[jamesmunns]

This is entirely incorrect, Ferrocene manages a specification of a subset of the language here: https://public-docs.ferrocene.dev/main/specification/index.h..., including things like a traceability matrix that links the specification to the implementation and the verification: https://public-docs.ferrocene.dev/main/qualification/traceab...

For each release of Ferrocene, this is kept up to date, and the same as C or C++, what is specified and stable can be relied upon, and implementation details are implementation details, the same as it would be if you switched from LLVM w/ SolidSands' SuperTest suite to IAR or GreenHills' toolchains which may have varying impl details but still maintain conformance with the specification.

The majority of safety critical teams will snapshot a single toolchain for the entire development lifecycle (sometimes updating if necessary, very rarely), but Ferrocene is releasing updates that are approaching the full Rust cadence (IIRC they've discussed going to every other release, so once every 12 weeks vs Rust's 6 week cadence), with all of the verification required to ensure the specification is still complete, and all tests are passing.

There's still work to specify and test more/all of the core/alloc/std library components, as well as third party crates, but from a toolchain perspective, it is much closer than you are giving them credit for. Unlike many proprietary C/C++ toolchains or verification suites, the majority of safety justification artifacts are publicly browseable here: https://public-docs.ferrocene.dev/main/index.html.

(I am a former founder of Ferrous Systems, and one of the people that pushed for the Ferrocene project to happen, but haven't worked there for a couple years and have no monetary stake in them anymore - I think they are just still doing the right thing, and doing it well.)