wat-compiler VS gc

For some time I've been fascinated by the codebase of a small WAT compiler written in JavaScript.

https://github.com/stagas/wat-compiler/blob/main/story.txt

And I mean "small" as a real complement to how readable the entire compiler is. It's also been a great way to appreciate the design of the WASM text format and WASM overall. It's not a Lisp but has a similar feel to it.

I've been meaning to get more fluent at writing WAT directly, not for any practical purpose but just for pleasure of it. I could see myself gradually building up some abstractions to help me deveolp larger programs, perhaps a slightly higher-level language.

I was also disappointed that this isn't included in the browsers given that it was designed to be very simple to parse and compile. So I tried as an exercise to build such a compiler[0] and indeed it was much easier than I expected (with a few shortcuts of course, being a POC). It is just 5kb gzipped and it compiles to binary most of the WAT code out there and also quite fast, just a few ms. That said, I think writing WAT by hand is only helpful for very small critical hot code, anything more complex and IMO you need an abstraction of some sort.

[0]: https://github.com/stagas/wel

It may take some time for WasmGC to be usable by .NET. Based on the discussions the first version of WasmGC does not have a good way to handle a few .NET specific scenarios, and said scenarios are "post-post-mvp". [0]

My concern, of course, is that there is not much incentive for those features to be added if .NET is the only platform that needs them... at that point having a form of 'include' (to where a specific GC version can just be cached and loaded by another WASM assembly) would be more useful, despite the pain it would create.

[0] - https://github.com/WebAssembly/gc/issues/77

The WASM GC support is intentionally kept as simple as possible, see https://github.com/WebAssembly/gc/blob/main/proposals/gc/MVP... . Building a "universal" or "generic" VM supporting many languages on an equally seamless basis is explicitly not a goal of WASM-GC; it is expected that each implementation might require its own hacks on top of the basic support WASM provides, but this is okay because FFI/cross-language interop is seen as an entirely separate issue.

Yes, that's definitely true: a single GC will not be optimal for everything, or even possible. Atm interior pointers are not supported at all, for example, but they are on the roadmap for later:

https://github.com/WebAssembly/gc/blob/main/proposals/gc/Pos...

What launched now is enough WasmGC to support a big and useful set of languages (Java, Kotlin, Dart, OCaml, Scheme), but a lot more work will be required here!

GC proposal is from 2018: https://github.com/WebAssembly/proposals/issues/16 and there’s code: https://github.com/WebAssembly/gc/blob/master/proposals/gc/O...

Seems like an awefully long time for progress to be made, given all the possibilities it would unlock.

First is the size. Writing a server-side and client-side program is possible with Rust, and the resulting WASM package will be small enough. At the same time, Microsoft Blazor converts C# code to WASM, but the client delivery has to include the reduced .NET runtime, taking several megabytes for a script. The same is true for GoLang, even with an attempt to reduce the runtime delivery in TinyGo WASM. Developers want to work with their favorite languages, whether it is Java, Kotlin, Dart, C#, F#, Swift, Ruby, Python, C, C++, GoLang, or Rust. These languages produce groups of runtimes. For example, JVM and .NET have many common parts, Ruby and Python are dynamically interpreted at runtime, and all mentioned depend on automatic garbage collection. For smaller WASM packages, browser vendors can include extended runtime implementations, for example, by delivering a general garbage collector as part of WASM. Garbage collection support by WASM is currently in progress: WASM GC, .NET WASM Notes.

My understanding is that the main limitation is technical. WASM doens't do GC or the host system calling conventions and cannot interact directly with object from Javascript because of this. However, this is being worked[0] on and will be solved eventually. Even without this the performance overhead of bridging to JS is low enough that WASM frameworks can beat out React.

0: https://github.com/WebAssembly/gc/blob/main/proposals/gc/Ove...

The .net team has given their notes on it, the concern is more on the memory layout from what I remember. Though it may be possible still. The runtime would likely still ship some gc code, but only a subset for cases not supported by the wasm gc itself and a few more for interfacing with the gc service, which overall should still result on smaller payloads compared to current sizes.

I assume that's one of the parts of the work done at https://github.com/WebAssembly/gc - not happening any soon yet, but it'll eventually be done.

To be fair, there is a GC proposal and some runtimes might even already be working on it, but as of today we have no WASM runtime that handles garbage collection.

Actually, Wasm goes into the direction you are pointing. A Wasm runtime should add a little overhead to the requirements of the Wasm module.

However, it's true Wasm is not on that point yet. There are open threads about deallocate Wasm memory [1]. However, I expect these features, as well as Garbage Collection [2] will come to the stardard over time. This will allow modules and runtimes to properly manage memory usage.

[1] https://stackoverflow.com/a/51544868

[2] https://github.com/WebAssembly/gc