[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++] 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 transitive includes from empty headers (#116295)

This removes transitive includes that are only in a header that is empty
in a given C++ version.

[libc++][RFC] Only include what is required by-version in the umbrella headers (#83740)

This is a relatively low cost way of reducing the include sizes in older
language modes compared to the effec

[libc++][RFC] Only include what is required by-version in the umbrella headers (#83740)

This is a relatively low cost way of reducing the include sizes in older
language modes compared to the effect. For example, in C++14 mode the
include time of `<algorithm>` is reduced from 198ms to 127ms.

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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++] Fix the signature of std::rotl and std::rotr

- Changed parameters type in `std::rotr` and `std::rorl` functions from `unsigned int` to `int`.
- Implemented behaviour for negative parameter

[libc++] Fix the signature of std::rotl and std::rotr

- Changed parameters type in `std::rotr` and `std::rorl` functions from `unsigned int` to `int`.
- Implemented behaviour for negative parameter values.

Fixes #64544

Reviewed By: #libc, philnik

Spies: arichardson, philnik, libcxx-commits

Differential Revision: https://reviews.llvm.org/D157569

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[libc++] Remove <cstdlib> includes

We changed the `abort` calls when trying to throw exceptions in `-fno-exceptions` mode to `__verbose_abort` calls, which removes the dependency in most files.

Rev

[libc++] Remove <cstdlib> includes

We changed the `abort` calls when trying to throw exceptions in `-fno-exceptions` mode to `__verbose_abort` calls, which removes the dependency in most files.

Reviewed By: ldionne, #libc

Spies: dim, emaste, mikhail.ramalho, smeenai, libcxx-commits

Differential Revision: https://reviews.llvm.org/D146076

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[libc++] Granularize <bit> and remove <__bits>

Reviewed By: Mordante, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D141225

[libc++] Remove MSVC code

It's been one and a half months now and nobody said anything, so I guess this code can be removed.

Reviewed By: ldionne, #libc

Spies: Mordante, libcxx-commits, mgorny, ms

[libc++] Remove MSVC code

It's been one and a half months now and nobody said anything, so I guess this code can be removed.

Reviewed By: ldionne, #libc

Spies: Mordante, libcxx-commits, mgorny, mstorsjo

Differential Revision: https://reviews.llvm.org/D132943

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[NFC][libc++] Moves transitive includes location.

As discussed in D132284 they will be moved to the end.

Reviewed By: #libc, Mordante

Differential Revision: https://reviews.llvm.org/D133212

[libc++] Reduces the number of transitive includes.

This defines a new policy for removal of transitive includes.
The goal of the policy it to make it relatively easy to remove
headers when needed,

[libc++] Reduces the number of transitive includes.

This defines a new policy for removal of transitive includes.
The goal of the policy it to make it relatively easy to remove
headers when needed, but avoid breaking developers using and
vendors shipping libc++.

The method used is to guard transitive includes based on the
C++ language version. For the upcoming C++23 we can remove
headers when we want, but for other language versions we try
to keep it to a minimum.

In this code the transitive include of `<chrono>` is removed
since D128577 introduces a header cycle between `<format>`
and `<chrono>`. This cycle is indirectly required by the
Standard. Our cycle dependency tool basically is a grep based
tool, so it needs some hints to ignore cycles. With the input
of our transitive include tests we can create a better tool.
However that's out of the scope of this patch.

Note the flag `_LIBCPP_REMOVE_TRANSITIVE_INCLUDES` remains
unchanged. So users can still opt-out of transitives includes
entirely.

Reviewed By: #libc, ldionne, philnik

Differential Revision: https://reviews.llvm.org/D132284

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[libc++][NFC] Rename the constexpr macros

This was discussed on Discord with the consensus that we should rename the macros.

Reviewed By: ldionne, Mordante, var-const, avogelsgesang, jloser, #libc

[libc++][NFC] Rename the constexpr macros

This was discussed on Discord with the consensus that we should rename the macros.

Reviewed By: ldionne, Mordante, var-const, avogelsgesang, jloser, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D131498

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[libcxx][AIX][z/OS] Remove headers included via `_IBMCPP__`

D127650 removed support for non-clang-based XL compilers, but left some
of the headers used only by this compiler and included under the
_

[libcxx][AIX][z/OS] Remove headers included via `_IBMCPP__`

D127650 removed support for non-clang-based XL compilers, but left some
of the headers used only by this compiler and included under the
__IBMCPP__ macro. This change cleans this up by deleting these headers.

Reviewed By: hubert.reinterpretcast, fanbo-meng

Differential Revision: https://reviews.llvm.org/D129491

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[libc++] Re-add transitive includes that had been removed since LLVM 14

This commit re-adds transitive includes that had been removed by
4cd04d1687f1, c36870c8e79c, a83f4b9cda57, 1458458b558d, 2e2f3

[libc++] Re-add transitive includes that had been removed since LLVM 14

This commit re-adds transitive includes that had been removed by
4cd04d1687f1, c36870c8e79c, a83f4b9cda57, 1458458b558d, 2e2f3158c604,
and 489637e66dd3. This should cover almost all the includes that had
been removed since LLVM 14 and that would contribute to breaking user
code when releasing LLVM 15.

It is possible to disable the inclusion of these headers by defining
_LIBCPP_REMOVE_TRANSITIVE_INCLUDES. The intent is that vendors will
enable that macro and start fixing downstream issues immediately. We
can then remove the macro (and the transitive includes) by default in
a future release. That way, we will break users only once by removing
transitive includes in bulk instead of doing it bit by bit a every
release, which is more disruptive for users.

Note 1: The set of headers to re-add was found by re-generating the
transitive include test on a checkout of release/14.x, which
provided the list of all transitive includes we used to provide.

Note 2: Several includes of <vector>, <optional>, <array> and <unordered_map>
have been added in this commit. These transitive inclusions were
added when we implemented boyer_moore_searcher in <functional>.

Note 3: This is a best effort patch to try and resolve downstream breakage
caused since branching LLVM 14. I wasn't able to perfectly mirror
transitive includes in LLVM 14 for a few headers, so I added a
release note explaining it. To summarize, adding boyer_moore_searcher
created a bunch of circular dependencies, so we have to break
backwards compatibility in a few cases.

Differential Revision: https://reviews.llvm.org/D128661

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[libc++][NFC] Merges unused functions in callers.

This is a follow up based on a request of @jloser in D127594.

As drive-by qualified the function calls in the <bit> header.

Reviewed By: #libc, Er

[libc++][NFC] Merges unused functions in callers.

This is a follow up based on a request of @jloser in D127594.

As drive-by qualified the function calls in the <bit> header.

Reviewed By: #libc, EricWF

Differential Revision: https://reviews.llvm.org/D127760

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[libc++][NFC] Use concepts in <bit>.

All supported compilers have concepts support so use that in the C++20
functions in <bit>.

s/_LIBCPP_INLINE_VISIBILITY/_LIBCPP_HIDE_FROM_ABI/ as drive-by fix.

[libc++][NFC] Use concepts in <bit>.

All supported compilers have concepts support so use that in the C++20
functions in <bit>.

s/_LIBCPP_INLINE_VISIBILITY/_LIBCPP_HIDE_FROM_ABI/ as drive-by fix.

Reviewed By: #libc, ldionne

Differential Revision: https://reviews.llvm.org/D127594

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[libc++] Ensure that all public C++ headers include <__assert>

This patch changes the requirement for getting the declaration of the
assertion handler from including <__assert> to including any publ

[libc++] Ensure that all public C++ headers include <__assert>

This patch changes the requirement for getting the declaration of the
assertion handler from including <__assert> to including any public
C++ header of the library. Note that C compatibility headers are
excluded because we don't implement all the C headers ourselves --
some of them are taken straight from the C library, like assert.h.

It also adds a generated test to check it. Furthermore, this new
generated test is designed in a way that will make it possible to
replace almost all the existing test-generation scripts with this
system in upcoming patches.

Differential Revision: https://reviews.llvm.org/D122506

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[libc++] [LWG3656] Update the return type of std::bit_width.

Fixes LWG3656, "Inconsistent bit operations returning a count".
https://cplusplus.github.io/LWG/issue3656

The fix has been approved for

[libc++] [LWG3656] Update the return type of std::bit_width.

Fixes LWG3656, "Inconsistent bit operations returning a count".
https://cplusplus.github.io/LWG/issue3656

The fix has been approved for C++23 and left to vendors' discretion
in C++20 (but it sounds like everyone's on the same page that
of course it should be DR'ed back to C++20 too).

Differential Revision: https://reviews.llvm.org/D120444

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[libc++] Move everything related solely to _LIBCPP_ASSERT to its own file

This is the first step towards disentangling the debug mode and assertions
in libc++. This patch doesn't make any functional

[libc++] Move everything related solely to _LIBCPP_ASSERT to its own file

This is the first step towards disentangling the debug mode and assertions
in libc++. This patch doesn't make any functional change: it simply moves
_LIBCPP_ASSERT-related stuff to its own file so as to make it clear that
libc++ assertions and the debug mode are different things. Future patches
will make it possible to enable assertions without enabling the debug
mode.

Differential Revision: https://reviews.llvm.org/D119769

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[libc++] Normalize all our '#pragma GCC system_header', and regression-test.

Now we'll notice if a header forgets to include this magic phrase.

Differential Revision: https://reviews.llvm.org/D1188

[libc++] Normalize all our '#pragma GCC system_header', and regression-test.

Now we'll notice if a header forgets to include this magic phrase.

Differential Revision: https://reviews.llvm.org/D118800

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[libc++] Disable _LIBCPP_DEBUG_ASSERT during constant evaluation

Disable `_LIBCPP_DEBUG_ASSERT` and debug iterators in <string> during constant evaluation

Reviewed By: ldionne, #libc

Spies: goncha

[libc++] Disable _LIBCPP_DEBUG_ASSERT during constant evaluation

Disable `_LIBCPP_DEBUG_ASSERT` and debug iterators in <string> during constant evaluation

Reviewed By: ldionne, #libc

Spies: goncharov, libcxx-commits

Differential Revision: https://reviews.llvm.org/D115788

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[libc++] Implement P1272R4 (std::byteswap)

Implement P1274R4

Reviewed By: Quuxplusone, Mordante, #libc

Spies: jloser, lebedev.ri, mgorny, libcxx-commits, arichardson

Differential Revision: https:

[libc++] Implement P1272R4 (std::byteswap)

Implement P1274R4

Reviewed By: Quuxplusone, Mordante, #libc

Spies: jloser, lebedev.ri, mgorny, libcxx-commits, arichardson

Differential Revision: https://reviews.llvm.org/D114074

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[runtimes][NFC] Remove filenames at the top of the license notice

We've stopped doing it in libc++ for a while now because these names
would end up rotting as we move things around and copy/paste st

[runtimes][NFC] Remove filenames at the top of the license notice

We've stopped doing it in libc++ for a while now because these names
would end up rotting as we move things around and copy/paste stuff.
This cleans up all the existing files so as to stop the spreading
as people copy-paste headers around.

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[libc++] Implement C++20's P0476R2: std::bit_cast

Thanks to Arthur O'Dwyer for fixing up some of the tests.

Differential Revision: https://reviews.llvm.org/D75960

[libc++] Use enable_if_t instead of _EnableIf

I just ran into a compiler error involving __bind_back and some overloads
that were being disabled with _EnableIf. I noticed that the error message
was

[libc++] Use enable_if_t instead of _EnableIf

I just ran into a compiler error involving __bind_back and some overloads
that were being disabled with _EnableIf. I noticed that the error message
was quite bad and did not mention the reason for the overload being
excluded. Specifically, the error looked like this:

candidate template ignored: substitution failure [with _Args =
<ContiguousView>]: no member named '_EnableIfImpl' in 'std::_MetaBase<false>'

Instead, when using enable_if or enable_if_t, the compiler is clever and
can produce better diagnostics, like so:

candidate template ignored: requirement 'is_invocable_v<
std::__bind_back_op<1, std::integer_sequence<unsigned long, 0>>,
std::ranges::views::__transform::__fn &, std::tuple<PlusOne> &,
ContiguousView>' was not satisfied [with _Args = <ContiguousView>]

Basically, it tries to do a poor man's implementation of concepts, which
is already a lot better than simply complaining about substitution failure.

Hence, this commit uses enable_if_t instead of _EnableIf whenever
possible. That is both more straightforward than using the internal
helper, and also leads to better error messages in those cases.

I understand the motivation for _EnableIf's implementation was to improve
compile-time performance, however I believe striving to improve error
messages is even more important for our QOI, hence this patch. Furthermore,
it is unclear that _EnableIf actually improved compile-time performance
in any noticeable way (see discussion in the review for details).

Differential Revision: https://reviews.llvm.org/D108216

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