From 2efd82c9bb1de107144725ea382da553e1c693cb Mon Sep 17 00:00:00 2001 From: Ralf Jung Date: Sat, 6 Mar 2021 16:53:30 +0100 Subject: [PATCH] uninit blog post: update example so it still works with current rustc --- personal/_posts/2019-07-14-uninit.md | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/personal/_posts/2019-07-14-uninit.md b/personal/_posts/2019-07-14-uninit.md index 7d056c7..e6643ca 100644 --- a/personal/_posts/2019-07-14-uninit.md +++ b/personal/_posts/2019-07-14-uninit.md @@ -36,7 +36,7 @@ Here is an example to demonstrate why "random bit pattern" cannot describe unini use std::mem; fn always_returns_true(x: u8) -> bool { - x < 150 || x > 120 + x < 120 || x == 120 || x > 120 } fn main() { @@ -46,10 +46,10 @@ fn main() { {% endhighlight %} `always_returns_true` is a function that, clearly, will return `true` for any possible 8-bit unsigned integer. After all, *every* possible value for `x` will be less than 150 or bigger than 120. -A quick loop [confirms this](https://play.rust-lang.org/?version=stable&mode=release&edition=2018&gist=58168009e601a2f01b08981f907a473c). -However, if you [run the example](https://play.rust-lang.org/?version=stable&mode=release&edition=2018&gist=da278adb50142d14909df74ea1e43069), you can see the assertion fail.[^godbolt] +A quick loop [confirms this](https://play.rust-lang.org/?version=stable&mode=release&edition=2018&gist=65b690fa3c1691e11d4d45955358cdbe). +However, if you [run the example](https://play.rust-lang.org/?version=stable&mode=release&edition=2018&gist=812fe3c8655bfedcea37bb18bb70a945), you can see the assertion fail.[^godbolt] -[^godbolt]: In case this changes with future Rust versions, [here is the same example on godbolt](https://godbolt.org/z/JX4B4N); the `xor eax, eax` indicates that the function returns 0, aka `false`. And [here is a version for C++](https://godbolt.org/z/PvZGQB); imagine calling `make_true(true)` which *should* always return `true` but as the assembly shows will return `false`. +[^godbolt]: In case this changes with future Rust versions, [here is the same example on godbolt](https://godbolt.org/z/9G67hP); the `xor eax, eax` indicates that the function returns 0, aka `false`. And [here is a version for C++](https://godbolt.org/z/TWrvcq). ## What *is* uninitialized memory? -- 2.30.2