How to build an archive for and run it on a non-built-in Tier-3 target?

[lasiotus]

I work on a Tier-3 Rust target that does not support rust tools (no "native" rustc, no cargo, only cross-compiling from a Linux host). I can cross-compile tests using

cargo +dev-x86_64-unknown-motor test --no-run --target x86_64-unknown-motor

then hunt down test binaries (their names are randomized), copy them over to the VM running the target, and manually execute. The process is too cumbersome to be part of a normal workflow.

It looks like cargo-nextest, with its archive feature, could be used to solve this problem, but two issues are unclear. First of all, how do I build an archive? Running

cargo-nextest nextest archive --target x86_64-unknown-motor --archive-file foo.tar.zst

Resulits in

  error: unknown triple string: x86_64-unknown-motor
  ├─▶ triple not in builtin platforms and heuristic parsing failed
  ╰─▶ Unrecognized operating system: motor

and adding +dev leads to

error: unrecognized subcommand '+dev-x86_64-unknown-motor'

Usage: cargo <COMMAND>

For more information, try '--help'

So the first question is where should I poke at nextest source code to make cross-compiling archives for non-built-in targets work.

The second question is to how can I run binaries from an archive "manually", as cargo-nextest can't be cross-compiled for Motor OS, as the tool has many dependencies that work on Tier 1 targets only (plus a few unices, I guess).

[sunshowers]

Thanks for the issue.

For your first point, it looks like your target isn't built into Rust (at least Rust 1.91.0). You'll want to pass in your target JSON file as the argument to --target. So e.g. --target path/to/x86_64-unknown-motor.json.

For your second point, this is not currently supported directly. You'll want to try and extract the archive yourself, then use binaries-metadata.json as the list of binaries (but note that this isn't part of the stability guarantees of nextest). Doing this correctly (including setting up environment variables and such) is quite tricky.

Another option is to use a wrapper script on a supported host, executing commands remotely on the target platform.

as the tool has many dependencies that work on Tier 1 targets only (plus a few unices, I guess).

You may at least want to get Tokio working on your platform. Tokio works on several non-Tier 1 targets.

[lasiotus]

Thanks a lot for the reply! Unfortunately, passing the target json is not enough: rustc fails to find core for my target, and even if it somehow manages to compile core on the fly, this won't help with Rust stdlib, which is compiled locally and registered via rustup toolchain link dev-x86_64-unknown-motor <path>. I guess I'll have to wait for Rust 1.92 (Motor OS is currently in beta). I hope it will solve the issue, although I'm not fully confident: Rust doesn't ship Tier 3 build artifacts, so rustc will still need to pick up the local toolchain link...

Re: wrapper scripts: this should work, thanks - I can run things remotely over ssh.

Re: tokio: tokio works via patch.crates-io, but cargo-nextest pulls in things like socket2 via e.g. self-update, so just having tokio is not enough...

Anyway, thanks again for the pointers - I'll try again in a couple of months when Rust 1.92 is out.

[sunshowers]

Re: tokio: tokio works via patch.crates-io, but cargo-nextest pulls in things like socket2 via e.g. self-update, so just having tokio is not enough...

Ah you should be able to turn self-update off with --no-default-features --features default-no-update.