Comment by ralfj

> it is inconsistent with "fearless concurrency" when the Rust stdlib has UB.

It is not. "fearless X" only applies to safe code. Rust was always very clear about that. It turns out that in practice, if >90% of your code are "fearless", that actually significantly reduces the amount of bugs you have to worry about, even if the remaining 10% can still have UB. (I don't have hard numbers on how much code is unsafe, AFAIK it is much less than 10%.)

But yeah, Miri cannot find all UB bugs. We are also very clear about that. But you don't have to find all UB bugs to make progress in this space compared to the status quo in C/C++.