Compare native output against the compatibility oracle
The native path is faster but emits archives the existing decompressor accepts differently around empty blocks.
- Focused work estimate
- 4h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Differential testing · Compatibility
Estimated field mix
- Systems programming70%
- Quality engineering30%
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
Complete these dependencies, or supply their agreed outputs before taking this ticket.
- SFFI-102 · Validate lengths before converting JavaScript buffers
- SFFI-101 · Write the buffer ownership table before exposing the binding
- SFFI-103 · Map native errors without losing machine-readable causes
- SFFI-104 · Release native output after JavaScript cancellation
- SFFI-105 · Move blocking compression off the JavaScript event loop
- SFFI-106 · Negotiate ABI capability before the first compression call
Acceptance criteria
- Golden corpus defines byte compatibility or declared semantic compatibility
- Both providers round-trip every supported case
- Differences are classified before rollout
Implementation constraints
- Use generated non-sensitive bytes and pin provider versions in the report.
Verification to include
- Compare providers across corpus sizes and option combinations.
- Inject a one-byte divergence and show the gate blocks promotion.
Deliverables
- Differential harness and compatibility report
Rollout and recovery
Canary only corpus classes with reconciled outputs.
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.