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
5.1 Clause 16: Library Introduction
[expos.only.func]	synth-three-way synth-three-way-result	[cmp.concept]	Kent Ross	Complete
5.2 Clause 17: Language support library
[support.limits.general]		None	Unassigned	Nothing To Do
[type.info]	remove ops typeinfo	None	Adrian Vogelsgesang	Complete
[compare.syn]		[cmp.concept] [cmp.result] [cmp.object] [cmp.alg]	Unassigned	Complete
[cmp.weakeq] [cmp.strongeq]	removed by P1959R0	None	Unassigned	Nothing To Do
[cmp.partialord] [cmp.weakord] [cmp.strongord]	remove ops *_ordering	None	Christopher Di Bella	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
[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]
[coroutine.syn] [coroutine.handle.compare]	coroutine_handle	[comparisons.three.way]	Chuanqi Xu	Complete
5.3 Clause 18: Concepts Library
5.4 Clause 19: Diagnostics Library
[system.error.syn]		[syserr.errcat.nonvirtuals] [syserr.compare]	Unassigned	Complete
[syserr.errcat.overview] [syserr.errcat.nonvirtuals]	error_category	[comparisons.three.way]	Adrian Vogelsgesang	Complete
[syserr.compare]	error_code error_condition	None	Adrian Vogelsgesang	Complete
5.5 Clause 20: General utilities library
[utility.syn] [pairs.pair] [pairs.spec]	pair	[expos.only.func]	Kent Ross	Complete
[tuple.syn] [tuple.rel]	tuple	[expos.only.func]	Kent Ross	Complete
[optional.syn] [optional.relops] [optional.nullops] [optional.comp.with.t]	optional nullopt	None	Hristo Hristov	Complete
[variant.syn] [variant.relops] [variant.monostate.relops]	monostate variant	None	Kent Ross	Complete
[template.bitset] [bitset.members]	remove ops bitset	None	Hristo Hristov	Complete
[memory.syn]		None	Unassigned	Complete
[allocator.globals]	remove ops allocator	None	Hristo Hristov	Complete
[unique.ptr.special]	unique_ptr	[comparisons.three.way]	Adrian Vogelsgesang	Complete
[util.smartptr.shared.cmp]	shared_ptr	[comparisons.three.way]	Adrian Vogelsgesang	Complete
[mem.res.syn] [mem.res.eq] [mem.poly.allocator.eq]	remove ops memory_resource remove ops polymorphic_allocator	None	Hristo Hristov	Complete
[allocator.adaptor.syn] [scoped.adaptor.operators]	remove ops scoped_allocator_adaptor	None	Hristo Hristov	Complete
[functional.syn] [range.cmp] [func.wrap.func] [func.wrap.func.nullptr]	remove ops function	None	Hristo Hristov	Complete
[meta.unary.prop]	replaced by issue LWG3354	None	Unassigned	Nothing To Do
[meta.trans.other]		None	Unassigned	Not Started
[type.index.overview] [type.index.members]	type_index	None	Adrian Vogelsgesang	Complete
[charconv.syn]	to_chars_result	None	Mark de Wever	Complete
[charconv.syn]	from_chars_result	None	Mark de Wever	Complete
5.6 Clause 21: Strings library
[char.traits.specializations.char] [char.traits.specializations.char8.t] [char.traits.specializations.char16.t] [char.traits.specializations.char32.t] [char.traits.specializations.wchar.t] [string.syn] [string.cmp]	basic_string	None	Mark de Wever	Complete
[string.view.synop] [string.view.comparison]	basic_string_view	None	Mark de Wever	Complete
5.7 Clause 22: Containers library
[container.requirements.general]		None	Unassigned	Not Started
[array.syn] (general)	array	[expos.only.func]	Adrian Vogelsgesang Hristo Hristov	Complete
[deque.syn] (general)	deque	[expos.only.func]	Hristo Hristov	Complete
[forward.list.syn] (general)	forward_list	[expos.only.func]	Hristo Hristov	Complete
[list.syn] (general)	list	[expos.only.func]	Adrian Vogelsgesang	Complete
[vector.syn] (general)	vector	[expos.only.func]	Adrian Vogelsgesang Hristo Hristov	Complete
[array.overview] (general)	removed by issue LWG3347	None	Adrian Vogelsgesang Hristo Hristov	Complete
[associative.map.syn] (general)	map multimap	[expos.only.func]	Hristo Hristov	Complete
[associative.set.syn] (general)	multiset set	[expos.only.func]	Hristo Hristov	Complete
[unord.map.syn]	remove ops unordered_map remove ops unordered_multimap	None	Hristo Hristov	Complete
[unordered.set.syn]	remove ops unordered_set remove ops unordered_multiset	None	Hristo Hristov	Complete
[queue.syn]	queue	None	Hristo Hristov	Complete
[stack.syn]	stack	None	Hristo Hristov	Complete
[queue.ops]	queue	None	Hristo Hristov	Complete
[stack.ops]	stack	None	Hristo Hristov	Complete
5.8 Clause 23: Iterators library
[iterator.synopsis]		None	Unassigned	Complete
[reverse.iter.cmp]	reverse_iterator	None	Mikhail Maltsev	Complete
[move.iterator] [move.iter.op.comp]	move_iterator	None	Arthur O’Dwyer	Complete
[common.iterator] [common.iter.cmp]	common_iterator	None	Zoe Carver	Complete
[counted.iterator] [counted.iter.cmp]	counted_iterator	None	Zoe Carver	Complete
[unreachable.sentinel]	unreachable_sentinel_t	None	Zoe Carver	Complete
[istream.iterator] [istream.iterator.ops]	remove ops istream_iterator	None	Konstantin Varlamov	Complete
[istreambuf.iterator] [istreambuf.iterator.ops]	remove ops istreambuf_iterator	None	Konstantin Varlamov	Complete
5.9 Clause 24: Ranges library
[range.iota.iterator]	ranges::iota_view::iterator	[concepts.cmp]	Arthur O’Dwyer	Complete
[range.iota.sentinel]	remove ops iota_view::sentinel	None	Zoe Carver	Complete
[range.filter.iterator]	remove ops filter_view::iterator	None	Louis Dionne	Complete
[range.filter.sentinel]	remove ops filter_view::sentinel	None	Louis Dionne	Complete
[range.transform.iterator]	ranges::transform_view::iterator	[concepts.cmp]	Arthur O’Dwyer	Complete
[range.transform.sentinel]	remove ops transform_view::sentinel	None	Zoe Carver	Complete
[range.take.sentinel]	remove ops take_view::sentinel	None	Konstantin Varlamov	Complete
[range.join.iterator]	remove ops join_view::iterator	None	Zoe Carver	Complete
[range.join.sentinel]	remove ops join_view::sentinel	None	Zoe Carver	Complete
[range.split.outer]	remove ops split_view::outer_iterator	None	Hui Xie	Complete
[range.split.inner]	remove ops split_view::inner_iterator	None	Hui Xie	Complete
5.10 Clause 25: Algorithms library
[algorithm.syn] [alg.three.way]	lexicographical_compare_three_way	[comparisons.three.way]	Adrian Vogelsgesang	Complete
5.11 Clause 26: Numerics library
[complex.syn] [complex.ops]	remove ops complex	None	Hristo Hristov	Complete
[class.slice.overview] [slice.ops]	slice	None	Hristo Hristov	Complete
5.12 Clause 27: Time library
[time.syn]		None	Mark de Wever	In Progress
[time.duration.comparisons]	chrono::duration	None	Hristo Hristov	Complete
[time.point.comparisons]	chrono::time_point	None	Hristo Hristov	Complete
[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]	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	None	Mark de Wever	Complete
[time.cal.wd] [time.cal.wdidx] [time.cal.wdlast] [time.cal.mwd] [time.cal.mwdlast] [time.cal.ymwd] [time.cal.ymwdlast]	weekday weekday_indexed weekday_last month_weekday month_weekday_last year_month_weekday year_month_weekday_last	None	Hristo Hristov	Complete
[time.zone.nonmembers]	chrono::time_zone	A <chrono> implementation	Mark de Wever	In Progress
[time.zone.zonedtime.nonmembers]	chrono::zoned_time	A <chrono> implementation	Mark de Wever	In Progress
[time.zone.leap.nonmembers]	chrono::time_leap_seconds	A <chrono> implementation	Mark de Wever	In Progress
[time.zone.link.nonmembers]	chrono::time_zone_link	A <chrono> implementation	Mark de Wever	In Progress
5.13 Clause 28: Localization library
[locale] [locale.operators]	remove ops locale	None	Hristo Hristov	Complete
5.14 Clause 29: Input/output library
[fs.filesystem.syn]	filesystem::space_info	None	Adrian Vogelsgesang	Complete
[fs.class.path] [fs.path.nonmember]	filesystem::path	None	Adrian Vogelsgesang	Complete
[fs.class.file.status]	file_status	None	Hristo Hristov	Complete
[fs.class.directory.entry] [fs.dir.entry.obs]	filesystem::directory_entry	None	Adrian Vogelsgesang	Complete
5.15 Clause 30: Regular expressions library
[re.syn]		None	Mark de Wever	Complete
[re.submatch.op]	sub_match	None	Mark de Wever	Complete
[re.results.nonmember]	remove ops match_results	None	Mark de Wever	Complete
[re.regiter], [re.regiter.comp]	remove ops regex_iterator	None	Mark de Wever	Complete
[re.tokiter] [re.tokiter.comp]	remove ops regex_token_iterator	None	Mark de Wever	Complete
5.16 Clause 31: Atomic operations library
5.17 Clause 32: Thread support library
[thread.thread.id]	thread::id	None	Adrian Vogelsgesang	Complete
Misc (Not part of R1614)
[range.elements.iterator]	ranges::elements_view::iterator	[concepts.cmp]	Hui Xie	Complete
[stacktrace.entry.cmp]	stacktrace_entry	None	Nikolas Klauser	In Progress
[stacktrace.basic.cmp]	basic_stacktrace	[alg.three.way]	Nikolas Klauser	In Progress

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
P2404R3	Relaxing equality_comparable_with’s, totally_ordered_with’s, and three_way_comparable_with’s common reference requirements to support move-only types
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
P0905R1	Symmetry for spaceship
P1120R0	Consistency improvements for <=> and other comparison operators
LWG3431	<=> for containers should require three_way_comparable<T> instead of <=>