https://gcc.gnu.org/g:2d3142c00934c419755c17dd85ecdb0e72f249d1
commit r16-5697-g2d3142c00934c419755c17dd85ecdb0e72f249d1 Author: Patrick Palka <[email protected]> Date: Fri Nov 28 15:38:04 2025 -0500 libstdc++: Correctly implement LWG 3946 changes to const_iterator_t [PR122842] LWG 3946 made const_iterator_t/sentinel_t agree with ranges::cbegin/cend by defining the aliases in terms of the CPOs, but I defined it the other way around in an incorrect way that made the aliases not consider range-ness of const T via __possibly_const_range. This patch reimplements the proposed resolution in a more obviously correct way, mirroring the wording. PR libstdc++/122842 libstdc++-v3/ChangeLog: * include/bits/ranges_base.h (__access:_CBegin): Define in terms of const_iterator directly, not const_iterator_t. (__access::_CEnd): Likewise in terms of const_sentinel vs const_sentinel_t. (const_iterator_t): Move down definition and define in terms of ranges::cbegin as per LWG 3946. (const_sentinel_t): Likewise in terms of ranges::cend. * testsuite/24_iterators/const_iterator/1.cc (test02): Correct test for int[], std::array and std::vector. Also test std::string. Reviewed-by: Tomasz Kamiński <[email protected]> Reviewed-by: Jonathan Wakely <[email protected]> Diff: --- libstdc++-v3/include/bits/ranges_base.h | 20 +++++++++------ .../testsuite/24_iterators/const_iterator/1.cc | 29 ++++++++++++++++------ 2 files changed, 35 insertions(+), 14 deletions(-) diff --git a/libstdc++-v3/include/bits/ranges_base.h b/libstdc++-v3/include/bits/ranges_base.h index 1c4bf432c8f4..0b8151cd65dd 100644 --- a/libstdc++-v3/include/bits/ranges_base.h +++ b/libstdc++-v3/include/bits/ranges_base.h @@ -525,11 +525,7 @@ namespace ranges using sentinel_t = decltype(ranges::end(std::declval<_Range&>())); #if __glibcxx_ranges_as_const // >= C++23 - template<range _Range> - using const_iterator_t = const_iterator<iterator_t<_Range>>; - - template<range _Range> - using const_sentinel_t = const_sentinel<sentinel_t<_Range>>; + // const_iterator_t and const_sentinel_t defined below. template<range _Range> using range_const_reference_t = iter_const_reference_t<iterator_t<_Range>>; @@ -683,7 +679,7 @@ namespace ranges (ranges::begin(__access::__possibly_const_range(__t))); } { auto& __r = __access::__possibly_const_range(__t); - return const_iterator_t<decltype(__r)>(ranges::begin(__r)); + return const_iterator<decltype(ranges::begin(__r))>(ranges::begin(__r)); } #else template<typename _Tp> @@ -711,7 +707,7 @@ namespace ranges (ranges::end(__access::__possibly_const_range(__t))); } { auto& __r = __access::__possibly_const_range(__t); - return const_sentinel_t<decltype(__r)>(ranges::end(__r)); + return const_sentinel<decltype(ranges::end(__r))>(ranges::end(__r)); } #else template<typename _Tp> @@ -815,6 +811,16 @@ namespace ranges inline constexpr ranges::__access::_CData cdata{}; } +#if __glibcxx_ranges_as_const // >= C++23 + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3946. The definition of const_iterator_t should be reworked + template<range _Range> + using const_iterator_t = decltype(ranges::cbegin(std::declval<_Range&>())); + + template<range _Range> + using const_sentinel_t = decltype(ranges::cend(std::declval<_Range&>())); +#endif + namespace __detail { template<typename _Tp> diff --git a/libstdc++-v3/testsuite/24_iterators/const_iterator/1.cc b/libstdc++-v3/testsuite/24_iterators/const_iterator/1.cc index fe952bfad148..f2bcad4f09c9 100644 --- a/libstdc++-v3/testsuite/24_iterators/const_iterator/1.cc +++ b/libstdc++-v3/testsuite/24_iterators/const_iterator/1.cc @@ -42,12 +42,13 @@ test01() } } -template<class Range, bool Const> +template<class Range, bool Const, bool Constable = Const> void test02() { if constexpr (Const) { + static_assert(Constable); static_assert( ranges::constant_range<Range> ); static_assert( std::same_as<ranges::const_iterator_t<Range>, ranges::iterator_t<Range>> ); static_assert( std::same_as<ranges::const_sentinel_t<Range>, ranges::sentinel_t<Range>> ); @@ -64,9 +65,21 @@ test02() static_assert( !ranges::constant_range<Range> ); using Wrapped = std::basic_const_iterator<ranges::iterator_t<Range>>; - static_assert( std::same_as<ranges::const_iterator_t<Range>, Wrapped> ); - if constexpr (ranges::common_range<Range>) - static_assert( std::same_as<ranges::const_sentinel_t<Range>, Wrapped> ); + if constexpr (Constable) + { + // Verify LWG 3946 changes to const_iterator/sentinel_t (PR122842). + static_assert( std::same_as<ranges::const_iterator_t<Range>, + ranges::iterator_t<const Range>> ); + static_assert( std::same_as<ranges::const_sentinel_t<Range>, + ranges::sentinel_t<const Range>> ); + } + else + { + static_assert( std::same_as<ranges::const_iterator_t<Range>, Wrapped> ); + if constexpr (ranges::common_range<Range>) + static_assert( std::same_as<ranges::const_sentinel_t<Range>, Wrapped> ); + } + static_assert( std::same_as<ranges::range_const_reference_t<Range>, std::iter_reference_t<Wrapped>> ); @@ -138,13 +151,14 @@ main() test01<std::string_view::iterator, true>(); test01<std::vector<bool>::const_iterator, true>(); - test02<int[42], false>(); + test02<int[42], false, true>(); test02<test_input_range<int>, false>(); test02<test_forward_range<int>, false>(); test02<test_bidirectional_range<int>, false>(); test02<test_random_access_range<int>, false>(); - test02<std::array<int, 3>, false>(); - test02<std::vector<bool>, false>(); + test02<std::array<int, 3>, false, true>(); + test02<std::vector<bool>, false, true>(); + test02<std::string, false, true>(); test02<const int[42], true>(); test02<test_input_range<const int>, true>(); @@ -155,6 +169,7 @@ main() test02<const std::array<int, 3>, true>(); test02<std::string_view, true>(); test02<const std::vector<bool>, true>(); + test02<const std::string, true>(); test03(); test04();
