core - Rust
Description: API documentation for the Rust `core` crate.
Keywords: rust, rustlang, rust-lang, core

# 1.6.0[−][src]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` - 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 rlibc 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`.

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

## Modules

alloc | Memory allocation APIs
any | This module implements the `Any` trait, which enables dynamic typing of any `'static` type through runtime reflection.
arch | Platform dependent vendor intrinsics.
ascii | Operations on ASCII strings and characters.
borrow | A module for working with borrowed data.
cell | Shareable mutable containers.
char | A character type.
clone | The `Clone` trait for types that cannot be 'implicitly copied'.
cmp | Functionality for ordering and comparison.
convert | Traits for conversions between types.
default | The `Default` trait for types which may have meaningful default values.
f32 | This module provides constants which are specific to the implementation of the `f32` floating point data type.
f64 | This module provides constants which are specific to the implementation of the `f64` floating point data type.
ffi | Utilities related to FFI bindings.
fmt | Utilities for formatting and printing strings.
hash | Generic hashing support.
hint | Hints to compiler that affects how code should be emitted or optimized.
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.
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.
pin | Types which pin data to its location in memory
prelude | The libcore prelude
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
time | Temporal quantification.
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.
usize | The pointer-sized unsigned integer type.
array | [ Experimental ] Implementations of things like `Eq` for fixed-length arrays up to a certain length. Eventually we should able to generalize to all lengths.
future | [ Experimental ] Asynchronous values.
intrinsics | [ Experimental ] rustc compiler intrinsics.
panic | [ Experimental ] Panic support in the standard library.
panicking | [ Experimental ] Panic support for libcore
raw | [ Experimental ] Contains struct definitions for the layout of compiler built-in types.
task | [ Experimental ] Types and Traits for working with asynchronous tasks.
unicode | [ Experimental ]

## Macros

assert | Ensure 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 | Boolean evaluation of configuration flags, at compile-time.
column | A macro which expands to the column number on which it was invoked.
compile_error | Unconditionally causes compilation to fail with the given error message when encountered.
concat | Concatenates literals into a static string slice.
debug_assert | Ensure 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 | Inspect an environment variable at compile time.
file | A macro which expands to the file name from which it was invoked.
format_args | The core macro for formatted string creation & output.
include | Parse 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 utf8-encoded file as a string.
line | A macro which expands to the line number on which it was invoked.
module_path | Expands to a string that represents the current module path.
option_env | Optionally inspect an environment variable at compile time.
panic | Entry point of thread panic, for details, see std::macros
stringify | A macro which stringifies its arguments.
try | Helper macro for reducing boilerplate code for matching `Result` together with converting downstream errors.
unimplemented | A standardized placeholder for marking unfinished code.
unreachable | A utility macro for indicating unreachable code.
write | Write formatted data into a buffer.
writeln | Write formatted data into a buffer, with a newline appended.
concat_idents | [ Experimental ] Concatenate identifiers into one identifier.

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g., `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g., `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g., `str,u8` or `String,struct:Vec,test`)