[libc++] P2747R2: `constexpr` placement new (library part) (#105768)

This patch implements https://wg21.link/P2747R2.

The library changes affect direct `operator new` and `operator new[]`
calls

[libc++] P2747R2: `constexpr` placement new (library part) (#105768)

This patch implements https://wg21.link/P2747R2.

The library changes affect direct `operator new` and `operator new[]`
calls even when the core language changes are absent.

The changes are not available for MS ABI because the `operator new` and
`operator new[]` are from VCRuntime's `<vcruntime_new.h>`. A feature
request was submitted for that [1].

As a drive-by change, the patch reformatted the whole `new.pass.cpp` and
`new_array.pass.cpp` tests.

Closes #105427

[1]: https://developercommunity.visualstudio.com/t/constexpr-for-placement-operator-newope/10730304.

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[libc++] Update status after the St. Louis meeting. (#97951)

This updates:
- The status tables
- Feature test macros
- New headers for modules

[libc++][test] Make the feature-test macro tests more portable (#74185)

Found while running libc++'s test suite with MSVC's STL.

This is a followup to @philnik777's recent #71002 (thank you!) whi

[libc++][test] Make the feature-test macro tests more portable (#74185)

Found while running libc++'s test suite with MSVC's STL.

This is a followup to @philnik777's recent #71002 (thank you!) which
provided the existing examples of `__cpp_lib_barrier` and
`__cpp_lib_polymorphic_allocator`:

https://github.com/llvm/llvm-project/blob/66a3e4fafb6eae19764f8a192ca3a116c0554211/libcxx/utils/generate_feature_test_macro_components.py#L199-L203

https://github.com/llvm/llvm-project/blob/66a3e4fafb6eae19764f8a192ca3a116c0554211/libcxx/utils/generate_feature_test_macro_components.py#L866-L870

Applying that new pattern to the feature-test macros here gets their
corresponding tests passing for us.

:robot: Only `generate_feature_test_macro_components.py` was manually
updated; the other files were regenerated.

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[libc++] Adds C++26 support.

Clang has been updated to support C++26, this adds the same support for
libc++. At the moment C++23 and C++26 are identical. During the next
plenary in June the first C+

[libc++] Adds C++26 support.

Clang has been updated to support C++26, this adds the same support for
libc++. At the moment C++23 and C++26 are identical. During the next
plenary in June the first C++26 papers will be voted on.

Note like Clang this patch uses C++26 is the internal part and C++2c in
the user visible part.

Depends on D150795

Reviewed By: ldionne, #libc

Differential Revision: https://reviews.llvm.org/D151026

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[libc++] Updates C++2b to C++23.

During the ISO C++ Committee meeting plenary session the C++23 Standard
has been voted as technical complete.

This updates the reference to c++2b to c++23 and updat

[libc++] Updates C++2b to C++23.

During the ISO C++ Committee meeting plenary session the C++23 Standard
has been voted as technical complete.

This updates the reference to c++2b to c++23 and updates the __cplusplus
macro.

Note since we use clang-tidy 16 a small work-around is needed. Clang
knows -std=c++23 but clang-tidy not so for now force the lit compiler
flag to use -std=c++2b instead of -std=c++23.

Reviewed By: #libc, philnik, jloser, ldionne

Differential Revision: https://reviews.llvm.org/D150795

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[libc++] Improves feature-test macro diagnostics.

This was mentioned in review D131326.

Reviewed By: var-const, #libc, philnik

Differential Revision: https://reviews.llvm.org/D132293

[libc++] Implement P0154R1 (Hardware inference size)

`__GCC_CONSTRUCTIVE_SIZE` and `__GCC_DESTRUCTIVE_SIZE` are available since GCC 12. I'm assuming clang will also implement these for compatability

[libc++] Implement P0154R1 (Hardware inference size)

`__GCC_CONSTRUCTIVE_SIZE` and `__GCC_DESTRUCTIVE_SIZE` are available since GCC 12. I'm assuming clang will also implement these for compatability with libstdc++.

Reviewed By: ldionne, #libc

Spies: h-vetinari, libcxx-commits, arichardson

Differential Revision: https://reviews.llvm.org/D122276

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[libc++] Make .version.pass.cpp tests be compile-only tests

We don't really need to run them.