================================ libc++ C++20 Status

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.. contents:: :local:

Overview

In July 2017, the C++ standard committee created a draft for the next version of the C++ standard, initially known as "C++2a". In September 2020, the C++ standard committee approved this draft, and sent it to ISO for approval as C++20.

This page shows the status of libc++; the status of clang's support of the language features is here.

.. attention:: Features in unreleased drafts of the standard are subject to change.

The groups that have contributed papers:

CWG - Core Language Working group
LWG - Library working group
SG1 - Study group #1 (Concurrency working group)

.. note:: "Nothing to do" means that no library changes were needed to implement this change.

.. _paper-status-cxx20:

Paper Status

.. csv-table:: :file: Cxx20Papers.csv :header-rows: 1 :widths: auto

.. note::

.. [#note-P0591] P0591: The changes in [mem.poly.allocator.mem] are missing. .. [#note-P0645] P0645: The paper is implemented but still marked as an incomplete feature (the feature-test macro is not set). .. [#note-P0966] P0966: It was previously erroneously marked as complete in version 8.0. See bug 45368. .. [#note-P0619] P0619: Only sections D.8, D.9, D.10 and D.13 are implemented. Sections D.4, D.7, D.11, and D.12 remain undone. .. [#note-P0883.1] P0883: shared_ptr and floating-point changes weren't applied as they themselves aren't implemented yet. .. [#note-P0883.2] P0883: ATOMIC_FLAG_INIT was marked deprecated in version 14.0, but was undeprecated with the implementation of LWG3659 in version 15.0. .. [#note-P0660] P0660: The paper is implemented but the features are experimental and can be enabled via -fexperimental-library. .. [#note-P1614] P1614: std::strong_order(long double, long double) is partly implemented. .. [#note-P0355] P0355: The implementation status is:

  * ``Calendars`` mostly done in Clang 7
  * ``Input parsers`` not done
  * ``Stream output`` Obsolete due to [P1361R2](https://wg21.link/P1361R2) "Integration of chrono with text formatting"
  * ``Time zone and leap seconds`` In Progress
  * ``TAI clock`` not done
  * ``GPS clock`` not done
  * ``UTC clock`` not done

.. _issues-status-cxx20:

Library Working Group Issues Status

.. csv-table:: :file: Cxx20Issues.csv :header-rows: 1 :widths: auto