Rustaceans at the border

gcc has _plenty_ of non-backward-compatible changes. Try compiling the kernel with gcc 3, for example.

As it is, Linux has a minimum version requirement for gcc (or clang) that gets raised pretty often. I believe it's at 5.1 right now: https://lore.kernel.org/lkml/20210910234047.1019925-2-nde...

So in practice, the _current_ Linux policy is worse than Rust. Instead of a well-defined edition, the kernel depends on an informal compiler version.