From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 2C44B397EC25 for ; Fri, 2 Jul 2021 11:16:48 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 2C44B397EC25 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-184-rZKSfWknNRye3QZiHRI7Fg-1; Fri, 02 Jul 2021 07:16:46 -0400 X-MC-Unique: rZKSfWknNRye3QZiHRI7Fg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5BA5B1084F63; Fri, 2 Jul 2021 11:16:45 +0000 (UTC) Received: from localhost (unknown [10.33.36.175]) by smtp.corp.redhat.com (Postfix) with ESMTP id E081E19C59; Fri, 2 Jul 2021 11:16:44 +0000 (UTC) Date: Fri, 2 Jul 2021 12:16:43 +0100 From: Jonathan Wakely To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: [committed] libstdc++: Revert changes to std::unique_ptr::operator[] [PR 101271] Message-ID: References: MIME-Version: 1.0 In-Reply-To: X-Clacks-Overhead: GNU Terry Pratchett X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/mixed; boundary="AEAy8CVQYI4eefqv" Content-Disposition: inline X-Spam-Status: No, score=-14.0 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, GIT_PATCH_0, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, 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: libstdc++@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++ mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 02 Jul 2021 11:16:49 -0000 --AEAy8CVQYI4eefqv Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline On 28/06/21 14:24 +0100, Jonathan Wakely wrote: >PR libstdc++/101236 shows that LLVM depends on being able to use >unique_ptr::operator[] when T is incomplete. This is undefined, but >previously worked with libstdc++. When I added the conditional noexcept >to that operator we started to diagnose the incomplete type. > >This change restores support for that case, by making the noexcept >condition check that the type is complete before checking whether >indexing on the pointer can throw. A workaround for PR c++/101239 is >needed to avoid a bogus error where G++ fails to do SFINAE on the >ill-formed p[n] expression and gets an ICE. Instead of checking that the >p[n] expression is valid in the trailing-return-type, we only check that >the element_type is complete. > >libstdc++-v3/ChangeLog: > > PR libstdc++/101236 > * include/bits/unique_ptr.h (unique_ptr::operator[]): > Fail gracefully if element_type is incomplete. > * testsuite/20_util/unique_ptr/cons/incomplete.cc: Clarify that > the standard doesn't require this test to work for array types. > * testsuite/20_util/unique_ptr/lwg2762.cc: Check that incomplete > types can be used with array specialization. > * testsuite/20_util/unique_ptr/101236.cc: New test. This (and the previous change that it tried to fix) needs to be reverted, as attached. Tested powerpc64le-linux. Committed to trunk. --AEAy8CVQYI4eefqv Content-Type: text/x-patch; charset=us-ascii Content-Disposition: attachment; filename="patch.txt" commit bc8f0ed7042280282035168428f6afc839997cf0 Author: Jonathan Wakely Date: Fri Jul 2 08:46:18 2021 libstdc++: Revert changes to std::unique_ptr::operator[] [PR 101271] This reverts the changes in r12-1778 which added a noexcept-specifier to std::unique_ptr::operator[], and the changes in r12-1844 which tried to make it work with incomplete types (for PR 101236). The noexcept-specifier is not required by the standard, and is causing regressions, so just remove it. Signed-off-by: Jonathan Wakely libstdc++-v3/ChangeLog: PR libstdc++/101271 * include/bits/unique_ptr.h (unique_ptr::operator[]): Remove noexcept-specifier. (unique_ptr::_S_nothrow_deref): Remove. * testsuite/20_util/unique_ptr/lwg2762.cc: Remove checks for operator[]. diff --git a/libstdc++-v3/include/bits/unique_ptr.h b/libstdc++-v3/include/bits/unique_ptr.h index e478056c755..d483f13f2b0 100644 --- a/libstdc++-v3/include/bits/unique_ptr.h +++ b/libstdc++-v3/include/bits/unique_ptr.h @@ -491,20 +491,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION = __and_< is_base_of<_Tp, _Up>, __not_, __remove_cv<_Up>>> >; - // This checks whether p[n] is noexcept, but fails gracefully when - // element_type is incomplete. The standard requires a complete type - // for unique_ptr, but we try to support it anyway (PR 101236). - template - static constexpr auto - _S_nothrow_deref(size_t __n) - -> decltype(sizeof(_Elt) != 0) // PR c++/101239 - { return noexcept(std::declval<_Ptr>()[__n]); } - - template - static constexpr bool - _S_nothrow_deref(...) - { return false; } - public: using pointer = typename __uniq_ptr_impl<_Tp, _Dp>::pointer; using element_type = _Tp; @@ -669,7 +655,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION /// Access an element of owned array. typename std::add_lvalue_reference::type operator[](size_t __i) const - noexcept(_S_nothrow_deref(0)) { __glibcxx_assert(get() != pointer()); return get()[__i]; diff --git a/libstdc++-v3/testsuite/20_util/unique_ptr/lwg2762.cc b/libstdc++-v3/testsuite/20_util/unique_ptr/lwg2762.cc index c88237dd9ea..ea067eb3af3 100644 --- a/libstdc++-v3/testsuite/20_util/unique_ptr/lwg2762.cc +++ b/libstdc++-v3/testsuite/20_util/unique_ptr/lwg2762.cc @@ -12,11 +12,6 @@ struct deleter int& operator*() && noexcept(B); // this is used by unique_ptr int& operator*() const& = delete; // this should not be - int& operator[](std::size_t) && noexcept(B); // this is used by unique_ptr - int& operator[](std::size_t) const& = delete; // should not be used - int& operator[](int) && = delete; // should not be used - int& operator[](double) && = delete; // should not be used - int* operator->() noexcept(false); // noexcept here doesn't affect anything // Needed for NullablePointer requirements @@ -40,16 +35,3 @@ static_assert( noexcept(std::declval>().operator->()), "operator-> is always noexcept" ); static_assert( noexcept(std::declval&>().operator->()), "operator-> is always noexcept" ); - -// This is not required by the standard, but we make it depend on the pointer. -static_assert( noexcept(std::declval>()[0]), "QoI" ); -static_assert( noexcept(std::declval&>()[0]), "QoI" ); -static_assert( ! noexcept(std::declval&>()[0]), "QoI" ); - -// This is forbidden by the standard ("T shall be a complete type") -// but we try to support it anyway, see PR libstdc++/101236. -struct Incomplete; -static_assert( ! noexcept(std::declval>()[0]), - "this would be noexcept if the type was complete"); -static_assert( ! noexcept(std::declval>()[0]), - "this would still be noexcept(false) if the type was complete"); --AEAy8CVQYI4eefqv--