Stop infinite programs with a deterministic instruction budget
A backward jump with an always-true condition consumes a worker indefinitely.
- Focused work estimate
- 4h + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Resource metering · Determinism
Estimated field mix
- Systems programming60%
- Security40%
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 rules engine executes a tiny arithmetic bytecode over synthetic integers. Its interpreter trusts jump offsets and can run forever. Build a local Rust runtime; it has no filesystem, network, dynamic loading, host calls, or candidate-source execution.
Setup prerequisites
- Stacks
- Instruction decoding
- Control flow
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Caller supplies a positive maximum instruction count
- Every executed instruction consumes budget
- Exhaustion returns current offset and no successful result
Implementation constraints
- Wall-clock timeout can be defense in depth but is not the deterministic oracle.
Verification to include
- Run a terminating loop at exactly the declared budget.
- Run an infinite loop and verify failure at the same step in repeated executions.
Deliverables
- Instruction metering and loop-bound tests
Rollout and recovery
Begin with a conservative budget and expose exhaustion separately from invalid bytecode.
Value of the work
For the engineer: Practice runtime invariants, validation, resource accounting and compatibility.
For the team: Review a constrained execution component whose malformed programs fail deterministically without gaining host capabilities.
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.