Add multi-memory example

[hamishwillee]

This adds an example of how to use multiple memories in Web Assembly.

• It shows how to create two memories in JavaScript and import to the WASM, and one memory in WASM and export to the JavaScript.
• It updates each with different text that gets printed to screen (uses screen based logging rather than console logging, which is much nicer)
• It shows that the default memory is the 0 index one.

Still working on docs

This is part of work for mdn/content#32777

[hamishwillee]

@bsmth Do you have reviewer rights here?

[bsmth]

@bsmth Do you have reviewer rights here?

I do, yes. I can take a look - adding myself as a reviewer

[hamishwillee]

Thanks @bsmth !

[hamishwillee]

FYI, would be good if this could be merged somewhat soon. The release is this week.

[bsmth]

Thanks, Hamish. To get this running I did:

# Get wabt tools (https://github.com/WebAssembly/wabt)
brew install wabt

wat2wasm --enable-multi-memory multi-memory.wat -o multi-memory.wasm

Should we capture that somewhere? Can be on the content side

[bsmth]

Back over to you, @hamishwillee - do you want to check the comments I've left? I think we can merge afterwards 🚢

[bsmth]

LGTM pending the comment about overrunning the memory, the code comment looks like a good way to flag what's happening

[hamishwillee]

@bsmth Thanks for merging (and happy with your changes)

Should we capture that somewhere? Can be on the content side

I am not sure. The "right" think to do would be to allow support for building WASM in live examples. However that's a bit of a step because you'd need to be able to dynamically generate wasm from wat. It is actually not possible for this example because the tools that are used by interactive examples don't support the multimemory (which is what we'd used).

I don't think we'd do it in content.

The best compromise way to do it would be to add "Running/Setup" into this project's README. Thoughts?

[bsmth]

Thanks, Hamish!

I wasn't sure if we covered how to do this in a generic way in mdn/content docs, but I see we have this: https://developer.mozilla.org/en-US/docs/WebAssembly/Text_format_to_Wasm#converting_the_text_.wat_into_a_binary_.wasm_file which is exactly what I was looking for, so problem solved. We could link to that from the README, I think that's a good help.

On a related note, I see there's some work ongoing for wat support:

• feat!(wat): migrate from wabt (npm) to wat (cargo) to support latest features bob#1776
• Update WASM playground to support the latest features bob#1745
• Add return_call example for WASM interactive-examples#2693

[hamishwillee]

Thanks @bsmth - that's cool, particularly the bob update. Though it is hard to tell from https://crates.io/crates/wasm-pack or the bob updates whether the features will "all" be supported (or even which ones are).

Fixed up readme here #36

[bsmth]

whether the features will "all" be supported (or even which ones are).

Good question, Florian / Vadim would have better context on it, it looks promising so far!