fix(wit): export module functions through interfaces so write cannot shadow libc

[DenhamPreen]

Summary

Found while getting CI green: decoder_then_stdout_roundtrip and stdout_and_blackhole_sinks_accept_writes_and_flushes fail on main, locally and on the Linux runner, with a trap in stdout_sink.wasm!dlfree.

Cause. The sink world exported write at world level, so the core module carries a symbol literally named write. wasm-ld resolves wasi-libc's write(2) to it instead of pulling libc's own. Current stable Rust routes wasip2 stdout/stderr through libc write, so the moment a guest prints (the stdout sink, or any module's panic message) it calls its own write export with libc's arguments and corrupts its heap. The backtrace shows exactly that chain: Stderr::write_all → write → _export_write_cabi → dlfree trap.

Fix. Exports move into processor-impl and sink-impl interfaces (wit/hyperpipe.wit, mirrored in examples/wit and the ARCHITECTURE excerpt). Core symbols become envio:hyperpipe/sink-impl#write and cannot collide with anything. Host side calls bindings.envio_hyperpipe_sink_impl().call_write(..); the SDK export macros implement the interface Guest; the raw-bindgen blackhole-sink imports it. Modules written against the SDK need no source change, just a rebuild.

This is a WIT change, so existing compiled .wasm artifacts must be rebuilt (./scripts/build-modules.sh, just build-example-module).

Test plan

• cargo test -p hp-wasm-host: lib 44/44, integration 32/32 (was 30/32)
• cargo test -p hp-cli, cd modules && cargo test
• All guest modules and examples/modules/enrich build for wasm32-wasip2

Touches crates/wasm-host/src/lib.rs near the same lines as #19 (wasmtime bump); whichever merges second gets a trivial conflict.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Tj76igEYjgdV7iZ7kaMxN8

Summary by CodeRabbit

• Improvements
  • Processor and sink operations are now grouped under dedicated interfaces, providing clearer namespacing and avoiding conflicts with standard symbols.
  • Updated component integrations and examples to use the new processor and sink interfaces.
  • Existing processing, writing, flushing, error handling, and pooling behavior remains unchanged.
• Documentation
  • Added guidance explaining the interface organization and symbol-collision considerations.

[coderabbitai]

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Configuration used: Organization UI

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Run ID: 665a93ae-0480-4ece-9d24-9965092d3a89

📥 Commits

Reviewing files that changed from the base of the PR and between fda25af and 45ba8e5.

📒 Files selected for processing (6)

• ARCHITECTURE.md
• crates/wasm-host/src/lib.rs
• examples/wit/hyperpipe.wit
• modules/blackhole-sink/src/lib.rs
• modules/sdk/src/lib.rs
• wit/hyperpipe.wit

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📝 Walkthrough

Walkthrough

The WIT contracts now export processor and sink operations through named implementation interfaces. SDK Guest implementations and wasm-host calls use the generated interface-specific bindings.

Changes

Interface namespacing

Layer / File(s)	Summary
WIT interface contracts ARCHITECTURE.md, wit/hyperpipe.wit, examples/wit/hyperpipe.wit	Adds processor-impl and sink-impl interfaces and exports them from the corresponding worlds.
Component binding updates modules/sdk/src/lib.rs, modules/blackhole-sink/src/lib.rs	Updates shared type re-exports and Guest implementations to use the generated implementation interfaces.
Host interface calls crates/wasm-host/src/lib.rs	Routes processor initialization, processing, sink initialization, writing, and flushing through the new interface bindings.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to 45ba8

The processor and sink exports are consistently namespaced to prevent the libc write-symbol collision. Modules must be rebuilt, but no actionable merge-blocking issue remains.

Suggested reviewers: nikbhintade

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 42.86% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 3 files. (3 skipped: 3…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: moving module function exports into interfaces to prevent the write symbol from shadowing libc.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 42.86% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 7 functions across 3 files. (3 skipped: 3 unsupported.)

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✨ Finishing Touches 💡 1

📝 Generate docstrings 💡

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