Linux kernel mirror (for testing)
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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#![warn(multiple_supertrait_upcastable)]
93//
94// Library features:
95// tidy-alphabetical-start
96#![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
97#![cfg_attr(not(no_global_oom_handling), feature(const_btree_len))]
98#![cfg_attr(test, feature(is_sorted))]
99#![cfg_attr(test, feature(new_uninit))]
100#![feature(alloc_layout_extra)]
101#![feature(allocator_api)]
102#![feature(array_chunks)]
103#![feature(array_into_iter_constructors)]
104#![feature(array_methods)]
105#![feature(array_windows)]
106#![feature(ascii_char)]
107#![feature(assert_matches)]
108#![feature(async_iterator)]
109#![feature(coerce_unsized)]
110#![feature(const_align_of_val)]
111#![feature(const_box)]
112#![cfg_attr(not(no_borrow), feature(const_cow_is_borrowed))]
113#![feature(const_eval_select)]
114#![feature(const_maybe_uninit_as_mut_ptr)]
115#![feature(const_maybe_uninit_write)]
116#![feature(const_maybe_uninit_zeroed)]
117#![feature(const_pin)]
118#![feature(const_refs_to_cell)]
119#![feature(const_size_of_val)]
120#![feature(const_waker)]
121#![feature(core_intrinsics)]
122#![feature(core_panic)]
123#![feature(dispatch_from_dyn)]
124#![feature(error_generic_member_access)]
125#![feature(error_in_core)]
126#![feature(exact_size_is_empty)]
127#![feature(extend_one)]
128#![feature(fmt_internals)]
129#![feature(fn_traits)]
130#![feature(hasher_prefixfree_extras)]
131#![feature(inline_const)]
132#![feature(inplace_iteration)]
133#![feature(iter_advance_by)]
134#![feature(iter_next_chunk)]
135#![feature(iter_repeat_n)]
136#![feature(layout_for_ptr)]
137#![feature(maybe_uninit_slice)]
138#![feature(maybe_uninit_uninit_array)]
139#![feature(maybe_uninit_uninit_array_transpose)]
140#![feature(pattern)]
141#![feature(pointer_byte_offsets)]
142#![feature(provide_any)]
143#![feature(ptr_internals)]
144#![feature(ptr_metadata)]
145#![feature(ptr_sub_ptr)]
146#![feature(receiver_trait)]
147#![feature(saturating_int_impl)]
148#![feature(set_ptr_value)]
149#![feature(sized_type_properties)]
150#![feature(slice_from_ptr_range)]
151#![feature(slice_group_by)]
152#![feature(slice_ptr_get)]
153#![feature(slice_ptr_len)]
154#![feature(slice_range)]
155#![feature(std_internals)]
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// tidy-alphabetical-end
167//
168// Language features:
169// tidy-alphabetical-start
170#![cfg_attr(not(test), feature(generator_trait))]
171#![cfg_attr(test, feature(panic_update_hook))]
172#![cfg_attr(test, feature(test))]
173#![feature(allocator_internals)]
174#![feature(allow_internal_unstable)]
175#![feature(associated_type_bounds)]
176#![feature(c_unwind)]
177#![feature(cfg_sanitize)]
178#![feature(const_mut_refs)]
179#![feature(const_precise_live_drops)]
180#![feature(const_ptr_write)]
181#![feature(const_trait_impl)]
182#![feature(const_try)]
183#![feature(dropck_eyepatch)]
184#![feature(exclusive_range_pattern)]
185#![feature(fundamental)]
186#![feature(hashmap_internals)]
187#![feature(lang_items)]
188#![feature(min_specialization)]
189#![feature(multiple_supertrait_upcastable)]
190#![feature(negative_impls)]
191#![feature(never_type)]
192#![feature(pointer_is_aligned)]
193#![feature(rustc_allow_const_fn_unstable)]
194#![feature(rustc_attrs)]
195#![feature(slice_internals)]
196#![feature(staged_api)]
197#![feature(stmt_expr_attributes)]
198#![feature(unboxed_closures)]
199#![feature(unsized_fn_params)]
200#![feature(with_negative_coherence)]
201// tidy-alphabetical-end
202//
203// Rustdoc features:
204#![feature(doc_cfg)]
205#![feature(doc_cfg_hide)]
206// Technically, this is a bug in rustdoc: rustdoc sees the documentation on `#[lang = slice_alloc]`
207// blocks is for `&[T]`, which also has documentation using this feature in `core`, and gets mad
208// that the feature-gate isn't enabled. Ideally, it wouldn't check for the feature gate for docs
209// from other crates, but since this can only appear for lang items, it doesn't seem worth fixing.
210#![feature(intra_doc_pointers)]
211
212// Allow testing this library
213#[cfg(test)]
214#[macro_use]
215extern crate std;
216#[cfg(test)]
217extern crate test;
218#[cfg(test)]
219mod testing;
220
221// Module with internal macros used by other modules (needs to be included before other modules).
222#[cfg(not(no_macros))]
223#[macro_use]
224mod macros;
225
226mod raw_vec;
227
228// Heaps provided for low-level allocation strategies
229
230pub mod alloc;
231
232// Primitive types using the heaps above
233
234// Need to conditionally define the mod from `boxed.rs` to avoid
235// duplicating the lang-items when building in test cfg; but also need
236// to allow code to have `use boxed::Box;` declarations.
237#[cfg(not(test))]
238pub mod boxed;
239#[cfg(test)]
240mod boxed {
241 pub use std::boxed::Box;
242}
243#[cfg(not(no_borrow))]
244pub mod borrow;
245pub mod collections;
246#[cfg(all(not(no_rc), not(no_sync), not(no_global_oom_handling)))]
247pub mod ffi;
248#[cfg(not(no_fmt))]
249pub mod fmt;
250#[cfg(not(no_rc))]
251pub mod rc;
252pub mod slice;
253#[cfg(not(no_str))]
254pub mod str;
255#[cfg(not(no_string))]
256pub mod string;
257#[cfg(all(not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
258pub mod sync;
259#[cfg(all(not(no_global_oom_handling), not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
260pub mod task;
261#[cfg(test)]
262mod tests;
263pub mod vec;
264
265#[doc(hidden)]
266#[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")]
267pub mod __export {
268 pub use core::format_args;
269}
270
271#[cfg(test)]
272#[allow(dead_code)] // Not used in all configurations
273pub(crate) mod test_helpers {
274 /// Copied from `std::test_helpers::test_rng`, since these tests rely on the
275 /// seed not being the same for every RNG invocation too.
276 pub(crate) fn test_rng() -> rand_xorshift::XorShiftRng {
277 use std::hash::{BuildHasher, Hash, Hasher};
278 let mut hasher = std::collections::hash_map::RandomState::new().build_hasher();
279 std::panic::Location::caller().hash(&mut hasher);
280 let hc64 = hasher.finish();
281 let seed_vec =
282 hc64.to_le_bytes().into_iter().chain(0u8..8).collect::<crate::vec::Vec<u8>>();
283 let seed: [u8; 16] = seed_vec.as_slice().try_into().unwrap();
284 rand::SeedableRng::from_seed(seed)
285 }
286}