Rust is in a very different situation though. Safe Rust has no undefined behavior - if something is behaving in an unsound manner, then that's a compiler bug.

Rust is in a very different situation though. Safe Rust has no undefined behavior - if something is behaving in an unsound manner, then that's a compiler bug. Safe Rust does have some implementation-specific behavior - for instance, panics can either unwind or abort. In Unsafe Rust, all bets are off, and the programmer may trigger Undefined Behavior if they're not careful. The upshot is that it's easier to maintain the compiler's invariants because you only need to be careful in a single place about making sure everything is in order. By clearly marking places where the programmer is in charge of maintaining the invariants instead of the compiler, the hope is that mistakes will be minimized (thanks to careful code review and making the programmer think a lot about what they're writing). Further helping with that, the goal is to have tools to help catch UB at runtime. For instance, miri is an interpreter for MIR (an intermediate language between rust and the LLVM IR) that checks for UB. I agree that in C, UB has probably be stretched way beyond its intended purpose. But in Rust, this new definition of UB is taken advantage of in much less WTF-inducing ways, allowing us to enjoy those performance guarantees without losing our minds.