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 // To run alloc tests without x.py without ending up with two copies of alloc, Miri needs to be 60 // able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>. 61 // rustc itself never sets the feature, so this line has no affect there. 62 #![cfg(any(not(feature = "miri-test-libstd"), test, doctest))] 63 // 64 #![allow(unused_attributes)] 65 #![stable(feature = "alloc", since = "1.36.0")] 66 #![doc( 67 html_playground_url = "https://play.rust-lang.org/", 68 issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/", 69 test(no_crate_inject, attr(allow(unused_variables), deny(warnings))) 70 )] 71 #![doc(cfg_hide( 72 not(test), 73 not(any(test, bootstrap)), 74 any(not(feature = "miri-test-libstd"), test, doctest), 75 no_global_oom_handling, 76 not(no_global_oom_handling), 77 not(no_rc), 78 not(no_sync), 79 target_has_atomic = "ptr" 80 ))] 81 #![no_std] 82 #![needs_allocator] 83 // Lints: 84 #![deny(unsafe_op_in_unsafe_fn)] 85 #![deny(fuzzy_provenance_casts)] 86 #![warn(deprecated_in_future)] 87 #![warn(missing_debug_implementations)] 88 #![warn(missing_docs)] 89 #![allow(explicit_outlives_requirements)] 90 #![warn(multiple_supertrait_upcastable)] 91 // 92 // Library features: 93 // tidy-alphabetical-start 94 #![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))] 95 #![cfg_attr(not(no_global_oom_handling), feature(const_btree_len))] 96 #![cfg_attr(test, feature(is_sorted))] 97 #![cfg_attr(test, feature(new_uninit))] 98 #![feature(alloc_layout_extra)] 99 #![feature(allocator_api)] 100 #![feature(array_chunks)] 101 #![feature(array_into_iter_constructors)] 102 #![feature(array_methods)] 103 #![feature(array_windows)] 104 #![feature(ascii_char)] 105 #![feature(assert_matches)] 106 #![feature(async_iterator)] 107 #![feature(coerce_unsized)] 108 #![feature(const_align_of_val)] 109 #![feature(const_box)] 110 #![feature(const_cow_is_borrowed)] 111 #![feature(const_eval_select)] 112 #![feature(const_maybe_uninit_as_mut_ptr)] 113 #![feature(const_maybe_uninit_write)] 114 #![feature(const_maybe_uninit_zeroed)] 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(core_panic)] 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 #![feature(iter_advance_by)] 132 #![feature(iter_next_chunk)] 133 #![feature(iter_repeat_n)] 134 #![feature(layout_for_ptr)] 135 #![feature(maybe_uninit_slice)] 136 #![feature(maybe_uninit_uninit_array)] 137 #![feature(maybe_uninit_uninit_array_transpose)] 138 #![feature(pattern)] 139 #![feature(pointer_byte_offsets)] 140 #![feature(provide_any)] 141 #![feature(ptr_internals)] 142 #![feature(ptr_metadata)] 143 #![feature(ptr_sub_ptr)] 144 #![feature(receiver_trait)] 145 #![feature(saturating_int_impl)] 146 #![feature(set_ptr_value)] 147 #![feature(sized_type_properties)] 148 #![feature(slice_from_ptr_range)] 149 #![feature(slice_group_by)] 150 #![feature(slice_ptr_get)] 151 #![feature(slice_ptr_len)] 152 #![feature(slice_range)] 153 #![feature(std_internals)] 154 #![feature(str_internals)] 155 #![feature(strict_provenance)] 156 #![feature(trusted_len)] 157 #![feature(trusted_random_access)] 158 #![feature(try_trait_v2)] 159 #![feature(tuple_trait)] 160 #![feature(unchecked_math)] 161 #![feature(unicode_internals)] 162 #![feature(unsize)] 163 #![feature(utf8_chunks)] 164 // tidy-alphabetical-end 165 // 166 // Language features: 167 // tidy-alphabetical-start 168 #![cfg_attr(not(test), feature(generator_trait))] 169 #![cfg_attr(test, feature(panic_update_hook))] 170 #![cfg_attr(test, feature(test))] 171 #![feature(allocator_internals)] 172 #![feature(allow_internal_unstable)] 173 #![feature(associated_type_bounds)] 174 #![feature(c_unwind)] 175 #![feature(cfg_sanitize)] 176 #![feature(const_mut_refs)] 177 #![feature(const_precise_live_drops)] 178 #![feature(const_ptr_write)] 179 #![feature(const_trait_impl)] 180 #![feature(const_try)] 181 #![feature(dropck_eyepatch)] 182 #![feature(exclusive_range_pattern)] 183 #![feature(fundamental)] 184 #![feature(hashmap_internals)] 185 #![feature(lang_items)] 186 #![feature(min_specialization)] 187 #![feature(multiple_supertrait_upcastable)] 188 #![feature(negative_impls)] 189 #![feature(never_type)] 190 #![feature(pointer_is_aligned)] 191 #![feature(rustc_allow_const_fn_unstable)] 192 #![feature(rustc_attrs)] 193 #![feature(slice_internals)] 194 #![feature(staged_api)] 195 #![feature(stmt_expr_attributes)] 196 #![feature(unboxed_closures)] 197 #![feature(unsized_fn_params)] 198 #![feature(with_negative_coherence)] 199 // tidy-alphabetical-end 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] 213 extern crate std; 214 #[cfg(test)] 215 extern crate test; 216 #[cfg(test)] 217 mod testing; 218 219 // Module with internal macros used by other modules (needs to be included before other modules). 220 #[macro_use] 221 mod macros; 222 223 mod raw_vec; 224 225 // Heaps provided for low-level allocation strategies 226 227 pub mod alloc; 228 229 // Primitive types using the heaps above 230 231 // Need to conditionally define the mod from `boxed.rs` to avoid 232 // duplicating the lang-items when building in test cfg; but also need 233 // to allow code to have `use boxed::Box;` declarations. 234 #[cfg(not(test))] 235 pub mod boxed; 236 #[cfg(test)] 237 mod boxed { 238 pub use std::boxed::Box; 239 } 240 pub mod borrow; 241 pub mod collections; 242 #[cfg(all(not(no_rc), not(no_sync), not(no_global_oom_handling)))] 243 pub mod ffi; 244 pub mod fmt; 245 #[cfg(not(no_rc))] 246 pub mod rc; 247 pub mod slice; 248 pub mod str; 249 pub mod string; 250 #[cfg(all(not(no_rc), not(no_sync), target_has_atomic = "ptr"))] 251 pub mod sync; 252 #[cfg(all(not(no_global_oom_handling), not(no_rc), not(no_sync), target_has_atomic = "ptr"))] 253 pub mod task; 254 #[cfg(test)] 255 mod tests; 256 pub mod vec; 257 258 #[doc(hidden)] 259 #[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")] 260 pub mod __export { 261 pub use core::format_args; 262 } 263 264 #[cfg(test)] 265 #[allow(dead_code)] // Not used in all configurations 266 pub(crate) mod test_helpers { 267 /// Copied from `std::test_helpers::test_rng`, since these tests rely on the 268 /// seed not being the same for every RNG invocation too. test_rng() -> rand_xorshift::XorShiftRng269 pub(crate) fn test_rng() -> rand_xorshift::XorShiftRng { 270 use std::hash::{BuildHasher, Hash, Hasher}; 271 let mut hasher = std::collections::hash_map::RandomState::new().build_hasher(); 272 std::panic::Location::caller().hash(&mut hasher); 273 let hc64 = hasher.finish(); 274 let seed_vec = 275 hc64.to_le_bytes().into_iter().chain(0u8..8).collect::<crate::vec::Vec<u8>>(); 276 let seed: [u8; 16] = seed_vec.as_slice().try_into().unwrap(); 277 rand::SeedableRng::from_seed(seed) 278 } 279 } 280