Free large spill blocks without double-releasing arena pages
Oversized records spill to separate blocks. Error cleanup releases a spill block, then arena teardown releases the same block again.
- Focused work estimate
- 2h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Ownership · Cleanup · Memory diagnostics
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 telemetry collector copies decoded packet fields into a small native arena. The prototype misaligns wide values and reuses memory while readers still hold views. Create a local Rust crate or C library with generated byte fixtures; no device traffic or production allocator replacement is supplied.
Setup prerequisites
- Pointers and slices
- Integer overflow
- Memory alignment
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Each spill block has one recorded owner
- Cleanup is safe when invoked repeatedly
- Arena teardown releases only blocks still attached
Implementation constraints
- Model ownership explicitly; a boolean freed flag cannot authorize access after release.
Verification to include
- Allocate and release several spill blocks in different orders.
- Inject a decode error after spill allocation and run teardown twice under a memory checker.
Deliverables
- Spill ownership model and double-free regression
Rollout and recovery
Disable spill allocation if the checker reports any invalid release.
Value of the work
For the engineer: Practice representation invariants, lifetimes, unsafe-boundary review and memory diagnostics.
For the team: Review a component whose allocation failures and corruption cases are explicit before reuse in latency-sensitive code.
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.