[libc++][doc] Update the release notes

[Mordante]

Summary

I had a look at the changes since the last release and updated the release notes with interesting changes.

If there are more interesting changes, please let me know and I'll update the patch. I'd like to commit these changes before branching the 12.0 release. Branching is planned for the 26th of January.

I've added most active libc++ contributors. If I forgot anybody please add them.

[ldionne]

Thanks a lot for doing this! This is great - historically we haven't been very good at communicating what we've done in libc++ from one release to another, but this is much better.

libcxx/docs/ReleaseNotes.rst

40

We also added support for systems without a random device. It can be disabled with -DLIBCXX_ENABLE_RANDOM_DEVICE=OFF.

[tschuett]

libcxx/docs/ReleaseNotes.rst

49–50

modernized? look much better now is like opinion?

[tschuett]

libcxx/docs/ReleaseNotes.rst

52

significant?

[Mordante]

libcxx/docs/ReleaseNotes.rst

40

Thanks! I'll add this information.

49–50

Good point, I'll change the wording.

52

I've been doubting that myself. But if felt a bit empty without being able to mention some concrete improvement. However I don't object against removing it.

[tschuett]

Do what ever you want, but a lot sounds a bit cheap. Or give some concrete examples?

[Mordante]

In D95248#2516233, @tschuett wrote:

Do what ever you want, but a lot sounds a bit cheap. Or give some concrete examples?

Good point. I'll update the wording and include headers that have been modified.

[tschuett]

Maybe you could the same for the status page? It was changed from XXX to YYY? It is claiming success without giving numbers.

[• Quuxplusone]

libcxx/docs/ReleaseNotes.rst

52

One way to make this wording correct would be to ship D93512 D93557 D93661. ;)

[Mordante]

libcxx/docs/ReleaseNotes.rst

52

I had a look and it seems finding the headers which are complete finished with the constexpr changes is a bit tricky. I thought <algorithm> was done after P0202. However the revisions @Quuxplusone mentions also affect <algorithm> and are part of P0879. So now I prefer to omit the constexpr part. A number of papers have been done, but I didn't see a lot that can be easily communicated to users of libc++, unless using terms like "a lot".

[Mordante]

Addresses review comments.
Updates C++2b status on the index page.

[tschuett]

libcxx/docs/ReleaseNotes.rst

56

instead of html

[Mordante]

libcxx/docs/ReleaseNotes.rst

56

Good catch, thanks.

[Mordante]

Fixes a grammar error found by @tschuett.

[curdeius]

libcxx/docs/ReleaseNotes.rst

49

Nit: double space after "e.g.".

58–59

Maybe note that libc++ is built using -std=c++20 when available (i.e. it's not required and CMake will fall back to c++17, previously c++17 was required)?

[Mordante]

libcxx/docs/ReleaseNotes.rst

49

Thanks will fix.

58–59

I think it would be good to mention this. Thanks!

[Mordante]

Addresses @curdeius' review comments.

@ldionne All review comments have been addressed, can you have a final look?

[ldionne]

Thanks a lot! This looks good.

[Mordante]

You're welcome. Thanks again for everybody's input.

libcxx/docs/ReleaseNotes.rst

 the current one. To see the release notes for a specific release, please
 see the `releases page <https://llvm.org/releases/>`_.
 
 What's New in Libc++ 12.0.0?
 ============================
 
 New Features
 ------------
+- Random device support has been made optional. It's enabled by default and can
+  be disabled by building libc++ with ``-DLIBCXX_ENABLE_RANDOM_DEVICE=OFF``.
+  Disabling random device support can be useful when building the library for
+  platforms that don't have a source of randomness, such as some embedded
+  platforms. When this is not supported, most of ``<random>`` will still be
+  available, but ``std::random_device`` will not.
+- Localization support has been made optional. It's enabled by default and can
+  be disabled by building libc++ with ``-DLIBCXX_ENABLE_LOCALIZATION=OFF``.
+  Disabling localization can be useful when porting to platforms that don't
+  support the C locale API (e.g. embedded). When localization is not
+  supported, several parts of the library will be disabled: ``<iostream>``,
+  ``<regex>``, ``<locale>`` will be completely unusable, and other parts may be
+  only partly available.
+- If libc++ is compiled with a C++20 capable compiler it will be compiled in
+  C++20 mode. Else libc++ will be compiled in C++17 mode.
+- Several unqualified lookups in libc++ have been changed to qualified lookups.
+  This makes libc++ more ADL-proof.
+- The libc++ implementation status pages have been overhauled. Like other parts
+  documentation they now use restructured text instead of html. Starting with
+  libc++12 the status pages are part of libc++'s documentation.
+- More C++20 features have been implemented. :doc:`Cxx2aStatus` has the full
+  overview of libc++'s C++20 implementation status.
+- Work has started to implement new C++2b features. :doc:`Cxx2bStatus` has the
+  full overview of libc++'s C++2b implementation status.
 
-- ...
 
 API Changes
 -----------
 - By default, libc++ will _not_ include the definition for new and delete,
   since those are provided in libc++abi. Vendors wishing to provide new and
   delete in libc++ can build the library with ``-DLIBCXX_ENABLE_NEW_DELETE_DEFINITIONS=ON``
   to get back the old behavior. This was done to avoid providing new and delete
   in both libc++ and libc++abi, which is technically an ODR violation. Also

libcxx/docs/index.rst

 
 C++ Dialect Support
 ---------------------
 
 * C++11 - Complete
 * :ref:`C++14 - Complete <cxx1y-status>`
 * :ref:`C++17 - In Progress <cxx1z-status>`
 * :ref:`C++20 - In Progress <cxx2a-status>`
-* :ref:`C++2b - Not Started <cxx2b-status>`
+* :ref:`C++2b - In Progress <cxx2b-status>`
 * `Post C++14 Technical Specifications - In Progress <http://libcxx.llvm.org/ts1z_status.html>`__
 * :ref:`C++ Feature Test Macro Status <feature-status>`
 
 Notes and Known Issues
 ----------------------
 
 This list contains known issues with libc++