A no_std Rust Environment

There are two general Embedded Programming classifications:

In a bare metal environment no code has been loaded before your program. Without the software provided by an OS we can not load the standard library. Instead the program, along with the crates it uses, can only use the hardware (bare metal) to run. To prevent rust from loading the standard library use . The platform-agnostic parts of the standard library are available through . libcore also excludes things which are not always desirable in an embedded environment. One of these things is a memory allocator for dynamic memory allocation. If you require this or any other functionalities there are often crates which provide these.

is a crate-level attribute that indicates that the crate will link to the core-crate instead of the std-crate. The libcore crate in turn is a platform-agnostic subset of the std crate which makes no assumptions about the system the program will run on. As such, it provides APIs for language primitives like floats, strings and slices, as well as APIs that expose processor features like atomic operations and SIMD instructions. However it lacks APIs for anything that involves platform integration. Because of these properties no_std and code can be used for any kind of bootstrapping (stage 0) code like bootloaders, firmware or kernels.

** Only if you use the crate and configure a global default allocator.