From: Ralf Jung Date: Tue, 16 Jul 2019 12:26:56 +0000 (+0200) Subject: clarify X-Git-Url: https://git.ralfj.de/web.git/commitdiff_plain/870cbaeae3b06465ceabd15a89ab74edf9f7acc0 clarify --- diff --git a/personal/_posts/2019-07-14-uninit.md b/personal/_posts/2019-07-14-uninit.md index 85c8dcb..0b16076 100644 --- a/personal/_posts/2019-07-14-uninit.md +++ b/personal/_posts/2019-07-14-uninit.md @@ -60,7 +60,7 @@ The `x` that is passed to `always_return_true` is *not* the 8-bit representation Performing operations such as comparison on uninitialized bytes is [undefined behavior]({% post_url 2017-07-14-undefined-behavior %}). As a consequence, our program has undefined behavior, so we should not be surprised that it acts "weirdly". -Of course, there is a reason for this undefined behavior. +Of course, there is a reason for this undefined behavior; there is a reason the "abstract machine" is defined the way it is. Compilers don't just want to annoy programmers. Ruling out operations such as comparison on uninitialized data is useful, because it means the compiler does not have to "remember" which exact bit pattern an uninitialized variable has! A well-behaved (UB-free) program cannot observe that bit pattern anyway.