[kajaktum]

You can get 80% there with rust which is what is impressive. Then you have a reference implementation that you can always check against. If a Rust library have 0 unsafe, i dont care if it is written by a dog, it still have 0 UB.

[klabb3]

UB is especially bad but also not as big as all other concerns combined. Two of the most reliable software ever to exist, curl and SQLite, are C/C++. There are also cases in system programming, drivers etc where the unsafe is necessary and then your code is only as good as the boundary, and lots of bugs can seep in. Another issue with Rust is ecosystem - the dependency trees required to do fairly basic things are often deep and vast, meaning other risks.

That said if something like rsync was written today, I still think Rust may be a better choice. Mainly because a 95 percentile skilled Rust programmer is less dangerous than for C. The people that are skilled enough to be trusted with C are few and diminishing every year.