Many (most?) projects bypass this by simply not specifying which platforms are supported, and making decisions about breaking support on an ad hoc basis. Of cou

Many (most?) projects bypass this by simply not specifying which platforms are supported, and making decisions about breaking support on an ad hoc basis. Of course OSS developers are entitled to do this if they think it's best, but that's a good way to either create a burden for yourself when people start using your package in unintended ways, or to annoy people when something suddenly stops working because you never intended to support it. Rust is doing it right by explicitly stating which targets are supported and to what extent. You can use it for other targets (I've written a lot of code for AVR which isn't supported at all) but if something breaks they stated up front that it wasn't supported.