[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++] Mark standard-mandated includes as such

Reviewed By: ldionne, Mordante, #libc, saugustine

Spies: saugustine, MaskRay, arichardson, mstorsjo, jloser, libcxx-commits, arphaman

Differential

[libc++] Mark standard-mandated includes as such

Reviewed By: ldionne, Mordante, #libc, saugustine

Spies: saugustine, MaskRay, arichardson, mstorsjo, jloser, libcxx-commits, arphaman

Differential Revision: https://reviews.llvm.org/D127953

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[libc++] Granularize even more of type_traits

Reviewed By: ldionne, #libc

Spies: libcxx-commits, mgorny

Differential Revision: https://reviews.llvm.org/D126593

[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++] Implement P0627R6 (Function to mark unreachable code)

Reviewed By: ldionne, Quuxplusone, #libc

Spies: arichardson, mstorsjo, libcxx-commits, mgorny

Differential Revision: https://reviews.

[libc++] Implement P0627R6 (Function to mark unreachable code)

Reviewed By: ldionne, Quuxplusone, #libc

Spies: arichardson, mstorsjo, libcxx-commits, mgorny

Differential Revision: https://reviews.llvm.org/D119152

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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++][P2321R2] Add specializations of basic_common_reference and common_type for pair

Add specializations of basic_common_reference and common_type for pair

Reviewed By: Quuxplusone, Mordante, #

[libc++][P2321R2] Add specializations of basic_common_reference and common_type for pair

Add specializations of basic_common_reference and common_type for pair

Reviewed By: Quuxplusone, Mordante, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D117506

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[libc++] [ranges] Introduce _LIBCPP_AUTO_CAST(x) for auto(x).

Clang is gaining `auto(x)` support in D113393; sadly there
seems to be no feature-test macro for it. Zhihao is opening
a core issue for

[libc++] [ranges] Introduce _LIBCPP_AUTO_CAST(x) for auto(x).

Clang is gaining `auto(x)` support in D113393; sadly there
seems to be no feature-test macro for it. Zhihao is opening
a core issue for that macro.

Use `_LIBCPP_AUTO_CAST` where C++20 specifies we should use `auto(x)`;
stop using `__decay_copy(x)` in those places.
In fact, remove `__decay_copy` entirely. As of C++20, it's purely
a paper specification tool signifying "Return just `x`, but it was
perfect-forwarded, so we understand you're going to have to call
its move-constructor sometimes." I believe there's no reason we'd
ever need to do its operation explicitly in code.

This heisenbugs away a test failure on MinGW; see D112214.

Differential Revision: https://reviews.llvm.org/D115686

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[libc++] Add a helper class to write code with the strong exception guarantee

__transaction is a helper class that allows rolling back code in case an
exception is thrown. The main goal is to reduce

[libc++] Add a helper class to write code with the strong exception guarantee

__transaction is a helper class that allows rolling back code in case an
exception is thrown. The main goal is to reduce the clutter when code
needs to be guarded with `#if _LIBCPP_NO_EXCEPTIONS`.

Differential Revision: https://reviews.llvm.org/D115730

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[libc++] Add missing `#pragma GCC system_header` in a few headers. NFCI.

[libc++] [P1614] Implement [cmp.alg]'s std::{strong,weak,partial}_order.

This does not include `std::compare_*_fallback`; those are coming later.

There's still an open question of how to implement

[libc++] [P1614] Implement [cmp.alg]'s std::{strong,weak,partial}_order.

This does not include `std::compare_*_fallback`; those are coming later.

There's still an open question of how to implement std::strong_order
for `long double`, which has 80 value bits and 48 padding bits on x86-64,
and which is presumably *not* IEEE 754-compliant on PPC64 and so on.
So that part is left unimplemented.

Differential Revision: https://reviews.llvm.org/D110738

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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++] P0433R2: add the remaining deduction guides.

Add deduction guides to `valarray` and `scoped_allocator_adaptor`. This largely
finishes implementation of the paper:

* deduction guides for ot

[libc++] P0433R2: add the remaining deduction guides.

Add deduction guides to `valarray` and `scoped_allocator_adaptor`. This largely
finishes implementation of the paper:

* deduction guides for other classes mentioned in the paper were
implemented previously (see the list below);
* deduction guides for several classes contained in the proposal
(`reference_wrapper`, `lock_guard`, `scoped_lock`, `unique_lock`,
`shared_lock`) were removed by [LWG2981](https://wg21.link/LWG2981).

Also add deduction guides to the synopsis for the few classes (e.g. `pair`)
where they were missing.

The only part of the paper that isn't fully implemented after this patch is
making sure certain deduction guides don't participate in overload resolution
when given incorrect template parameters.

List of significant commits implementing the other parts of P0433 (omitting some
minor fixes):

* [pair](https://github.com/llvm/llvm-project/commit/af65856eec160d163c764faad250d93357be7c83)
* [basic_string](https://github.com/llvm/llvm-project/commit/6d9f750dec29e8ae5366092e64cd343dae2c7464)
* [array](https://github.com/llvm/llvm-project/commit/0ca8c0895c6034615593c295dd955f29b25bf3d4)
* [deque](https://github.com/llvm/llvm-project/commit/dbb6f8a8179b0604e25707b5c1b72be6164f62d9)
* [forward_list](https://github.com/llvm/llvm-project/commit/e076700b7786959206acef136ecf05d54078e4e1)
* [list](https://github.com/llvm/llvm-project/commit/4a227e582b2f13880ea049b29988a37a0f7c0742)
* [vector](https://github.com/llvm/llvm-project/commit/df8f75479278d5ce16eede342ceb5ba2fd71460b)
* [queue/stack/priority_queue](https://github.com/llvm/llvm-project/commit/5b8b8b5dce587f1e5a4a31cc24f09b18bd53ff9a)
* [basic_regex](https://github.com/llvm/llvm-project/commit/edd5e29cfe9f67ec8e7e0eda12eb05e616fdeebc)
* [optional](https://github.com/llvm/llvm-project/commit/f35b4bc3954f3b01051fc0848535ff784809e9e2)
* [map/multimap](https://github.com/llvm/llvm-project/commit/edfe8525de1f7278f4754f2bffd47b13ec291a17)
* [set/multiset](https://github.com/llvm/llvm-project/commit/e20865c387e09ea0ebd5add15c762cd5271ff65f)
* [unordered_set/unordered_multiset](https://github.com/llvm/llvm-project/commit/296a80102a9b72c3eda80558fb78a3ed8849b341)
* [unordered_map/unordered_multimap](https://github.com/llvm/llvm-project/commit/dfcd4384cbcac0eeb7e5cbce350f875ba4da79d5)
* [function](https://github.com/llvm/llvm-project/commit/e1eabcdfad89f67ae575b0c86aa4a72d277378b4)
* [tuple](https://github.com/llvm/llvm-project/commit/1308011e1b5c5382281a63dd4191a1784f8d2295)
* [shared_ptr/weak_ptr](https://github.com/llvm/llvm-project/commit/83564056d4b186c9fcf016cdbb388755009f7b5a)

Additional notes:
* It was revision 2 of the paper that was voted into the Standard.
P0433R3 is a separate paper that is not part of the Standard.
* The paper also mandates removing several `make_*_searcher` functions
(e.g. `make_boyer_moore_searcher`) which are currently not implemented
(except in `experimental/`).
* The `__cpp_lib_deduction_guides` feature test macro from the paper was
accidentally omitted from the Standard.

Differential Revision: https://reviews.llvm.org/D112510

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[libc++] P2401: conditional noexcept for std::exchange

Implement P2401 which adds a `noexcept` specification to
`std::exchange`. Treated as a defect fix which is the motivation for
applying this cha

[libc++] P2401: conditional noexcept for std::exchange

Implement P2401 which adds a `noexcept` specification to
`std::exchange`. Treated as a defect fix which is the motivation for
applying this change to all standards mode rather than just C++23 or
later as the paper suggests.

Reviewed By: Quuxplusone, Mordante, #libc

Differential Revision: https://reviews.llvm.org/D111481

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[libc++][spaceship] Implement std::pair::operator<=>

Implements parts of P1614, including synth-three-way and three way comparison for std::pair.

Reviewed By: #libc, Quuxplusone, Mordante

Differen

[libc++][spaceship] Implement std::pair::operator<=>

Implements parts of P1614, including synth-three-way and three way comparison for std::pair.

Reviewed By: #libc, Quuxplusone, Mordante

Differential Revision: https://reviews.llvm.org/D107721

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[libc++] Implement P1951, default arguments for pair's forwarding constructor

Differential Revision: https://reviews.llvm.org/D109066

[libcxx][modularisation] splits `<utility>` into self-contained headers

* moves `std::hash` and `std::unary_function` into `__functional`
* Everything else goes into `__utility/${NAME}.h`

Different

[libcxx][modularisation] splits `<utility>` into self-contained headers

* moves `std::hash` and `std::unary_function` into `__functional`
* Everything else goes into `__utility/${NAME}.h`

Differential Revision: https://reviews.llvm.org/D104002

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[libcxx][modularisation] moves <utility> content out of <type_traits>

Moves:

* `std::move`, `std::forward`, `std::declval`, and `std::swap` into
`__utility/${FUNCTION_NAME}`.
* `std::swap_ranges`

[libcxx][modularisation] moves <utility> content out of <type_traits>

Moves:

* `std::move`, `std::forward`, `std::declval`, and `std::swap` into
`__utility/${FUNCTION_NAME}`.
* `std::swap_ranges` and `std::iter_swap` into
`__algorithm/${FUNCTION_NAME}`

Differential Revision: https://reviews.llvm.org/D103734

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[libcxx][NFC] prepares `<type_traits>` for moving out forward and swap

* `<type_traits>` depends on `std::forward`, so we replaced it with
`static_cast<T&&>`.
* `swap`'s return type is confusing,

[libcxx][NFC] prepares `<type_traits>` for moving out forward and swap

* `<type_traits>` depends on `std::forward`, so we replaced it with
`static_cast<T&&>`.
* `swap`'s return type is confusing, so it's been rearranged to improve
readabilitiy.

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[libc++] [P0619] Add _LIBCPP_ABI_NO_BINDER_BASES and remove binder typedefs in C++20.

Differential Revision: https://reviews.llvm.org/D103753

[libc++] Alphabetize and include-what-you-use. NFCI.

Differential Revision: https://reviews.llvm.org/D102781

[libc++] Adds __utility/to_underlying.h.

During the review of D97115 it was mentioned adding the `<utility>`
header for `__to_underlying` was a bit unfortunate. Nowadays we tend to
implement smaller

[libc++] Adds __utility/to_underlying.h.

During the review of D97115 it was mentioned adding the `<utility>`
header for `__to_underlying` was a bit unfortunate. Nowadays we tend to
implement smaller headers, so a good reason to move `std::to_underlying`
to its own header and adjust `<charconv>` to use the new header.

Differential Revision: https://reviews.llvm.org/D101233

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[libc++] s/_LIBCPP_NO_HAS_CHAR8_T/_LIBCPP_HAS_NO_CHAR8_T/g

This was raised in D94511.

Differential Revision: https://reviews.llvm.org/D100736

[libc++] NFC: Normalize `#endif //` comment indentation

[libc++] [C++20] [P0586] Implement safe integral comparisons

* https://wg21.link/P0586

Reviewed By: #libc, curdeius, Quuxplusone

Differential Revision: https://reviews.llvm.org/D94511