[nitrogen]

Does bare metal Rust also use memcpy() or other library functions? If so, how are those linked into the final binary?

[steveklabnik]

Yes, LLVM will assume three or four functions exist regardless. The rlibc crate provides a Rust implementation of them, so you just add it and you're done. https://github.com/alexcrichton/rlibc

[kzrdude]

They are usually provided by libc, but if you do low level stuff they are provided by other means.