Fix Wasmtime C++ API without wat feature.

[PiotrSikora]

No description provided.

[dicej]

Thanks! I take it CI didn't cover this case, correct? Would you mind adding a line to e.g. here which covers the scenario to ensure this doesn't regress in the future?

[PiotrSikora]

Thanks! I take it CI didn't cover this case, correct?

Correct.

Would you mind adding a line to e.g. here which covers the scenario to ensure this doesn't regress in the future?

There are actually 2 separate cases here (bundled into single PR per contributing guidelines against trivial changes), that I've run into within a few days from each other, and neither would be covered by those tests.

1. The C++ API issue requires linking C++ code against Wasmtime built without wat feature enabled (i.e. running test_capi job with cmake -S examples -B examples/build [...] -DWASMTIME_FEATURE_WAT=OFF and then building the examples). I don't mind adding this, but it seems quite costly in terms of the CPU time, and it would target only this single feature, so in practice we'd need to add the whole matrix if we want to be exhaustive.

2. The unused variable case could be detected with cargo check build with default-features = false, features = ["cranelift", "compile-time-builtins"], but detecting issues like that would require building with all possible combinations, unless we want to target this very specific case.

Let me know how to proceed. Thanks!

[dicej]

Let me know how to proceed. Thanks!

Thanks for the explanation. Let's add the additional cargo check but not the cmake job; I agree that the extra CPU time of the cmake one is not worth it.

[PiotrSikora]

Thanks for the explanation. Let's add the additional cargo check but not the cmake job; I agree that the extra CPU time of the cmake one is not worth it.

Actually, I'm going to split this into C++ API fixes (this PR) and other feature-related build fixes (#12719) after all.

Since we don't want to add cmake check, this one should be good to go. Thanks!

[PiotrSikora]

Oops! I forgot to push the version with the unrelated build fix removed. Luckily, I caught it before it was merged. Not sure if you need to re-queue it. Sorry for the noise!