mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-22 08:49:45 +00:00
![Miguel Ojeda](/assets/img/avatar_default.png)
This is the first upgrade to the Rust toolchain since the initial Rust
merge, from 1.62.0 to 1.68.2 (i.e. the latest).
# Context
The kernel currently supports only a single Rust version [1] (rather
than a minimum) given our usage of some "unstable" Rust features [2]
which do not promise backwards compatibility.
The goal is to reach a point where we can declare a minimum version for
the toolchain. For instance, by waiting for some of the features to be
stabilized. Therefore, the first minimum Rust version that the kernel
will support is "in the future".
# Upgrade policy
Given we will eventually need to reach that minimum version, it would be
ideal to upgrade the compiler from time to time to be as close as
possible to that goal and find any issues sooner. In the extreme, we
could upgrade as soon as a new Rust release is out. Of course, upgrading
so often is in stark contrast to what one normally would need for GCC
and LLVM, especially given the release schedule: 6 weeks for Rust vs.
half a year for LLVM and a year for GCC.
Having said that, there is no particular advantage to updating slowly
either: kernel developers in "stable" distributions are unlikely to be
able to use their distribution-provided Rust toolchain for the kernel
anyway [3]. Instead, by routinely upgrading to the latest instead,
kernel developers using Linux distributions that track the latest Rust
release may be able to use those rather than Rust-provided ones,
especially if their package manager allows to pin / hold back /
downgrade the version for some days during windows where the version may
not match. For instance, Arch, Fedora, Gentoo and openSUSE all provide
and track the latest version of Rust as they get released every 6 weeks.
Then, when the minimum version is reached, we will stop upgrading and
decide how wide the window of support will be. For instance, a year of
Rust versions. We will probably want to start small, and then widen it
over time, just like the kernel did originally for LLVM, see commit
3519c4d6e0
("Documentation: add minimum clang/llvm version").
# Unstable features stabilized
This upgrade allows us to remove the following unstable features since
they were stabilized:
- `feature(explicit_generic_args_with_impl_trait)` (1.63).
- `feature(core_ffi_c)` (1.64).
- `feature(generic_associated_types)` (1.65).
- `feature(const_ptr_offset_from)` (1.65, *).
- `feature(bench_black_box)` (1.66, *).
- `feature(pin_macro)` (1.68).
The ones marked with `*` apply only to our old `rust` branch, not
mainline yet, i.e. only for code that we may potentially upstream.
With this patch applied, the only unstable feature allowed to be used
outside the `kernel` crate is `new_uninit`, though other code to be
upstreamed may increase the list.
Please see [2] for details.
# Other required changes
Since 1.63, `rustdoc` triggers the `broken_intra_doc_links` lint for
links pointing to exported (`#[macro_export]`) `macro_rules`. An issue
was opened upstream [4], but it turns out it is intended behavior. For
the moment, just add an explicit reference for each link. Later we can
revisit this if `rustdoc` removes the compatibility measure.
Nevertheless, this was helpful to discover a link that was pointing to
the wrong place unintentionally. Since that one was actually wrong, it
is fixed in a previous commit independently.
Another change was the addition of `cfg(no_rc)` and `cfg(no_sync)` in
upstream [5], thus remove our original changes for that.
Similarly, upstream now tests that it compiles successfully with
`#[cfg(not(no_global_oom_handling))]` [6], which allow us to get rid
of some changes, such as an `#[allow(dead_code)]`.
In addition, remove another `#[allow(dead_code)]` due to new uses
within the standard library.
Finally, add `try_extend_trusted` and move the code in `spec_extend.rs`
since upstream moved it for the infallible version.
# `alloc` upgrade and reviewing
There are a large amount of changes, but the vast majority of them are
due to our `alloc` fork being upgraded at once.
There are two kinds of changes to be aware of: the ones coming from
upstream, which we should follow as closely as possible, and the updates
needed in our added fallible APIs to keep them matching the newer
infallible APIs coming from upstream.
Instead of taking a look at the diff of this patch, an alternative
approach is reviewing a diff of the changes between upstream `alloc` and
the kernel's. This allows to easily inspect the kernel additions only,
especially to check if the fallible methods we already have still match
the infallible ones in the new version coming from upstream.
Another approach is reviewing the changes introduced in the additions in
the kernel fork between the two versions. This is useful to spot
potentially unintended changes to our additions.
To apply these approaches, one may follow steps similar to the following
to generate a pair of patches that show the differences between upstream
Rust and the kernel (for the subset of `alloc` we use) before and after
applying this patch:
# Get the difference with respect to the old version.
git -C rust checkout $(linux/scripts/min-tool-version.sh rustc)
git -C linux ls-tree -r --name-only HEAD -- rust/alloc |
cut -d/ -f3- |
grep -Fv README.md |
xargs -IPATH cp rust/library/alloc/src/PATH linux/rust/alloc/PATH
git -C linux diff --patch-with-stat --summary -R > old.patch
git -C linux restore rust/alloc
# Apply this patch.
git -C linux am rust-upgrade.patch
# Get the difference with respect to the new version.
git -C rust checkout $(linux/scripts/min-tool-version.sh rustc)
git -C linux ls-tree -r --name-only HEAD -- rust/alloc |
cut -d/ -f3- |
grep -Fv README.md |
xargs -IPATH cp rust/library/alloc/src/PATH linux/rust/alloc/PATH
git -C linux diff --patch-with-stat --summary -R > new.patch
git -C linux restore rust/alloc
Now one may check the `new.patch` to take a look at the additions (first
approach) or at the difference between those two patches (second
approach). For the latter, a side-by-side tool is recommended.
Link: https://rust-for-linux.com/rust-version-policy [1]
Link: https://github.com/Rust-for-Linux/linux/issues/2 [2]
Link: https://lore.kernel.org/rust-for-linux/CANiq72mT3bVDKdHgaea-6WiZazd8Mvurqmqegbe5JZxVyLR8Yg@mail.gmail.com/ [3]
Link: https://github.com/rust-lang/rust/issues/106142 [4]
Link: https://github.com/rust-lang/rust/pull/89891 [5]
Link: https://github.com/rust-lang/rust/pull/98652 [6]
Reviewed-by: Björn Roy Baron <bjorn3_gh@protonmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-By: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Tested-by: Ariel Miculas <amiculas@cisco.com>
Tested-by: David Gow <davidgow@google.com>
Tested-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20230418214347.324156-4-ojeda@kernel.org
[ Removed `feature(core_ffi_c)` from `uapi` ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
284 lines
9.3 KiB
Rust
284 lines
9.3 KiB
Rust
// SPDX-License-Identifier: Apache-2.0 OR MIT
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//! # The Rust core allocation and collections library
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//!
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//! This library provides smart pointers and collections for managing
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//! heap-allocated values.
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//!
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//! This library, like core, normally doesn’t need to be used directly
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//! since its contents are re-exported in the [`std` crate](../std/index.html).
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//! Crates that use the `#![no_std]` attribute however will typically
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//! not depend on `std`, so they’d use this crate instead.
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//!
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//! ## Boxed values
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//!
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//! The [`Box`] type is a smart pointer type. There can only be one owner of a
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//! [`Box`], and the owner can decide to mutate the contents, which live on the
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//! heap.
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//!
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//! This type can be sent among threads efficiently as the size of a `Box` value
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//! is the same as that of a pointer. Tree-like data structures are often built
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//! with boxes because each node often has only one owner, the parent.
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//!
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//! ## Reference counted pointers
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//!
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//! The [`Rc`] type is a non-threadsafe reference-counted pointer type intended
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//! for sharing memory within a thread. An [`Rc`] pointer wraps a type, `T`, and
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//! only allows access to `&T`, a shared reference.
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//!
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//! This type is useful when inherited mutability (such as using [`Box`]) is too
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//! constraining for an application, and is often paired with the [`Cell`] or
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//! [`RefCell`] types in order to allow mutation.
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//!
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//! ## Atomically reference counted pointers
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//!
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//! The [`Arc`] type is the threadsafe equivalent of the [`Rc`] type. It
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//! provides all the same functionality of [`Rc`], except it requires that the
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//! contained type `T` is shareable. Additionally, [`Arc<T>`][`Arc`] is itself
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//! sendable while [`Rc<T>`][`Rc`] is not.
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//!
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//! This type allows for shared access to the contained data, and is often
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//! paired with synchronization primitives such as mutexes to allow mutation of
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//! shared resources.
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//!
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//! ## Collections
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//!
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//! Implementations of the most common general purpose data structures are
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//! defined in this library. They are re-exported through the
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//! [standard collections library](../std/collections/index.html).
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//!
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//! ## Heap interfaces
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//!
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//! The [`alloc`](alloc/index.html) module defines the low-level interface to the
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//! default global allocator. It is not compatible with the libc allocator API.
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//!
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//! [`Arc`]: sync
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//! [`Box`]: boxed
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//! [`Cell`]: core::cell
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//! [`Rc`]: rc
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//! [`RefCell`]: core::cell
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#![allow(unused_attributes)]
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#![stable(feature = "alloc", since = "1.36.0")]
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#![doc(
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html_playground_url = "https://play.rust-lang.org/",
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issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
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test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))
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)]
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#![doc(cfg_hide(
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not(test),
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not(any(test, bootstrap)),
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any(not(feature = "miri-test-libstd"), test, doctest),
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no_global_oom_handling,
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not(no_global_oom_handling),
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not(no_rc),
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not(no_sync),
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target_has_atomic = "ptr"
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))]
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#![no_std]
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#![needs_allocator]
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// To run alloc tests without x.py without ending up with two copies of alloc, Miri needs to be
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// able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
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// rustc itself never sets the feature, so this line has no affect there.
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#![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
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//
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// Lints:
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#![deny(unsafe_op_in_unsafe_fn)]
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#![deny(fuzzy_provenance_casts)]
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#![warn(deprecated_in_future)]
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#![warn(missing_debug_implementations)]
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#![warn(missing_docs)]
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#![allow(explicit_outlives_requirements)]
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//
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// Library features:
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#![feature(alloc_layout_extra)]
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#![feature(allocator_api)]
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#![feature(array_chunks)]
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#![feature(array_into_iter_constructors)]
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#![feature(array_methods)]
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#![feature(array_windows)]
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#![feature(assert_matches)]
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#![feature(async_iterator)]
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#![feature(coerce_unsized)]
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#![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
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#![feature(const_box)]
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#![cfg_attr(not(no_global_oom_handling), feature(const_btree_len))]
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#![cfg_attr(not(no_borrow), feature(const_cow_is_borrowed))]
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#![feature(const_convert)]
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#![feature(const_size_of_val)]
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#![feature(const_align_of_val)]
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#![feature(const_ptr_read)]
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#![feature(const_maybe_uninit_zeroed)]
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#![feature(const_maybe_uninit_write)]
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#![feature(const_maybe_uninit_as_mut_ptr)]
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#![feature(const_refs_to_cell)]
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#![feature(core_intrinsics)]
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#![feature(core_panic)]
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#![feature(const_eval_select)]
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#![feature(const_pin)]
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#![feature(const_waker)]
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#![feature(cstr_from_bytes_until_nul)]
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#![feature(dispatch_from_dyn)]
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#![feature(error_generic_member_access)]
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#![feature(error_in_core)]
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#![feature(exact_size_is_empty)]
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#![feature(extend_one)]
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#![feature(fmt_internals)]
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#![feature(fn_traits)]
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#![feature(hasher_prefixfree_extras)]
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#![feature(inline_const)]
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#![feature(inplace_iteration)]
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#![cfg_attr(test, feature(is_sorted))]
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#![feature(iter_advance_by)]
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#![feature(iter_next_chunk)]
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#![feature(iter_repeat_n)]
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#![feature(layout_for_ptr)]
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#![feature(maybe_uninit_slice)]
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#![feature(maybe_uninit_uninit_array)]
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#![feature(maybe_uninit_uninit_array_transpose)]
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#![cfg_attr(test, feature(new_uninit))]
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#![feature(nonnull_slice_from_raw_parts)]
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#![feature(pattern)]
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#![feature(pointer_byte_offsets)]
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#![feature(provide_any)]
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#![feature(ptr_internals)]
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#![feature(ptr_metadata)]
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#![feature(ptr_sub_ptr)]
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#![feature(receiver_trait)]
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#![feature(saturating_int_impl)]
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#![feature(set_ptr_value)]
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#![feature(sized_type_properties)]
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#![feature(slice_from_ptr_range)]
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#![feature(slice_group_by)]
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#![feature(slice_ptr_get)]
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#![feature(slice_ptr_len)]
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#![feature(slice_range)]
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#![feature(str_internals)]
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#![feature(strict_provenance)]
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#![feature(trusted_len)]
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#![feature(trusted_random_access)]
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#![feature(try_trait_v2)]
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#![feature(tuple_trait)]
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#![feature(unchecked_math)]
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#![feature(unicode_internals)]
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#![feature(unsize)]
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#![feature(utf8_chunks)]
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#![feature(std_internals)]
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//
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// Language features:
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#![feature(allocator_internals)]
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#![feature(allow_internal_unstable)]
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#![feature(associated_type_bounds)]
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#![feature(cfg_sanitize)]
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#![feature(const_deref)]
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#![feature(const_mut_refs)]
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#![feature(const_ptr_write)]
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#![feature(const_precise_live_drops)]
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#![feature(const_trait_impl)]
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#![feature(const_try)]
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#![feature(dropck_eyepatch)]
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#![feature(exclusive_range_pattern)]
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#![feature(fundamental)]
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#![cfg_attr(not(test), feature(generator_trait))]
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#![feature(hashmap_internals)]
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#![feature(lang_items)]
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#![feature(min_specialization)]
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#![feature(negative_impls)]
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#![feature(never_type)]
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#![feature(rustc_allow_const_fn_unstable)]
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#![feature(rustc_attrs)]
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#![feature(pointer_is_aligned)]
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#![feature(slice_internals)]
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#![feature(staged_api)]
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#![feature(stmt_expr_attributes)]
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#![cfg_attr(test, feature(test))]
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#![feature(unboxed_closures)]
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#![feature(unsized_fn_params)]
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#![feature(c_unwind)]
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#![feature(with_negative_coherence)]
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#![cfg_attr(test, feature(panic_update_hook))]
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//
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// Rustdoc features:
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#![feature(doc_cfg)]
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#![feature(doc_cfg_hide)]
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// Technically, this is a bug in rustdoc: rustdoc sees the documentation on `#[lang = slice_alloc]`
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// blocks is for `&[T]`, which also has documentation using this feature in `core`, and gets mad
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// that the feature-gate isn't enabled. Ideally, it wouldn't check for the feature gate for docs
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// from other crates, but since this can only appear for lang items, it doesn't seem worth fixing.
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#![feature(intra_doc_pointers)]
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// Allow testing this library
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#[cfg(test)]
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#[macro_use]
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extern crate std;
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#[cfg(test)]
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extern crate test;
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#[cfg(test)]
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mod testing;
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// Module with internal macros used by other modules (needs to be included before other modules).
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#[cfg(not(no_macros))]
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#[macro_use]
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mod macros;
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mod raw_vec;
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// Heaps provided for low-level allocation strategies
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pub mod alloc;
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// Primitive types using the heaps above
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// Need to conditionally define the mod from `boxed.rs` to avoid
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// duplicating the lang-items when building in test cfg; but also need
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// to allow code to have `use boxed::Box;` declarations.
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#[cfg(not(test))]
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pub mod boxed;
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#[cfg(test)]
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mod boxed {
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pub use std::boxed::Box;
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}
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#[cfg(not(no_borrow))]
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pub mod borrow;
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pub mod collections;
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#[cfg(all(not(no_rc), not(no_sync), not(no_global_oom_handling)))]
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pub mod ffi;
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#[cfg(not(no_fmt))]
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pub mod fmt;
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#[cfg(not(no_rc))]
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pub mod rc;
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pub mod slice;
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#[cfg(not(no_str))]
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pub mod str;
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#[cfg(not(no_string))]
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pub mod string;
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#[cfg(all(not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
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pub mod sync;
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#[cfg(all(not(no_global_oom_handling), not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
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pub mod task;
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#[cfg(test)]
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mod tests;
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pub mod vec;
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#[doc(hidden)]
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#[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")]
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pub mod __export {
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pub use core::format_args;
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}
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#[cfg(test)]
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#[allow(dead_code)] // Not used in all configurations
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pub(crate) mod test_helpers {
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/// Copied from `std::test_helpers::test_rng`, since these tests rely on the
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/// seed not being the same for every RNG invocation too.
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pub(crate) fn test_rng() -> rand_xorshift::XorShiftRng {
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use std::hash::{BuildHasher, Hash, Hasher};
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let mut hasher = std::collections::hash_map::RandomState::new().build_hasher();
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std::panic::Location::caller().hash(&mut hasher);
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let hc64 = hasher.finish();
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let seed_vec =
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hc64.to_le_bytes().into_iter().chain(0u8..8).collect::<crate::vec::Vec<u8>>();
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let seed: [u8; 16] = seed_vec.as_slice().try_into().unwrap();
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rand::SeedableRng::from_seed(seed)
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}
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}
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