Jakub Hlusička (May 07 2020 at 21:42): Jakub Hlusička (May 07 2020 at 21:42):Hello,
I have a couple of questions regarding the usage of wasmtime:
First, I have noticed that Instance is !Send and !Sync, but individual Func::get closures are not. Does that mean I can "extract" a functions via this method and invoke it from multiple threads, simultaneously?
Second, is it currently possible to use String as a parameter/return type for exported functions? I tried using version 0.16.0, but ran into some compilation errors in the wasmtime macro, related to the "wasmtime-interface-types" crate. I am able to use Strings in version 0.8.0.
Alex Crichton (May 07 2020 at 21:49):@Jakub Hlusička oh dear that's a bug, Func closures extracted should not be Send or Sync
Alex Crichton (May 07 2020 at 21:49):otherwise interface types are currently not implemented in wasmtime so you can't pass a string right now
Alex Crichton (May 07 2020 at 21:49):you'll need to manually copy in/out of wasm memory
Alex Crichton (May 07 2020 at 21:49):We hope to implement it in the near future though!
Alex Crichton (May 07 2020 at 21:51):hm although testing now Func::get return values aren't Send/Sync for me?
Alex Crichton (May 07 2020 at 21:51):this may have been something which accidentally regressed which we ended up fixing recently though
Jakub Hlusička (May 07 2020 at 21:53):Hmm, I thought I could tell by looking at the function signature: https://docs.rs/wasmtime/0.16.0/wasmtime/struct.Func.html#method.get1
Alex Crichton (May 07 2020 at 21:53):oh so not always, in that case it returns impl Fn() which means the compiler is still auto-inferring Send/Sync
Alex Crichton (May 07 2020 at 21:53):I don't believe the documentation renders the Send/Sync inference right now
Jakub Hlusička (May 07 2020 at 21:58):I see, that makes sense. I am intending on using WebAssembly for stateless scripting for a game, and I am trying to make it possible to invoke certain functions exported by a module in parallel. I guess the only option, then, is to instantiate several modules on separate threads, and then distribute the work across those instances.
Alex Crichton (May 07 2020 at 22:09):Ah yes currently you can't share wasm instances across threads
Alex Crichton (May 07 2020 at 22:09):(or, rather, you'll never be able to do that)
Alex Crichton (May 07 2020 at 22:09):eventually we'll support two instances sharing a memory across threads
Alex Crichton (May 07 2020 at 22:09):but we don't have support for that yet
Jakub Hlusička (May 07 2020 at 22:11):Alright, thank you for the help! Have a nice day.
Last updated: Nov 22 2024 at 16:03 UTC