search

rust-diplomat / diplomat

Experimental Rust tool for generating FFI definitions allowing many other languages to call Rust code
https://rust-diplomat.github.io/book/
Other
532 stars 51 forks source link

Fix primitive slice js #722

Closed jcrist1 closed 2 weeks ago

jcrist1 commented 2 weeks ago

This PR attempts to address #699. According to the generated ts files primitive slices are returned as an Array<number> on the js side, but the generated js code looks like it's trying to return types of Float64Array. I personally think it makes more sense to return typed arrays which have a perfectly ergonomic API and allow the caller to decide what to do with, but don't really want to challenge the existing implementation. Just checking that I understand it correctly. I had to add an Array.from wrap to get that to work. However, it appears there is a bug in the actual interpretation of the raw bytes that causes the first byte to not be interpreted correctly, I tried to get to the bottom of it, but couldn't quickly figure it out, so I thought I'd open the PR, and solicit help. Does anyone know what might be going on, and why the wasm backed array seems to be incorrect?

jcrist1 commented 2 weeks ago

I'm going to open this up as ready for review despite the failing test, in the hope that a reviewer can point me out to where the byte interpretation goes wrong. I got as far as seeing that, the value - 2.26666497653787e-308, seems to come from the uninitialized bytes, but as far as I could see the bytes get correctly written to when the array is passed to the native call.

jcrist1 commented 2 weeks ago

Okay I think I realised the issue. The method newFromOwned creates a slice and which is the backing Vec of the Float64Vec, but we free this slice as part of the method call, in

...
    } finally {
      functionCleanupArena.free();
    }

I didn't actually check if the js backend supports owned slices in parameters. I've got a better test now.