A fejlesztő által felsorolt lehetséges okok közt első helyen szerepel, hogy a Rust nem elérhető számos olyan architektúrán, amit a NetBSD támogat:

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Note that in general, NetBSD is more conservative in its technical decisions than FreeBSD or Linux. Rust in the core of NetBSD is probably a non-starter for multiple reasons:

• There are many architectures that NetBSD supports where Rust is not available. This is probably the most important argument against Rust.
• Today, even getting a Rust compiler running in the first place is hard. Keeping Rust working (in pkgsrc) is quite a bit of work, resting on the shoulders of a few developers.
• In general, the bootstrap relies on a binary package of the previous version. This is unacceptable for an otherwise source-only, self-contained distribution like the NetBSD sources.
• For Rust to be used in base or in the kernel, the compiler would also have to be part of the base system. This means adding a lot of code and maintenance. It would not be impossible though – we already have LLVM (a major dependency) in base. But again, the binary bootstrap kits are a significant hurdle.
• Finally, the release cycles of Rust are not compatible with the NetBSD ones. We support the last two major releases. Today, that’s NetBSD 9 and 10. NetBSD 9.0 was released in 2020. Rust 1.41 was the current version back then. If Rust 1.41 had been part of NetBSD 9, it would be useless for anything except compiling NetBSD itself – Rust 1.41 is so old that basically no modern code would compile with it. Not great.

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Részletek itt.