I wrote a simple example of calling out into Rust from Python using cffi: https://github.com/maciejkula/python-rustlearn.

The gist of it is: it's really easy.

I don't know when this was last updated, but:

http://jakegoulding.com/rust-ffi-omnibus/

It's got a nice breakdown of how to bring rust libraries into a few languages. There are a few tutorials about how to make rust produce a static or shared library, but it's pretty straightforward.

You don't necessarily need C header files. Rust is able to export symbols easily with the C ABI; if your language has the ability to take a library and call such symbols (Python/Ruby do; for example), you're fine. It's only C++ where you need a header file because that's how C++ binds with any library. It's not a Rust-to-any-language issue, header files are a Rust-to-C++ issue only; really, an any-language-to-C++-or-C issue (I think such a tool exists, too).

A C header is not needed at runtime, it is purely a way to easily describe the symbols in a library that exist in a (somewhat) type-safe way. It's the lingua franca for describing libraries, and tooling (such as Rust's bindgen, or Python's cffi) can consume them to do the setup/create the information necessary to call functions from other languages. This is much nicer than manually trying to transcribe the Rust (or whatever) signatures into your application.

> header files are a Rust-to-C++ issue only

Or... C? (And of course other languages too, as just discussed.)

> It's the lingua franca for describing libraries, and tooling (such as Rust's bindgen, or Python's cffi) can consume them to do the setup/create the information necessary to call functions from other languages.

Hence the "not necessarily" in my comment. The parent seemed to be painting this as extra unnecessary work; I was saying that a header file is _not_ necessary except for binding to C/C++.

If you want to write a C API that will be called from many languages; you should have a header file so that bindgen tools can consume it. If you want an API that will only be called by Python .... not so necessary, you may want a header file anyway but it depends on the situation.

> Or... C?

Sure, goes without saying :)

Too late for me to edit, but regarding the C header file situation, this tool has been around for a bit:

https://github.com/Sean1708/rusty-cheddar

I haven't used it personally, but it looks useful.

Skylight[1] from what I understand is a ruby gem written in Rust. It monitors your ruby runtime and sends the data to the central servers for analysis.

1: https://www.skylight.io/

It was also one of the first production uses of Rust.