[libc++] Granularize <cstddef> includes (#108696)

[libc++][NFC] Run clang-format on libcxx/include

This re-formats a few headers that had become out-of-sync with respect
to formatting since we ran clang-format on the whole codebase. There's
surpris

[libc++][NFC] Run clang-format on libcxx/include

This re-formats a few headers that had become out-of-sync with respect
to formatting since we ran clang-format on the whole codebase. There's
surprisingly few instances of it.

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[libc++] Fix invalid escape sequences in Python comments (#94032)

[libc++] Fix SyntaxWarning messages from python 3.12 (#93637)

This fixes "SyntaxWarning: invalid escape sequence" and "SyntaxWarning: `is` with int literal".
transitive_includes.gen.py was also ref

[libc++] Fix SyntaxWarning messages from python 3.12 (#93637)

This fixes "SyntaxWarning: invalid escape sequence" and "SyntaxWarning: `is` with int literal".
transitive_includes.gen.py was also reformatted with darker per the style guide.

Signed-off-by: Sv. Lockal <lockalsash@gmail.com>

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[libc++][format] Adds ABI tags to inline constexpr variables. (#86293)

This uses the macro on record types and inline constexpr variables. The
tagged declarations are very likely to change in futur

[libc++][format] Adds ABI tags to inline constexpr variables. (#86293)

This uses the macro on record types and inline constexpr variables. The
tagged declarations are very likely to change in future versions of
libc++:
- __fields are internal types used to control the formatter's parse
functions which fields to expect. Newer formatters may add new fields.
For example the filesystem::path formatter accepted in the recent Tokyo
meeting added a new 'g' flag, which differs from the 'g' type.
- The Unicode tables. The number of entries in these table likely differ
between Unicode versions. The tables contain only a part of all Unicode
properties. Typically they are stored in a 32-bit entry where some bits
contain the properties and other bits the size of the range. Changes in
the Unicode or C++ algorithms may require more properties to be
available in C++. This may affect the number of bits available in the
range. If needed, other declarations get the macro. This is mainly a
first time to review this approach.

This was originally https://reviews.llvm.org/D143494 where a new macro
_LIBCPP_HIDE_FROM_ABI_TYPE was defined. Testing revealed the existing
macro _LIBCPP_HIDE_FROM_ABI could be used. The "parts" of the macro that
do not affect records are not harmful. Based on this information the
existing macro was used and additional documentation was written.

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[libc++] Remove unused Python imports (#73724)

VSCode's Pylance extension informed me, and text searching confirmed,
that these imports are unused. I believe we should be able to remove
them harml

[libc++] Remove unused Python imports (#73724)

VSCode's Pylance extension informed me, and text searching confirmed,
that these imports are unused. I believe we should be able to remove
them harmlessly.

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[NFC][Py Reformat] Reformat python files in libcxx/libcxxabi

This is an ongoing series of commits that are reformatting our
Python code.

Reformatting is done with `black`.

If you end up having pro

[NFC][Py Reformat] Reformat python files in libcxx/libcxxabi

This is an ongoing series of commits that are reformatting our
Python code.

Reformatting is done with `black`.

If you end up having problems merging this commit because you
have made changes to a python file, the best way to handle that
is to run git checkout --ours <yourfile> and then reformat it
with black.

If you run into any problems, post to discourse about it and
we will try to help.

RFC Thread below:

https://discourse.llvm.org/t/rfc-document-and-standardize-python-code-style

Reviewed By: #libc, kwk, Mordante

Differential Revision: https://reviews.llvm.org/D150763

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[libc++][format] Improves width estimate.

As obvious from the paper's title this is an LWG issue and thus retroactively
applied to C++20. This change may the output for certain code points:
1 Consid

[libc++][format] Improves width estimate.

As obvious from the paper's title this is an LWG issue and thus retroactively
applied to C++20. This change may the output for certain code points:
1 Considers 8477 extra codepoints as having a width 2 (as of Unicode 15)
(mostly Tangut Ideographs)
2 Change the width of 85 unassigned code points from 2 to 1
3 Change the width of 8 codepoints (in the range U+3248 CIRCLED NUMBER
TEN ON BLACK SQUARE ... U+324F CIRCLED NUMBER EIGHTY ON BLACK
SQUARE) from 2 to 1, because it seems questionable to make an exception
for those without input from Unicode

Note that libc++ already uses Unicode 15, while the Standard requires Unicode 12.
(The last time I checked MSVC STL used Unicode 14.)

So in practice the only notable change is item 3.

Implements
P2675 LWG3780: The Paper
format's width estimation is too approximate and not forward compatible

Benchmark before these changes
--------------------------------------------------------------------
Benchmark Time CPU Iterations
--------------------------------------------------------------------
BM_ascii_text<char> 3928 ns 3928 ns 178131
BM_unicode_text<char> 75231 ns 75230 ns 9158
BM_cyrillic_text<char> 59837 ns 59834 ns 11529
BM_japanese_text<char> 39842 ns 39832 ns 17501
BM_emoji_text<char> 3931 ns 3930 ns 177750
BM_ascii_text<wchar_t> 4024 ns 4024 ns 174190
BM_unicode_text<wchar_t> 63756 ns 63751 ns 11136
BM_cyrillic_text<wchar_t> 44639 ns 44638 ns 15597
BM_japanese_text<wchar_t> 34425 ns 34424 ns 20283
BM_emoji_text<wchar_t> 3937 ns 3937 ns 177684

Benchmark after these changes
--------------------------------------------------------------------
Benchmark Time CPU Iterations
--------------------------------------------------------------------
BM_ascii_text<char> 3914 ns 3913 ns 178814
BM_unicode_text<char> 70380 ns 70378 ns 9694
BM_cyrillic_text<char> 51889 ns 51877 ns 13488
BM_japanese_text<char> 41707 ns 41705 ns 16723
BM_emoji_text<char> 3908 ns 3907 ns 177912
BM_ascii_text<wchar_t> 3949 ns 3948 ns 177525
BM_unicode_text<wchar_t> 64591 ns 64587 ns 10649
BM_cyrillic_text<wchar_t> 44089 ns 44078 ns 15721
BM_japanese_text<wchar_t> 39369 ns 39367 ns 17779
BM_emoji_text<wchar_t> 3936 ns 3934 ns 177821

Benchmarks without "if(__code_point < (__entries[0] >> 14))"
--------------------------------------------------------------------
Benchmark Time CPU Iterations
--------------------------------------------------------------------
BM_ascii_text<char> 3922 ns 3922 ns 178587
BM_unicode_text<char> 94474 ns 94474 ns 7351
BM_cyrillic_text<char> 69202 ns 69200 ns 10157
BM_japanese_text<char> 42735 ns 42692 ns 16382
BM_emoji_text<char> 3920 ns 3919 ns 178704
BM_ascii_text<wchar_t> 3951 ns 3950 ns 177224
BM_unicode_text<wchar_t> 81003 ns 80988 ns 8668
BM_cyrillic_text<wchar_t> 57020 ns 57018 ns 12048
BM_japanese_text<wchar_t> 39695 ns 39687 ns 17582
BM_emoji_text<wchar_t> 3977 ns 3976 ns 176479

This optimization does carry its weight for the Unicode and Cyrillic
test. For the Japanese tests the gains are minor and for emoji it seems
to have no effect.

Reviewed By: ldionne, tahonermann, #libc

Differential Revision: https://reviews.llvm.org/D144499

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