M_next;\n \t __node->_M_prev = __xnode->_M_prev;\n \t __node->_M_next->_M_prev = __node->_M_prev->_M_next = __node;\n-# if _GLIBCXX_USE_CXX11_ABI\n-\t _M_size = __x._M_size;\n-# endif\n+\t _List_size::operator=(__x);\n \t __x._M_init();\n \t }\n }\n@@ -154,9 +154,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n _M_init() _GLIBCXX_NOEXCEPT\n {\n \tthis->_M_next = this->_M_prev = this;\n-#if _GLIBCXX_USE_CXX11_ABI\n-\tthis->_M_size = 0;\n-#endif\n+\t_List_size::operator=(_List_size());\n }\n \n private:\n@@ -436,21 +434,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n \trebind<_List_node<_Tp> >::other _Node_alloc_type;\n typedef __gnu_cxx::__alloc_traits<_Node_alloc_type> _Node_alloc_traits;\n \n-#if !_GLIBCXX_INLINE_VERSION\n- static size_t\n- _S_distance(const __detail::_List_node_base* __first,\n-\t\t const __detail::_List_node_base* __last)\n- {\n-\tsize_t __n = 0;\n-\twhile (__first != __last)\n-\t {\n-\t __first = __first->_M_next;\n-\t ++__n;\n-\t }\n-\treturn __n;\n- }\n-#endif\n-\n struct _List_impl\n : public _Node_alloc_type\n {\n@@ -488,33 +471,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n void _M_inc_size(size_t __n) { _M_impl._M_node._M_size += __n; }\n \n void _M_dec_size(size_t __n) { _M_impl._M_node._M_size -= __n; }\n-\n-# if !_GLIBCXX_INLINE_VERSION\n- size_t\n- _M_distance(const __detail::_List_node_base* __first,\n-\t\t const __detail::_List_node_base* __last) const\n- { return _S_distance(__first, __last); }\n-\n- // return the stored size\n- size_t _M_node_count() const { return _M_get_size(); }\n-# endif\n #else\n // dummy implementations used when the size is not stored\n size_t _M_get_size() const { return 0; }\n void _M_set_size(size_t) { }\n void _M_inc_size(size_t) { }\n void _M_dec_size(size_t) { }\n-\n-# if !_GLIBCXX_INLINE_VERSION\n- size_t _M_distance(const void*, const void*) const { return 0; }\n-\n- // count the number of nodes\n- size_t _M_node_count() const\n- {\n-\treturn _S_distance(_M_impl._M_node._M_next,\n-\t\t\t std::__addressof(_M_impl._M_node));\n- }\n-# endif\n #endif\n \n typename _Node_alloc_traits::pointer\n@@ -549,16 +511,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n #if __cplusplus >= 201103L\n _List_base(_List_base&&) = default;\n \n-# if !_GLIBCXX_INLINE_VERSION\n- _List_base(_List_base&& __x, _Node_alloc_type&& __a)\n- : _M_impl(std::move(__a))\n- {\n-\tif (__x._M_get_Node_allocator() == _M_get_Node_allocator())\n-\t _M_move_nodes(std::move(__x));\n-\t// else caller must move individual elements.\n- }\n-# endif\n-\n // Used when allocator is_always_equal.\n _List_base(_Node_alloc_type&& __a, _List_base&& __x)\n : _M_impl(std::move(__a), std::move(__x._M_impl))\n@@ -584,6 +536,57 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n void\n _M_init() _GLIBCXX_NOEXCEPT\n { this->_M_impl._M_node._M_init(); }\n+\n+#if !_GLIBCXX_INLINE_VERSION\n+ // XXX GLIBCXX_ABI Deprecated\n+ // These members are unused by std::list now, but we keep them here\n+ // so that an explicit instantiation of std::list will define them.\n+ // This ensures that explicit instantiations still define these symbols,\n+ // so that explicit instantiation declarations of std::list that were\n+ // compiled with old versions of GCC can still find these old symbols.\n+\n+# if __cplusplus >= 201103L\n+ _List_base(_List_base&& __x, _Node_alloc_type&& __a)\n+ : _M_impl(std::move(__a))\n+ {\n+\tif (__x._M_get_Node_allocator() == _M_get_Node_allocator())\n+\t _M_move_nodes(std::move(__x));\n+\t// else caller must move individual elements.\n+ }\n+# endif\n+\n+ static size_t\n+ _S_distance(const __detail::_List_node_base* __first,\n+\t\t const __detail::_List_node_base* __last)\n+ {\n+\tsize_t __n = 0;\n+\twhile (__first != __last)\n+\t {\n+\t __first = __first->_M_next;\n+\t ++__n;\n+\t }\n+\treturn __n;\n+ }\n+\n+#if _GLIBCXX_USE_CXX11_ABI\n+ size_t\n+ _M_distance(const __detail::_List_node_base* __first,\n+\t\t const __detail::_List_node_base* __last) const\n+ { return _S_distance(__first, __last); }\n+\n+ // return the stored size\n+ size_t _M_node_count() const { return _M_get_size(); }\n+#else\n+ size_t _M_distance(const void*, const void*) const { return 0; }\n+\n+ // count the number of nodes\n+ size_t _M_node_count() const\n+ {\n+\treturn _S_distance(_M_impl._M_node._M_next,\n+\t\t\t std::__addressof(_M_impl._M_node));\n+ }\n+#endif\n+#endif // ! INLINE_VERSION\n };\n \n /**\n@@ -721,27 +724,6 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n \t}\n #endif\n \n-#if _GLIBCXX_USE_CXX11_ABI\n- static size_t\n- _S_distance(const_iterator __first, const_iterator __last)\n- { return std::distance(__first, __last); }\n-\n- // return the stored size\n- size_t\n- _M_node_count() const\n- { return this->_M_get_size(); }\n-#else\n- // dummy implementations used when the size is not stored\n- static size_t\n- _S_distance(const_iterator, const_iterator)\n- { return 0; }\n-\n- // count the number of nodes\n- size_t\n- _M_node_count() const\n- { return std::distance(begin(), end()); }\n-#endif\n-\n public:\n // [23.2.2.1] construct/copy/destroy\n // (assign() and get_allocator() are also listed in this section)\n@@ -1193,7 +1175,13 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n _GLIBCXX_NODISCARD\n size_type\n size() const _GLIBCXX_NOEXCEPT\n- { return _M_node_count(); }\n+ {\n+#if _GLIBCXX_USE_CXX11_ABI\n+\treturn this->_M_get_size(); // return the stored size\n+#else\n+\treturn std::distance(begin(), end()); // count the number of nodes\n+#endif\n+ }\n \n /** Returns the size() of the largest possible %list. */\n _GLIBCXX_NODISCARD\n@@ -1851,9 +1839,11 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n \t if (this != std::__addressof(__x))\n \t _M_check_equal_allocators(__x);\n \n-\t size_t __n = _S_distance(__first, __last);\n+#if _GLIBCXX_USE_CXX11_ABI\n+\t size_t __n = std::distance(__first, __last);\n \t this->_M_inc_size(__n);\n \t __x._M_dec_size(__n);\n+#endif\n \n \t this->_M_transfer(__position._M_const_cast(),\n \t\t\t __first._M_const_cast(),\n@@ -2213,6 +2203,31 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n { explicit _Finalize_merge(list&, list&, const iterator&) { } };\n #endif\n \n+#if !_GLIBCXX_INLINE_VERSION\n+ // XXX GLIBCXX_ABI Deprecated\n+ // These members are unused by std::list now, but we keep them here\n+ // so that an explicit instantiation of std::list will define them.\n+ // This ensures that any objects or libraries compiled against old\n+ // versions of GCC will still be able to use the symbols.\n+\n+#if _GLIBCXX_USE_CXX11_ABI\n+ static size_t\n+ _S_distance(const_iterator __first, const_iterator __last)\n+ { return std::distance(__first, __last); }\n+\n+ size_t\n+ _M_node_count() const\n+ { return this->_M_get_size(); }\n+#else\n+ static size_t\n+ _S_distance(const_iterator, const_iterator)\n+ { return 0; }\n+\n+ size_t\n+ _M_node_count() const\n+ { return std::distance(begin(), end()); }\n+#endif\n+#endif // ! INLINE_VERSION\n };\n \n #if __cpp_deduction_guides >= 201606\n","prefixes":["v1","1/4"]}