Speaker notes for “Runtime Guarantees”

src/why-rust/runtime.md

@@ -4,3 +4,19 @@ No undefined behavior at runtime:
 
 * Array access is bounds checked.
 * Integer overflow is defined.
+
+<details>
+
+Key points:
+
+* Integer overflow is defined via a compile-time flag. The options are
+  either a panic (a controlled crash of the program) or wrap-around
+  semantics. By default, you get panics in debug mode (`cargo build`)
+  and wrap-around in release mode (`cargo build --release`).
+
+* Bounds checking cannot be disabled with a compiler flag. It can also
+  not be disabled directly with the `unsafe` keyword. However,
+  `unsafe` allows you to call functions such as `slice::get_unchecked`
+  which does not do bounds checking.
+
+</details>