# Crate core [−] [src]

# 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

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_unwind` - This function takes three arguments, a `fmt::Arguments`, a `&str`, and a `u32`. These three arguments dictate the panic message, the file at which panic was invoked, and the line. It is up to consumers of this core library to define this panic function; it is only required to never return.

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

## Modules

any | This module implements the `Any` trait, which enables dynamic typing of any `'static` type through runtime reflection.
borrow | A module for working with borrowed data.
cell | Shareable mutable containers.
char | Character manipulation.
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 | Operations and constants for 32-bits floats (`f32` type)
f64 | Operations and constants for 64-bits floats (`f64` type)
fmt | Utilities for formatting and printing strings
hash | Generic hashing support.
i16 | The 16-bit signed integer type.
i32 | The 32-bit signed integer type.
i64 | The 64-bit signed integer type.
i8 | The 8-bit signed integer type.
isize | The pointer-sized signed integer type.
iter | Composable external iteration
marker | Primitive traits and marker types representing basic 'kinds' 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
prelude | The libcore prelude
ptr | Raw, unsafe pointers, `*const T`, and `*mut T`
result | Error handling with the `Result` type
slice | Slice management and manipulation
str | String manipulation
sync | Synchronization primitives
u16 | The 16-bit unsigned integer type.
u32 | The 32-bit unsigned integer type.
u64 | The 64-bit unsigned integer type.
u8 | The 8-bit unsigned integer type.
usize | The pointer-sized unsigned integer type.
array | [Unstable] Implementations of things like `Eq` for fixed-length arrays up to a certain length. Eventually we should able to generalize to all lengths.
intrinsics | [Unstable] rustc compiler intrinsics.
nonzero | [Unstable] Exposes the NonZero lang item which provides optimization hints.
panicking | [Unstable] Panic support for libcore
raw | [Unstable] Contains struct definitions for the layout of compiler built-in types.

## Macros

assert! | Ensure that a boolean expression is `true` at runtime.
assert_eq! | Asserts that two expressions are equal to each other.
debug_assert! | Ensure that a boolean expression is `true` at runtime.
debug_assert_eq! | Asserts that two expressions are equal to each other.
panic! | Entry point of thread panic, for details, see std::macros
try! | Helper macro for unwrapping `Result` values while returning early with an error if the value of the expression is `Err`. Can only be used in functions that return `Result` because of the early return of `Err` that it provides.
unimplemented! | A standardized placeholder for marking unfinished code. It panics with the message `"not yet implemented"` when executed.
unreachable! | A utility macro for indicating unreachable code.
write! | Use the `format!` syntax to write data into a buffer.
writeln! | Use the `format!` syntax to write data into a buffer, appending a newline.

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