Function references support

[zherczeg]

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I would like to parse some test files using wabt from the function reference (Phase 5) proposal such as call_ref.wast.

https://github.com/WebAssembly/function-references/blob/main/test/core/call_ref.wast

I have enabled the feature with --enable-function-references.

However, I get errors such as:

call_ref.wast:5:15: error: unexpected token $ii, expected ).
    (call_ref $ii (local.get $x) (local.get $f))
              ^^^

The format of call_ref was changed in: https://github.com/WebAssembly/function-references/commit/2b194cef87ba7f71c187b063a2ff8fea878e900a

May I ask the status of function reference support in wabt? Do you plan to support these proposal changes?

Thank you very much for the help!

[sbc100]

This proposal is not yet fully supported. If you would like to take a look at adding support that would be great. Sadly wabt doesn't have many folks contributing these days to its hard to say when the proposal might get implemented.

[keithw]

I think my own long-term plan is to get wasm-tools's wat2wasm and wasm2wat (https://github.com/bytecodealliance/wasm-tools/) to the point where they can substitute fully for WABT's wat2wasm/wasm2wat, and then sunset WABT. wasm-tools already supports function-references and GC.

It would be helpful to hear: what are some of the features that you use from WABT, that wasm-tools is currently missing?

[zherczeg]

Thank you for the information. Contributing to wabt might be possible, but I cannot promise anything at the moment.

Wabt is C++, and can be added to C++ projects.

[zherczeg]

I will try to make a patch for this, but I have little experience with the project, so I need your guidance.

Could you help me with these questions:

1. How can I represent an s33 value? For example type can be a value type or func index: https://github.com/WebAssembly/wabt/blob/main/include/wabt/binary-reader.h#L298

2. How can I store a type in Val structure? Is this correct? The index is a large value, but still part of uint32_t range. https://github.com/WebAssembly/wabt/blob/main/src/wast-parser.cc#L959

3. Type with argument looks like something new. -0x1c type (ref ht) has a $t : heaptype. How can I represent this?

[zherczeg]

To start from somewhere, I have created a branch: #2562

[zherczeg]

This issue can be closed. There are 6 patches implementing the whole GC support.

[sbc100]

My apologies Zoltan for the lack of progress reviewing your changes. I do hope to find time to do it, and perhaps we can find others to help too.