libstdc++: Implement spaceship for std::pair (P1614R2)
This defines operator<=> as a non-member function template and does not alter operator==. This contradicts the changes made by P1614R2, which specify both as hidden friends, but that specification of operator<=> is broken and the subject of a soon-to-be-published LWG issue. * include/bits/stl_pair.h [__cpp_lib_three_way_comparison] (operator<=>): Define for C++20. * libsupc++/compare (__cmp2way_res_t): Rename to __cmp3way_res_t, move into __detail namespace. Do not turn argument types into lvalues. (__cmp3way_helper): Rename to __cmp3way_res_impl, move into __detail namespace. Constrain with concepts instead of using void_t. (compare_three_way_result): Adjust name of base class. (compare_three_way_result_t): Use __cmp3way_res_impl directly. (__detail::__3way_cmp_with): Add workaround for PR 91073. (compare_three_way): Use workaround. (__detail::__synth3way, __detail::__synth3way_t): Define new helpers implementing synth-three-way and synth-three-way-result semantics. * testsuite/20_util/pair/comparison_operators/constexpr_c++20.cc: New test. From-SVN: r278951
This commit is contained in:
Jonathan Wakely
Jonathan Wakely
parent
6fb3d28f13
commit
7f397e4519
@ -1,5 +1,20 @@
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2019-12-03 Jonathan Wakely <jwakely@redhat.com>
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* include/bits/stl_pair.h [__cpp_lib_three_way_comparison]
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(operator<=>): Define for C++20.
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* libsupc++/compare (__cmp2way_res_t): Rename to __cmp3way_res_t,
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move into __detail namespace. Do not turn argument types into lvalues.
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(__cmp3way_helper): Rename to __cmp3way_res_impl, move into __detail
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namespace. Constrain with concepts instead of using void_t.
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(compare_three_way_result): Adjust name of base class.
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(compare_three_way_result_t): Use __cmp3way_res_impl directly.
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(__detail::__3way_cmp_with): Add workaround for PR 91073.
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(compare_three_way): Use workaround.
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(__detail::__synth3way, __detail::__synth3way_t): Define new helpers
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implementing synth-three-way and synth-three-way-result semantics.
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* testsuite/20_util/pair/comparison_operators/constexpr_c++20.cc: New
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test.
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* include/bits/stl_pair.h (pair): Remove stray Doxygen closing marker.
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* testsuite/util/slow_clock.h: Fix copyright date.
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@ -59,7 +59,10 @@
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#include <bits/move.h> // for std::move / std::forward, and std::swap
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#if __cplusplus >= 201103L
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#include <type_traits> // for std::__decay_and_strip too
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# include <type_traits> // for std::__decay_and_strip, std::is_reference_v
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#endif
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#if __cplusplus > 201703L
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# include <compare>
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#endif
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namespace std _GLIBCXX_VISIBILITY(default)
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@ -447,7 +450,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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_GLIBCXX20_CONSTEXPR
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pair(tuple<_Args1...>&, tuple<_Args2...>&,
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_Index_tuple<_Indexes1...>, _Index_tuple<_Indexes2...>);
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#endif
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#endif // C++11
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};
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/// @relates pair @{
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@ -462,6 +465,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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operator==(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
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{ return __x.first == __y.first && __x.second == __y.second; }
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#if __cpp_lib_three_way_comparison && __cpp_lib_concepts
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template<typename _T1, typename _T2>
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constexpr common_comparison_category_t<__detail::__synth3way_t<_T1>,
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__detail::__synth3way_t<_T2>>
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operator<=>(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
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{
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if (auto __c = __detail::__synth3way(__x.first, __y.first); __c != 0)
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return __c;
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return __detail::__synth3way(__x.second, __y.second);
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}
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#else
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/** Defines a lexicographical order for pairs.
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*
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* For two pairs of the same type, `P` is ordered before `Q` if
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@ -498,6 +512,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
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inline _GLIBCXX_CONSTEXPR bool
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operator>=(const pair<_T1, _T2>& __x, const pair<_T1, _T2>& __y)
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{ return !(__x < __y); }
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#endif // !(three_way_comparison && concepts)
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#if __cplusplus >= 201103L
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/** Swap overload for pairs. Calls std::pair::swap().
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@ -509,34 +509,41 @@ namespace std
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{ __t <=> __u } -> __detail::__compares_as<_Cat>;
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{ __u <=> __t } -> __detail::__compares_as<_Cat>;
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};
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#endif
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template<typename _Tp, typename _Up>
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using __cmp2way_res_t
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= decltype(std::declval<_Tp&>() <=> std::declval<_Up&>());
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namespace __detail
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{
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template<typename _Tp, typename _Up>
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using __cmp3way_res_t
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= decltype(std::declval<_Tp>() <=> std::declval<_Up>());
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template<typename _Tp, typename _Up = _Tp, typename = void>
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struct __cmp3way_helper
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{ };
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// Implementation of std::compare_three_way_result.
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// It is undefined for a program to add specializations of
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// std::compare_three_way_result, so the std::compare_three_way_result_t
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// alias ignores std::compare_three_way_result and uses
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// __detail::__cmp3way_res_impl directly instead.
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template<typename _Tp, typename _Up>
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struct __cmp3way_res_impl
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{ };
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template<typename _Tp, typename _Up>
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struct __cmp3way_helper<_Tp, _Up, void_t<__cmp2way_res_t<_Tp, _Up>>>
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{
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using type = __cmp2way_res_t<_Tp, _Up>;
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using __type = type;
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};
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template<typename _Tp, typename _Up>
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requires requires { typename __cmp3way_res_t<__cref<_Tp>, __cref<_Up>>; }
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struct __cmp3way_res_impl<_Tp, _Up>
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{
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using type = __cmp3way_res_t<__cref<_Tp>, __cref<_Up>>;
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};
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} // namespace __detail
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/// [cmp.result], result of three-way comparison
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template<typename _Tp, typename _Up = _Tp>
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struct compare_three_way_result
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: __cmp3way_helper<_Tp, _Up>
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: __detail::__cmp3way_res_impl<_Tp, _Up>
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{ };
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/// [cmp.result], result of three-way comparison
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template<typename _Tp, typename _Up = _Tp>
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using compare_three_way_result_t
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= typename compare_three_way_result<_Tp, _Up>::__type;
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= typename __detail::__cmp3way_res_impl<_Tp, _Up>::type;
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#if __cpp_lib_concepts
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namespace __detail
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{
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// BUILTIN-PTR-THREE-WAY(T, U)
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@ -548,13 +555,17 @@ namespace std
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{ operator<=>(static_cast<_Tp&&>(__t), static_cast<_Up&&>(__u)); }
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&& ! requires(_Tp&& __t, _Up&& __u)
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{ static_cast<_Tp&&>(__t).operator<=>(static_cast<_Up&&>(__u)); };
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// FIXME: workaround for PR c++/91073
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template<typename _Tp, typename _Up>
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concept __3way_cmp_with = three_way_comparable_with<_Tp, _Up>;
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} // namespace __detail
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// [cmp.object], typename compare_three_way
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struct compare_three_way
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{
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template<typename _Tp, typename _Up>
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requires (three_way_comparable_with<_Tp, _Up>
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requires (__detail::__3way_cmp_with<_Tp, _Up>
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|| __detail::__3way_builtin_ptr_cmp<_Tp, _Up>)
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constexpr auto
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operator()(_Tp&& __t, _Up&& __u) const noexcept
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@ -915,6 +926,40 @@ namespace std
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inline constexpr __cmp_cust::_Partial_fallback
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compare_partial_order_fallback{};
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}
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namespace __detail
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{
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// [expos.only.func]
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inline constexpr struct _Synth3way
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{
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template<typename _Tp, typename _Up>
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constexpr auto
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operator()(const _Tp& __t, const _Up& __u) const
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requires requires
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{
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{ __t < __u } -> convertible_to<bool>;
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{ __u < __t } -> convertible_to<bool>;
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}
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{
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if constexpr (__3way_cmp_with<_Tp, _Up>)
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return __t <=> __u;
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else
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{
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if (__t < __u)
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return weak_ordering::less;
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else if (__u < __t)
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return weak_ordering::greater;
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else
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return weak_ordering::equivalent;
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}
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}
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} __synth3way = {};
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template<typename _Tp, typename _Up = _Tp>
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using __synth3way_t
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= decltype(__detail::__synth3way(std::declval<_Tp&>(),
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std::declval<_Up&>()));
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} // namespace __detail
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#endif // concepts
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} // namespace std
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@ -0,0 +1,31 @@
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// { dg-options "-std=gnu++2a" }
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// { dg-do compile { target c++2a } }
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// Copyright (C) 2019 Free Software Foundation, Inc.
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//
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// This file is part of the GNU ISO C++ Library. This library is free
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// software; you can redistribute it and/or modify it under the
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// terms of the GNU General Public License as published by the
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// Free Software Foundation; either version 3, or (at your option)
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// any later version.
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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// You should have received a copy of the GNU General Public License along
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// with this library; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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#include <utility>
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#include <testsuite_common_types.h>
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int main()
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{
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__gnu_test::constexpr_comparison_operators test;
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test.operator()<std::pair<int, int>>();
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constexpr std::pair<int, int> p{1, 2}, q{3, 0};
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static_assert( p <=> q == std::strong_ordering::less );
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}
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