Test a small cargo-miri smoke test even in run_tests_minimal

[Noratrieb]

This makes sure that cargo-miri works on all targets.

Implements the first step of #2685 (comment) to get that PR tested.

[Noratrieb]

libtest needs std, right. So uh, how exactly should I do this test crate? It should be no_std, but how should I do this? no_std binaries are tricky and platform specific and this should work on all platforms (and the ones that don't support std are the more funky ones usually :D).

[RalfJung]

Yeah that's why I suggested a 'cargo run' smoketest, not 'cargo test'. Or is that still too platform-specific?

[Noratrieb]

Getting a no_std binary running is still platform specific. I tried getting one to work (just on x86_64-unknown-linux-gnu) and after adding panic = "abort" and a #[panic_handler] it still needs an entry point and I didn't quite figure out what the best way to do that would be. Adding a #[start] function yielded linker errors about mising libc symbols (since libc isn't linked anymore) and I assume fixing this would require platform specific code to link the right things.

[RalfJung]

This is Miri, no linking should be required...

We successfully do run https://github.com/rust-lang/miri/blob/master/tests/pass/no_std.rs on no_std targets in our test suite. Does that not also work with cargo miri run?

[Noratrieb]

Oh yes, this is Miri, I forgot about that :D

The example you have looks good, I think I can use that.

[RalfJung]

If this is excluded, why is it listed in the lockfile...?

[RalfJung]

@bors r+

[bors]

📌 Commit d9b7035 has been approved by RalfJung

It is now in the queue for this repository.

[bors]

⌛ Testing commit d9b7035 with merge c2eac58...

[bors]

☀️ Test successful - checks-actions
Approved by: RalfJung
Pushing c2eac58 to master...