There's hardly another mainstream language out there that's more stable than Rust: the standard library as well as the language itself follow a strict backward compatibility policy – breaking changes are only allowed to fix safety-relevant bugs.
But it is not ready for critical infrastructure for two reasons:
1) It is not defined. the definition of rust is "the compiler accepts it"
2) There is one implementation
I use rust for a lot of things, things that I really want to be solid and reliable.
But I would not want to use it for systems where lives were at risk.
That is not a domain I work in, so I am hazy on what is available but I know the avionics people have systems and processes. Have they adopted Rust yet?
Rust will be excellent in this space. But it needs definition and alternative implementations first. Probably will not be long.
Also, there are multiple implementations, though they are in various stages of completion.
Sorry for the daft question. Just to clarify, do you mean that the vendor modifies gcc and doesn’t release the source, or that the vendor has its home-grown C compiler that is functionally equivalent to gcc?