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Comment by shp0ngle | Hacker News Reader

Not directly related to this thread, but I was recently unpleasantly surprised how under-defined and undocumented is WASI.

I was looking into some detail of a WASI call and there is… basically nothing.

Also the latest version of the docs is called something like “snapshot3” or whatever. I thought “wait this is it? that’s the whole definition”? apparently it is.

edit: here. The actual latest definition is in "legacy/preview1". Yes that is the latest WASI definition.

https://github.com/WebAssembly/WASI/blob/main/legacy/preview...

What do the inputs mean? How should it behave in some extreme conditions? Eh YOLO who knows. All implementation dependent. This document is literally all there is. That's it, that's the WASI definition.

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Nobody is documenting anything because all that matters for people in this area is for existing C/C++/Rust code to run without modifications on WASM, which means whatever low level POSIX APIs they use is what WASI will support. A large number of software has been ported to run on WASM/WASI, and you can ask yourself how is that possible if WASI doesn't even have a formal API? Because the API is basically being reverse engineered.

So the situation is even worse than I had predicted: https://news.ycombinator.com/item?id=19502801

We (Wasmer), and other community members, were already aware of this.

Because of that, we tried to be as detailed as possible about the system calls. We might to define them further, but hopefully the WASIX docs are a good start! https://wasix.org/docs/api-reference

Oh that's great! I needed this one month ago, lol.

ahhh actual definitions!

https://wasix.org/docs/api-reference/wasi/fd_read

I work on WASI, and completely agree. A lot of things are not clearly documented right now, and we're working on fixing it.

As an implementer of WASI, I applaud this. Also, we are using wasi-testsuite and plan to contribute to it as Wizard finally has a full-time project for WASI.

I agree. I implemented a subset of WASI, and the best resource was an autogenerated C header with function signatures and very terse comments, buried in the WASI SDK repo.

I'm also currently implementing a subset of WASI, would you mind sharing a link to that file?

Actually, it was in wasi-libc: https://github.com/WebAssembly/wasi-libc/blob/main/libc-bott...

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