Write the buffer ownership table before exposing the binding
JavaScript and Rust both believe the other side frees an output buffer when conversion throws.
- Focused work estimate
- 1h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- FFI · Ownership · Resource cleanup
Estimated field mix
- Systems programming70%
- Developer tooling30%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
A fictional desktop backup tool calls a small Rust compression library from Node.js. The binding leaks buffers on exceptions and treats ABI mismatches as corrupted input. Build against generated byte arrays and a local native library; no production archive format or user files are supplied.
Setup prerequisites
- FFI ownership
- Binary compatibility
- Error handling
Preceding work
No earlier ticket is required. Complete the project setup above.
Acceptance criteria
- Document owner for every input, output, error, and callback value
- Each transfer has one release operation and allowed thread
- Borrowed memory cannot outlive its originating call
Implementation constraints
- Do not infer ownership from constness or language garbage collection.
Verification to include
- Trace success and error paths through the ownership table.
- Inject failure after native allocation and verify exactly one release.
Deliverables
- FFI ownership contract and allocation counter test
Rollout and recovery
Keep the pure-language fallback until every path has an owner.
Value of the work
For the engineer: Practice language-boundary contracts, native resource safety and version negotiation.
For the team: Review a binding that fails safely and can be rolled back before native code enters additional application paths.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.