The library uses `unsafe` so the consumer doesn't have to. But more to the point, to say "it uses the `unsafe` keyword, therefore it can't be safe" would be dis

The library uses `unsafe` so the consumer doesn't have to. But more to the point, to say "it uses the `unsafe` keyword, therefore it can't be safe" would be disingenuous, or at least very ignorant. The "certain kind of definition of safety" you're looking for would be 'soundness'[1]: a library using `unsafe` is considered 'sound' iff calling into it from safe Rust can never corrupt memory. When people say Rust is better for memory safety than e.g. C++, it's not because you can't write a provably-safe library with C++—you can do that with some effort. It's because the Rust language differentiates compiler-asserted safety from programmer-asserted safety via the `unsafe` keyword, an opt-in. [1]: https://rust-lang.github.io/unsafe-code-guidelines/glossary.html#soundness-of-code--of-a-library https://rust-lang.github.io/unsafe-code-guidelines/glossary.... (edit: Sniped, but I believe I've expanded upon the sibling comment.)