wasmtime-wiggle: make it possible to add host funcs to a config under an alias

[pchickey]

This addition to wasmtime-wiggle makes it possible to add a function to a Config under an arbitrary name.

Embeddings that allow Wasm functions defined by wiggle to be imported under additional names (for example, for legacy compatibility) can do so by writing their own Linker invocation, but functions were added to a Config under only the name specified by the witx file. Now, in addition to the default add_to_config behavior, you can add_<functionname>_to_config(&mut config, module: &str, field: &str) as well.

[github-actions]

Subscribe to Label Action

cc @kubkon

Details

This issue or pull request has been labeled: "wasi"

Thus the following users have been cc'd because of the following labels:

• kubkon: wasi

To subscribe or unsubscribe from this label, edit the .github/subscribe-to-label.json configuration file.

Learn more.

[alexcrichton]

Would this be something we could perhaps configure at the wiggle-macro-invocation level? It seems like this would add a lot of functions that are rarely used, which isn't necessarily a bad thing just wondering if we could move this to compile time instead of runtime.

[pchickey]

Yeah, we could do this at compile time instead of at run-time. This does add a lot of API surface but effectively its just out-lining the functionality that is already there for add_to_config, which is implemented in terms of these new functions.

I'd like to defer adding compile-time config for this for a little bit. It is an optimization, but for code should get called once per engine creation. I expect plenty more structural changes to wiggle coming down the pipe as witx and friends evolve, so I don't want to add more complexity to the macro right now if we don't have to.

[alexcrichton]

Ok sounds reasonable!