From: Ralf Jung Date: Mon, 15 Jul 2019 11:48:29 +0000 (+0200) Subject: mention abstract machine earlier X-Git-Url: https://git.ralfj.de/web.git/commitdiff_plain/f16f46f51c208f0bcebdb6f143a07af2ae580738?hp=3aebce766fc1b8e6edd84bab9517f48b0fd7f23f mention abstract machine earlier --- diff --git a/personal/_posts/2019-07-14-uninit.md b/personal/_posts/2019-07-14-uninit.md index c5043ff..5aa60df 100644 --- a/personal/_posts/2019-07-14-uninit.md +++ b/personal/_posts/2019-07-14-uninit.md @@ -54,7 +54,7 @@ However, if you [run the example](https://play.rust-lang.org/?version=stable&mod ## What *is* uninitialized memory? How is this possible? -The answer is that every byte in memory cannot just have a value in `0..256` (this is Rust/Ruby syntax for a left-inclusive right-exclusive range), it can also be "uninitialized". +The answer is that, in the "abstract machine" that is used to specify the behavior of our program, every byte in memory cannot just have a value in `0..256` (this is Rust/Ruby syntax for a left-inclusive right-exclusive range), it can also be "uninitialized". Memory *remembers* if you initialized it. The `x` that is passed to `always_return_true` is *not* the 8-bit representation of some number, it is an uninitialized byte. Performing operations such as comparison on uninitialized bytes is undefined behavior.