Rust is actually few steps above from the bare metal, to enforce its security invariants. Boundary checks (which breaks auto-vectorization of loops), stack probe, fat pointer (wastes register), fixed index type (uint), etc.

There are other hidden costs coming from usage of std. Even `Result` is a bit of inefficiency.

I'm not saying any of these are bad. I'm just saying Rust would be slower than C if *naively* used.