projects/linux·blob v6.5 · refs

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1// SPDX-License-Identifier: Apache-2.0 OR MIT
2
3//! # The Rust core allocation and collections library
4//!
5//! This library provides smart pointers and collections for managing
6//! heap-allocated values.
7//!
8//! This library, like core, normally doesn’t need to be used directly
9//! since its contents are re-exported in the [`std` crate](../std/index.html).
10//! Crates that use the `#![no_std]` attribute however will typically
11//! not depend on `std`, so they’d use this crate instead.
12//!
13//! ## Boxed values
14//!
15//! The [`Box`] type is a smart pointer type. There can only be one owner of a
16//! [`Box`], and the owner can decide to mutate the contents, which live on the
17//! heap.
18//!
19//! This type can be sent among threads efficiently as the size of a `Box` value
20//! is the same as that of a pointer. Tree-like data structures are often built
21//! with boxes because each node often has only one owner, the parent.
22//!
23//! ## Reference counted pointers
24//!
25//! The [`Rc`] type is a non-threadsafe reference-counted pointer type intended
26//! for sharing memory within a thread. An [`Rc`] pointer wraps a type, `T`, and
27//! only allows access to `&T`, a shared reference.
28//!
29//! This type is useful when inherited mutability (such as using [`Box`]) is too
30//! constraining for an application, and is often paired with the [`Cell`] or
31//! [`RefCell`] types in order to allow mutation.
32//!
33//! ## Atomically reference counted pointers
34//!
35//! The [`Arc`] type is the threadsafe equivalent of the [`Rc`] type. It
36//! provides all the same functionality of [`Rc`], except it requires that the
37//! contained type `T` is shareable. Additionally, [`Arc<T>`][`Arc`] is itself
38//! sendable while [`Rc<T>`][`Rc`] is not.
39//!
40//! This type allows for shared access to the contained data, and is often
41//! paired with synchronization primitives such as mutexes to allow mutation of
42//! shared resources.
43//!
44//! ## Collections
45//!
46//! Implementations of the most common general purpose data structures are
47//! defined in this library. They are re-exported through the
48//! [standard collections library](../std/collections/index.html).
49//!
50//! ## Heap interfaces
51//!
52//! The [`alloc`](alloc/index.html) module defines the low-level interface to the
53//! default global allocator. It is not compatible with the libc allocator API.
54//!
55//! [`Arc`]: sync
56//! [`Box`]: boxed
57//! [`Cell`]: core::cell
58//! [`Rc`]: rc
59//! [`RefCell`]: core::cell
60
61#![allow(unused_attributes)]
62#![stable(feature = "alloc", since = "1.36.0")]
63#![doc(
64 html_playground_url = "https://play.rust-lang.org/",
65 issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
66 test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))
67)]
68#![doc(cfg_hide(
69 not(test),
70 not(any(test, bootstrap)),
71 any(not(feature = "miri-test-libstd"), test, doctest),
72 no_global_oom_handling,
73 not(no_global_oom_handling),
74 not(no_rc),
75 not(no_sync),
76 target_has_atomic = "ptr"
77))]
78#![no_std]
79#![needs_allocator]
80// To run alloc tests without x.py without ending up with two copies of alloc, Miri needs to be
81// able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
82// rustc itself never sets the feature, so this line has no affect there.
83#![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
84//
85// Lints:
86#![deny(unsafe_op_in_unsafe_fn)]
87#![deny(fuzzy_provenance_casts)]
88#![warn(deprecated_in_future)]
89#![warn(missing_debug_implementations)]
90#![warn(missing_docs)]
91#![allow(explicit_outlives_requirements)]
92//
93// Library features:
94#![feature(alloc_layout_extra)]
95#![feature(allocator_api)]
96#![feature(array_chunks)]
97#![feature(array_into_iter_constructors)]
98#![feature(array_methods)]
99#![feature(array_windows)]
100#![feature(assert_matches)]
101#![feature(async_iterator)]
102#![feature(coerce_unsized)]
103#![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
104#![feature(const_box)]
105#![cfg_attr(not(no_global_oom_handling), feature(const_btree_len))]
106#![cfg_attr(not(no_borrow), feature(const_cow_is_borrowed))]
107#![feature(const_convert)]
108#![feature(const_size_of_val)]
109#![feature(const_align_of_val)]
110#![feature(const_ptr_read)]
111#![feature(const_maybe_uninit_zeroed)]
112#![feature(const_maybe_uninit_write)]
113#![feature(const_maybe_uninit_as_mut_ptr)]
114#![feature(const_refs_to_cell)]
115#![feature(core_intrinsics)]
116#![feature(core_panic)]
117#![feature(const_eval_select)]
118#![feature(const_pin)]
119#![feature(const_waker)]
120#![feature(cstr_from_bytes_until_nul)]
121#![feature(dispatch_from_dyn)]
122#![feature(error_generic_member_access)]
123#![feature(error_in_core)]
124#![feature(exact_size_is_empty)]
125#![feature(extend_one)]
126#![feature(fmt_internals)]
127#![feature(fn_traits)]
128#![feature(hasher_prefixfree_extras)]
129#![feature(inline_const)]
130#![feature(inplace_iteration)]
131#![cfg_attr(test, feature(is_sorted))]
132#![feature(iter_advance_by)]
133#![feature(iter_next_chunk)]
134#![feature(iter_repeat_n)]
135#![feature(layout_for_ptr)]
136#![feature(maybe_uninit_slice)]
137#![feature(maybe_uninit_uninit_array)]
138#![feature(maybe_uninit_uninit_array_transpose)]
139#![cfg_attr(test, feature(new_uninit))]
140#![feature(nonnull_slice_from_raw_parts)]
141#![feature(pattern)]
142#![feature(pointer_byte_offsets)]
143#![feature(provide_any)]
144#![feature(ptr_internals)]
145#![feature(ptr_metadata)]
146#![feature(ptr_sub_ptr)]
147#![feature(receiver_trait)]
148#![feature(saturating_int_impl)]
149#![feature(set_ptr_value)]
150#![feature(sized_type_properties)]
151#![feature(slice_from_ptr_range)]
152#![feature(slice_group_by)]
153#![feature(slice_ptr_get)]
154#![feature(slice_ptr_len)]
155#![feature(slice_range)]
156#![feature(str_internals)]
157#![feature(strict_provenance)]
158#![feature(trusted_len)]
159#![feature(trusted_random_access)]
160#![feature(try_trait_v2)]
161#![feature(tuple_trait)]
162#![feature(unchecked_math)]
163#![feature(unicode_internals)]
164#![feature(unsize)]
165#![feature(utf8_chunks)]
166#![feature(std_internals)]
167//
168// Language features:
169#![feature(allocator_internals)]
170#![feature(allow_internal_unstable)]
171#![feature(associated_type_bounds)]
172#![feature(cfg_sanitize)]
173#![feature(const_deref)]
174#![feature(const_mut_refs)]
175#![feature(const_ptr_write)]
176#![feature(const_precise_live_drops)]
177#![feature(const_trait_impl)]
178#![feature(const_try)]
179#![feature(dropck_eyepatch)]
180#![feature(exclusive_range_pattern)]
181#![feature(fundamental)]
182#![cfg_attr(not(test), feature(generator_trait))]
183#![feature(hashmap_internals)]
184#![feature(lang_items)]
185#![feature(min_specialization)]
186#![feature(negative_impls)]
187#![feature(never_type)]
188#![feature(rustc_allow_const_fn_unstable)]
189#![feature(rustc_attrs)]
190#![feature(pointer_is_aligned)]
191#![feature(slice_internals)]
192#![feature(staged_api)]
193#![feature(stmt_expr_attributes)]
194#![cfg_attr(test, feature(test))]
195#![feature(unboxed_closures)]
196#![feature(unsized_fn_params)]
197#![feature(c_unwind)]
198#![feature(with_negative_coherence)]
199#![cfg_attr(test, feature(panic_update_hook))]
200//
201// Rustdoc features:
202#![feature(doc_cfg)]
203#![feature(doc_cfg_hide)]
204// Technically, this is a bug in rustdoc: rustdoc sees the documentation on `#[lang = slice_alloc]`
205// blocks is for `&[T]`, which also has documentation using this feature in `core`, and gets mad
206// that the feature-gate isn't enabled. Ideally, it wouldn't check for the feature gate for docs
207// from other crates, but since this can only appear for lang items, it doesn't seem worth fixing.
208#![feature(intra_doc_pointers)]
209
210// Allow testing this library
211#[cfg(test)]
212#[macro_use]
213extern crate std;
214#[cfg(test)]
215extern crate test;
216#[cfg(test)]
217mod testing;
218
219// Module with internal macros used by other modules (needs to be included before other modules).
220#[cfg(not(no_macros))]
221#[macro_use]
222mod macros;
223
224mod raw_vec;
225
226// Heaps provided for low-level allocation strategies
227
228pub mod alloc;
229
230// Primitive types using the heaps above
231
232// Need to conditionally define the mod from `boxed.rs` to avoid
233// duplicating the lang-items when building in test cfg; but also need
234// to allow code to have `use boxed::Box;` declarations.
235#[cfg(not(test))]
236pub mod boxed;
237#[cfg(test)]
238mod boxed {
239 pub use std::boxed::Box;
240}
241#[cfg(not(no_borrow))]
242pub mod borrow;
243pub mod collections;
244#[cfg(all(not(no_rc), not(no_sync), not(no_global_oom_handling)))]
245pub mod ffi;
246#[cfg(not(no_fmt))]
247pub mod fmt;
248#[cfg(not(no_rc))]
249pub mod rc;
250pub mod slice;
251#[cfg(not(no_str))]
252pub mod str;
253#[cfg(not(no_string))]
254pub mod string;
255#[cfg(all(not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
256pub mod sync;
257#[cfg(all(not(no_global_oom_handling), not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
258pub mod task;
259#[cfg(test)]
260mod tests;
261pub mod vec;
262
263#[doc(hidden)]
264#[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")]
265pub mod __export {
266 pub use core::format_args;
267}
268
269#[cfg(test)]
270#[allow(dead_code)] // Not used in all configurations
271pub(crate) mod test_helpers {
272 /// Copied from `std::test_helpers::test_rng`, since these tests rely on the
273 /// seed not being the same for every RNG invocation too.
274 pub(crate) fn test_rng() -> rand_xorshift::XorShiftRng {
275 use std::hash::{BuildHasher, Hash, Hasher};
276 let mut hasher = std::collections::hash_map::RandomState::new().build_hasher();
277 std::panic::Location::caller().hash(&mut hasher);
278 let hc64 = hasher.finish();
279 let seed_vec =
280 hc64.to_le_bytes().into_iter().chain(0u8..8).collect::<crate::vec::Vec<u8>>();
281 let seed: [u8; 16] = seed_vec.as_slice().try_into().unwrap();
282 rand::SeedableRng::from_seed(seed)
283 }
284}