diff --git a/libcxx/docs/Status/SpaceshipProjects.csv b/libcxx/docs/Status/SpaceshipProjects.csv
--- a/libcxx/docs/Status/SpaceshipProjects.csv
+++ b/libcxx/docs/Status/SpaceshipProjects.csv
@@ -38,7 +38,7 @@
| `[array.syn] <https://wg21.link/array.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),| `array <https://reviews.llvm.org/D132265>`_,[expos.only.func],Adrian Vogelsgesang,|In Progress|
| `[deque.syn] <https://wg21.link/deque.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),| deque,[expos.only.func],Unassigned,|Not Started|
| `[forward.list.syn] <https://wg21.link/forward.list.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),| forward_list,[expos.only.func],Unassigned,|Not Started|
-| `[list.syn] <https://wg21.link/list.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),| list,[expos.only.func],Unassigned,|Not Started|
+| `[list.syn] <https://wg21.link/list.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),| `list <https://reviews.llvm.org/D132312>`_,[expos.only.func],Adrian Vogelsgesang,|Complete|
| `[vector.syn] <https://wg21.link/vector.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),| `vector <https://reviews.llvm.org/D132268>`_,[expos.only.func],Adrian Vogelsgesang,|In Progress|
| `[associative.map.syn] <https://wg21.link/associative.map.syn>`_ (`general <https://wg21.link/container.opt.reqmts>`_),"| map
| multimap",[expos.only.func],Unassigned,|Not Started|
diff --git a/libcxx/include/list b/libcxx/include/list
--- a/libcxx/include/list
+++ b/libcxx/include/list
@@ -155,15 +155,18 @@
template <class T, class Alloc>
bool operator==(const list<T,Alloc>& x, const list<T,Alloc>& y);
template <class T, class Alloc>
- bool operator< (const list<T,Alloc>& x, const list<T,Alloc>& y);
+ bool operator< (const list<T,Alloc>& x, const list<T,Alloc>& y); // removed in C++20
template <class T, class Alloc>
- bool operator!=(const list<T,Alloc>& x, const list<T,Alloc>& y);
+ bool operator!=(const list<T,Alloc>& x, const list<T,Alloc>& y); // removed in C++20
template <class T, class Alloc>
- bool operator> (const list<T,Alloc>& x, const list<T,Alloc>& y);
+ bool operator> (const list<T,Alloc>& x, const list<T,Alloc>& y); // removed in C++20
template <class T, class Alloc>
- bool operator>=(const list<T,Alloc>& x, const list<T,Alloc>& y);
+ bool operator>=(const list<T,Alloc>& x, const list<T,Alloc>& y); // removed in C++20
template <class T, class Alloc>
- bool operator<=(const list<T,Alloc>& x, const list<T,Alloc>& y);
+ bool operator<=(const list<T,Alloc>& x, const list<T,Alloc>& y); // removed in C++20
+template<class T, class Allocator>
+ synth-three-way-result<T> operator<=>(const list<T, Allocator>& x,
+ const list<T, Allocator>& y); // since C++20
template <class T, class Alloc>
void swap(list<T,Alloc>& x, list<T,Alloc>& y)
@@ -171,10 +174,10 @@
template <class T, class Allocator, class U>
typename list<T, Allocator>::size_type
- erase(list<T, Allocator>& c, const U& value); // C++20
+ erase(list<T, Allocator>& c, const U& value); // since C++20
template <class T, class Allocator, class Predicate>
typename list<T, Allocator>::size_type
- erase_if(list<T, Allocator>& c, Predicate pred); // C++20
+ erase_if(list<T, Allocator>& c, Predicate pred); // since C++20
} // std
@@ -183,6 +186,7 @@
#include <__algorithm/comp.h>
#include <__algorithm/equal.h>
#include <__algorithm/lexicographical_compare.h>
+#include <__algorithm/lexicographical_compare_three_way.h>
#include <__algorithm/min.h>
#include <__assert> // all public C++ headers provide the assertion handler
#include <__config>
@@ -2289,6 +2293,8 @@
return __x.size() == __y.size() && _VSTD::equal(__x.begin(), __x.end(), __y.begin());
}
+#if _LIBCPP_STD_VER <= 17
+
template <class _Tp, class _Alloc>
inline _LIBCPP_INLINE_VISIBILITY
bool
@@ -2329,6 +2335,19 @@
return !(__y < __x);
}
+#else // _LIBCPP_STD_VER <= 17
+
+template<class _Tp, class _Allocator>
+inline _LIBCPP_HIDE_FROM_ABI
+__synth_three_way_result<_Tp>
+operator<=>(const list<_Tp, _Allocator>& __x, const list<_Tp, _Allocator>& __y)
+{
+ return std::lexicographical_compare_three_way(
+ __x.begin(), __x.end(), __y.begin(), __y.end(), __synth_three_way);
+}
+
+#endif // _LIBCPP_STD_VER <= 17
+
template <class _Tp, class _Alloc>
inline _LIBCPP_INLINE_VISIBILITY
void
diff --git a/libcxx/test/std/containers/sequences/list/compare.three_way.pass.cpp b/libcxx/test/std/containers/sequences/list/compare.three_way.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/containers/sequences/list/compare.three_way.pass.cpp
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <list>
+
+// template <class T, class Allocator> constexpr
+// synth-three-way-result<T>
+// operator<=>(const list<T, Allocator>& x, const list<T, Allocator>& y);
+
+#include <list>
+#include <cassert>
+
+#include "test_container_comparisons.h"
+
+int main(int, char**) {
+ assert(test_ordered_container_spaceship<std::list>());
+ // `std::list` is not constexpr, so no `static_assert` test here.
+ return 0;
+}
diff --git a/libcxx/test/support/test_container_comparisons.h b/libcxx/test/support/test_container_comparisons.h
new file mode 100644
--- /dev/null
+++ b/libcxx/test/support/test_container_comparisons.h
@@ -0,0 +1,84 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// Utility functions to test comparisons on containers.
+
+#ifndef TEST_CONTAINER_COMPARISONS
+#define TEST_CONTAINER_COMPARISONS
+
+#include "test_comparisons.h"
+
+// Implementation detail of `test_ordered_container_spaceship`
+template <template <typename...> typename Container, typename Elem, typename Order>
+constexpr void test_ordered_container_spaceship_with_type() {
+ // Empty containers
+ {
+ Container<Elem> l1;
+ Container<Elem> l2;
+ assert(testOrder(l1, l2, Order::equivalent));
+ }
+ // Identical contents
+ {
+ Container<Elem> l1{1, 1};
+ Container<Elem> l2{1, 1};
+ assert(testOrder(l1, l2, Order::equivalent));
+ }
+ // Less, due to contained values
+ {
+ Container<Elem> l1{1, 1};
+ Container<Elem> l2{1, 2};
+ assert(testOrder(l1, l2, Order::less));
+ }
+ // Greater, due to contained values
+ {
+ Container<Elem> l1{1, 3};
+ Container<Elem> l2{1, 2};
+ assert(testOrder(l1, l2, Order::greater));
+ }
+ // Shorter list
+ {
+ Container<Elem> l1{1};
+ Container<Elem> l2{1, 2};
+ assert(testOrder(l1, l2, Order::less));
+ }
+ // Longer list
+ {
+ Container<Elem> l1{1, 2};
+ Container<Elem> l2{1};
+ assert(testOrder(l1, l2, Order::greater));
+ }
+ // Unordered
+ if constexpr (std::is_same_v<Elem, PartialOrder>) {
+ Container<Elem> l1{1, std::numeric_limits<int>::min()};
+ Container<Elem> l2{1, 2};
+ assert(testOrder(l1, l2, Order::unordered));
+ }
+}
+
+// Tests the `operator<=>` on ordered containers
+template <template <typename...> typename Container>
+constexpr bool test_ordered_container_spaceship() {
+ // The container should fulfil `std::three_way_comparable`
+ static_assert(std::three_way_comparable<Container<int>>);
+
+ // Test different comparison categories
+ test_ordered_container_spaceship_with_type<Container, int, std::strong_ordering>();
+ test_ordered_container_spaceship_with_type<Container, StrongOrder, std::strong_ordering>();
+ test_ordered_container_spaceship_with_type<Container, WeakOrder, std::weak_ordering>();
+ test_ordered_container_spaceship_with_type<Container, PartialOrder, std::partial_ordering>();
+
+ // `LessAndEqComp` does not have `operator<=>`. ordering is sythesized based on `operator<`
+ test_ordered_container_spaceship_with_type<Container, LessAndEqComp, std::weak_ordering>();
+
+ // Thanks to SFINAE, the following is not a compiler error but returns `false`
+ struct NonComparable {};
+ static_assert(!std::three_way_comparable<Container<NonComparable>>);
+
+ return true;
+}
+
+#endif