wasm: support for wasm32-wasip2 target by eduardomourar · Pull Request #12653 · uutils/coreutils

eduardomourar · 2026-06-06T01:36:45Z

Add support for the wasm32-wasip2 (WASI Preview 2) target, enabling coreutils to compile and be used on sandboxed environments that can run WebAssembly components.

Changes

Add wasm32-wasip2 target to CI workflows
Update code for wasip2 compatibility (yes and uucore libraries)
Ensure unit tests pass on the new target
Update documentation about supported platforms

oech3 · 2026-06-06T01:59:58Z

But why? Is there any usecase wasip1 cannot cover? If wasip2 works on web browsers using shim, we should drop wasip1 at the same time.

eduardomourar · 2026-06-06T03:01:33Z

The main reason to have WASI Preview 2 is because Preview 1 is not being further developed. In wasip1, we would never get full support for streams and socket. With wasip2, on other hand, we will have those as well as support for the WebAssembly Component Model. This documentation might help answering you: https://component-model.bytecodealliance.org/design/why-component-model.html#interoperability

Should we drop wasip1? Probably not yet. There are few features that are missing in Preview2:

std::os::wasi::prelude::OsStrExt is still under the unstable flag as discussed here
WASI CLI Exit with code has stabilized but it has not been implemented in rust std
Generated WASM component cannot be easily loaded yet in the browser. You need JCO to transpile it and include the respective WASI shims in order to have something similar to the Uutils Playground.

oech3 · 2026-06-06T03:31:26Z

Ok. But do you want to publish release binaries too? Or is cargo check or cargo test on the CI enough?

sylvestre · 2026-06-06T06:03:33Z

    new_ucmd!()
        .args(&["--from=iec-i", "10M"])
-        .fails_with_code(2)
+        .fails_with_code(if cfg!(wasip2_runner) { 1 } else { 2 })


I have written now in docs/src/wasi-test-gaps.md some details on that. The WASI Preview 2, as currently implemented in Rust std, only allows to exit with code 0 (success) or 1 (failure).

It is limitation for wasip2 instead of ideal behaviour. So we should just guard the test by cfg.

Is exit 2 not buildable? or buildable with exit 1 fallback?

It will be done as part of other PR.

github-actions · 2026-06-06T06:14:26Z

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tty-eof (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/tail/retry (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/cut/cut-huge-range is now being skipped but was previously passing.
Congrats! The gnu test tests/rm/many-dir-entries-vs-OOM is now passing!

eduardomourar · 2026-06-06T20:52:17Z

Ok. But do you want to publish release binaries too? Or is cargo check or cargo test on the CI enough?

For me, I would benefit of having the released binary for wasip2. I understand it adds a bit more complexity to maintain it, but I think the burden to keep wasip2 is basically the same as wasip1.

oech3 · 2026-06-09T17:22:44Z

Correctness of error handling is unrelated with initial support (cargo build). Please split PR for less diff.

eduardomourar · 2026-06-09T20:53:28Z

@oech3, done. I only left the changes to run the build successfully. I am skipping the integration tests for wasip2 as it will be part of the PR related to error handling.

codspeed-hq · 2026-06-10T05:33:34Z

Merging this PR will not alter performance

✅ 64 untouched benchmarks
⏩ 305 skipped benchmarks¹

_{Comparing eduardomourar:feat/support-wasm32-wasip2 (02c6ba8) with main (d01be5b)}

305 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

eduardomourar · 2026-06-10T08:34:27Z

@codspeedbot fix this regression

sylvestre · 2026-06-10T08:38:45Z

this is probably noise, you can ignore the perf warning

eduardomourar · 2026-06-10T20:42:54Z

@sylvestre and @oech3, I have rebased it. So let me know if you need me to do anything about those perf warnings, ok?

eduardomourar · 2026-06-18T14:40:53Z

@sylvestre and @oech3, as far I aware there is no other pending issues. If so, this is ready to be approved and merged.

oech3 · 2026-06-18T14:52:46Z

(also I have no priv for merge)

eduardomourar · 2026-06-18T17:52:08Z

Please fix yes's as_encoded_bytes cfg issue.

That was already fixed. I pushed a small change in order to run the integration test of yes command for both wasip1 and wasip2.

eduardomourar · 2026-06-23T15:23:29Z

@sylvestre, could I get your approval on this one, please? I just need that into main so I can create the other PR to enable the integration tests for wasip2.

sylvestre · 2026-06-23T15:39:26Z

-        cargo test --target wasm32-wasip1 --no-default-features $UTILS
+        cargo test --target ${{ matrix.job.target }} --no-default-features $UTILS
    - name: Run integration tests via wasmtime
+      if:  matrix.job.target == 'wasm32-wasip1'


no case for wasm32-wasip2 ?

Skipping integration tests for now until I fix all the error handling issues. It will be in the next PR.

sylvestre · 2026-06-23T15:41:06Z

 #[cfg(unix)]
 use std::os::unix::ffi::{OsStrExt, OsStringExt};
-#[cfg(target_os = "wasi")]
+#[cfg(all(target_os = "wasi", target_env = "p1"))]


sorry, what happens when using p2 ?

It fails to compile with:

error[E0658]: use of unstable library feature wasip2
--> src/uucore/src/lib/lib.rs:151:26
|
151 | use std::os::wasi::ffi::{OsStrExt, OsStringExt};

I am avoiding it so not to deal with needing Rust nightly. Additionally, WASI should only expect valid UTF-8 paths (as stated here and in other parts of the WASI specification).

oech3 · 2026-06-09T17:26:58Z

 // TODO(#7542): Re-enable on Android once we figure out why setting limit is broken.
 // #[cfg(any(target_os = "linux", target_os = "android"))]
 #[cfg(target_os = "linux")]
+#[cfg_attr(wasi_runner, ignore = "WASI: resource limits not supported")]


allready guarded by linux. Why is this needed? Same for other tests.

As I have removed those changes per your request, I will address them as part of the next PR, ok?

oech3 · 2026-06-10T04:21:54Z

    new_ucmd!()
        .args(&["--from=iec-i", "10M"])
-        .fails_with_code(2)
+        .fails_with_code(if cfg!(wasip2_runner) { 1 } else { 2 })


Is exit 2 not buildable? or buildable with exit 1 fallback?

oech3 · 2026-06-23T15:58:19Z

My comments were pending. Sorry for noise

Co-authored-by: oech3 <79379754+oech3@users.noreply.github.com>

sylvestre reviewed Jun 6, 2026

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sylvestre force-pushed the feat/support-wasm32-wasip2 branch from 5feb45e to 732f48f Compare June 7, 2026 20:31

eduardomourar force-pushed the feat/support-wasm32-wasip2 branch 2 times, most recently from db9d3ff to 712ff58 Compare June 9, 2026 17:09

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eduardomourar force-pushed the feat/support-wasm32-wasip2 branch from 712ff58 to e5bfc97 Compare June 9, 2026 20:51

eduardomourar force-pushed the feat/support-wasm32-wasip2 branch from e5bfc97 to 042f481 Compare June 9, 2026 21:14

eduardomourar force-pushed the feat/support-wasm32-wasip2 branch from 042f481 to 749d289 Compare June 18, 2026 13:08

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eduardomourar force-pushed the feat/support-wasm32-wasip2 branch 2 times, most recently from 484c0af to 02c6ba8 Compare June 19, 2026 20:00

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sylvestre reviewed Jun 23, 2026

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eduardomourar and others added 4 commits June 23, 2026 22:21

feat(wasi): ensure build works for wasm32-wasip2

485b672

ci: add new wasm32-wasip2 target to workflow

9472e85

yes: fix for non sigpipe in wasi

4aa6ff1

uucore: os string guaranteed to be encoded in unix and wasi

dca4733

Co-authored-by: oech3 <79379754+oech3@users.noreply.github.com>

eduardomourar force-pushed the feat/support-wasm32-wasip2 branch from d843910 to dca4733 Compare June 23, 2026 22:52

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Merging this PR will not alter performance

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