On Wed, 24 Aug 2022, Patrick Palka wrote: > r13-2159-g72886fcc626953 introduced some testsuite regressions in C++23 > mode: > > FAIL: 20_util/pair/requirements/explicit_instantiation/1.cc (test for > excess errors) > FAIL: 20_util/tuple/53648.cc (test for excess errors) > FAIL: 20_util/tuple/cons/noexcept_specs.cc (test for excess errors) > FAIL: 20_util/tuple/requirements/explicit_instantiation.cc (test for excess > errors) > > The test noexcept_specs.cc just needs to be updated to consider the > additional converting constructors of tuple in C++23 mode, which happen > to improve constructing from a const tuple rvalue containing rvalue > reference elements (for the better, as far as I can tell). > > The other three tests fail because they explicitly instantiate a > specialization > of tuple whose elements are not all const swappable, which in C++23 mode now > results in a hard error due to tuple's new const swap member function. Rather > than XFAILing the tests in C++23 mode, this patch adds non-standard > constraints > to this member function so that we continue to accept such explicit > instantiations. > > Tested on x86_64-pc-linux-gnu with and without > --target_board=unix/-std=gnu++23, > does this look OK for trunk? > > libstdc++-v3/ChangeLog: > > * include/std/tuple (tuple::swap const): Add is_swappable_v constraints.
D'oh, pair's const swap needs the same workaround: -- >8 -- libstdc++-v3/ChangeLog: * include/bits/stl_pair.h (pair::swap const): Add non-standard is_swappable_v constraints. * include/std/tuple (tuple::swap const): Likewise. * testsuite/20_util/tuple/cons/noexcept_specs.cc: Update some asserts in C++23 mode. --- libstdc++-v3/include/bits/stl_pair.h | 8 ++++ libstdc++-v3/include/std/tuple | 9 ++++ .../20_util/tuple/cons/noexcept_specs.cc | 41 +++++++++++++++++++ 3 files changed, 58 insertions(+) diff --git a/libstdc++-v3/include/bits/stl_pair.h b/libstdc++-v3/include/bits/stl_pair.h index bffca0daf65..a65a4763c54 100644 --- a/libstdc++-v3/include/bits/stl_pair.h +++ b/libstdc++-v3/include/bits/stl_pair.h @@ -213,10 +213,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION } #if __cplusplus > 202002L + // As an extension, we constrain the const swap member function + // in order to continue accepting explicit instantiation of tuple + // specializations whose elements are not all const swappable. + // Without this constraint, such an explicit instantiation would + // also instantiate the ill-formed body of this function and yield + // a hard error. This constraint shouldn't affect the behavior of + // valid programs. constexpr void swap(const pair& __p) const noexcept(__and_v<__is_nothrow_swappable<const _T1>, __is_nothrow_swappable<const _T2>>) + requires is_swappable_v<const _T1> && is_swappable_v<const _T2> { using std::swap; swap(first, __p.first); diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple index 05433d5ae36..9d1abc2f80e 100644 --- a/libstdc++-v3/include/std/tuple +++ b/libstdc++-v3/include/std/tuple @@ -1176,9 +1176,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION { _Inherited::_M_swap(__in); } #if __cplusplus > 202002L + // As an extension, we constrain this const swap member function + // in order to continue accepting explicit instantiation of tuple + // specializations whose elements are not all const swappable. + // Without this constraint, such an explicit instantiation would + // also instantiate the ill-formed body of this function and + // yield a hard error. This constraint shouldn't affect the behavior of + // valid programs. constexpr void swap(const tuple& __in) const noexcept(__and_v<__is_nothrow_swappable<const _Elements>...>) + requires (is_swappable_v<const _Elements> && ...) { _Inherited::_M_swap(__in); } #endif // C++23 }; @@ -1730,6 +1738,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION swap(const tuple& __in) const noexcept(__and_v<__is_nothrow_swappable<const _T1>, __is_nothrow_swappable<const _T2>>) + requires is_swappable_v<const _T1> && is_swappable_v<const _T2> { _Inherited::_M_swap(__in); } #endif // C++23 }; diff --git a/libstdc++-v3/testsuite/20_util/tuple/cons/noexcept_specs.cc b/libstdc++-v3/testsuite/20_util/tuple/cons/noexcept_specs.cc index 6044a377348..a326d1bc228 100644 --- a/libstdc++-v3/testsuite/20_util/tuple/cons/noexcept_specs.cc +++ b/libstdc++-v3/testsuite/20_util/tuple/cons/noexcept_specs.cc @@ -503,7 +503,17 @@ namespace NothrowCopyThrowMoveThrowCopyConversionNothrowMoveConversion static_assert(!std::is_nothrow_constructible<BT, IT&>::value, ""); static_assert(!std::is_nothrow_constructible<BT, const IT &>::value, ""); static_assert(!std::is_nothrow_constructible<BT, std::tuple<int&>>::value, ""); +#if __cplusplus > 202002L + // C++23 extended tuple's constructor overload set as part of P2321R2, after + // which its converting constructors more accurately forward the elements + // from a non-const tuple lvalue and from a const tuple rvalue. In particular + // for the below test we now forward int&& as an rvalue reference instead of + // as an lvalue reference, which means we now select the noexcept B(int&&) + // ctor instead of the non-noexcept B(const int&) ctor. + static_assert(std::is_nothrow_constructible<BT, const std::tuple<int&&>>::value, ""); +#else static_assert(!std::is_nothrow_constructible<BT, const std::tuple<int&&>>::value, ""); +#endif static_assert(test_trait::is_nothrow_convertible<int,BT>::value,""); static_assert(!test_trait::is_nothrow_convertible<const int,BT>::value,""); @@ -515,7 +525,13 @@ namespace NothrowCopyThrowMoveThrowCopyConversionNothrowMoveConversion static_assert(!test_trait::is_nothrow_convertible<IT&,BT>::value,""); static_assert(!test_trait::is_nothrow_convertible<const IT &,BT>::value,""); static_assert(!test_trait::is_nothrow_convertible<std::tuple<int&>,BT>::value,""); +#if __cplusplus > 202002L + // See the note about P2321R2 above. + static_assert(test_trait::is_nothrow_convertible<const std::tuple<int&&>,BT>::value,""); +#else static_assert(!test_trait::is_nothrow_convertible<const std::tuple<int&&>,BT>::value,""); +#endif + static_assert(!std::is_nothrow_constructible<BT, B>::value, ""); @@ -528,7 +544,12 @@ namespace NothrowCopyThrowMoveThrowCopyConversionNothrowMoveConversion static_assert(std::is_nothrow_constructible<BT, BT&>::value, ""); static_assert(std::is_nothrow_constructible<BT, const BT &>::value, ""); static_assert(std::is_nothrow_constructible<BT, std::tuple<B&>>::value, ""); +#if __cplusplus > 202002L + // See the note about P2321R2 above. + static_assert(!std::is_nothrow_constructible<BT, const std::tuple<B&&>>::value, ""); +#else static_assert(std::is_nothrow_constructible<BT, const std::tuple<B&&>>::value, ""); +#endif static_assert(!test_trait::is_nothrow_convertible<B,BT>::value,""); static_assert(test_trait::is_nothrow_convertible<const B,BT>::value,""); @@ -540,7 +561,12 @@ namespace NothrowCopyThrowMoveThrowCopyConversionNothrowMoveConversion static_assert(test_trait::is_nothrow_convertible<BT&,BT>::value,""); static_assert(test_trait::is_nothrow_convertible<const BT &,BT>::value,""); static_assert(test_trait::is_nothrow_convertible<std::tuple<B&>,BT>::value,""); +#if __cplusplus > 202002L + // See the note about P2321R2 above. + static_assert(!test_trait::is_nothrow_convertible<const std::tuple<B&&>,BT>::value,""); +#else static_assert(test_trait::is_nothrow_convertible<const std::tuple<B&&>,BT>::value,""); +#endif /* explicit */ static_assert(std::is_nothrow_constructible<DT, int>::value, ""); @@ -553,7 +579,12 @@ namespace NothrowCopyThrowMoveThrowCopyConversionNothrowMoveConversion static_assert(!std::is_nothrow_constructible<DT, IT&>::value, ""); static_assert(!std::is_nothrow_constructible<DT, const IT &>::value, ""); static_assert(!std::is_nothrow_constructible<DT, std::tuple<int&>>::value, ""); +#if __cplusplus > 202002L + // See the note about P2321R2 above. + static_assert(std::is_nothrow_constructible<DT, const std::tuple<int&&>>::value, ""); +#else static_assert(!std::is_nothrow_constructible<DT, const std::tuple<int&&>>::value, ""); +#endif static_assert(!std::is_nothrow_constructible<DT, D>::value, ""); static_assert(std::is_nothrow_constructible<DT,const D>::value, ""); @@ -565,7 +596,12 @@ namespace NothrowCopyThrowMoveThrowCopyConversionNothrowMoveConversion static_assert(std::is_nothrow_constructible<DT, DT&>::value, ""); static_assert(std::is_nothrow_constructible<DT, const DT &>::value, ""); static_assert(std::is_nothrow_constructible<DT, std::tuple<D&>>::value, ""); +#if __cplusplus > 202002L + // See note about P2321R2 above. + static_assert(!std::is_nothrow_constructible<DT, const std::tuple<D&&>>::value, ""); +#else static_assert(std::is_nothrow_constructible<DT, const std::tuple<D&&>>::value, ""); +#endif static_assert(!test_trait::is_nothrow_convertible<DT,DT>::value,""); static_assert(test_trait::is_nothrow_convertible<const DT,DT>::value,""); @@ -884,7 +920,12 @@ namespace ThrowMoveNothrowConversion static_assert(std::is_nothrow_constructible<DT, IT&>::value, ""); static_assert(std::is_nothrow_constructible<DT, const IT &>::value, ""); static_assert(std::is_nothrow_constructible<DT, std::tuple<int&>>::value, ""); +#if __cplusplus > 202002L + // See the note about P2321R2 above. + static_assert(!std::is_nothrow_constructible<DT, const std::tuple<int&&>>::value, ""); +#else static_assert(std::is_nothrow_constructible<DT, const std::tuple<int&&>>::value, ""); +#endif static_assert(test_trait::is_nothrow_convertible<DT,DT>::value,""); static_assert(test_trait::is_nothrow_convertible<D,DT>::value,""); -- 2.37.2.382.g795ea8776b