[libc++] Pass type information down to __libcpp_allocate (#118837)

Currently, places where we call __libcpp_allocate must drop type
information on the ground even when they actually have such infor

[libc++] Pass type information down to __libcpp_allocate (#118837)

Currently, places where we call __libcpp_allocate must drop type
information on the ground even when they actually have such information
available. That is unfortunate since some toolchains and system
allocators are able to provide improved security when they know what
type is being allocated.

This is the purpose of http://wg21.link/p2719, where we introduce a new
variant of `operator new` which takes a type in its interface. A
different but related issue is that `std::allocator` does not honor any
in-class `T::operator new` since it is specified to call the global
`::operator new` instead.

This patch closes the gap to make it trivial for implementations that
provide typed memory allocators to actually benefit from that
information in more contexts, and also makes libc++ forward-compatible
with future proposals that would fix the existing defects in
`std::allocator`. It also makes the internal allocation API higher level
by operating on objects instead of operating on bytes of memory.

Since this is a widely-used function and making this a template could
have an impact on debug info sizes, I tried minimizing the number of
templated layers by removing `__do_deallocate_handle_size`, which was
easy to replace with a macro (and IMO this leads to cleaner code).

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

[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++][modules] Modularize <cstddef> (#107254)

Many headers include `<cstddef>` just for size_t, and pulling in
additional content (e.g. the traits used for std::byte) is unnecessary.
To solve t

[libc++][modules] Modularize <cstddef> (#107254)

Many headers include `<cstddef>` just for size_t, and pulling in
additional content (e.g. the traits used for std::byte) is unnecessary.
To solve this problem, this patch splits up `<cstddef>` into
subcomponents so that headers can include only the parts that they
actually require.

This has the added benefit of making the modules build a lot stricter
with respect to IWYU, and also providing a canonical location where we
define `std::size_t` and friends (which were previously defined in
multiple headers like `<cstddef>` and `<ctime>`).

After this patch, there's still many places in the codebase where we
include `<cstddef>` when `<__cstddef/size_t.h>` would be sufficient.
This patch focuses on removing `<cstddef>` includes from __type_traits
to make these headers non-circular with `<cstddef>`. Additional
refactorings can be tackled separately.

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[libc++] Optimize lexicographical_compare (#65279)

If the comparison operation is equivalent to < and that is a total
order, we know that we can use equality comparison on that type instead
to ext

[libc++] Optimize lexicographical_compare (#65279)

If the comparison operation is equivalent to < and that is a total
order, we know that we can use equality comparison on that type instead
to extract some information. Furthermore, if equality comparison on that
type is trivial, the user can't observe that we're calling it. So
instead of using the user-provided total order, we use std::mismatch,
which uses equality comparison (and is vertorized). Additionally, if the
type is trivially lexicographically comparable, we can go one step
further and use std::memcmp directly instead of calling std::mismatch.

Benchmarks:
```
-------------------------------------------------------------------------------------
Benchmark old new
-------------------------------------------------------------------------------------
bm_lexicographical_compare<unsigned char>/1 1.17 ns 2.34 ns
bm_lexicographical_compare<unsigned char>/2 1.64 ns 2.57 ns
bm_lexicographical_compare<unsigned char>/3 2.23 ns 2.58 ns
bm_lexicographical_compare<unsigned char>/4 2.82 ns 2.57 ns
bm_lexicographical_compare<unsigned char>/5 3.34 ns 2.11 ns
bm_lexicographical_compare<unsigned char>/6 3.94 ns 2.21 ns
bm_lexicographical_compare<unsigned char>/7 4.56 ns 2.11 ns
bm_lexicographical_compare<unsigned char>/8 5.25 ns 2.11 ns
bm_lexicographical_compare<unsigned char>/16 9.88 ns 2.11 ns
bm_lexicographical_compare<unsigned char>/64 38.9 ns 2.36 ns
bm_lexicographical_compare<unsigned char>/512 317 ns 6.54 ns
bm_lexicographical_compare<unsigned char>/4096 2517 ns 41.4 ns
bm_lexicographical_compare<unsigned char>/32768 20052 ns 488 ns
bm_lexicographical_compare<unsigned char>/262144 159579 ns 4409 ns
bm_lexicographical_compare<unsigned char>/1048576 640456 ns 20342 ns
bm_lexicographical_compare<signed char>/1 1.18 ns 2.37 ns
bm_lexicographical_compare<signed char>/2 1.65 ns 2.60 ns
bm_lexicographical_compare<signed char>/3 2.23 ns 2.83 ns
bm_lexicographical_compare<signed char>/4 2.81 ns 3.06 ns
bm_lexicographical_compare<signed char>/5 3.35 ns 3.30 ns
bm_lexicographical_compare<signed char>/6 3.90 ns 3.99 ns
bm_lexicographical_compare<signed char>/7 4.56 ns 3.78 ns
bm_lexicographical_compare<signed char>/8 5.20 ns 4.02 ns
bm_lexicographical_compare<signed char>/16 9.80 ns 6.21 ns
bm_lexicographical_compare<signed char>/64 39.0 ns 3.16 ns
bm_lexicographical_compare<signed char>/512 318 ns 7.58 ns
bm_lexicographical_compare<signed char>/4096 2514 ns 47.4 ns
bm_lexicographical_compare<signed char>/32768 20096 ns 504 ns
bm_lexicographical_compare<signed char>/262144 156617 ns 4146 ns
bm_lexicographical_compare<signed char>/1048576 624265 ns 19810 ns
bm_lexicographical_compare<int>/1 1.15 ns 2.12 ns
bm_lexicographical_compare<int>/2 1.60 ns 2.36 ns
bm_lexicographical_compare<int>/3 2.21 ns 2.59 ns
bm_lexicographical_compare<int>/4 2.74 ns 2.83 ns
bm_lexicographical_compare<int>/5 3.26 ns 3.06 ns
bm_lexicographical_compare<int>/6 3.81 ns 4.53 ns
bm_lexicographical_compare<int>/7 4.41 ns 4.72 ns
bm_lexicographical_compare<int>/8 5.08 ns 2.36 ns
bm_lexicographical_compare<int>/16 9.54 ns 3.08 ns
bm_lexicographical_compare<int>/64 37.8 ns 4.71 ns
bm_lexicographical_compare<int>/512 309 ns 24.6 ns
bm_lexicographical_compare<int>/4096 2422 ns 204 ns
bm_lexicographical_compare<int>/32768 19362 ns 1947 ns
bm_lexicographical_compare<int>/262144 155727 ns 19793 ns
bm_lexicographical_compare<int>/1048576 623614 ns 80180 ns
bm_ranges_lexicographical_compare<unsigned char>/1 1.07 ns 2.35 ns
bm_ranges_lexicographical_compare<unsigned char>/2 1.72 ns 2.13 ns
bm_ranges_lexicographical_compare<unsigned char>/3 2.46 ns 2.12 ns
bm_ranges_lexicographical_compare<unsigned char>/4 3.17 ns 2.12 ns
bm_ranges_lexicographical_compare<unsigned char>/5 3.86 ns 2.12 ns
bm_ranges_lexicographical_compare<unsigned char>/6 4.55 ns 2.12 ns
bm_ranges_lexicographical_compare<unsigned char>/7 5.25 ns 2.12 ns
bm_ranges_lexicographical_compare<unsigned char>/8 5.95 ns 2.13 ns
bm_ranges_lexicographical_compare<unsigned char>/16 11.7 ns 2.13 ns
bm_ranges_lexicographical_compare<unsigned char>/64 45.5 ns 2.36 ns
bm_ranges_lexicographical_compare<unsigned char>/512 366 ns 6.35 ns
bm_ranges_lexicographical_compare<unsigned char>/4096 2886 ns 40.9 ns
bm_ranges_lexicographical_compare<unsigned char>/32768 23054 ns 489 ns
bm_ranges_lexicographical_compare<unsigned char>/262144 185302 ns 4339 ns
bm_ranges_lexicographical_compare<unsigned char>/1048576 741576 ns 19430 ns
bm_ranges_lexicographical_compare<signed char>/1 1.10 ns 2.12 ns
bm_ranges_lexicographical_compare<signed char>/2 1.66 ns 2.35 ns
bm_ranges_lexicographical_compare<signed char>/3 2.23 ns 2.58 ns
bm_ranges_lexicographical_compare<signed char>/4 2.82 ns 2.82 ns
bm_ranges_lexicographical_compare<signed char>/5 3.34 ns 3.06 ns
bm_ranges_lexicographical_compare<signed char>/6 3.92 ns 3.99 ns
bm_ranges_lexicographical_compare<signed char>/7 4.64 ns 4.10 ns
bm_ranges_lexicographical_compare<signed char>/8 5.21 ns 4.61 ns
bm_ranges_lexicographical_compare<signed char>/16 9.79 ns 7.42 ns
bm_ranges_lexicographical_compare<signed char>/64 38.9 ns 2.93 ns
bm_ranges_lexicographical_compare<signed char>/512 317 ns 7.31 ns
bm_ranges_lexicographical_compare<signed char>/4096 2500 ns 47.5 ns
bm_ranges_lexicographical_compare<signed char>/32768 19940 ns 496 ns
bm_ranges_lexicographical_compare<signed char>/262144 159166 ns 4393 ns
bm_ranges_lexicographical_compare<signed char>/1048576 638206 ns 19786 ns
bm_ranges_lexicographical_compare<int>/1 1.10 ns 2.12 ns
bm_ranges_lexicographical_compare<int>/2 1.64 ns 3.04 ns
bm_ranges_lexicographical_compare<int>/3 2.23 ns 2.58 ns
bm_ranges_lexicographical_compare<int>/4 2.81 ns 2.81 ns
bm_ranges_lexicographical_compare<int>/5 3.35 ns 3.05 ns
bm_ranges_lexicographical_compare<int>/6 3.94 ns 4.60 ns
bm_ranges_lexicographical_compare<int>/7 4.60 ns 4.81 ns
bm_ranges_lexicographical_compare<int>/8 5.19 ns 2.35 ns
bm_ranges_lexicographical_compare<int>/16 9.85 ns 2.87 ns
bm_ranges_lexicographical_compare<int>/64 38.9 ns 4.70 ns
bm_ranges_lexicographical_compare<int>/512 318 ns 24.5 ns
bm_ranges_lexicographical_compare<int>/4096 2494 ns 202 ns
bm_ranges_lexicographical_compare<int>/32768 20000 ns 1939 ns
bm_ranges_lexicographical_compare<int>/262144 160433 ns 19730 ns
bm_ranges_lexicographical_compare<int>/1048576 642636 ns 80760 ns
```

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[libc++] Fix failures with GCC 14 (#92663)

Fixes #91831

[libc++][NFC] Refactor __libcpp_datasizeof to be a variable template (#87769)

This decreases memory consumption and compiles times slightly and
removes a bit of boilderplate.

[libc++] Optimize char_traits a bit (#72799)

This implements two kinds of optimizations. Specifically
- `char_traits<char8_t>` uses `char` code paths; these are heavily
optimized and the operati

[libc++] Optimize char_traits a bit (#72799)

This implements two kinds of optimizations. Specifically
- `char_traits<char8_t>` uses `char` code paths; these are heavily
optimized and the operations are equivalent
- `char16_t` and `char32_t` `find` uses `std::find` to forward to
`wmemchr` if they have the same size

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[libc++] Fix std::move algorithm with trivial move-only types

As reported in https://reviews.llvm.org/D151953#4472195, the std::move
algorithm (and various other functions that relied on it) stopped

[libc++] Fix std::move algorithm with trivial move-only types

As reported in https://reviews.llvm.org/D151953#4472195, the std::move
algorithm (and various other functions that relied on it) stopped working
after starting to use `__constexpr_memmove` in its implementation. This
patch fixes the underlying issue in `__constexpr_memmove` and adds tests
for various related algorithms and functions that were not exercising
trivial move-only types.

Differential Revision: https://reviews.llvm.org/D154613

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[libc++] Fix std::copy and std::move for ranges with potentially overlapping tail padding

This fixes thr bug reported in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108846.

Reviewed By: ldionne, #

[libc++] Fix std::copy and std::move for ranges with potentially overlapping tail padding

This fixes thr bug reported in https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108846.

Reviewed By: ldionne, #libc

Spies: mstorsjo, libcxx-commits

Differential Revision: https://reviews.llvm.org/D151953

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[libc++][NFC] Add __element_count and use it in the constexpr C functions

This makes it less ambiguous what the parameter is meant to get.

Reviewed By: #libc, ldionne

Spies: ldionne, libcxx-commit

[libc++][NFC] Add __element_count and use it in the constexpr C functions

This makes it less ambiguous what the parameter is meant to get.

Reviewed By: #libc, ldionne

Spies: ldionne, libcxx-commits

Differential Revision: https://reviews.llvm.org/D152040

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[libc++] Forward to std::{,w}memchr in std::find

Reviewed By: #libc, ldionne

Spies: Mordante, libcxx-commits, ldionne, mikhail.ramalho

Differential Revision: https://reviews.llvm.org/D144394

[libc++] Use the __is_trivially_equality_comparable builtin

Reviewed By: ldionne, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D148553

[libc++][NFC] rename __is_trivially_equality_comparable to __libcpp_is_trivially_equality_comparable

This is required for D147175.

Reviewed By: ldionne, Mordante, #libc

Spies: libcxx-commits

Diff

[libc++][NFC] rename __is_trivially_equality_comparable to __libcpp_is_trivially_equality_comparable

This is required for D147175.

Reviewed By: ldionne, Mordante, #libc

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D147953

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[libc++] Forward to std::memcmp for trivially comparable types in equal

Reviewed By: #libc, ldionne

Spies: ldionne, Mordante, libcxx-commits

Differential Revision: https://reviews.llvm.org/D139554

[libc++] Move constexpr <cstring> functions into their own headers and remove unused <cstring> includes

Reviewed By: ldionne, Mordante, #libc, #libc_abi

Spies: libcxx-commits

Differential Revision

[libc++] Move constexpr <cstring> functions into their own headers and remove unused <cstring> includes

Reviewed By: ldionne, Mordante, #libc, #libc_abi

Spies: libcxx-commits

Differential Revision: https://reviews.llvm.org/D143329

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