1//! # The Rust core allocation and collections library
2//!
3//! This library provides smart pointers and collections for managing
4//! heap-allocated values.
5//!
6//! This library, like core, normally doesn’t need to be used directly
7//! since its contents are re-exported in the [`std` crate](../std/index.html).
8//! Crates that use the `#![no_std]` attribute however will typically
9//! not depend on `std`, so they’d use this crate instead.
10//!
11//! ## Boxed values
12//!
13//! The [`Box`] type is a smart pointer type. There can only be one owner of a
14//! [`Box`], and the owner can decide to mutate the contents, which live on the
15//! heap.
16//!
17//! This type can be sent among threads efficiently as the size of a `Box` value
18//! is the same as that of a pointer. Tree-like data structures are often built
19//! with boxes because each node often has only one owner, the parent.
20//!
21//! ## Reference counted pointers
22//!
23//! The [`Rc`] type is a non-threadsafe reference-counted pointer type intended
24//! for sharing memory within a thread. An [`Rc`] pointer wraps a type, `T`, and
25//! only allows access to `&T`, a shared reference.
26//!
27//! This type is useful when inherited mutability (such as using [`Box`]) is too
28//! constraining for an application, and is often paired with the [`Cell`] or
29//! [`RefCell`] types in order to allow mutation.
30//!
31//! ## Atomically reference counted pointers
32//!
33//! The [`Arc`] type is the threadsafe equivalent of the [`Rc`] type. It
34//! provides all the same functionality of [`Rc`], except it requires that the
35//! contained type `T` is shareable. Additionally, [`Arc<T>`][`Arc`] is itself
36//! sendable while [`Rc<T>`][`Rc`] is not.
37//!
38//! This type allows for shared access to the contained data, and is often
39//! paired with synchronization primitives such as mutexes to allow mutation of
40//! shared resources.
41//!
42//! ## Collections
43//!
44//! Implementations of the most common general purpose data structures are
45//! defined in this library. They are re-exported through the
46//! [standard collections library](../std/collections/index.html).
47//!
48//! ## Heap interfaces
49//!
50//! The [`alloc`](alloc/index.html) module defines the low-level interface to the
51//! default global allocator. It is not compatible with the libc allocator API.
52//!
53//! [`Arc`]: sync
54//! [`Box`]: boxed
55//! [`Cell`]: core::cell
56//! [`Rc`]: rc
57//! [`RefCell`]: core::cell
58
59#![allow(unused_attributes)]
60#![stable(feature = "alloc", since = "1.36.0")]
61#![doc(
62 html_playground_url = "https://play.rust-lang.org/",
63 issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
64 test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))
65)]
66#![doc(cfg_hide(
67 not(test),
68 not(any(test, bootstrap)),
69 no_global_oom_handling,
70 not(no_global_oom_handling),
71 not(no_rc),
72 not(no_sync),
73 target_has_atomic = "ptr"
74))]
75#![doc(rust_logo)]
76#![feature(rustdoc_internals)]
77#![no_std]
78#![needs_allocator]
79// Lints:
80#![deny(unsafe_op_in_unsafe_fn)]
81#![deny(fuzzy_provenance_casts)]
82#![warn(deprecated_in_future)]
83#![warn(missing_debug_implementations)]
84#![warn(missing_docs)]
85#![allow(explicit_outlives_requirements)]
86#![warn(multiple_supertrait_upcastable)]
87#![allow(internal_features)]
88#![allow(rustdoc::redundant_explicit_links)]
89#![deny(ffi_unwind_calls)]
90//
91// Library features:
92// tidy-alphabetical-start
93#![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
94#![cfg_attr(not(no_global_oom_handling), feature(const_btree_len))]
95#![cfg_attr(test, feature(is_sorted))]
96#![cfg_attr(test, feature(new_uninit))]
97#![feature(alloc_layout_extra)]
98#![feature(allocator_api)]
99#![feature(array_chunks)]
100#![feature(array_into_iter_constructors)]
101#![feature(array_windows)]
102#![feature(ascii_char)]
103#![feature(assert_matches)]
104#![feature(async_fn_traits)]
105#![feature(async_iterator)]
106#![feature(coerce_unsized)]
107#![feature(const_align_of_val)]
108#![feature(const_box)]
109#![feature(const_cow_is_borrowed)]
110#![feature(const_eval_select)]
111#![feature(const_heap)]
112#![feature(const_maybe_uninit_as_mut_ptr)]
113#![feature(const_maybe_uninit_write)]
114#![feature(const_option)]
115#![feature(const_pin)]
116#![feature(const_refs_to_cell)]
117#![feature(const_size_of_val)]
118#![feature(const_waker)]
119#![feature(core_intrinsics)]
120#![feature(deprecated_suggestion)]
121#![feature(deref_pure_trait)]
122#![feature(dispatch_from_dyn)]
123#![feature(error_generic_member_access)]
124#![feature(error_in_core)]
125#![feature(exact_size_is_empty)]
126#![feature(extend_one)]
127#![feature(fmt_internals)]
128#![feature(fn_traits)]
129#![feature(hasher_prefixfree_extras)]
130#![feature(hint_assert_unchecked)]
131#![feature(inplace_iteration)]
132#![feature(iter_advance_by)]
133#![feature(iter_next_chunk)]
134#![feature(iter_repeat_n)]
135#![feature(layout_for_ptr)]
136#![feature(local_waker)]
137#![feature(maybe_uninit_slice)]
138#![feature(maybe_uninit_uninit_array)]
139#![feature(maybe_uninit_uninit_array_transpose)]
140#![feature(non_null_convenience)]
141#![feature(panic_internals)]
142#![feature(pattern)]
143#![feature(ptr_internals)]
144#![feature(ptr_metadata)]
145#![feature(ptr_sub_ptr)]
146#![feature(receiver_trait)]
147#![feature(set_ptr_value)]
148#![feature(sized_type_properties)]
149#![feature(slice_from_ptr_range)]
150#![feature(slice_index_methods)]
151#![feature(slice_ptr_get)]
152#![feature(slice_range)]
153#![feature(std_internals)]
154#![feature(str_internals)]
155#![feature(strict_provenance)]
156#![feature(trusted_fused)]
157#![feature(trusted_len)]
158#![feature(trusted_random_access)]
159#![feature(try_trait_v2)]
160#![feature(try_with_capacity)]
161#![feature(tuple_trait)]
162#![feature(unicode_internals)]
163#![feature(unsize)]
164#![feature(utf8_chunks)]
165#![feature(vec_pop_if)]
166// tidy-alphabetical-end
167//
168// Language features:
169// tidy-alphabetical-start
170#![cfg_attr(bootstrap, feature(associated_type_bounds))]
171#![cfg_attr(bootstrap, feature(inline_const))]
172#![cfg_attr(not(bootstrap), rustc_preserve_ub_checks)]
173#![cfg_attr(not(test), feature(coroutine_trait))]
174#![cfg_attr(test, feature(panic_update_hook))]
175#![cfg_attr(test, feature(test))]
176#![feature(allocator_internals)]
177#![feature(allow_internal_unstable)]
178#![feature(c_unwind)]
179#![feature(cfg_sanitize)]
180#![feature(const_mut_refs)]
181#![feature(const_precise_live_drops)]
182#![feature(const_ptr_write)]
183#![feature(const_trait_impl)]
184#![feature(const_try)]
185#![feature(decl_macro)]
186#![feature(dropck_eyepatch)]
187#![feature(exclusive_range_pattern)]
188#![feature(fundamental)]
189#![feature(hashmap_internals)]
190#![feature(lang_items)]
191#![feature(min_specialization)]
192#![feature(multiple_supertrait_upcastable)]
193#![feature(negative_impls)]
194#![feature(never_type)]
195#![feature(rustc_allow_const_fn_unstable)]
196#![feature(rustc_attrs)]
197#![feature(slice_internals)]
198#![feature(staged_api)]
199#![feature(stmt_expr_attributes)]
200#![feature(unboxed_closures)]
201#![feature(unsized_fn_params)]
202#![feature(with_negative_coherence)]
203// tidy-alphabetical-end
204//
205// Rustdoc features:
206#![feature(doc_cfg)]
207#![feature(doc_cfg_hide)]
208// Technically, this is a bug in rustdoc: rustdoc sees the documentation on `#[lang = slice_alloc]`
209// blocks is for `&[T]`, which also has documentation using this feature in `core`, and gets mad
210// that the feature-gate isn't enabled. Ideally, it wouldn't check for the feature gate for docs
211// from other crates, but since this can only appear for lang items, it doesn't seem worth fixing.
212#![feature(intra_doc_pointers)]
213
214// Allow testing this library
215#[cfg(test)]
216#[macro_use]
217extern crate std;
218#[cfg(test)]
219extern crate test;
220#[cfg(test)]
221mod testing;
222
223// Module with internal macros used by other modules (needs to be included before other modules).
224#[macro_use]
225mod macros;
226
227mod raw_vec;
228
229// Heaps provided for low-level allocation strategies
230
231pub mod alloc;
232
233// Primitive types using the heaps above
234
235// Need to conditionally define the mod from `boxed.rs` to avoid
236// duplicating the lang-items when building in test cfg; but also need
237// to allow code to have `use boxed::Box;` declarations.
238#[cfg(not(test))]
239pub mod boxed;
240#[cfg(test)]
241mod boxed {
242 pub use std::boxed::Box;
243}
244pub mod borrow;
245pub mod collections;
246#[cfg(all(not(no_rc), not(no_sync), not(no_global_oom_handling)))]
247pub mod ffi;
248pub mod fmt;
249#[cfg(not(no_rc))]
250pub mod rc;
251pub mod slice;
252pub mod str;
253pub mod string;
254#[cfg(all(not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
255pub mod sync;
256#[cfg(all(not(no_global_oom_handling), not(no_rc), not(no_sync)))]
257pub mod task;
258#[cfg(test)]
259mod tests;
260pub mod vec;
261
262#[doc(hidden)]
263#[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")]
264pub mod __export {
265 pub use core::format_args;
266}
267
268#[cfg(test)]
269#[allow(dead_code)] // Not used in all configurations
270pub(crate) mod test_helpers {
271 /// Copied from `std::test_helpers::test_rng`, since these tests rely on the
272 /// seed not being the same for every RNG invocation too.
273 pub(crate) fn test_rng() -> rand_xorshift::XorShiftRng {
274 use std::hash::{BuildHasher, Hash, Hasher};
275 let mut hasher = std::hash::RandomState::new().build_hasher();
276 std::panic::Location::caller().hash(&mut hasher);
277 let hc64 = hasher.finish();
278 let seed_vec =
279 hc64.to_le_bytes().into_iter().chain(0u8..8).collect::<crate::vec::Vec<u8>>();
280 let seed: [u8; 16] = seed_vec.as_slice().try_into().unwrap();
281 rand::SeedableRng::from_seed(seed)
282 }
283}
284