[libc++][C++03] Use `__cxx03/` headers in C++03 mode (#109002)

This patch implements the forwarding to frozen C++03 headers as
discussed in
https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-

[libc++][C++03] Use `__cxx03/` headers in C++03 mode (#109002)

This patch implements the forwarding to frozen C++03 headers as
discussed in
https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc. In the
RFC, we initially proposed selecting the right headers from the Clang
driver, however consensus seemed to steer towards handling this in the
library itself. This patch implements that direction.

At a high level, the changes basically amount to making each public
header look like this:

```
// inside <vector>
#ifdef _LIBCPP_CXX03_LANG
# include <__cxx03/vector>
#else
// normal <vector> content
#endif
```

In most cases, public headers are simple umbrella headers so there isn't
much code in the #else branch. In other cases, the #else branch contains
the actual implementation of the header.

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[libc++] Granularize the <new> header (#119270)

This disentangles the code which previously had a mix of many #ifdefs, a
non-versioned namespace and a versioned namespace. It also makes it
clearer

[libc++] Granularize the <new> header (#119270)

This disentangles the code which previously had a mix of many #ifdefs, a
non-versioned namespace and a versioned namespace. It also makes it
clearer which parts of <new> are implemented on Windows by including <new.h>.

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[libc++] Add #if 0 block to all the top-level headers (#119234)

Including The frozen C++03 headers results in a lot of formatting
changes in the main headers, so this splits these changes into a
sep

[libc++] Add #if 0 block to all the top-level headers (#119234)

Including The frozen C++03 headers results in a lot of formatting
changes in the main headers, so this splits these changes into a
separate commit instead.

This is part of
https://discourse.llvm.org/t/rfc-freezing-c-03-headers-in-libc.

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[libc++] Remove obsolete accessors in std::list and std::forward_list (#115748)

We don't need these accessors anymore now that we stopped using
compressed-pair.

[libc++] Refactor the configuration macros to being always defined (#112094)

This is a follow-up to #89178. This updates the `<__config_site>`
macros.

[libc++] __uglify non-conforming member typedef `base` (#112843)

Currently, libc++'s `bitset`, `forward_list`, and `list` have
non-conforming member typedef name `base`. The typedef is private, but

[libc++] __uglify non-conforming member typedef `base` (#112843)

Currently, libc++'s `bitset`, `forward_list`, and `list` have
non-conforming member typedef name `base`. The typedef is private, but
can cause ambiguity in name lookup.

Some other classes in libc++ that are either implementation details or
not precisely specified by the standard also have member typdef `base`.
I think this can still be conforming.

Follows up #80706 and #111127.

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[libc++] Add container_traits (prework for `std::flat_map`) (#109578)

This PR is extracted from
https://github.com/llvm/llvm-project/pull/98643, as per code review
request
https://github.com/llvm

[libc++] Add container_traits (prework for `std::flat_map`) (#109578)

This PR is extracted from
https://github.com/llvm/llvm-project/pull/98643, as per code review
request
https://github.com/llvm/llvm-project/pull/98643#discussion_r1768967793

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[libc++][RFC] Always define internal feature test macros (#89178)

Currently, the library-internal feature test macros are only defined if
the feature is not available, and always have the prefix
`

[libc++][RFC] Always define internal feature test macros (#89178)

Currently, the library-internal feature test macros are only defined if
the feature is not available, and always have the prefix
`_LIBCPP_HAS_NO_`. This patch changes that, so that they are always
defined and have the prefix `_LIBCPP_HAS_` instead. This changes the
canonical use of these macros to `#if _LIBCPP_HAS_FEATURE`, which means
that using an undefined macro (e.g. due to a missing include) is
diagnosed now. While this is rather unlikely currently, a similar change
in `<__configuration/availability.h>` caught a few bugs. This also
improves readability, since it removes the double-negation of `#ifndef
_LIBCPP_HAS_NO_FEATURE`.

The current patch only touches the macros defined in `<__config>`. If
people are happy with this approach, I'll make a follow-up PR to also
change the macros defined in `<__config_site>`.

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[libc++] Take the ABI break for `std::list`'s pointer UB unconditionally (#100585)

This ABI break only affects fancy pointer which have a different value
representation when pointing to a base of T

[libc++] Take the ABI break for `std::list`'s pointer UB unconditionally (#100585)

This ABI break only affects fancy pointer which have a different value
representation when pointing to a base of T instead of T itself. This
seems like a rather small set of fancy pointers, which themselves
already represent a very small niche. This patch swaps a pointer to T
with a pointer to base of T in a few library-internal types.

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[libc++] Replace `__compressed_pair` with `[[no_unique_address]]` (#76756)

This significantly simplifies the code, improves compile times and
improves the object layout of types using `__compressed_

[libc++] Replace `__compressed_pair` with `[[no_unique_address]]` (#76756)

This significantly simplifies the code, improves compile times and
improves the object layout of types using `__compressed_pair` in the
unstable ABI. The only downside is that this is extremely ABI sensitive
and pedantically breaks the ABI for empty final types, since the address
of the subobject may change. The ABI of the whole object should not be
affected.

Fixes #91266
Fixes #93069

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[libc++][NFC] Use [[__nodiscard__]] unconditionally (#80454)

`__has_cpp_attribute(__nodiscard__)` is always true now, so we might as
well replace `_LIBCPP_NODISCARD`. It's one less macro that can r

[libc++][NFC] Use [[__nodiscard__]] unconditionally (#80454)

`__has_cpp_attribute(__nodiscard__)` is always true now, so we might as
well replace `_LIBCPP_NODISCARD`. It's one less macro that can result in
bad diagnostics.

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[libc++] Add miscellaneous missing includes

[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++] Restore `__synth_three_way` lambda (#90398)

Restore `__synth_three_way` lambda to match the Standard.
GH-57222 is done, restoring the Standard wording implementation should
be possible.

[libc++] Restore `__synth_three_way` lambda (#90398)

Restore `__synth_three_way` lambda to match the Standard.
GH-57222 is done, restoring the Standard wording implementation should
be possible.


https://github.com/llvm/llvm-project/blob/df28d4412c1d21b0e18896c92ac77d2fac7729f1/libcxx/include/__compare/synth_three_way.h#L28

According to comment
https://github.com/llvm/llvm-project/issues/59513#issuecomment-2068338762,
GH-59513 is not a blocker.

Co-authored-by: Hristo Hristov <zingam@outlook.com>

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[libc++] Move allocator assertion into allocator_traits (#94750)

There is code duplication in all containers that static_assert the
allocator matches the allocator requirements in the spec. This ch

[libc++] Move allocator assertion into allocator_traits (#94750)

There is code duplication in all containers that static_assert the
allocator matches the allocator requirements in the spec. This check can
be moved into a more centralised place.

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[libc++][NFC] Replace _NOEXCEPT and _LIBCPP_CONSTEXPR macros with the keywords in C++11 code (#96387)

[libc++] Refactor<__type_traits/is_swappable.h> (#86822)

This changes the `is_swappable` implementation to use variable templates
first and basing the class templates on that. This avoids instantia

[libc++] Refactor<__type_traits/is_swappable.h> (#86822)

This changes the `is_swappable` implementation to use variable templates
first and basing the class templates on that. This avoids instantiating
them when the `_v` versions are used, which are generally less resource
intensive.

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[libc++] Enable modernize-use-equals-delete (#93293)

Differential Revision: https://reviews.llvm.org/D121213

[libc++][NFC] Remove unnecessary parens in static_asserts (#95605)

These were required a long time ago due to `static_assert` not actually
being available in C++03. Now `static_assert` is simply ma

[libc++][NFC] Remove unnecessary parens in static_asserts (#95605)

These were required a long time ago due to `static_assert` not actually
being available in C++03. Now `static_assert` is simply mapped to
`_Static_assert` in C++03, making the additional parens unnecessary.

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[libc++] Make the __availability header a sub-header of __config (#93083)

In essence, this header has always been related to configuration of
the library but we didn't want to put it inside <__conf

[libc++] Make the __availability header a sub-header of __config (#93083)

In essence, this header has always been related to configuration of
the library but we didn't want to put it inside <__config> due to
complexity reasons. Now that we have sub-headers in <__config>, we
can move <__availability> to it and stop including it everywhere since
we already obtain the required macros via <__config>.

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Removed redundant template in '__delete_node()' member function of '__forward_list_base' and '__list_imp' classes. (#84323)

[libc++] Remove _LIBCPP_DISABLE_NODISCARD_EXTENSIONS and refactor the tests (#87094)

This also adds a few tests that were missing.

[libc++][NFC] Merge is{,_nothrow,_trivially}{,_copy,_move,_default}{_assignable,_constructible} (#85308)

These headers have become very small by using compiler builtins, often
containing only two d

[libc++][NFC] Merge is{,_nothrow,_trivially}{,_copy,_move,_default}{_assignable,_constructible} (#85308)

These headers have become very small by using compiler builtins, often
containing only two declarations. This merges these headers, since
there doesn't seem to be much of a benefit keeping them separate.

Specifically, `is_{,_nothrow,_trivially}{assignable,constructible}` are
kept and the `copy`, `move` and `default` versions of these type traits
are moved in to the respective headers.

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[libc++] Clean up includes of <__assert> (#80091)

Originally, we used __libcpp_verbose_abort to handle assertion failures.
That function was declared from all public headers. Since we don't use
th

[libc++] Clean up includes of <__assert> (#80091)

Originally, we used __libcpp_verbose_abort to handle assertion failures.
That function was declared from all public headers. Since we don't use
that mechanism anymore, we don't need to declare __libcpp_verbose_abort
from all public headers, and we can clean up a lot of unnecessary
includes.

This patch also moves the definition of the various assertion categories
to the <__assert> header, since we now rely on regular IWYU for these
assertion macros.

rdar://105510916

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[libc++] Refactor more __enable_ifs to the canonical style (#81457)

This brings the code base closer to having only a single style of
`enable_if`s.