Stream: git-wasmtime

Topic: wasmtime / PR #8568 wasmtime: Implement Extended Constant...

Wasmtime GitHub notifications bot (May 07 2024 at 09:52):

jameysharp opened PR #8568 from jameysharp:extended-const to bytecodealliance:main:

This implements https://github.com/webassembly/extended-const for Wasmtime.

Currently the documentation comment for the wasm_extended_const configuration option says it's false by default, but Config::new sets it to true. One of those should be fixed and I'm not sure which. Other config-related things are still to-do as well, such as adding the appropriate CLI flag.

Also, I could use a little help understanding why one of the funcrefs spec tests fails:

Caused by:
    0: failed directive on tests/spec_testsuite/proposals/function-references/elem.wast:539:1
    1: assert_invalid: expected "constant expression required", got "failed to parse WebAssembly module

       Caused by:
           type mismatch: expected funcref, found i32 (at offset 0x1b)"

cc: @fitzgen

Wasmtime GitHub notifications bot (May 07 2024 at 12:49):

github-actions[bot] commented on PR #8568:

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Wasmtime GitHub notifications bot (May 07 2024 at 14:35):

alexcrichton commented on PR #8568:

For the failure here I think you'll need to set wasm_extended_const(false) in Config when running the tests. Spec proposals aren't always in-sync with one another and it takes quite some time to merge into the official spec, so tests often assert that a specific construct is invalid when another proposal specifically makes it valid, meaning that we have to be careful about enabled features when testing various proposals.

Wasmtime GitHub notifications bot (May 07 2024 at 15:46):

fitzgen commented on PR #8568:

Yeah that failure is just because it is using an i32.add in a constant expression which used to be disallowed but is now allowed with the extended constants proposal.

We can ignore that particular failure by adding a clause here: https://github.com/bytecodealliance/wasmtime/blob/main/crates/wast/src/wast.rs#L544

Would be nice to ideally send a PR upstream to fix the issue (switch the add to some operator that isn't allowed even with the extended constants proposal) or at least make a local copy for the misc_testsuite that does that same thing.

Wasmtime GitHub notifications bot (May 07 2024 at 15:48):

fitzgen commented on PR #8568:

Currently the documentation comment for the wasm_extended_const configuration option says it's false by default, but Config::new sets it to true. One of those should be fixed and I'm not sure which.

I think it is fine to have it enabled by default since it is a phase 4 proposal (basically done) and will have more than 2 weeks fuzzing before it hits a release.

Wasmtime GitHub notifications bot (May 07 2024 at 16:04):

alexcrichton commented on PR #8568:

Oh I'll note that wasm-smith doesn't have support for extended consts right now I think, so AFAIK we won't fuzz this at all

Wasmtime GitHub notifications bot (May 07 2024 at 16:09):

fitzgen commented on PR #8568:

Ah yes, we should add that support before enabling this proposal by default.

Last updated: Dec 23 2024 at 12:05 UTC