{"id":2226219,"url":"http://patchwork.ozlabs.org/api/patches/2226219/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/patch/bmm.hhub8n5f78.gcc.gcc-TEST.redi.15.1.7@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":"2026-04-22T10:25:16","name":"[v1,07/12] libstdc++: Use RAII in _Hashtable","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"9338498feb389bc0c1b3b513e457ef319ff8337f","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.hhub8n5f78.gcc.gcc-TEST.redi.15.1.7@forge-stage.sourceware.org/mbox/","series":[{"id":500966,"url":"http://patchwork.ozlabs.org/api/series/500966/?format=json","web_url":"http://patchwork.ozlabs.org/project/gcc/list/?series=500966","date":"2026-04-22T10:25:11","name":"WIP: libstdc++: Refactor hash table code","version":1,"mbox":"http://patchwork.ozlabs.org/series/500966/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2226219/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2226219/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=2620:52:6:3111::32; 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server2.sourceware.org","From":"Jonathan Wakely via Sourceware Forge\n ","Date":"Wed, 22 Apr 2026 10:25:16 +0000","Subject":"[PATCH v1 07/12] libstdc++: Use RAII in _Hashtable","MIME-Version":"1.0","Content-Type":"text/plain; charset=UTF-8","Content-Transfer-Encoding":"8bit","To":"gcc-patches mailing list ","Message-ID":"\n ","X-Mailer":"batrachomyomachia","X-Requested-Reviewer":"fdumont","X-Pull-Request-Organization":"gcc","X-Pull-Request-Repository":"gcc-TEST","X-Pull-Request":"https://forge.sourceware.org/gcc/gcc-TEST/pulls/15","References":"\n ","In-Reply-To":"\n ","X-Patch-URL":"\n https://forge.sourceware.org/redi/gcc/commit/7b3dba81e0d90ff95396d8e334631e15783707a4","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\nUse scoped guard types to clean up if an exception is thrown. This\nallows some try-catch blocks to be removed.\n\nlibstdc++-v3/ChangeLog:\n\n\t* include/bits/hashtable.h (operator=(const _Hashtable&)): Use\n\tRAII instead of try-catch.\n\t(_M_assign(_Ht&&, _NodeGenerator&)): Likewise.\n\nReviewed-by: François Dumont \n---\n libstdc++-v3/include/bits/hashtable.h | 99 +++++++++++++++------------\n 1 file changed, 55 insertions(+), 44 deletions(-)","diff":"diff --git a/libstdc++-v3/include/bits/hashtable.h b/libstdc++-v3/include/bits/hashtable.h\nindex f1c30896bcb0..a46a94e2ecd5 100644\n--- a/libstdc++-v3/include/bits/hashtable.h\n+++ b/libstdc++-v3/include/bits/hashtable.h\n@@ -1307,17 +1307,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n \t _M_bucket_count = __ht._M_bucket_count;\n \t _M_element_count = __ht._M_element_count;\n \t _M_rehash_policy = __ht._M_rehash_policy;\n-\t __try\n-\t\t{\n-\t\t _M_assign(__ht);\n-\t\t}\n-\t __catch(...)\n-\t\t{\n-\t\t // _M_assign took care of deallocating all memory. Now we\n-\t\t // must make sure this instance remains in a usable state.\n-\t\t _M_reset();\n-\t\t __throw_exception_again;\n-\t\t}\n+\n+\t struct _Guard\n+\t {\n+\t\t~_Guard() { if (_M_ht) _M_ht->_M_reset(); }\n+\t\t_Hashtable* _M_ht;\n+\t };\n+\t // If _M_assign exits via an exception it will have deallocated\n+\t // all memory. This guard will ensure *this is in a usable state.\n+\t _Guard __guard{this};\n+\t _M_assign(__ht);\n+\t __guard._M_ht = nullptr;\n \t return *this;\n \t }\n \t std::__alloc_on_copy(__this_alloc, __that_alloc);\n@@ -1390,46 +1390,57 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION\n \t\t _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::\n _M_assign(_Ht&& __ht, _NodeGenerator& __node_gen)\n {\n-\t__buckets_ptr __buckets = nullptr;\n-\tif (!_M_buckets)\n-\t _M_buckets = __buckets = _M_allocate_buckets(_M_bucket_count);\n+\tstruct _Guard\n+\t{\n+\t ~_Guard()\n+\t {\n+\t if (_M_ht)\n+\t {\n+\t\t_M_ht->clear();\n+\t\tif (_M_dealloc_buckets)\n+\t\t _M_ht->_M_deallocate_buckets();\n+\t }\n+\t }\n+\t _Hashtable* _M_ht = nullptr;\n+\t bool _M_dealloc_buckets = false;\n+\t};\n+\t_Guard __guard;\n \n-\t__try\n+\tif (!_M_buckets)\n \t {\n-\t if (!__ht._M_before_begin._M_nxt)\n-\t return;\n+\t _M_buckets = _M_allocate_buckets(_M_bucket_count);\n+\t __guard._M_dealloc_buckets = true;\n+\t }\n \n-\t using _FromVal = __conditional_t::value,\n-\t\t\t\t\t const value_type&, value_type&&>;\n+\tif (!__ht._M_before_begin._M_nxt)\n+\t return;\n \n-\t // First deal with the special first node pointed to by\n-\t // _M_before_begin.\n-\t __node_ptr __ht_n = __ht._M_begin();\n-\t __node_ptr __this_n\n-\t = __node_gen(static_cast<_FromVal>(__ht_n->_M_v()));\n-\t this->_M_copy_code(*__this_n, *__ht_n);\n-\t _M_update_bbegin(__this_n);\n+\t__guard._M_ht = this;\n \n-\t // Then deal with other nodes.\n-\t __node_ptr __prev_n = __this_n;\n-\t for (__ht_n = __ht_n->_M_next(); __ht_n; __ht_n = __ht_n->_M_next())\n-\t {\n-\t\t__this_n = __node_gen(static_cast<_FromVal>(__ht_n->_M_v()));\n-\t\t__prev_n->_M_nxt = __this_n;\n-\t\tthis->_M_copy_code(*__this_n, *__ht_n);\n-\t\tsize_type __bkt = _M_bucket_index(*__this_n);\n-\t\tif (!_M_buckets[__bkt])\n-\t\t _M_buckets[__bkt] = __prev_n;\n-\t\t__prev_n = __this_n;\n-\t }\n-\t }\n-\t__catch(...)\n+\tusing _FromVal = __conditional_t::value,\n+\t\t\t\t\t const value_type&, value_type&&>;\n+\n+\t// First deal with the special first node pointed to by\n+\t// _M_before_begin.\n+\t__node_ptr __ht_n = __ht._M_begin();\n+\t__node_ptr __this_n\n+\t = __node_gen(static_cast<_FromVal>(__ht_n->_M_v()));\n+\tthis->_M_copy_code(*__this_n, *__ht_n);\n+\t_M_update_bbegin(__this_n);\n+\n+\t// Then deal with other nodes.\n+\t__node_ptr __prev_n = __this_n;\n+\tfor (__ht_n = __ht_n->_M_next(); __ht_n; __ht_n = __ht_n->_M_next())\n \t {\n-\t clear();\n-\t if (__buckets)\n-\t _M_deallocate_buckets();\n-\t __throw_exception_again;\n+\t __this_n = __node_gen(static_cast<_FromVal>(__ht_n->_M_v()));\n+\t __prev_n->_M_nxt = __this_n;\n+\t this->_M_copy_code(*__this_n, *__ht_n);\n+\t size_type __bkt = _M_bucket_index(*__this_n);\n+\t if (!_M_buckets[__bkt])\n+\t _M_buckets[__bkt] = __prev_n;\n+\t __prev_n = __this_n;\n \t }\n+\t__guard._M_ht = nullptr;\n }\n \n template