It's not just unsafe, it's this:

    let r = unsafe { &*p };

It looks as if it's building structs out of information in (mutable pointers) to other structs without an Rc in sight. Which makes sense for a C parser: you've got a table with data, so you just link to it. It's fast, and when you know you're not going to touch it, it's safe. But this doesn't make the Rust code any better than the C code.