As mentioned in http://blog.phil-opp.com/rust-os/setup-rust.html

The core library is added implicitly when using #![no_std] and provides basic standard library features like Option or Iterator. According to the documentation it is “dependency-free”. But it actually has some dependencies, for example on fmod and fmodf.

This strikes me as a bug, either in the core library or in the documentation.

Previously reported at https://github.com/phil-opp/phil-opp.github.io/issues/7, moving here.