libc++ Spaceship Operator Status (operator<=>)

Overview

This document contains the status of the C++20 spaceship operator support in libc++. It is used to track both the status of the sub-projects of the effort and who is assigned to these sub-projects. This is imperative to effective implementation so that work is not duplicated and implementors are not blocked by each other.

If you are interested in contributing to this effort, please send a message to the #libcxx channel in the LLVM discord. Please do not start working on any of the assigned items below.

Sub-Projects in the Implementation Effort

Section	Description	Dependencies	Assignee	Complete
[cmp.concept]	three_way_comparable three_way_comparable_with	None	Ruslan Arutyunyan	Complete
[cmp.result]	compare_three_way_result	None	Arthur O’Dwyer	Complete
[expos.only.func]	synth-three-way synth-three-way-result	[cmp.concept]	Kent Ross	Complete
[comparisons.three.way]	compare_three_way	[cmp.concept]	Arthur O’Dwyer	Complete
[cmp.alg]	strong_order weak_order partial_order strong_order_fallback weak_order_fallback partial_order_fallback	None	Arthur O’Dwyer	Complete 1
[alg.three.way]	lexicographical_compare_three_way	[comparisons.three.way]	Christopher Di Bella	In Progress
[coroutine.handle.compare]	coroutine_handle	[comparisons.three.way]	Chuanqi Xu	Complete
[pairs.spec]	pair	[expos.only.func]	Kent Ross	Complete
[syserr.errcat.nonvirtuals]	error_category	[comparisons.three.way]	Unassigned	Not Started
[syserr.compare]	error_code error_condition	None	Unassigned	Not Started
[tuple.rel]	tuple	[expos.only.func]	Kent Ross	Complete
[optional.relops] [optional.nullops] [optional.comp.with.t]	optional nullopt	None	Kent Ross	In Progress
[variant.relops] [variant.monostate.relops]	monostate variant	None	Kent Ross	In Progress
[unique.ptr.special]	unique_ptr	[comparisons.three.way]	Unassigned	Not Started
[util.smartptr.shared.cmp]	shared_ptr	[comparisons.three.way]	Unassigned	Not Started
[type.index.members]	type_index	None	Unassigned	Not Started
[charconv.syn]	to_chars_result	None	Mark de Wever	Complete
[charconv.syn]	from_chars_result	None	Mark de Wever	Complete
[stacktrace.entry.cmp]	stacktrace_entry	None	Unassigned	Not Started
[stacktrace.basic.cmp]	basic_stacktrace	[alg.three.way]	Unassigned	Not Started
[string.cmp]	basic_string	None	Christopher Di Bella	In Progress
[string.view.comparison]	basic_string_view	None	Christopher Di Bella	In Progress
[array.syn] (general)	array	[expos.only.func]	Unassigned	Not Started
[deque.syn] (general)	deque	[expos.only.func]	Unassigned	Not Started
[forward.list.syn] (general)	forward_list	[expos.only.func]	Unassigned	Not Started
[list.syn] (general)	list	[expos.only.func]	Unassigned	Not Started
[vector.syn] (general)	vector	[expos.only.func]	Unassigned	Not Started
[associative.map.syn] (general)	map multimap	[expos.only.func]	Unassigned	Not Started
[associative.set.syn] (general)	multiset set	[expos.only.func]	Unassigned	Not Started
[queue.ops]	queue	None	Unassigned	Not Started
[stack.ops]	stack	None	Unassigned	Not Started
[reverse.iter.cmp]	reverse_iterator	None	Mikhail Maltsev	Complete
[move.iter.op.comp]	move_iterator	None	Unassigned	Not Started
[counted.iter.cmp]	counted_iterator	None	Unassigned	Not Started
[range.iota.iterator]	ranges::iota_view::iterator	[concepts.cmp]	Unassigned	Not Started
[range.transform.iterator]	ranges::transform_view::iterator	[concepts.cmp]	Unassigned	Not Started
[range.elements.iterator]	ranges::elements_view::iterator	[concepts.cmp]	Unassigned	Not Started
[time.duration.comparisons] [time.point.comparisons] [time.cal.day.nonmembers] [time.cal.month.nonmembers] [time.cal.year.nonmembers] [time.cal.md.nonmembers] [time.cal.mdlast] [time.cal.ym.nonmembers] [time.cal.ymd.nonmembers] [time.cal.ymdlast.nonmembers] [time.zone.nonmembers] [time.zone.leap.nonmembers] [time.zone.link.nonmembers]	chrono::duration chrono::time_point chrono::day chrono::month chrono::year chrono::month_day chrono::month_day_last chrono::year_month chrono::year_month_day chrono::year_month_day_last chrono::time_zone chrono::leap_second chrono::time_zone_link	None	Unassigned	Not Started
[fs.path.nonmember]	filesystem::path	None	Unassigned	Not Started
[fs.dir.entry.obs]	filesystem::directory_entry	None	Unassigned	Not Started
[re.submatch.op]	sub_match	None	Unassigned	Not Started
[thread.thread.id]	thread::id	None	Unassigned	Not Started

Note

1

std::strong_order(long double, long double) is not yet implemented.

Misc. Items and TODOs

(Note: files with required updates will contain the TODO at the beginning of the list item so they can be easily found via global search.)

Paper and Issue Status

Number	Name	Status	First released version
P1614R2	The Mothership has Landed	In Progress
P2404R0	Relaxing equality_comparable_with’s, totally_ordered_with’s, and three_way_comparable_with’s common reference requirements to support move-only types
P2405R0	nullopt_t and nullptr_t should both have operator<=> and operator==
LWG3330	Include <compare> from most library headers	Complete	13.0
LWG3347	std::pair<T, U> now requires T and U to be less-than-comparable	Nothing To Do
LWG3350	Simplify return type of lexicographical_compare_three_way	Nothing To Do
LWG3360	three_way_comparable_with is inconsistent with similar concepts	Nothing To Do
LWG3380	common_type and comparison categories	Nothing To Do
LWG3395	Definition for three-way comparison needs to be updated	Nothing To Do