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 [216.205.24.124]) by sourceware.org (Postfix) with ESMTP id 13B35385380B for ; Mon, 17 May 2021 16:17:48 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 13B35385380B Received: from mail-qv1-f70.google.com (mail-qv1-f70.google.com [209.85.219.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-149-ooSMlQsmOGi4ptvmRP7bhg-1; Mon, 17 May 2021 12:17:46 -0400 X-MC-Unique: ooSMlQsmOGi4ptvmRP7bhg-1 Received: by mail-qv1-f70.google.com with SMTP id x2-20020a0cda020000b02901edb4c412fdso5104023qvj.11 for ; Mon, 17 May 2021 09:17:45 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=v+P62xdF+++jIp1ciqsRZAMaR/9HCCaoaYyc7iCxNvY=; b=FI2mYilSZ48NPT4y/xWCVgKZJS8VumUe962xLVPeJIncheb+XC1xkxmOtg1dedSyJZ /3tK7d1CYd8ogurY1ZhmX5CxRhWmxIRBn1VB++mhnZDEoVoqxwaVSjRK1tcxuWQH9VQF uv6K7PqliilHTYAGY84UlX89XseTKW4A4f7ZxJ32NFtMe4iNPCFy/iU2wCohbBVKmZGb exoQNgoXOhxlvMMQXUA8E7tacHfCZTXjR5OXX0xpc/GwEunEcaMHm/D2nCoe0fCaL8Wu V6UHEf8wGwOoohhgeaJH7ffAwDXh3mifLrUG+Aeqq137YDdxBMdPKnHbwv34nqCDi6tH 1RCQ== X-Gm-Message-State: AOAM533o6y8NGcy4HNA9M/pUDNpyqrJy86uLB+QAY1QZQQmwSrgLbHGc g7yAHAHwBunp0v1WrchvPBo1nsGmKKQIjidFXpeoVeuWjQ6UQZMVH6+UUey5PSlYw0OfjMjo3H8 BgZhgSXcw13OxbnQ= X-Received: by 2002:a37:317:: with SMTP id 23mr659542qkd.66.1621268265530; Mon, 17 May 2021 09:17:45 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwtMr74TJvXlGDBTeFk2zGXcTfxkMBe0UyJpybu5oxg7K5T5X+AU3CkkpG2LT2hWYroBzMczw== X-Received: by 2002:a37:317:: with SMTP id 23mr659526qkd.66.1621268265335; Mon, 17 May 2021 09:17:45 -0700 (PDT) Received: from localhost.localdomain (ool-457d493a.dyn.optonline.net. [69.125.73.58]) by smtp.gmail.com with ESMTPSA id 97sm10661092qte.20.2021.05.17.09.17.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 May 2021 09:17:44 -0700 (PDT) From: Patrick Palka To: gcc-patches@gcc.gnu.org Cc: libstdc++@gcc.gnu.org, Patrick Palka Subject: [PATCH] libstdc++: Fix condition for memoizing reverse_view::begin() [PR100621] Date: Mon, 17 May 2021 12:17:43 -0400 Message-Id: <20210517161743.870382-1-ppalka@redhat.com> X-Mailer: git-send-email 2.31.1.621.g97eea85a0a MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset="US-ASCII" X-Spam-Status: No, score=-16.2 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_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) 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: Mon, 17 May 2021 16:17:49 -0000 A range being a random access range is not a sufficient condition for ranges::next(iter, sent) to have constant time complexity; the range must also have a sized sentinel. This adjusts the memoization condition for reverse_view accordingly. Tested on x86_64-pc-linxu-gnu, does this look OK for trunk? Doesn't seem to be worth backporting. libstdc++-v3/ChangeLog: * include/std/ranges (reverse_view::_S_needs_cached_begin): Set to false if the underlying non-common random-access range doesn't have a sized sentinel. --- libstdc++-v3/include/std/ranges | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index bf52074ca05..e93469ca3b4 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -3340,7 +3340,9 @@ namespace views::__adaptor { private: static constexpr bool _S_needs_cached_begin - = !common_range<_Vp> && !random_access_range<_Vp>; + = !common_range<_Vp> && !(random_access_range<_Vp> + && sized_sentinel_for, + iterator_t<_Vp>>); [[no_unique_address]] __detail::__maybe_present_t<_S_needs_cached_begin, -- 2.31.1.621.g97eea85a0a