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Sun, 13 Oct 2024 19:53:13 -0400 X-MC-Unique: f4QhnWlsPVe9uY13fv4sjA-1 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id E5E251956096; Sun, 13 Oct 2024 23:53:12 +0000 (UTC) Received: from localhost (unknown [10.42.28.16]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 47E7919560A2; Sun, 13 Oct 2024 23:53:11 +0000 (UTC) From: Jonathan Wakely To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org Subject: [PATCH] libstdc++: Implement LWG 3564 for ranges::transform_view Date: Mon, 14 Oct 2024 00:52:58 +0100 Message-ID: <20241013235310.1722385-1-jwakely@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-Spam-Status: No, score=-12.0 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_NONE, RCVD_IN_MSPIKE_H3, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_NONE, TXREP autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: gcc-patches-bounces~incoming=patchwork.ozlabs.org@gcc.gnu.org Tested x86_64-linux. -- >8 -- The _Iterator type returned by begin() const uses const F& to transform the elements, so it should use const F& to determine the iterator's value_type and iterator_category as well. This was accepted into the WP in July 2022. libstdc++-v3/ChangeLog: * include/std/ranges (transform_view:_Iterator): Use const F& to determine value_type and iterator_category of _Iterator, as per LWG 3564. * testsuite/std/ranges/adaptors/transform.cc: Check value_type and iterator_category. --- libstdc++-v3/include/std/ranges | 9 +++++++-- .../std/ranges/adaptors/transform.cc | 19 +++++++++++++++++++ 2 files changed, 26 insertions(+), 2 deletions(-) diff --git a/libstdc++-v3/include/std/ranges b/libstdc++-v3/include/std/ranges index 6e6e3b97d82..f0d81cbea0c 100644 --- a/libstdc++-v3/include/std/ranges +++ b/libstdc++-v3/include/std/ranges @@ -1886,8 +1886,12 @@ namespace views::__adaptor static auto _S_iter_cat() { + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3564. transform_view::iterator::value_type and + // iterator_category should use const F& + using _Fpc = __detail::__maybe_const_t<_Const, _Fp>; using _Base = transform_view::_Base<_Const>; - using _Res = invoke_result_t<_Fp&, range_reference_t<_Base>>; + using _Res = invoke_result_t<_Fpc&, range_reference_t<_Base>>; if constexpr (is_lvalue_reference_v<_Res>) { using _Cat @@ -1927,6 +1931,7 @@ namespace views::__adaptor return input_iterator_tag{}; } + using _Fpc = __detail::__maybe_const_t<_Const, _Fp>; using _Base_iter = iterator_t<_Base>; _Base_iter _M_current = _Base_iter(); @@ -1936,7 +1941,7 @@ namespace views::__adaptor using iterator_concept = decltype(_S_iter_concept()); // iterator_category defined in __transform_view_iter_cat using value_type - = remove_cvref_t>>; + = remove_cvref_t>>; using difference_type = range_difference_t<_Base>; _Iterator() requires default_initializable<_Base_iter> = default; diff --git a/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc b/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc index bcb18a3fc6c..ca695349650 100644 --- a/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc +++ b/libstdc++-v3/testsuite/std/ranges/adaptors/transform.cc @@ -196,6 +196,24 @@ test09() #endif } +void +test10() +{ + struct F { + short operator()(int) { return 0; } + const int& operator()(const int& i) const { return i; } + }; + + int x[] {2, 4}; + const auto xform = x | views::transform(F{}); + using const_iterator = decltype(xform.begin()); + // LWG 3564. transform_view::iterator::value_type and iterator_category + // should use const F& + static_assert(std::same_as, int>); + using cat = std::iterator_traits::iterator_category; + static_assert(std::same_as); +} + int main() { @@ -208,4 +226,5 @@ main() test07(); test08(); test09(); + test10(); }