[barrucadu]

Don't the C parts of Linux heavily depend on GCC extensions too? Seems depending on specific compiler features isn't really a blocker.

[tambre]

The difference probably is that GCC extensions have been stable for decades. Meanwhile Rust experimental features have breaking changes between versions. So a Rust version 6 months from now likely won't be able to compile the kernel we have today, but a GCC version in a decade will still work.