I know that Ferrocene and AdaCore were working together, but then parted ways. I am assuming they're both doing roughly the same thing: qualifying the upstream compiler with some patches. I know that Ferrocene's patches are mostly adding a new platform, they've upstreamed all the other stuff.

> Isn't that only for a very small subset of Rust and its standard library?

It is currently for the compiler only. This ties into the next bit, though:

> Also, do you happen to be able to explain this comment?

Yeah, you can see me posting in that thread, though not that specific sub-thread. Rust has a layered standard library: core, alloc (which layers memory allocation on top of core), and std (which layers OS specific things on top of that). There's three parts to this comment:

First, because it's only core, you don't get the stuff from alloc and std. So, no dynamic memory allocation or OS specific things like filesystem access. That's usually not a problem for these kinds of projects. But that's what they mean by 'some language features will not be available', but they're mistaken: all language features are available, it's some standard library features that are not. No language features require allocation, for example.

Second, they qualified a subset of libcore for IEC61508. A founder of Ferrous mentions that IS 26262 is coming next, they just had a customer that needed IEC61508 quickly, so they prioritized that. This is how it relates to the above, for ISO 26262, it's just the compiler currently.