Crate core

The Rust Core Library

The Rust Core Library is the dependency-free¹ foundation of The Rust Standard Library. It is the portable glue between the language and its libraries, defining the intrinsic and primitive building blocks of all Rust code. It links to no upstream libraries, no system libraries, and no libc.

The core library is minimal: it isn’t even aware of heap allocation, nor does it provide concurrency or I/O. These things require platform integration, and this library is platform-agnostic.

How to use the core library

Please note that all of these details are currently not considered stable.

This library is built on the assumption of a few existing symbols:

• memcpy, memcmp, memset, strlen - These are core memory routines which are often generated by LLVM. Additionally, this library can make explicit calls to these functions. Their signatures are the same as found in C. These functions are often provided by the system libc, but can also be provided by the compiler-builtins crate.

• rust_begin_panic - This function takes four arguments, a fmt::Arguments, a &'static str, and two u32’s. These four arguments dictate the panic message, the file at which panic was invoked, and the line and column inside the file. It is up to consumers of this core library to define this panic function; it is only required to never return. This requires a lang attribute named panic_impl.

• rust_eh_personality - is used by the failure mechanisms of the compiler. This is often mapped to GCC’s personality function, but crates which do not trigger a panic can be assured that this function is never called. The lang attribute is called eh_personality.

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1. Strictly speaking, there are some symbols which are needed but they aren’t always necessary. ↩

Primitive Types

neverExperimental

The ! type, also called “never”.

array

A fixed-size array, denoted [T; N], for the element type, T, and the non-negative compile-time constant size, N.

bool

The boolean type.

char

A character type.

f32

A 32-bit floating point type (specifically, the “binary32” type defined in IEEE 754-2008).

f64

A 64-bit floating point type (specifically, the “binary64” type defined in IEEE 754-2008).

fn

Function pointers, like fn(usize) -> bool.

i8

The 8-bit signed integer type.

i16

The 16-bit signed integer type.

i32

The 32-bit signed integer type.

i64

The 64-bit signed integer type.

i128

The 128-bit signed integer type.

isize

The pointer-sized signed integer type.

pointer

Raw, unsafe pointers, *const T, and *mut T.

reference

References, &T and &mut T.

slice

A dynamically-sized view into a contiguous sequence, [T]. Contiguous here means that elements are laid out so that every element is the same distance from its neighbors.

str

String slices.

tuple

A finite heterogeneous sequence, (T, U, ..).

u8

The 8-bit unsigned integer type.

u16

The 16-bit unsigned integer type.

u32

The 32-bit unsigned integer type.

u64

The 64-bit unsigned integer type.

u128

The 128-bit unsigned integer type.

unit

The () type, also called “unit”.

usize

The pointer-sized unsigned integer type.

Modules

assert_matchesExperimental

Unstable module containing the unstable assert_matches macro.

async_iterExperimental

Composable asynchronous iteration.

errorExperimental

Interfaces for working with Errors.

intrinsicsExperimental

Compiler intrinsics.

panickingExperimental

Panic support for libcore

simdExperimental

Portable SIMD module.

unicodeExperimental

alloc

Memory allocation APIs

any

Utilities for dynamic typing or type reflection.

arch

SIMD and vendor intrinsics module.

array

Utilities for the array primitive type.

ascii

Operations on ASCII strings and characters.

borrow

Utilities for working with borrowed data.

cell

Shareable mutable containers.

char

Utilities for the char primitive type.

clone

The Clone trait for types that cannot be ‘implicitly copied’.

cmp

Utilities for comparing and ordering values.

convert

Traits for conversions between types.

default

The Default trait for types with a default value.

f32

Constants for the f32 single-precision floating point type.

f64

Constants for the f64 double-precision floating point type.

ffi

Platform-specific types, as defined by C.

fmt

Utilities for formatting and printing strings.

future

Asynchronous basic functionality.

hash

Generic hashing support.

hint

Hints to compiler that affects how code should be emitted or optimized. Hints may be compile time or runtime.

i8Deprecation planned

Constants for the 8-bit signed integer type.

i16Deprecation planned

Constants for the 16-bit signed integer type.

i32Deprecation planned

Constants for the 32-bit signed integer type.

i64Deprecation planned

Constants for the 64-bit signed integer type.

i128Deprecation planned

Constants for the 128-bit signed integer type.

isizeDeprecation planned

Constants for the pointer-sized signed integer type.

iter

Composable external iteration.

marker

Primitive traits and types representing basic properties of types.

mem

Basic functions for dealing with memory.

num

Numeric traits and functions for the built-in numeric types.

ops

Overloadable operators.

option

Optional values.

panic

Panic support in the standard library.

pin

Types that pin data to its location in memory.

prelude

The libcore prelude

primitive

This module reexports the primitive types to allow usage that is not possibly shadowed by other declared types.

ptr

Manually manage memory through raw pointers.

result

Error handling with the Result type.

slice

Slice management and manipulation.

str

String manipulation.

sync

Synchronization primitives

task

Types and Traits for working with asynchronous tasks.

time

Temporal quantification.

u8Deprecation planned

Constants for the 8-bit unsigned integer type.

u16Deprecation planned

Constants for the 16-bit unsigned integer type.

u32Deprecation planned

Constants for the 32-bit unsigned integer type.

u64Deprecation planned

Constants for the 64-bit unsigned integer type.

u128Deprecation planned

Constants for the 128-bit unsigned integer type.

usizeDeprecation planned

Constants for the pointer-sized unsigned integer type.

Macros

concat_bytesExperimental

Concatenates literals into a byte slice.

concat_identsExperimental

Concatenates identifiers into one identifier.

const_format_argsExperimental

Same as format_args, but can be used in some const contexts.

format_args_nlExperimental

Same as format_args, but adds a newline in the end.

log_syntaxExperimental

Prints passed tokens into the standard output.

trace_macrosExperimental

Enables or disables tracing functionality used for debugging other macros.

assert

Asserts that a boolean expression is true at runtime.

assert_eq

Asserts that two expressions are equal to each other (using PartialEq).

assert_ne

Asserts that two expressions are not equal to each other (using PartialEq).

cfg

Evaluates boolean combinations of configuration flags at compile-time.

column

Expands to the column number at which it was invoked.

compile_error

Causes compilation to fail with the given error message when encountered.

concat

Concatenates literals into a static string slice.

debug_assert

Asserts that a boolean expression is true at runtime.

debug_assert_eq

Asserts that two expressions are equal to each other.

debug_assert_ne

Asserts that two expressions are not equal to each other.

env

Inspects an environment variable at compile time.

file

Expands to the file name in which it was invoked.

format_args

Constructs parameters for the other string-formatting macros.

include

Parses a file as an expression or an item according to the context.

include_bytes

Includes a file as a reference to a byte array.

include_str

Includes a UTF-8 encoded file as a string.

line

Expands to the line number on which it was invoked.

matches

Returns whether the given expression matches any of the given patterns.

module_path

Expands to a string that represents the current module path.

option_env

Optionally inspects an environment variable at compile time.

panic

Panics the current thread.

stringify

Stringifies its arguments.

todo

Indicates unfinished code.

tryDeprecated

Unwraps a result or propagates its error.

unimplemented

Indicates unimplemented code by panicking with a message of “not implemented”.

unreachable

Indicates unreachable code.

write

Writes formatted data into a buffer.

writeln

Write formatted data into a buffer, with a newline appended.