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From: Patrick Palka <ppalka@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-1195] libstdc++: Avoid hard error in ranges::unique_copy [PR100770] Date: Thu, 3 Jun 2021 16:31:27 +0000 (GMT) [thread overview] Message-ID: <20210603163127.C303D3858034@sourceware.org> (raw) https://gcc.gnu.org/g:0614bbbe59c6953e088cffa39dfe63d86fc1fa96 commit r12-1195-g0614bbbe59c6953e088cffa39dfe63d86fc1fa96 Author: Patrick Palka <ppalka@redhat.com> Date: Thu Jun 3 12:30:29 2021 -0400 libstdc++: Avoid hard error in ranges::unique_copy [PR100770] Here, in the constexpr if condition within ranges::unique_copy, when input_iterator<_Out> isn't satisfied we must avoid substituting into iter_value_t<_Out> because the latter isn't necessarily well-formed then. To that end, this patch factors out the condition into a concept and uses it throughout. This patch also makes the definition of our testsuite output_iterator_wrapper more minimal by setting its value_type, pointer and reference member types to void. This means our existing tests for unique_copy already exercise the fix for this bug, so we don't need to add another test. The only other fallout of this testsuite iterator change appears in std/ranges/range.cc, where the use of range_value_t on a test_output_range is now ill-formed. libstdc++-v3/ChangeLog: * include/bits/ranges_algo.h (__detail::__can_reread_output): Factor out this concept from ... (__unique_copy_fn::operator()): ... here. Use the concept throughout. * testsuite/std/ranges/range.cc: Remove now ill-formed use of range_value_t on an output_range. * testsuite/util/testsuite_iterators.h (output_iterator_wrapper): Define value_type, pointer and reference member types to void. Diff: --- libstdc++-v3/include/bits/ranges_algo.h | 16 ++++++++++------ libstdc++-v3/testsuite/std/ranges/range.cc | 3 --- libstdc++-v3/testsuite/util/testsuite_iterators.h | 2 +- 3 files changed, 11 insertions(+), 10 deletions(-) diff --git a/libstdc++-v3/include/bits/ranges_algo.h b/libstdc++-v3/include/bits/ranges_algo.h index cda3042c11f..ecf1378742d 100644 --- a/libstdc++-v3/include/bits/ranges_algo.h +++ b/libstdc++-v3/include/bits/ranges_algo.h @@ -1396,6 +1396,13 @@ namespace ranges inline constexpr __unique_fn unique{}; + namespace __detail + { + template<typename _Out, typename _Tp> + concept __can_reread_output = input_iterator<_Out> + && same_as<_Tp, iter_value_t<_Out>>; + } + template<typename _Iter, typename _Out> using unique_copy_result = in_out_result<_Iter, _Out>; @@ -1407,8 +1414,7 @@ namespace ranges projected<_Iter, _Proj>> _Comp = ranges::equal_to> requires indirectly_copyable<_Iter, _Out> && (forward_iterator<_Iter> - || (input_iterator<_Out> - && same_as<iter_value_t<_Iter>, iter_value_t<_Out>>) + || __detail::__can_reread_output<_Out, iter_value_t<_Iter>> || indirectly_copyable_storable<_Iter, _Out>) constexpr unique_copy_result<_Iter, _Out> operator()(_Iter __first, _Sent __last, _Out __result, @@ -1432,8 +1438,7 @@ namespace ranges } return {__next, std::move(++__result)}; } - else if constexpr (input_iterator<_Out> - && same_as<iter_value_t<_Iter>, iter_value_t<_Out>>) + else if constexpr (__detail::__can_reread_output<_Out, iter_value_t<_Iter>>) { *__result = *__first; while (++__first != __last) @@ -1467,8 +1472,7 @@ namespace ranges projected<iterator_t<_Range>, _Proj>> _Comp = ranges::equal_to> requires indirectly_copyable<iterator_t<_Range>, _Out> && (forward_iterator<iterator_t<_Range>> - || (input_iterator<_Out> - && same_as<range_value_t<_Range>, iter_value_t<_Out>>) + || __detail::__can_reread_output<_Out, range_value_t<_Range>> || indirectly_copyable_storable<iterator_t<_Range>, _Out>) constexpr unique_copy_result<borrowed_iterator_t<_Range>, _Out> operator()(_Range&& __r, _Out __result, diff --git a/libstdc++-v3/testsuite/std/ranges/range.cc b/libstdc++-v3/testsuite/std/ranges/range.cc index 795aca472e5..aa29af471a4 100644 --- a/libstdc++-v3/testsuite/std/ranges/range.cc +++ b/libstdc++-v3/testsuite/std/ranges/range.cc @@ -75,9 +75,6 @@ static_assert( same_as<std::ranges::range_difference_t<C>, static_assert( same_as<std::ranges::range_difference_t<O>, std::ptrdiff_t> ); -static_assert( same_as<std::ranges::range_value_t<O>, - char> ); - static_assert( same_as<std::ranges::range_reference_t<I>, char&> ); static_assert( same_as<std::ranges::range_reference_t<O>, diff --git a/libstdc++-v3/testsuite/util/testsuite_iterators.h b/libstdc++-v3/testsuite/util/testsuite_iterators.h index 67da06b8482..4e668d648f2 100644 --- a/libstdc++-v3/testsuite/util/testsuite_iterators.h +++ b/libstdc++-v3/testsuite/util/testsuite_iterators.h @@ -122,7 +122,7 @@ namespace __gnu_test */ template<class T> struct output_iterator_wrapper - : public std::iterator<std::output_iterator_tag, T, std::ptrdiff_t, T*, T&> + : public std::iterator<std::output_iterator_tag, void, std::ptrdiff_t, void, void> { protected: output_iterator_wrapper() : ptr(0), SharedInfo(0)
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