Document how to invoke Miri driver directly

[ojeda]

Miri currently relies on Cargo and Xargo.

It would be nice to support non-Cargo projects, at least via documenting the expected flags, sysroot, etc. (including bits out of CONTRIBUTING.md etc.).

[bjorn3]

I believe you need to compile everything (including the sysroot) with -Zalways-encode-mir and then for the executable that you want to test use miri in the place of the compiler. (There is no rustup shim for miri so you need to use rustup which miri to get it's path)

[bjorn3]

You can compile everything with --emit metadata to prevent unnecessary codegen that the default --emit link would do. Miri doesn't use the compiled object files anyway.

[RalfJung]

Non-cargo use will not be supported for the foreseeable future (we simply don't have the resources for that), but documentation PRs are always welcome and if there are concrete questions for the right invocations, I'm happy to help. :)

cargo miri run -v should also help; that will print the exact invocations of the Miri binary that our cargo wrapper generates.

[RalfJung]

Btw, the implementation of ./miri run also invokes the driver directly, so you can use that for some inspiration as well.

[ojeda]

Thanks both of you! I will write some docs along the way then :)

[Yinwhe]

Does this issue have any further discussions? I also need to use Miri on non-cargo projects.

I think this is quite a useful feature, since Rust is integrated into many mix-language projects. And among these projects, Rust may be used in non-cargo workspaces.

[RalfJung]

Miri doesn't really work in mixed-language projects though, so it's unclear whether there's a good use-case here.