1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

//! # The Rust Standard Library
//!
//! The Rust Standard Library is the foundation of portable Rust software, a
//! set of minimal and battle-tested shared abstractions for the [broader Rust
//! ecosystem][crates.io]. It offers core types, like [`Vec<T>`] and
//! [`Option<T>`], library-defined [operations on language
//! primitives](#primitives), [standard macros](#macros), [I/O] and
//! [multithreading], among [many other things][other].
//!
//! `std` is available to all Rust crates by default, just as if each one
//! contained an `extern crate std;` import at the [crate root]. Therefore the
//! standard library can be accessed in [`use`] statements through the path
//! `std`, as in [`use std::env`], or in expressions through the absolute path
//! `::std`, as in [`::std::env::args`].
//!
//! # How to read this documentation
//!
//! If you already know the name of what you are looking for, the fastest way to
//! find it is to use the <a href="#" onclick="focusSearchBar();">search
//! bar</a> at the top of the page.
//!
//! Otherwise, you may want to jump to one of these useful sections:
//!
//! * [`std::*` modules](#modules)
//! * [Primitive types](#primitives)
//! * [Standard macros](#macros)
//! * [The Rust Prelude](prelude/index.html)
//!
//! If this is your first time, the documentation for the standard library is
//! written to be casually perused. Clicking on interesting things should
//! generally lead you to interesting places. Still, there are important bits
//! you don't want to miss, so read on for a tour of the standard library and
//! its documentation!
//!
//! Once you are familiar with the contents of the standard library you may
//! begin to find the verbosity of the prose distracting. At this stage in your
//! development you may want to press the `[-]` button near the top of the
//! page to collapse it into a more skimmable view.
//!
//! While you are looking at that `[-]` button also notice the `[src]`
//! button. Rust's API documentation comes with the source code and you are
//! encouraged to read it. The standard library source is generally high
//! quality and a peek behind the curtains is often enlightening.
//!
//! # What is in the standard library documentation?
//!
//! First of all, The Rust Standard Library is divided into a number of focused
//! modules, [all listed further down this page](#modules). These modules are
//! the bedrock upon which all of Rust is forged, and they have mighty names
//! like [`std::slice`] and [`std::cmp`]. Modules' documentation typically
//! includes an overview of the module along with examples, and are a smart
//! place to start familiarizing yourself with the library.
//!
//! Second, implicit methods on [primitive types] are documented here. This can
//! be a source of confusion for two reasons:
//!
//! 1. While primitives are implemented by the compiler, the standard library
//!    implements methods directly on the primitive types (and it is the only
//!    library that does so), which are [documented in the section on
//!    primitives](#primitives).
//! 2. The standard library exports many modules *with the same name as
//!    primitive types*. These define additional items related to the primitive
//!    type, but not the all-important methods.
//!
//! So for example there is a [page for the primitive type
//! `i32`](primitive.i32.html) that lists all the methods that can be called on
//! 32-bit integers (very useful), and there is a [page for the module
//! `std::i32`](i32/index.html) that documents the constant values [`MIN`] and
//! [`MAX`](i32/constant.MAX.html) (rarely useful).
//!
//! Note the documentation for the primitives [`str`] and [`[T]`][slice] (also
//! called 'slice'). Many method calls on [`String`] and [`Vec<T>`] are actually
//! calls to methods on [`str`] and [`[T]`][slice] respectively, via [deref
//! coercions][deref-coercions].
//!
//! Third, the standard library defines [The Rust Prelude], a small collection
//! of items - mostly traits - that are imported into every module of every
//! crate. The traits in the prelude are pervasive, making the prelude
//! documentation a good entry point to learning about the library.
//!
//! And finally, the standard library exports a number of standard macros, and
//! [lists them on this page](#macros) (technically, not all of the standard
//! macros are defined by the standard library - some are defined by the
//! compiler - but they are documented here the same). Like the prelude, the
//! standard macros are imported by default into all crates.
//!
//! # Contributing changes to the documentation
//!
//! Check out the rust contribution guidelines [here](
//! https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md).
//! The source for this documentation can be found on [Github](https://github.com/rust-lang).
//! To contribute changes, make sure you read the guidelines first, then submit
//! pull-requests for your suggested changes.
//!
//! Contributions are appreciated! If you see a part of the docs that can be
//! improved, submit a PR, or chat with us first on irc.mozilla.org #rust-docs.
//!
//! # A Tour of The Rust Standard Library
//!
//! The rest of this crate documentation is dedicated to pointing out notable
//! features of The Rust Standard Library.
//!
//! ## Containers and collections
//!
//! The [`option`] and [`result`] modules define optional and error-handling
//! types, [`Option<T>`] and [`Result<T, E>`]. The [`iter`] module defines
//! Rust's iterator trait, [`Iterator`], which works with the [`for`] loop to
//! access collections.
//!
//! The standard library exposes three common ways to deal with contiguous
//! regions of memory:
//!
//! * [`Vec<T>`] - A heap-allocated *vector* that is resizable at runtime.
//! * [`[T; n]`][array] - An inline *array* with a fixed size at compile time.
//! * [`[T]`][slice] - A dynamically sized *slice* into any other kind of contiguous
//!   storage, whether heap-allocated or not.
//!
//! Slices can only be handled through some kind of *pointer*, and as such come
//! in many flavors such as:
//!
//! * `&[T]` - *shared slice*
//! * `&mut [T]` - *mutable slice*
//! * [`Box<[T]>`][owned slice] - *owned slice*
//!
//! [`str`], a UTF-8 string slice, is a primitive type, and the standard library
//! defines many methods for it. Rust [`str`]s are typically accessed as
//! immutable references: `&str`. Use the owned [`String`] for building and
//! mutating strings.
//!
//! For converting to strings use the [`format!`] macro, and for converting from
//! strings use the [`FromStr`] trait.
//!
//! Data may be shared by placing it in a reference-counted box or the [`Rc`]
//! type, and if further contained in a [`Cell`] or [`RefCell`], may be mutated
//! as well as shared. Likewise, in a concurrent setting it is common to pair an
//! atomically-reference-counted box, [`Arc`], with a [`Mutex`] to get the same
//! effect.
//!
//! The [`collections`] module defines maps, sets, linked lists and other
//! typical collection types, including the common [`HashMap<K, V>`].
//!
//! ## Platform abstractions and I/O
//!
//! Besides basic data types, the standard library is largely concerned with
//! abstracting over differences in common platforms, most notably Windows and
//! Unix derivatives.
//!
//! Common types of I/O, including [files], [TCP], [UDP], are defined in the
//! [`io`], [`fs`], and [`net`] modules.
//!
//! The [`thread`] module contains Rust's threading abstractions. [`sync`]
//! contains further primitive shared memory types, including [`atomic`] and
//! [`mpsc`], which contains the channel types for message passing.
//!
//! [I/O]: io/index.html
//! [`MIN`]: i32/constant.MIN.html
//! [TCP]: net/struct.TcpStream.html
//! [The Rust Prelude]: prelude/index.html
//! [UDP]: net/struct.UdpSocket.html
//! [`::std::env::args`]: env/fn.args.html
//! [`Arc`]: sync/struct.Arc.html
//! [owned slice]: boxed/index.html
//! [`Cell`]: cell/struct.Cell.html
//! [`FromStr`]: str/trait.FromStr.html
//! [`HashMap<K, V>`]: collections/struct.HashMap.html
//! [`Iterator`]: iter/trait.Iterator.html
//! [`Mutex`]: sync/struct.Mutex.html
//! [`Option<T>`]: option/enum.Option.html
//! [`Rc`]: rc/index.html
//! [`RefCell`]: cell/struct.RefCell.html
//! [`Result<T, E>`]: result/enum.Result.html
//! [`String`]: string/struct.String.html
//! [`Vec<T>`]: vec/index.html
//! [array]: primitive.array.html
//! [slice]: primitive.slice.html
//! [`atomic`]: sync/atomic/index.html
//! [`collections`]: collections/index.html
//! [`for`]: ../book/first-edition/loops.html#for
//! [`format!`]: macro.format.html
//! [`fs`]: fs/index.html
//! [`io`]: io/index.html
//! [`iter`]: iter/index.html
//! [`mpsc`]: sync/mpsc/index.html
//! [`net`]: net/index.html
//! [`option`]: option/index.html
//! [`result`]: result/index.html
//! [`std::cmp`]: cmp/index.html
//! [`std::slice`]: slice/index.html
//! [`str`]: primitive.str.html
//! [`sync`]: sync/index.html
//! [`thread`]: thread/index.html
//! [`use std::env`]: env/index.html
//! [`use`]: ../book/first-edition/crates-and-modules.html#importing-modules-with-use
//! [crate root]: ../book/first-edition/crates-and-modules.html#basic-terminology-crates-and-modules
//! [crates.io]: https://crates.io
//! [deref-coercions]: ../book/second-edition/ch15-02-deref.html#implicit-deref-coercions-with-functions-and-methods
//! [files]: fs/struct.File.html
//! [multithreading]: thread/index.html
//! [other]: #what-is-in-the-standard-library-documentation
//! [primitive types]: ../book/first-edition/primitive-types.html

#![stable(feature = "rust1", since = "1.0.0")]
#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
       html_root_url = "https://doc.rust-lang.org/nightly/",
       html_playground_url = "https://play.rust-lang.org/",
       issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
       test(no_crate_inject, attr(deny(warnings))),
       test(attr(allow(dead_code, deprecated, unused_variables, unused_mut))))]

// Don't link to std. We are std.
#![no_std]

#![deny(missing_docs)]
#![deny(missing_debug_implementations)]

// Tell the compiler to link to either panic_abort or panic_unwind
#![needs_panic_runtime]

// std may use features in a platform-specific way
#![allow(unused_features)]

// std is implemented with unstable features, many of which are internal
// compiler details that will never be stable
#![feature(alloc)]
#![feature(alloc_error_handler)]
#![feature(alloc_system)]
#![feature(allocator_api)]
#![feature(allocator_internals)]
#![feature(allow_internal_unsafe)]
#![feature(allow_internal_unstable)]
#![feature(align_offset)]
#![feature(arbitrary_self_types)]
#![feature(array_error_internals)]
#![feature(ascii_ctype)]
#![feature(asm)]
#![feature(attr_literals)]
#![feature(box_syntax)]
#![feature(cfg_target_has_atomic)]
#![feature(cfg_target_thread_local)]
#![feature(cfg_target_vendor)]
#![feature(char_error_internals)]
#![feature(char_internals)]
#![feature(collections_range)]
#![feature(compiler_builtins_lib)]
#![feature(const_fn)]
#![feature(core_intrinsics)]
#![feature(dropck_eyepatch)]
#![feature(exact_size_is_empty)]
#![feature(external_doc)]
#![feature(fs_read_write)]
#![feature(fixed_size_array)]
#![feature(float_from_str_radix)]
#![feature(fn_traits)]
#![feature(fnbox)]
#![feature(futures_api)]
#![feature(generator_trait)]
#![feature(hashmap_internals)]
#![feature(int_error_internals)]
#![feature(integer_atomics)]
#![feature(into_cow)]
#![feature(lang_items)]
#![feature(libc)]
#![feature(link_args)]
#![feature(linkage)]
#![feature(macro_vis_matcher)]
#![feature(needs_panic_runtime)]
#![feature(never_type)]
#![feature(exhaustive_patterns)]
#![feature(num_bits_bytes)]
#![feature(old_wrapping)]
#![feature(on_unimplemented)]
#![feature(oom)]
#![feature(optin_builtin_traits)]
#![feature(panic_internals)]
#![feature(panic_unwind)]
#![feature(peek)]
#![feature(pin)]
#![feature(placement_new_protocol)]
#![feature(prelude_import)]
#![feature(ptr_internals)]
#![feature(rand)]
#![feature(raw)]
#![feature(rustc_attrs)]
#![feature(std_internals)]
#![feature(stdsimd)]
#![feature(shrink_to)]
#![feature(slice_bytes)]
#![feature(slice_concat_ext)]
#![feature(slice_internals)]
#![feature(slice_patterns)]
#![feature(staged_api)]
#![feature(stmt_expr_attributes)]
#![feature(str_char)]
#![feature(str_internals)]
#![feature(str_utf16)]
#![feature(test, rustc_private)]
#![feature(thread_local)]
#![feature(toowned_clone_into)]
#![feature(try_from)]
#![feature(try_reserve)]
#![feature(unboxed_closures)]
#![feature(untagged_unions)]
#![feature(unwind_attributes)]
#![feature(use_extern_macros)]
#![feature(vec_push_all)]
#![feature(doc_cfg)]
#![feature(doc_masked)]
#![feature(doc_spotlight)]
#![cfg_attr(test, feature(update_panic_count))]
#![cfg_attr(windows, feature(used))]
#![feature(doc_alias)]
#![feature(doc_keyword)]
#![feature(float_internals)]
#![feature(panic_info_message)]
#![feature(panic_implementation)]

#![default_lib_allocator]

// Always use alloc_system during stage0 since we don't know if the alloc_*
// crate the stage0 compiler will pick by default is enabled (e.g.
// if the user has disabled jemalloc in `./configure`).
// `force_alloc_system` is *only* intended as a workaround for local rebuilds
// with a rustc without jemalloc.
// FIXME(#44236) shouldn't need MSVC logic
#[cfg(all(not(target_env = "msvc"),
          any(all(stage0, not(test)), feature = "force_alloc_system")))]
#[global_allocator]
static ALLOC: alloc_system::System = alloc_system::System;

// Explicitly import the prelude. The compiler uses this same unstable attribute
// to import the prelude implicitly when building crates that depend on std.
#[prelude_import]
#[allow(unused)]
use prelude::v1::*;

// Access to Bencher, etc.
#[cfg(test)] extern crate test;
#[cfg(test)] extern crate rand;

// Re-export a few macros from core
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::{assert_eq, assert_ne, debug_assert, debug_assert_eq, debug_assert_ne};
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::{unreachable, unimplemented, write, writeln, try};

#[allow(unused_imports)] // macros from `alloc` are not used on all platforms
#[macro_use]
extern crate alloc as alloc_crate;
extern crate alloc_system;
#[doc(masked)]
extern crate libc;

// We always need an unwinder currently for backtraces
#[doc(masked)]
#[allow(unused_extern_crates)]
extern crate unwind;

// During testing, this crate is not actually the "real" std library, but rather
// it links to the real std library, which was compiled from this same source
// code. So any lang items std defines are conditionally excluded (or else they
// would generate duplicate lang item errors), and any globals it defines are
// _not_ the globals used by "real" std. So this import, defined only during
// testing gives test-std access to real-std lang items and globals. See #2912
#[cfg(test)] extern crate std as realstd;

// The standard macros that are not built-in to the compiler.
#[macro_use]
mod macros;

// The Rust prelude
pub mod prelude;

// Public module declarations and re-exports
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::any;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::cell;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::clone;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::cmp;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::convert;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::default;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::hash;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::intrinsics;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::iter;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::marker;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::mem;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::ops;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::ptr;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::raw;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::result;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::option;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::isize;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::i8;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::i16;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::i32;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::i64;
#[stable(feature = "i128", since = "1.26.0")]
pub use core::i128;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::usize;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::u8;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::u16;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::u32;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::u64;
#[stable(feature = "rust1", since = "1.0.0")]
pub use alloc_crate::boxed;
#[stable(feature = "rust1", since = "1.0.0")]
pub use alloc_crate::rc;
#[stable(feature = "rust1", since = "1.0.0")]
pub use alloc_crate::borrow;
#[stable(feature = "rust1", since = "1.0.0")]
pub use alloc_crate::fmt;
#[stable(feature = "rust1", since = "1.0.0")]
pub use alloc_crate::format;
#[stable(feature = "rust1", since = "1.0.0")]
pub use alloc_crate::slice;
#[stable(feature = "rust1", since = "1.0.0")]
pub use alloc_crate::str;
#[stable(feature = "rust1", since = "1.0.0")]
pub use alloc_crate::string;
#[stable(feature = "rust1", since = "1.0.0")]
pub use alloc_crate::vec;
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::char;
#[stable(feature = "i128", since = "1.26.0")]
pub use core::u128;
#[stable(feature = "core_hint", since = "1.27.0")]
pub use core::hint;

pub mod f32;
pub mod f64;

#[macro_use]
pub mod thread;
pub mod ascii;
pub mod collections;
pub mod env;
pub mod error;
pub mod ffi;
pub mod fs;
pub mod io;
pub mod net;
pub mod num;
pub mod os;
pub mod panic;
pub mod path;
pub mod process;
pub mod sync;
pub mod time;

#[unstable(feature = "futures_api",
           reason = "futures in libcore are unstable",
           issue = "50547")]
pub mod task {
    //! Types and Traits for working with asynchronous tasks.
    #[doc(inline)]
    pub use core::task::*;
    #[doc(inline)]
    pub use alloc_crate::task::*;
}

#[unstable(feature = "futures_api",
           reason = "futures in libcore are unstable",
           issue = "50547")]
pub mod future;

// Platform-abstraction modules
#[macro_use]
mod sys_common;
mod sys;

pub mod alloc;

// Private support modules
mod panicking;
mod memchr;

// The runtime entry point and a few unstable public functions used by the
// compiler
pub mod rt;

// Pull in the the `stdsimd` crate directly into libstd. This is the same as
// libcore's arch/simd modules where the source of truth here is in a different
// repository, but we pull things in here manually to get it into libstd.
//
// Note that the #[cfg] here is intended to do two things. First it allows us to
// change the rustc implementation of intrinsics in stage0 by not compiling simd
// intrinsics in stage0. Next it doesn't compile anything in test mode as
// stdsimd has tons of its own tests which we don't want to run.
#[path = "../stdsimd/stdsimd/mod.rs"]
#[allow(missing_debug_implementations, missing_docs, dead_code)]
#[unstable(feature = "stdsimd", issue = "48556")]
#[cfg(all(not(stage0), not(test)))]
mod stdsimd;

// A "fake" module needed by the `stdsimd` module to compile, not actually
// exported though.
#[cfg(not(stage0))]
mod coresimd {
    pub use core::arch;
}

#[stable(feature = "simd_arch", since = "1.27.0")]
#[cfg(all(not(stage0), not(test)))]
pub use stdsimd::arch;

// Include a number of private modules that exist solely to provide
// the rustdoc documentation for primitive types. Using `include!`
// because rustdoc only looks for these modules at the crate level.
include!("primitive_docs.rs");

// Include a number of private modules that exist solely to provide
// the rustdoc documentation for the existing keywords. Using `include!`
// because rustdoc only looks for these modules at the crate level.
include!("keyword_docs.rs");