From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: by sourceware.org (Postfix, from userid 1888) id 2CB81383D03D; Tue, 18 May 2021 04:35:16 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 2CB81383D03D MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="utf-8" From: Patrick Palka To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-855] libstdc++: Fix condition for memoizing reverse_view::begin() [PR100621] X-Act-Checkin: gcc X-Git-Author: Patrick Palka X-Git-Refname: refs/heads/master X-Git-Oldrev: 2e2eef80ac0c21f9533e6791ccf5e29458cbb77c X-Git-Newrev: 03cf8d54e5c27cfe6b184cc96757cab30d8fa1df Message-Id: <20210518043517.2CB81383D03D@sourceware.org> Date: Tue, 18 May 2021 04:35:16 +0000 (GMT) X-BeenThere: libstdc++-cvs@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libstdc++-cvs mailing list List-Unsubscribe: , List-Archive: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 18 May 2021 04:35:17 -0000 https://gcc.gnu.org/g:03cf8d54e5c27cfe6b184cc96757cab30d8fa1df commit r12-855-g03cf8d54e5c27cfe6b184cc96757cab30d8fa1df Author: Patrick Palka Date: Tue May 18 00:26:25 2021 -0400 libstdc++: Fix condition for memoizing reverse_view::begin() [PR100621] A range being a random access range isn't a sufficient condition for ranges::next(iter, sent) to have constant time complexity -- it must also have a sized sentinel. This adjusts the memoization condition for reverse_view accordingly. libstdc++-v3/ChangeLog: PR libstdc++/100621 * include/std/ranges (reverse_view::_S_needs_cached_begin): Set to true if the underlying non-common random-access range doesn't have a sized sentinel. Diff: --- 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 36bccd6b33b..70794251ec7 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -3228,7 +3228,9 @@ 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,