wasmtime / PR #14151 cranelift-module: fix the no_std bui... · git-wasmtime

Stream: git-wasmtime

Topic: wasmtime / PR #14151 cranelift-module: fix the no_std bui...

Wasmtime GitHub notifications bot (Aug 18 2026 at 11:35):

Lstarsky0 requested fitzgen for a review on PR #14151.

Wasmtime GitHub notifications bot (Aug 18 2026 at 11:35):

Lstarsky0 opened PR #14151 from Lstarsky0:fix/cranelift-module-no-std to bytecodealliance:main:

cargo check -p cranelift-module --no-default-features fails on main with 11 errors, and --no-default-features --features core fails with 6. Both have been broken since #5173 (2022-11-03).

What is broken

cranelift/module/src/lib.rs is #![no_std] and aliases alloc as std when the std feature is off:
#[cfg(not(feature = "std"))]
extern crate alloc as std;
module.rs then uses three paths that only exist in real std:

site path

ModuleError::Allocation payload std::io::Error

the Error impl and its source() std::error::Error

two From impls std::convert::From

--features core does not help — it only pulls in hashbrown, so the same three paths still fail. Bare --no-default-features fails on those plus hashbrown itself, which the manifest only supplies through core.

Why it went unnoticed

cranelift-module appears in no file under .github/, so no job builds it in any non-default configuration.

The one configuration that forwards to it cannot catch it either. cranelift's core feature lists cranelift-module?/core, but the umbrella declares
cranelift-module = { workspace = true, optional = true }
without default-features = false, and the workspace entry does not set it either, so cranelift-module/std is on whenever the dep is. cargo tree -e features -p cranelift --no-default-features --features core,module shows core and std both active. cranelift-codegen is declared with default-features = false at the workspace level; cranelift-frontend and cranelift-module are not.

I have left that alone — whether cranelift's core should actually mean core is a separate call, and it would need this fix first anyway.

The change

Allocation is gated on std. The payload is a std::io::Error and the only producer is cranelift-jit (compiled_blob.rs), which needs std regardless.

core::error::Error instead of std::error::Error — stable since 1.81, MSRV here is 1.95. Plain From instead of std::convert::From.

hashbrown becomes non-optional, matching cranelift-frontend, which has the identical #[cfg(not(feature = "std"))] use hashbrown::... and a non-optional hashbrown. The hashbrown feature is dropped from core as a result.

That last one removes the cranelift-module/hashbrown feature. Nothing in the workspace names it; the umbrella only forwards ?/std and ?/core.

Testing

Three checks added to the micro_checks matrix. On unpatched main they fail:

check main with this PR

-p cranelift-module --no-default-features 11 errors ok

-p cranelift-module --no-default-features --features core 6 errors ok

-p cranelift-module --no-default-features --features core,enable-serde 6 errors ok

Also run locally, all clean: -p cranelift-module --all-features, cargo test -p cranelift-module, cargo clippy -p cranelift-module --all-targets and the same with --no-default-features, cargo fmt --all -- --check, and cargo check for cranelift-jit, cranelift-object, cranelift, cranelift-filetests and cranelift-tools. Cargo.lock is unchanged.

This does not make the crate buildable for a bare-metal target on its own — anyhow is a hard dependency carrying features = ['std']. It makes the configurations the crate already advertises compile again.

site	path
`ModuleError::Allocation` payload	`std::io::Error`
the `Error` impl and its `source()`	`std::error::Error`
two `From` impls	`std::convert::From`

check	main	with this PR
`-p cranelift-module --no-default-features`	11 errors	ok
`-p cranelift-module --no-default-features --features core`	6 errors	ok
`-p cranelift-module --no-default-features --features core,enable-serde`	6 errors	ok

Wasmtime GitHub notifications bot (Aug 18 2026 at 11:35):

Lstarsky0 requested wasmtime-compiler-reviewers for a review on PR #14151.

Wasmtime GitHub notifications bot (Aug 18 2026 at 11:35):

Lstarsky0 requested wasmtime-default-reviewers for a review on PR #14151.

Wasmtime GitHub notifications bot (Aug 18 2026 at 12:02):

bjorn3 commented on PR #14151:

std::error::Error is just a re-export of core::error::Error.

Wasmtime GitHub notifications bot (Aug 18 2026 at 12:03):

bjorn3 deleted a comment on PR #14151:

std::error::Error is just a re-export of core::error::Error.

Wasmtime GitHub notifications bot (Aug 18 2026 at 14:54):

github-actions[bot] added the label cranelift on PR #14151.

Wasmtime GitHub notifications bot (Aug 18 2026 at 14:54):

github-actions[bot] added the label cranelift:module on PR #14151.

Wasmtime GitHub notifications bot (Aug 18 2026 at 16:38):

:repeat: pchickey submitted PR review:

First, please review the AI tool policy https://github.com/bytecodealliance/governance/blob/main/AI_TOOL_POLICY.md

Second, cranelift-codegen's Cargo.toml describes that the core feature is no longer used, remaining in name only for compatibility purposes. So, cranelift-module's use of that feature also no longer needs to exist, and does not need to consume CI resources with test coverage.

Wasmtime GitHub notifications bot (Aug 19 2026 at 09:34):

Lstarsky0 updated PR #14151.

Wasmtime GitHub notifications bot (Aug 19 2026 at 09:45):

Lstarsky0 commented on PR #14151:

Read the policy. you are right about core, codegen has it as core = [], name only now. Dropped the forward and the two --features core CI lines with it. I left it as core = [] rather than deleting outright, since umbrella forwards cranelift-module?/core and the crate is published. Happy to delete both if you'd rather. frontend and native carry the same dead forward; left those alone.
The build fix underneath is a separate thing from core though. cargo check -p cranelift-module --no-default-features is 8 errors on main right now — hashbrown is imported unconditionally but was only pulled in by core, and a few impls reach for std::. That's what the one remaining CI line covers.

Wasmtime GitHub notifications bot (Aug 21 2026 at 17:46):

:thumbs_up: pchickey submitted PR review.

Wasmtime GitHub notifications bot (Aug 21 2026 at 17:46):

pchickey added PR #14151 cranelift-module: fix the no_std build and cover it in CI to the merge queue.

Wasmtime GitHub notifications bot (Aug 21 2026 at 17:46):

pchickey commented on PR #14151:

Thank you

Wasmtime GitHub notifications bot (Aug 21 2026 at 18:12):

:check: pchickey merged PR #14151.

Wasmtime GitHub notifications bot (Aug 21 2026 at 18:12):

pchickey removed PR #14151 cranelift-module: fix the no_std build and cover it in CI from the merge queue.

Last updated: Aug 30 2026 at 09:07 UTC