Document the compatability status of 4GB heap

[kzhsw]

After WebAssembly/spec#1116, limit of max pages is updated to 65,536, but not all browser and runtimes have support of this feature, so it might worth to document somewhere for the compatability status.
Emscripten does not document the exact version of compatability status of 4GB heap in its docs.

Compatability status of browsers found yet:

• Chrome 83 https://v8.dev/blog/4gb-wasm-memory
• Firefox 89 https://bugzilla.mozilla.org/show_bug.cgi?id=1676441
• Safari 15.2 https://webkit.org/blog/12140/new-webkit-features-in-safari-15-2/

[tomayac]

Apart from tool documentation like emscripten's, this seems to be more a topic for developer-facing documentation to cover, like that of MDN. I don't think it is a proper feature, so don't think the Wasm website should cover this. If you disagree, feel free to comment and we can re-open the Issue no questions asked.

[dschuff]

I dunno, the feature list page is essentially developer-facing documentation, isn't it? It's true that 4G heap isn't a full proposal that's gone through the full 5-phase standards process, but it is part of the spec that has the same kind of non-uniform browser rollout that matters to developers, and that the features page is attempting to document. There is a tradeoff with making the features page more busy with smaller changes, but maybe it's worth it. This might also apply to a few JS API changes that didn't get the 5-phase process because of how they integrate with TC39/JS (e.g. ResizableArrayBuffer). I'd be curious if others have thoughts about those.

@kzhsw I think we'd also be willing to accept a PR against emscripten's documentation for this.
Thanks for bringing this up!

[tomayac]

Friendly ping for other opinions.

As an additional data point, this is also not a feature tracked by browser-compat-data.

[kzhsw]

Friendly ping for other opinions.

As an additional data point, this is also not a feature tracked by browser-compat-data.

Link the issue for browser-compat-data here: mdn/browser-compat-data#27777

[tomayac]

In the features.json file, the anatomy of a feature is:

{
  "bigInt": {
      "description": "JS BigInt to Wasm i64 Integration",
      "url": "https://github.com/WebAssembly/JS-BigInt-integration",
      "phase": 5
  }
}

The description is clear, but I'm not sure what we'd put for url (the Issue?) and for phase. The Features page is ordered by descending Phase.