Comment by Measter

You've misunderstood what Steve is saying, and what safe/unsafe means in Rust. In Rust, if I have a block of code that doesn't use any operations that require the unsafe keyword, then I am guaranteed (modulo compiler bugs) that this block of code is free of all undefined behaviour.

It does not guarantee that code in any function being called within that block is free of it, but it does guarantee this block of code is.

Profiles don't give you that.