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[web.git] / personal / _posts / 2020-07-15-unused-data.md

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@@ -30,6 +30,7 @@ fn example(b: bool) -> i32 {
 
 I hope it is not very surprising that calling `example` on, e.g., `3` transmuted to `bool` is Undefined Behavior (UB).
 When compiling `if`, the compiler assumes that `0` and `1` are the only possible values; there is no saying what could go wrong when that assumption is violated.
+For example, the compiler might use a [jump table](https://en.wikipedia.org/wiki/Branch_table); an out-of-bounds index in that table could literally execute any code, so there is no way to bound the behavior in that case.
 (This is a compiler-understood *validity invariant* that is fixed in the language specification, which is very different from a user-defined *safety invariant*.
 See [this earlier post]({% post_url 2018-08-22-two-kinds-of-invariants %}) for more details on that distinction.)