It appears the compiler optimizes out bounds checking if and only if it can tell during compile time that the index is correct [1]. Arrays of dynamic size or wi

It appears the compiler optimizes out bounds checking if and only if it can tell during compile time that the index is correct [1]. Arrays of dynamic size or with dynamic references are bound checked. In dynamic cases you should be writing manual bound checking guards in C anyway. [1]: https://github.com/mozilla/rust/issues/9024 https://github.com/mozilla/rust/issues/9024