I work in a safety critical critical software and we're starting to use Rust. Most other things at work are C or Ada, with a sprinkling of C++. Having a formal spec is nice I guess? But 90% of our chips are obscure special purpose CPUs anyway, so we're always trusting the vendors closed source version of gcc, and we find plenty of bugs. One of the upsides (from my perspective) of rust is that obscure platforms are less well supported, so we'll likely end up with an ARM core. This limits chip choices, but it means we end up using the same backend that apple does for their watch/phone/etc, which gives us a lot of confidence.