Expose get_module_export from Caller

[richardpringle]

Not necessarily trying to get this merged, just using it as an example for my comment here

[alexcrichton]

What I might recommend for your use case is to store a TypedFunc<P, R> within the T of your Store<T>. That'd probably start as Option<TypedFunc<...>> and be None on store construction. After instantiation you'd load the function, set it in the store, and then all your host functions have access to that allocation function.

Alternatively if you want the absolute fastest route what I think you'd do is:

• Load a Module
• Load the export and type-check it manually
• Load the ModuleExport
• Use InstancePre to instantiate quickly
• Use the ModuleExport to get the exported function
• Use TypedFunc::new_unchecked with the resulting function

That front-loads as much as possible at the cost of safety, so I'd recommend using .get_typed_func if possible after the initial instantiation of the module.

[alexcrichton]

(although if you'd like adding the API like in this PR I also think is reasonable!)

[richardpringle]

Docs are effectively a copy/paste of Instance::get_module_export. Happy to take recommendations or if you want to make a suggestion, I will definitely accept it. I think see [Instance::get_module_export] for details would probably also be fine so long as it's clear that the caller has access to the instance (wasn't clear to me without looking at the code).

[alexcrichton]

Looks good to me! Mind adding a small smoke test too?

[richardpringle]

Looks good to me! Mind adding a small smoke test too?

@alexcrichton not sure if this is what you meant by a smoke test, but it works as one, haha 😅 .

[alexcrichton]

Thanks!