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+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+//! # The Rust core allocation and collections library
+//!
+//! This library provides smart pointers and collections for managing
+//! heap-allocated values.
+//!
+//! This library, like core, normally doesn’t need to be used directly
+//! since its contents are re-exported in the [`std` crate](../std/index.html).
+//! Crates that use the `#![no_std]` attribute however will typically
+//! not depend on `std`, so they’d use this crate instead.
+//!
+//! ## Boxed values
+//!
+//! The [`Box`] type is a smart pointer type. There can only be one owner of a
+//! [`Box`], and the owner can decide to mutate the contents, which live on the
+//! heap.
+//!
+//! This type can be sent among threads efficiently as the size of a `Box` value
+//! is the same as that of a pointer. Tree-like data structures are often built
+//! with boxes because each node often has only one owner, the parent.
+//!
+//! ## Reference counted pointers
+//!
+//! The [`Rc`] type is a non-threadsafe reference-counted pointer type intended
+//! for sharing memory within a thread. An [`Rc`] pointer wraps a type, `T`, and
+//! only allows access to `&T`, a shared reference.
+//!
+//! This type is useful when inherited mutability (such as using [`Box`]) is too
+//! constraining for an application, and is often paired with the [`Cell`] or
+//! [`RefCell`] types in order to allow mutation.
+//!
+//! ## Atomically reference counted pointers
+//!
+//! The [`Arc`] type is the threadsafe equivalent of the [`Rc`] type. It
+//! provides all the same functionality of [`Rc`], except it requires that the
+//! contained type `T` is shareable. Additionally, [`Arc<T>`][`Arc`] is itself
+//! sendable while [`Rc<T>`][`Rc`] is not.
+//!
+//! This type allows for shared access to the contained data, and is often
+//! paired with synchronization primitives such as mutexes to allow mutation of
+//! shared resources.
+//!
+//! ## Collections
+//!
+//! Implementations of the most common general purpose data structures are
+//! defined in this library. They are re-exported through the
+//! [standard collections library](../std/collections/index.html).
+//!
+//! ## Heap interfaces
+//!
+//! The [`alloc`](alloc/index.html) module defines the low-level interface to the
+//! default global allocator. It is not compatible with the libc allocator API.
+//!
+//! [`Arc`]: sync
+//! [`Box`]: boxed
+//! [`Cell`]: core::cell
+//! [`Rc`]: rc
+//! [`RefCell`]: core::cell
+
+#![allow(unused_attributes)]
+#![stable(feature = "alloc", since = "1.36.0")]
+#![doc(
+ html_playground_url = "https://play.rust-lang.org/",
+ issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
+ test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))
+)]
+#![doc(cfg_hide(
+ not(test),
+ not(any(test, bootstrap)),
+ any(not(feature = "miri-test-libstd"), test, doctest),
+ no_global_oom_handling,
+ not(no_global_oom_handling),
+ not(no_rc),
+ not(no_sync),
+ target_has_atomic = "ptr"
+))]
+#![no_std]
+#![needs_allocator]
+// To run alloc tests without x.py without ending up with two copies of alloc, Miri needs to be
+// able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
+// rustc itself never sets the feature, so this line has no affect there.
+#![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
+//
+// Lints:
+#![deny(unsafe_op_in_unsafe_fn)]
+#![deny(fuzzy_provenance_casts)]
+#![warn(deprecated_in_future)]
+#![warn(missing_debug_implementations)]
+#![warn(missing_docs)]
+#![allow(explicit_outlives_requirements)]
+#![warn(multiple_supertrait_upcastable)]
+//
+// Library features:
+// tidy-alphabetical-start
+#![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
+#![cfg_attr(not(no_global_oom_handling), feature(const_btree_len))]
+#![cfg_attr(test, feature(is_sorted))]
+#![cfg_attr(test, feature(new_uninit))]
+#![feature(alloc_layout_extra)]
+#![feature(allocator_api)]
+#![feature(array_chunks)]
+#![feature(array_into_iter_constructors)]
+#![feature(array_methods)]
+#![feature(array_windows)]
+#![feature(ascii_char)]
+#![feature(assert_matches)]
+#![feature(async_iterator)]
+#![feature(coerce_unsized)]
+#![feature(const_align_of_val)]
+#![feature(const_box)]
+#![cfg_attr(not(no_borrow), feature(const_cow_is_borrowed))]
+#![feature(const_eval_select)]
+#![feature(const_maybe_uninit_as_mut_ptr)]
+#![feature(const_maybe_uninit_write)]
+#![feature(const_maybe_uninit_zeroed)]
+#![feature(const_pin)]
+#![feature(const_refs_to_cell)]
+#![feature(const_size_of_val)]
+#![feature(const_waker)]
+#![feature(core_intrinsics)]
+#![feature(core_panic)]
+#![feature(dispatch_from_dyn)]
+#![feature(error_generic_member_access)]
+#![feature(error_in_core)]
+#![feature(exact_size_is_empty)]
+#![feature(extend_one)]
+#![feature(fmt_internals)]
+#![feature(fn_traits)]
+#![feature(hasher_prefixfree_extras)]
+#![feature(inline_const)]
+#![feature(inplace_iteration)]
+#![feature(iter_advance_by)]
+#![feature(iter_next_chunk)]
+#![feature(iter_repeat_n)]
+#![feature(layout_for_ptr)]
+#![feature(maybe_uninit_slice)]
+#![feature(maybe_uninit_uninit_array)]
+#![feature(maybe_uninit_uninit_array_transpose)]
+#![feature(pattern)]
+#![feature(pointer_byte_offsets)]
+#![feature(provide_any)]
+#![feature(ptr_internals)]
+#![feature(ptr_metadata)]
+#![feature(ptr_sub_ptr)]
+#![feature(receiver_trait)]
+#![feature(saturating_int_impl)]
+#![feature(set_ptr_value)]
+#![feature(sized_type_properties)]
+#![feature(slice_from_ptr_range)]
+#![feature(slice_group_by)]
+#![feature(slice_ptr_get)]
+#![feature(slice_ptr_len)]
+#![feature(slice_range)]
+#![feature(std_internals)]
+#![feature(str_internals)]
+#![feature(strict_provenance)]
+#![feature(trusted_len)]
+#![feature(trusted_random_access)]
+#![feature(try_trait_v2)]
+#![feature(tuple_trait)]
+#![feature(unchecked_math)]
+#![feature(unicode_internals)]
+#![feature(unsize)]
+#![feature(utf8_chunks)]
+// tidy-alphabetical-end
+//
+// Language features:
+// tidy-alphabetical-start
+#![cfg_attr(not(test), feature(generator_trait))]
+#![cfg_attr(test, feature(panic_update_hook))]
+#![cfg_attr(test, feature(test))]
+#![feature(allocator_internals)]
+#![feature(allow_internal_unstable)]
+#![feature(associated_type_bounds)]
+#![feature(c_unwind)]
+#![feature(cfg_sanitize)]
+#![feature(const_mut_refs)]
+#![feature(const_precise_live_drops)]
+#![feature(const_ptr_write)]
+#![feature(const_trait_impl)]
+#![feature(const_try)]
+#![feature(dropck_eyepatch)]
+#![feature(exclusive_range_pattern)]
+#![feature(fundamental)]
+#![feature(hashmap_internals)]
+#![feature(lang_items)]
+#![feature(min_specialization)]
+#![feature(multiple_supertrait_upcastable)]
+#![feature(negative_impls)]
+#![feature(never_type)]
+#![feature(pointer_is_aligned)]
+#![feature(rustc_allow_const_fn_unstable)]
+#![feature(rustc_attrs)]
+#![feature(slice_internals)]
+#![feature(staged_api)]
+#![feature(stmt_expr_attributes)]
+#![feature(unboxed_closures)]
+#![feature(unsized_fn_params)]
+#![feature(with_negative_coherence)]
+// tidy-alphabetical-end
+//
+// Rustdoc features:
+#![feature(doc_cfg)]
+#![feature(doc_cfg_hide)]
+// Technically, this is a bug in rustdoc: rustdoc sees the documentation on `#[lang = slice_alloc]`
+// blocks is for `&[T]`, which also has documentation using this feature in `core`, and gets mad
+// that the feature-gate isn't enabled. Ideally, it wouldn't check for the feature gate for docs
+// from other crates, but since this can only appear for lang items, it doesn't seem worth fixing.
+#![feature(intra_doc_pointers)]
+
+// Allow testing this library
+#[cfg(test)]
+#[macro_use]
+extern crate std;
+#[cfg(test)]
+extern crate test;
+#[cfg(test)]
+mod testing;
+
+// Module with internal macros used by other modules (needs to be included before other modules).
+#[cfg(not(no_macros))]
+#[macro_use]
+mod macros;
+
+mod raw_vec;
+
+// Heaps provided for low-level allocation strategies
+
+pub mod alloc;
+
+// Primitive types using the heaps above
+
+// Need to conditionally define the mod from `boxed.rs` to avoid
+// duplicating the lang-items when building in test cfg; but also need
+// to allow code to have `use boxed::Box;` declarations.
+#[cfg(not(test))]
+pub mod boxed;
+#[cfg(test)]
+mod boxed {
+ pub use std::boxed::Box;
+}
+#[cfg(not(no_borrow))]
+pub mod borrow;
+pub mod collections;
+#[cfg(all(not(no_rc), not(no_sync), not(no_global_oom_handling)))]
+pub mod ffi;
+#[cfg(not(no_fmt))]
+pub mod fmt;
+#[cfg(not(no_rc))]
+pub mod rc;
+pub mod slice;
+#[cfg(not(no_str))]
+pub mod str;
+#[cfg(not(no_string))]
+pub mod string;
+#[cfg(all(not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
+pub mod sync;
+#[cfg(all(not(no_global_oom_handling), not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
+pub mod task;
+#[cfg(test)]
+mod tests;
+pub mod vec;
+
+#[doc(hidden)]
+#[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")]
+pub mod __export {
+ pub use core::format_args;
+}
+
+#[cfg(test)]
+#[allow(dead_code)] // Not used in all configurations
+pub(crate) mod test_helpers {
+ /// Copied from `std::test_helpers::test_rng`, since these tests rely on the
+ /// seed not being the same for every RNG invocation too.
+ pub(crate) fn test_rng() -> rand_xorshift::XorShiftRng {
+ use std::hash::{BuildHasher, Hash, Hasher};
+ let mut hasher = std::collections::hash_map::RandomState::new().build_hasher();
+ std::panic::Location::caller().hash(&mut hasher);
+ let hc64 = hasher.finish();
+ let seed_vec =
+ hc64.to_le_bytes().into_iter().chain(0u8..8).collect::<crate::vec::Vec<u8>>();
+ let seed: [u8; 16] = seed_vec.as_slice().try_into().unwrap();
+ rand::SeedableRng::from_seed(seed)
+ }
+}