Help test the 1.28.0 prerelease!


Rust 1.28.0 is released on Thursday and builds are available now for testing. Release artifacts are uploaded to dev ( currently and will be promoted to prod ( this Thursday. The URL is

You can test rustup with

RUSTUP_DIST_SERVER= rustup update stable

Please let us know if you run into any issues! Pending any detected regressions these are likely to be the exact artifacts that we’ll release on Thursday.

Release notes can be found here.


I am not new to this forum, and am not a new user; but I feel like when I see something like this I will ask first: where is the releast note? Without it I would not know What to test. Of cause, I am sure if I dig deeper I will find the information somewhere, but I think most people will not be motived enough to do so.

Even a simple copy-and-paste from the actual release note will be much better.


Oh, thank you! I thought I might’ve forgot something. Release notes are here:


In the “Stabilized APIs” section, nearly all of the documentation links to the alloc:: methods are 404-broken. Is that something that will automatically resolve itself at release time?


Yes; for now you can insert “beta” into the URL, like:


The now stabilized opt-levels s and z could use some better documentation. rustc -C help still only outputs:

opt-level=val -- optimize with possible levels 0-3, s, or z

I already asked this question some time ago, still without satisfactory answer. I just tried to research this again, but couldn’t find anything useful. I just keep reading s is to optimize for size, z is optimizing for size even moar! Now the release notes say something about z disabling loop vectorization. That’s the kind of information I’d like to easily find about this!


Please file an issue on rust-lang/rust, or, even better, add some docs to the rustc book:


As far as rustc is concerned this is probably “just” enabling a corresponding flag in LLVM. Unfortunately even in clang these docs are rather sparse :confused:


The noalias change may be worth mentioning in the release notes?


Curious - was there a reason this didn’t end up in the relnotes? Or did it simply slip through the cracks?


Mostly just slipped through the cracks – release notes are put together by hand so there’s always a chance for something to be missed.