[throwaway0010]

> Also, C is extensively standardised

Not really, at least not in the sense that you mean here: The generation of machine code in shared objects. There is a distinct lack of definition between C syntax and the resulting machine code.

> The best advantage of writing libraries in C is that it allows the library to be usable via FFIs in many other languages.

You can create C shared objects from Rust (or from a ton of other languages which generate native code). No big deal. It can do what you want.

[asuffield]

> There is a distinct lack of definition between C syntax and the resulting machine code.

And more importantly: there is a distinct lack of similarity in behavior in this respect between vendors, versions, architectures, language features, ambient temperatures, and times of day. Change any of those things and you can get different output from your C compiler.

[fithisux]

But not C include files. I think nimrodhas something here. Vala? I do not know.

[dbaupp]

That's just because Rust is still in development, and tooling like that is developed incrementally. There's already an issue about automatically creating C headers representing a Rust library, https://github.com/mozilla/rust/issues/10530 (and Alex Crichton has even started working on a tool for it, see his comment).