cargo-miri does not support target wasm32-unknown-unknown

[dvc94ch]

this works very nicely: cargo +nightly miri test --target mips64-unknown-linux-gnuabi64 however wasm32-unknown-unknown doesn't.

cargo +nightly miri test --target wasm32-unknown-unknown
   Compiling anyhow v1.0.45
   Compiling rust-ffi v0.1.0 (/home/dvc/rust-ffi)
    Finished test [unoptimized + debuginfo] target(s) in 0.82s
     Running unittests (target/miri/wasm32-unknown-unknown/debug/deps/rust_ffi-4a0413132da28d8a.wasm)
fatal error: `cargo-miri` called with unexpected first argument `/home/dvc/rust-ffi/target/miri/wasm32-unknown-unknown/debug/deps/rust_ffi-4a0413132da28d8a.wasm`; please only invoke this binary through `cargo miri`
error: test failed, to rerun pass '--lib'

[bjorn3]

I think we need to do the same as for windows .exe for wasm .wasm at

miri/cargo-miri/bin.rs

Lines 708 to 710 in b258eb3

	// For Windows, do the same thing again with `.exe` appended to the filename.
	// (Need to do this here as cargo moves that "binary" to a different place before running it.)
	info.store(&out_filename("", ".exe"));

[RalfJung]

Yeah I honestly have no ideas which targets work and which do not, it's kind of a case-by-case thing.^^

This issue is probably similar to #1867.

[RalfJung]

I know basically nothing about wasm targets and wouldn't even know what to test, so I marked this as "help-wanted".

[workingjubilee]

If it is acceptable to add a dependency, Miri could simply include the wasmtime crate as an embedding and simply execute the wasm file directly from Rust, like so:

https://docs.wasmtime.dev/lang-rust.html

[RalfJung]

That's not really what Miri is expected to do, though -- it should interpret the code, not run it like normal. Running it in wasmtime will not run all of the extra checks Miri is doing to detect UB.

[workingjubilee]

Ah, no idea then~!

[RalfJung]

This should be fixed by #2685.