Rust Example

[blhagadorn]

This adds an example of a simple Rust Hello World on STDOUT using the cc image

[blhagadorn]

I felt compelled to do this because I wanted to show the usage of the cc image, FYI

[blhagadorn]

@donmccasland

[loosebazooka]

We should probably get someone with some familiarity with rust to review this. But I might as well ask while I'm here:

1. Are the libraries required for cc enough for rust?
2. I think you need to include a BUILD file like: https://github.com/GoogleContainerTools/distroless/blob/master/examples/go/BUILD as these examples are built from source.

[blhagadorn]

We should probably get someone with some familiarity with rust to review this. But I might as well ask while I'm here:

1. Are the libraries required for cc enough for rust?

That's a great question, I think libc is all it needs for its basic functions for interfacing with the system library, I/O, networking, etc. rather than having an abstract layer like Golang where syscalls are built into the language. I agree this should definitely get the sign-off from someone much better at a novice like me though.

2. I think you need to include a BUILD file like: https://github.com/GoogleContainerTools/distroless/blob/master/examples/go/BUILD as these examples are built from source.

Ahh good point, I will work on a BUILD file for Bazel.

[briandealwis]

Thanks for the contribution! This makes sense — the cc/README.md suggests that it's suitable for languages like Rust.

[blhagadorn]

Alright thanks for the tip @briandealwis , new to Bazel but the documentation helped and I think I have things correct. Ready for review when any of you can!

[blhagadorn]

Are the libraries required for cc enough for rust?

To re-answer this question after research, for this example I think libc is enough for most standard Rust procedures. If there are other dependencies, however, they might need other items.

[briandealwis]

Thanks for your contribution!

[blhagadorn]

No problem, thanks for reviewing!

[CodesInChaos]

@blhagadorn is there a reason this needs cc and not just base?

[blhagadorn]

@CodesInChaos For libcc1 which isn't inside of base, and is sparsely found in different Unix operating systems. See this interesting discussion: rust-lang/rustup#2213 or this masterpiece: https://wiki.alopex.li/LetsBeRealAboutDependencies. Otherwise, users might see this error: error while loading shared libraries: libgcc_s.so.1: cannot open shared object file: No such file or directory

However I might be overcomplicating things, is there an alternative?

[CodesInChaos]

I didn't realize that rust applications link to libgcc at runtime. I thought that only the compiler depends on on it, while applications depend only on glibc.

[blhagadorn]

Yeah, I think it's heavily dependent on operation system, too (Linux is of course a spectrum). I might be wrong about this though.