From: Ralf Jung Date: Mon, 25 Jan 2021 17:15:37 +0000 (+0100) Subject: uninit post: add forward link to provenance post X-Git-Url: https://git.ralfj.de/web.git/commitdiff_plain/1f0413b8b626f2b69ec468a119603daa67656ab1?hp=267a99689acdfde661d09ba58c6186585b7037e7 uninit post: add forward link to provenance post --- diff --git a/personal/_posts/2019-07-14-uninit.md b/personal/_posts/2019-07-14-uninit.md index b25a052..7d056c7 100644 --- a/personal/_posts/2019-07-14-uninit.md +++ b/personal/_posts/2019-07-14-uninit.md @@ -122,7 +122,7 @@ The Rust abstract machine *does* make a distinction between "relaxed" and "relea After all, x86 does not have "uninitialized bytes" either, and still our example program above went wrong. Of course, to explain *why* the abstract machine is defined the way it is, we have to look at optimizations and hardware-level concerns. -But without an abstract machine, it is very hard to ensure that all the optimizations a compiler performs are consistent---in fact, both [LLVM](https://bugs.llvm.org/show_bug.cgi?id=35229) and [GCC](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65752) suffer from miscompilations caused by combining optimizations that all seem fine in isolation, but together cause incorrect code generation. +But without an abstract machine, it is very hard to ensure that all the optimizations a compiler performs are consistent---in fact, both [LLVM](https://bugs.llvm.org/show_bug.cgi?id=35229) and [GCC](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65752) suffer from miscompilations caused by combining optimizations that all seem [fine in isolation, but together cause incorrect code generation]({% post_url 2020-12-14-provenance %}). The abstract machine is needed as an ultimate arbiter that determines which optimizations can be safely combined with each other. I also think that when writing unsafe code, it is much easier to keep in your head a fixed abstract machine as opposed to a set of optimizations that might change any time, and might or might not be applied in any order.