What abstraction do you refer to?
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.
(and yeah, the opt out question gets right to what you're saying about "naively used", I saw "unavoidable" but you're not actually saying it's unavoidable.)