Vetting the cargo

The lines up pretty well with Linux's "stable userspace ABI" and the mess of the userland ABI story above the absolute basics (glibc, X11, and a handful of others).

Such reimpls have happened before (cf. libjpeg-turbo). I think the difference is that the ecosystem has a lot more room to move than the guarantees of the stdlib because of the "if it works today, it'll work tomorrow" mindset. And yes, your crate will continue to work because the old crates are still accessible but you might not have updates.

The Rust internals Discourse definitely catches features which lay out semver hazards (or at least I try to point them out) so that library authors are not caught unaware when they make some otherwise innocuous change that their major number needs bumped. However, it isn't really possible to wrap everything in bubblewrap.