From patchwork Fri Oct 8 23:59:08 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jonathan Wakely X-Patchwork-Id: 46017 Return-Path: X-Original-To: patchwork@sourceware.org Delivered-To: patchwork@sourceware.org Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 805F13858012 for ; Sat, 9 Oct 2021 00:00:20 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 805F13858012 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gcc.gnu.org; s=default; t=1633737620; bh=d07PKvI99f6n67Mz8BycNdVeIgwW3as0hp/PAde9XVY=; h=Date:To:Subject:List-Id:List-Unsubscribe:List-Archive:List-Post: List-Help:List-Subscribe:From:Reply-To:Cc:From; b=i//odS+Mm9dckhUmnU5u323++tnD9NHnzzVO0dB9KRMF3z1dBnmgng5qa3nA54cwM e186m9zEHJxPATFVLKuvgbgYcZolCzyXVTGOj20LiQ0Rm+/N8CruG7uGb+pmtrrYO8 8rzPRs1V8Akmiqj9tQR9SkYnP/SXb2jHIl9TnHrk= X-Original-To: gcc-patches@gcc.gnu.org Delivered-To: gcc-patches@gcc.gnu.org Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTP id 8F9233858C2C for ; Fri, 8 Oct 2021 23:59:14 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 8F9233858C2C Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-346-UFycCit1PdK0fkW-7iOUeA-1; Fri, 08 Oct 2021 19:59:10 -0400 X-MC-Unique: UFycCit1PdK0fkW-7iOUeA-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 76A15100C661; Fri, 8 Oct 2021 23:59:09 +0000 (UTC) Received: from localhost (unknown [10.33.37.44]) by smtp.corp.redhat.com (Postfix) with ESMTP id 06EC260C05; Fri, 8 Oct 2021 23:59:08 +0000 (UTC) Date: Sat, 9 Oct 2021 00:59:08 +0100 To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: [committed 1/2] libstdc++: Avoid instantiation of _Hash_node before it's needed Message-ID: MIME-Version: 1.0 X-Clacks-Overhead: GNU Terry Pratchett X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline X-Spam-Status: No, score=-13.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, KAM_SHORT, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H2, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-Patchwork-Original-From: Jonathan Wakely via Gcc-patches From: Jonathan Wakely Reply-To: Jonathan Wakely Cc: =?iso-8859-1?q?Fran=E7ois?= Dumont Errors-To: gcc-patches-bounces+patchwork=sourceware.org@gcc.gnu.org Sender: "Gcc-patches" This is a step towards restoring support for incomplete types in unordered containers (PR 53339). We do not need to instantiate the node type to get its value_type member, because we know that the value type is the first template parameter. We can deduce that template argument using a custom trait and a partial specialization for _Hash_node. If we wanted to support custom hash node types we could still use typename _Tp::value_type in the primary template of that trait, but that seems unnecessary. The other change needed is to defer a static assert at class scope, so that it is done when the types are complete. We must have a complete type in the destructor, so we can do it there instead. libstdc++-v3/ChangeLog: * include/bits/hashtable.h: Move static assertion to destructor. * include/bits/hashtable_policy.h: Deduce value type from node type without instantiating it. Tested powerpc64le-linux. Committed to trunk. This is the patch I referred to in: https://gcc.gnu.org/pipermail/gcc-patches/2021-July/576028.html commit 64acc43de1e33616e43b239887a260eb4a51fcc7 Author: Jonathan Wakely Date: Fri Oct 8 13:35:54 2021 libstdc++: Avoid instantiation of _Hash_node before it's needed This is a step towards restoring support for incomplete types in unordered containers (PR 53339). We do not need to instantiate the node type to get its value_type member, because we know that the value type is the first template parameter. We can deduce that template argument using a custom trait and a partial specialization for _Hash_node. If we wanted to support custom hash node types we could still use typename _Tp::value_type in the primary template of that trait, but that seems unnecessary. The other change needed is to defer a static assert at class scope, so that it is done when the types are complete. We must have a complete type in the destructor, so we can do it there instead. libstdc++-v3/ChangeLog: * include/bits/hashtable.h: Move static assertion to destructor. * include/bits/hashtable_policy.h: Deduce value type from node type without instantiating it. diff --git a/libstdc++-v3/include/bits/hashtable.h b/libstdc++-v3/include/bits/hashtable.h index 79a3096b62b..ff8af2201cd 100644 --- a/libstdc++-v3/include/bits/hashtable.h +++ b/libstdc++-v3/include/bits/hashtable.h @@ -329,14 +329,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION struct __hash_code_base_access : __hash_code_base { using __hash_code_base::_M_bucket_index; }; - // Getting a bucket index from a node shall not throw because it is used - // in methods (erase, swap...) that shall not throw. - static_assert(noexcept(declval() - ._M_bucket_index(declval(), - (std::size_t)0)), - "Cache the hash code or qualify your functors involved" - " in hash code and bucket index computation with noexcept"); - // To get bucket index we need _RangeHash not to throw. static_assert(is_nothrow_default_constructible<_RangeHash>::value, "Functor used to map hash code to bucket index" @@ -1556,6 +1548,15 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>:: ~_Hashtable() noexcept { + // Getting a bucket index from a node shall not throw because it is used + // in methods (erase, swap...) that shall not throw. Need a complete + // type to check this, so do it in the destructor not at class scope. + static_assert(noexcept(declval() + ._M_bucket_index(declval(), + (std::size_t)0)), + "Cache the hash code or qualify your functors involved" + " in hash code and bucket index computation with noexcept"); + clear(); _M_deallocate_buckets(); } diff --git a/libstdc++-v3/include/bits/hashtable_policy.h b/libstdc++-v3/include/bits/hashtable_policy.h index 2f8502588f5..75488da13f7 100644 --- a/libstdc++-v3/include/bits/hashtable_policy.h +++ b/libstdc++-v3/include/bits/hashtable_policy.h @@ -1840,6 +1840,13 @@ namespace __detail { private: using __ebo_node_alloc = _Hashtable_ebo_helper<0, _NodeAlloc>; + + template + struct __get_value_type; + template + struct __get_value_type<_Hash_node<_Val, _Cache_hash_code>> + { using type = _Val; }; + public: using __node_type = typename _NodeAlloc::value_type; using __node_alloc_type = _NodeAlloc; @@ -1847,7 +1854,7 @@ namespace __detail using __node_alloc_traits = __gnu_cxx::__alloc_traits<__node_alloc_type>; using __value_alloc_traits = typename __node_alloc_traits::template - rebind_traits; + rebind_traits::type>; using __node_ptr = __node_type*; using __node_base = _Hash_node_base;