From patchwork Wed Aug 26 14:51:29 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jonathan Wakely X-Patchwork-Id: 510895 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from sourceware.org (server1.sourceware.org [209.132.180.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id 62535140332 for ; Thu, 27 Aug 2015 00:51:41 +1000 (AEST) Authentication-Results: ozlabs.org; dkim=pass (1024-bit key; unprotected) header.d=gcc.gnu.org header.i=@gcc.gnu.org header.b=DoN7Qmqn; dkim-atps=neutral DomainKey-Signature: a=rsa-sha1; c=nofws; d=gcc.gnu.org; h=list-id :list-unsubscribe:list-archive:list-post:list-help:sender:date :from:to:subject:message-id:mime-version:content-type; q=dns; s= default; b=VFtX7++idg3H4+H21sCZsyipAtaXY4Nkl2nwmsXRrhUvXAUWzEqd8 ovHOtBDz343fQJUv0GC7JYf7oce77meHuXx4HyxPgDIZsI36/5MZ2UhCxTDJwxec eBo4OvybSSGd/umPCuz81eKXt1CUpg17s52vKEr5tvdL5n2gI7ELTY= DKIM-Signature: v=1; a=rsa-sha1; c=relaxed; d=gcc.gnu.org; h=list-id :list-unsubscribe:list-archive:list-post:list-help:sender:date :from:to:subject:message-id:mime-version:content-type; s= default; bh=xfAWo4WX22DG8+DhtXAjLuICVfA=; b=DoN7Qmqni1dMS/L4BwqD TCLUVk4IuVQNIM1NqK+AfR+lbdcVuO+e8sXDQKMUfHlhPX849xvzlJMHN7jBKFjB TV/Lnj6vJ7k3t0t800Aww0fo0RT4iWTaRz68grewc7wKf5o8WQ5XQ80ATaxsM/Ye TfZ05BCc6WCHRd8KqIPX53Q= Received: (qmail 75171 invoked by alias); 26 Aug 2015 14:51:35 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Delivered-To: mailing list gcc-patches@gcc.gnu.org Received: (qmail 75151 invoked by uid 89); 26 Aug 2015 14:51:34 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.0 required=5.0 tests=AWL, BAYES_00, KAM_LAZY_DOMAIN_SECURITY, RP_MATCHES_RCVD, SPF_HELO_PASS autolearn=ham version=3.3.2 X-Spam-User: qpsmtpd, 2 recipients X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Wed, 26 Aug 2015 14:51:32 +0000 Received: from int-mx14.intmail.prod.int.phx2.redhat.com (int-mx14.intmail.prod.int.phx2.redhat.com [10.5.11.27]) by mx1.redhat.com (Postfix) with ESMTPS id 1AF5A8CF41; Wed, 26 Aug 2015 14:51:31 +0000 (UTC) Received: from localhost (ovpn-116-95.ams2.redhat.com [10.36.116.95]) by int-mx14.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t7QEpU1u008557; Wed, 26 Aug 2015 10:51:30 -0400 Date: Wed, 26 Aug 2015 15:51:29 +0100 From: Jonathan Wakely To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: [v3 patch] Only set std::enable_shared_from_this member once. Message-ID: <20150826145129.GE2631@redhat.com> MIME-Version: 1.0 Content-Disposition: inline X-Clacks-Overhead: GNU Terry Pratchett User-Agent: Mutt/1.5.23 (2014-03-12) This adds a check to weak_ptr::_M_assign() so that calling __enable_shared_from_this_helper twice with the same pointer won't change which shared_ptr object the weak_ptr shares ownership with. On the lib reflector Peter Dimov convinced me that the boost::enable_shared_from_this behaviour is preferable to what we do now. I'm writing a proposal to specify this in the standard, but am changing it now in our implementation. Tested powerpc64le-linux, committing to trunk. commit a1cd60820fb1af7f3396ff4b28e0e1d3449bfacb Author: Jonathan Wakely Date: Tue Aug 25 17:10:36 2015 +0100 Only set std::enable_shared_from_this member once. * include/bits/shared_ptr.h (__enable_shared_from_this_helper): Use nullptr. * include/bits/shared_ptr_base.h (weak_ptr::_M_assign): Don't assign if ownership is already shared with a shared_ptr object. (__enable_shared_from_this_helper): Use nullptr. * testsuite/20_util/enable_shared_from_this/members/const.cc: New. * testsuite/20_util/enable_shared_from_this/members/reinit.cc: New. * testsuite/20_util/enable_shared_from_this/requirements/ explicit_instantiation.cc: Instantiate with const and incomplete types. diff --git a/libstdc++-v3/include/bits/shared_ptr.h b/libstdc++-v3/include/bits/shared_ptr.h index f96c078..2413b1b 100644 --- a/libstdc++-v3/include/bits/shared_ptr.h +++ b/libstdc++-v3/include/bits/shared_ptr.h @@ -588,7 +588,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION const enable_shared_from_this* __pe, const _Tp1* __px) noexcept { - if (__pe != 0) + if (__pe != nullptr) __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn); } diff --git a/libstdc++-v3/include/bits/shared_ptr_base.h b/libstdc++-v3/include/bits/shared_ptr_base.h index aec10fe..820edcb 100644 --- a/libstdc++-v3/include/bits/shared_ptr_base.h +++ b/libstdc++-v3/include/bits/shared_ptr_base.h @@ -1468,8 +1468,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION void _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount) noexcept { - _M_ptr = __ptr; - _M_refcount = __refcount; + if (use_count() == 0) + { + _M_ptr = __ptr; + _M_refcount = __refcount; + } } template friend class __shared_ptr; @@ -1549,7 +1552,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION const __enable_shared_from_this* __pe, const _Tp1* __px) noexcept { - if (__pe != 0) + if (__pe != nullptr) __pe->_M_weak_assign(const_cast<_Tp1*>(__px), __pn); } diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/const.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/const.cc new file mode 100644 index 0000000..fdf39c7 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/const.cc @@ -0,0 +1,60 @@ +// Copyright (C) 2015 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// . + +// { dg-options "-std=gnu++11" } + +#include +#include + +template + bool + share_ownership(const std::shared_ptr& p1, const std::shared_ptr& p2) + { + return !p1.owner_before(p2) && !p2.owner_before(p1); + } + +void +test01() +{ + struct X : public std::enable_shared_from_this { }; + using CX = const X; + std::shared_ptr p(new X); + VERIFY( share_ownership(p->shared_from_this(), p) ); + p.reset(new CX); + VERIFY( share_ownership(p->shared_from_this(), p) ); + auto p2 = std::const_pointer_cast(p)->shared_from_this(); + VERIFY( share_ownership(p2, p) ); +} + +void +test02() +{ + struct X; + using CX = const X; + struct X : public std::enable_shared_from_this { }; + std::shared_ptr p(new X); + VERIFY( share_ownership(p->shared_from_this(), p) ); + p.reset(new CX); + VERIFY( share_ownership(p->shared_from_this(), p) ); +} + +int +main() +{ + test01(); + test02(); +} diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/reinit.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/reinit.cc new file mode 100644 index 0000000..3740db8 --- /dev/null +++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/reinit.cc @@ -0,0 +1,49 @@ +// Copyright (C) 2015 Free Software Foundation, Inc. +// +// This file is part of the GNU ISO C++ Library. This library is free +// software; you can redistribute it and/or modify it under the +// terms of the GNU General Public License as published by the +// Free Software Foundation; either version 3, or (at your option) +// any later version. + +// This library is distributed in the hope that it will be useful, +// but WITHOUT ANY WARRANTY; without even the implied warranty of +// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +// GNU General Public License for more details. + +// You should have received a copy of the GNU General Public License along +// with this library; see the file COPYING3. If not see +// . + +// { dg-options "-std=gnu++11" } + +#include +#include + +struct X : public std::enable_shared_from_this { }; + +bool +share_ownership(const std::shared_ptr& p1, const std::shared_ptr& p2) +{ + return !p1.owner_before(p2) && !p2.owner_before(p1); +} + +void +test01() +{ + std::shared_ptr p1(new X); + VERIFY( share_ownership( p1->shared_from_this(), p1 ) ); + { + std::shared_ptr p2(p1.get(), [](X*){}); + // The weak_ptr member of the enable_shared_from_this base should not + // be reset by creating a second control block that owns the pointer. + VERIFY( share_ownership( p2->shared_from_this(), p1 ) ); + } + VERIFY( share_ownership( p1->shared_from_this(), p1 ) ); +} + +int +main() +{ + test01(); +} diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/requirements/explicit_instantiation.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/requirements/explicit_instantiation.cc index 270ee84..94638e1 100644 --- a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/requirements/explicit_instantiation.cc +++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/requirements/explicit_instantiation.cc @@ -21,3 +21,8 @@ #include template class std::enable_shared_from_this; +template class std::enable_shared_from_this; + +class Incomplete; +template class std::enable_shared_from_this; +template class std::enable_shared_from_this;