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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-1296] libstdc++: Finish implementing LWG 3413 for propagate_const Date: Tue, 8 Jun 2021 14:01:14 +0000 (GMT) [thread overview] Message-ID: <20210608140114.329C9395444C@sourceware.org> (raw) https://gcc.gnu.org/g:d319517e809ee50496db29e552f86a83a14c837c commit r12-1296-gd319517e809ee50496db29e552f86a83a14c837c Author: Jonathan Wakely <jwakely@redhat.com> Date: Tue Jun 8 14:56:57 2021 +0100 libstdc++: Finish implementing LWG 3413 for propagate_const We already have conditional noexcept so this just constrains the non-member swap overload. Signed-off-by: Jonathan Wakely <jwakely@redhat.com> libstdc++-v3/ChangeLog: * include/experimental/propagate_const (swap): Constrain. * testsuite/experimental/propagate_const/swap/lwg3413.cc: New test. Diff: --- libstdc++-v3/include/experimental/propagate_const | 8 ++++- .../experimental/propagate_const/swap/lwg3413.cc | 41 ++++++++++++++++++++++ 2 files changed, 48 insertions(+), 1 deletion(-) diff --git a/libstdc++-v3/include/experimental/propagate_const b/libstdc++-v3/include/experimental/propagate_const index 0d03c13c5e1..162b4783dd7 100644 --- a/libstdc++-v3/include/experimental/propagate_const +++ b/libstdc++-v3/include/experimental/propagate_const @@ -113,6 +113,7 @@ inline namespace fundamentals_v2 constexpr propagate_const() = default; propagate_const(const propagate_const& __p) = delete; constexpr propagate_const(propagate_const&& __p) = default; + template <typename _Up, typename enable_if<__and_<is_constructible<_Tp, _Up&&>, is_convertible<_Up&&, _Tp>>::value, bool @@ -120,6 +121,7 @@ inline namespace fundamentals_v2 constexpr propagate_const(propagate_const<_Up>&& __pu) : _M_t(std::move(get_underlying(__pu))) {} + template <typename _Up, typename enable_if<__and_<is_constructible<_Tp, _Up&&>, __not_<is_convertible<_Up&&, _Tp>>>::value, @@ -127,6 +129,7 @@ inline namespace fundamentals_v2 constexpr explicit propagate_const(propagate_const<_Up>&& __pu) : _M_t(std::move(get_underlying(__pu))) {} + template <typename _Up, typename enable_if<__and_<is_constructible<_Tp, _Up&&>, is_convertible<_Up&&, _Tp>, @@ -136,6 +139,7 @@ inline namespace fundamentals_v2 constexpr propagate_const(_Up&& __u) : _M_t(std::forward<_Up>(__u)) {} + template <typename _Up, typename enable_if<__and_<is_constructible<_Tp, _Up&&>, __not_<is_convertible<_Up&&, _Tp>>, @@ -399,8 +403,10 @@ inline namespace fundamentals_v2 } // [propagate_const.algorithms], specialized algorithms + // _GLIBCXX_RESOLVE_LIB_DEFECTS + // 3413. propagate_const's swap [...] needs to be constrained and use a trait template <typename _Tp> - constexpr void + constexpr enable_if_t<__is_swappable<_Tp>::value, void> swap(propagate_const<_Tp>& __pt, propagate_const<_Tp>& __pt2) noexcept(__is_nothrow_swappable<_Tp>::value) { diff --git a/libstdc++-v3/testsuite/experimental/propagate_const/swap/lwg3413.cc b/libstdc++-v3/testsuite/experimental/propagate_const/swap/lwg3413.cc new file mode 100644 index 00000000000..8dc13cfebdd --- /dev/null +++ b/libstdc++-v3/testsuite/experimental/propagate_const/swap/lwg3413.cc @@ -0,0 +1,41 @@ +// { dg-do compile { target c++14 } } + +// LWG 3413 +// propagate_const's swap's noexcept specification needs to be constrained +// and use a trait + +#include <experimental/propagate_const> + +using std::experimental::propagate_const; + +propagate_const<int*> i; +static_assert( noexcept(i.swap(i)), "member swap is noexcept" ); +static_assert( noexcept(swap(i, i)), "non-member swap is noexcept" ); + +struct P +{ + int i = 0; + int& operator*() const; +}; + +void swap(P&, P&) noexcept(false); + +propagate_const<P> p; +static_assert( ! noexcept(p.swap(p)), "member swap is conditionally noexcept" ); +static_assert( ! noexcept(swap(p, p)), "non-member swap is conditionally noexcept" ); + +// std::is_swappable not available for -std=c++14 +#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) +struct Q +{ + int i = 0; + int& operator*() const; + + Q& operator=(Q&&) = delete; +}; + +static_assert( ! std::is_swappable<Q>::value, "" ); + +static_assert( ! std::is_swappable<propagate_const<Q>>::value, + "non-member swap is constrained" ); +#endif
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