{"id":2226285,"url":"http://patchwork.ozlabs.org/api/1.1/patches/2226285/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/bmm.hhubkr2i8k.gcc.gcc-TEST.redi.26.1.1@forge-stage.sourceware.org/","project":{"id":17,"url":"http://patchwork.ozlabs.org/api/1.1/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},"msgid":"","date":"2026-04-22T10:37:35","name":"[v1,1/1] libstdc++: Add debug assertions to std::list and std::forward_list","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"350a6f67ecbc96f7ec0c94aedfaf97a3efdd9615","submitter":{"id":93210,"url":"http://patchwork.ozlabs.org/api/1.1/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.hhubkr2i8k.gcc.gcc-TEST.redi.26.1.1@forge-stage.sourceware.org/mbox/","series":[{"id":500986,"url":"http://patchwork.ozlabs.org/api/1.1/series/500986/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=500986","date":"2026-04-22T10:37:34","name":"libstdc++: Add debug assertions to std::list and std::forward_list","version":1,"mbox":"http://patchwork.ozlabs.org/series/500986/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2226285/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2226285/checks/","tags":{},"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=2620:52:6:3111::32; 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server2.sourceware.org","From":"Jonathan Wakely via Sourceware Forge\n ","Date":"Wed, 22 Apr 2026 10:37:35 +0000","Subject":"[PATCH v1 1/1] libstdc++: Add debug assertions to std::list and\n std::forward_list","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/26","References":"\n ","In-Reply-To":"\n ","X-Patch-URL":"\n https://forge.sourceware.org/redi/gcc/commit/96da5e678a0d3e346fec557485f3e8b770fe56a0","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\nWhile working on fancy pointer support for the linked lists I noticed\nthey didn't have any debug assertions. This adds the obvious non-empty\nassertions to front(), back(), pop_front() and pop_back().\n\nFor the pop members, adding an assertion to the underlying function that\nerases a member means it also check erase(end()), which is always\ninvalid, and erase(begin()) on an empty list. For those erase members we\ncan also add a check so that we return without doing anything if the\nassertion is disabled, but would have failed had it been enabled.\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/bits/forward_list.h (forward_list::front): Add\n\tnon-empty assertions.\n\t* include/bits/forward_list.tcc (_Fwd_list_base::_M_erase_after):\n\tLikewise. Return immediately if argument is invalid.\n\t* include/bits/stl_list.h (list::front, list::back): Add\n\tnon-empty assertions.\n\t(list::_M_erase): Likewise. Return immediately if argument is\n\tinvalid.\n---\n libstdc++-v3/include/bits/forward_list.h | 3 +++\n libstdc++-v3/include/bits/forward_list.tcc | 6 ++++++\n libstdc++-v3/include/bits/stl_list.h | 19 +++++++++++++++++--\n 3 files changed, 26 insertions(+), 2 deletions(-)","diff":"diff --git a/libstdc++-v3/include/bits/forward_list.h b/libstdc++-v3/include/bits/forward_list.h\nindex c9238cef96fa..3fac657518cc 100644\n--- a/libstdc++-v3/include/bits/forward_list.h\n+++ b/libstdc++-v3/include/bits/forward_list.h\n@@ -42,6 +42,7 @@\n #include \n #include \n #include \n+#include \n #if __glibcxx_ranges_to_container // C++ >= 23\n # include // ranges::begin, ranges::distance etc.\n # include // ranges::subrange\n@@ -884,6 +885,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER\n reference\n front()\n {\n+\t__glibcxx_requires_nonempty();\n \t_Node* __front = static_cast<_Node*>(this->_M_impl._M_head._M_next);\n \treturn *__front->_M_valptr();\n }\n@@ -896,6 +898,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER\n const_reference\n front() const\n {\n+\t__glibcxx_requires_nonempty();\n \t_Node* __front = static_cast<_Node*>(this->_M_impl._M_head._M_next);\n \treturn *__front->_M_valptr();\n }\ndiff --git a/libstdc++-v3/include/bits/forward_list.tcc b/libstdc++-v3/include/bits/forward_list.tcc\nindex 9750c7c0502b..50acdb9f26b7 100644\n--- a/libstdc++-v3/include/bits/forward_list.tcc\n+++ b/libstdc++-v3/include/bits/forward_list.tcc\n@@ -63,6 +63,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER\n _Fwd_list_base<_Tp, _Alloc>::\n _M_erase_after(_Fwd_list_node_base* __pos)\n {\n+ if (__pos == nullptr || __pos->_M_next == nullptr) [[__unlikely__]]\n+\t{\n+\t __glibcxx_assert(__pos != nullptr && __pos->_M_next != nullptr);\n+\t return nullptr;\n+\t}\n+\n _Node* __curr = static_cast<_Node*>(__pos->_M_next);\n __pos->_M_next = __curr->_M_next;\n _Node_alloc_traits::destroy(_M_get_Node_allocator(),\ndiff --git a/libstdc++-v3/include/bits/stl_list.h b/libstdc++-v3/include/bits/stl_list.h\nindex 7deb04b4bfe4..d70ba90b8fa7 100644\n--- a/libstdc++-v3/include/bits/stl_list.h\n+++ b/libstdc++-v3/include/bits/stl_list.h\n@@ -59,6 +59,7 @@\n \n #include \n #include \n+#include \n #if __cplusplus >= 201103L\n #include \n #include \n@@ -1249,7 +1250,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n _GLIBCXX_NODISCARD\n reference\n front() _GLIBCXX_NOEXCEPT\n- { return *begin(); }\n+ {\n+\t__glibcxx_requires_nonempty();\n+\treturn *begin();\n+ }\n \n /**\n * Returns a read-only (constant) reference to the data at the first\n@@ -1258,7 +1262,10 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n _GLIBCXX_NODISCARD\n const_reference\n front() const _GLIBCXX_NOEXCEPT\n- { return *begin(); }\n+ {\n+\t__glibcxx_requires_nonempty();\n+\treturn *begin();\n+ }\n \n /**\n * Returns a read/write reference to the data at the last element\n@@ -1268,6 +1275,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n reference\n back() _GLIBCXX_NOEXCEPT\n {\n+\t__glibcxx_requires_nonempty();\n \titerator __tmp = end();\n \t--__tmp;\n \treturn *__tmp;\n@@ -1281,6 +1289,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n const_reference\n back() const _GLIBCXX_NOEXCEPT\n {\n+\t__glibcxx_requires_nonempty();\n \tconst_iterator __tmp = end();\n \t--__tmp;\n \treturn *__tmp;\n@@ -2132,6 +2141,12 @@ _GLIBCXX_BEGIN_NAMESPACE_CXX11\n void\n _M_erase(iterator __position) _GLIBCXX_NOEXCEPT\n {\n+\tif (__builtin_expect(empty(), 0))\n+\t {\n+\t __glibcxx_requires_nonempty();\n+\t return;\n+\t }\n+\n \tthis->_M_dec_size(1);\n \t__position._M_node->_M_unhook();\n \t_Node* __n = static_cast<_Node*>(__position._M_node);\n","prefixes":["v1","1/1"]}