Bug 258219 – [Wasm-GC] Add support for bottom heap types

• Status: RESOLVED
• Resolution: DUPLICATE
• Component: WebAssembly

Created attachment 466719 [details]
test

Steps to reproduce:

1. Unpack the attached file.
2. Run `jsc --useWebAssemblyTypedFunctionReferences=true --useWebAssemblyGC=true --module-file=test.mjs`

Actual results:

Exception: CompileError: WebAssembly.Module doesn't parse at byte 3: ref.null heaptype must be funcref, externref or type_idx, in function at index 0 (evaluating 'new WebAssembly.Module(wasmBuffer)')
Module@[native code]

Expected results:

No errors

--

Related tests in the GC proposal repo:
https://github.com/WebAssembly/gc/blob/main/test/core/gc/ref_cast.wast
https://github.com/WebAssembly/gc/blob/main/test/core/gc/ref_test.wast

[Asumu Takikawa]

Thanks for this bug report, I think it might be a duplicate of this existing one though: https://bugs.webkit.org/show_bug.cgi?id=254695

[Radar WebKit Bug Importer]

<rdar://problem/111230425>

[David Degazio]

As far as I can tell, the encoding here has actually changed since this bug was opened, and the attached WASM binary is no longer valid. Specifically, it has the following sequence:

    d065 ;; ref.null none
    1a
    d069 ;; ref.null nofunc
    1a
    d068 ;; ref.null noextern
    1a

Specifically using 0x65, 0x69, and 0x68 to represent heap types none, nofunc, and noextern respectively. Per the current GC proposal spec though (https://webassembly.github.io/gc/core/binary/types.html#binary-heaptype), these should actually be encoded as 0x71, 0x73, and 0x72. Recompiling the attached test.wat with wasm-as version 118 produces a different binary with these new heaptypes, which JSC seems to handle without issue.

So, support for none, nofunc, and noextern is working as expected, and I'll resolve this as a dupe of Asumu's other bug.

*** This bug has been marked as a duplicate of bug 254695 ***