I don't understand what you mean. You can always use "unsafe" anywhere in your code, if autoCXX marked all interface code as unsafe you'd never be stuck because

I don't understand what you mean. You can always use "unsafe" anywhere in your code, if autoCXX marked all interface code as unsafe you'd never be stuck because of it, it would just mean that you'd had to check the safety of the C++ function yourself and, if you deem that your usage is kosher, add an unsafe block around your call. If you erroneously tag unsafe interfaces as safe then you basically throw all of Rust's safety out of the window. You can end up with multiple mutable borrows, or borrows with a bogus lifetime or whatever.