Validate stack depth across both sides of a branch
One branch pushes a value and the other does not, so the merge point underflows only for certain inputs.
- Focused work estimate
- 1h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Data-flow analysis · Stacks
Estimated field mix
- Systems programming60%
- Compiler and language tooling40%
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
- Validator computes required and resulting depth per instruction
- Control-flow merges require compatible stack shape
- Maximum stack depth is bounded before execution
Implementation constraints
- Validation must terminate on loops through a visited-state worklist.
Verification to include
- Validate a diamond control flow with matching stack shapes.
- Change one branch to omit a push and reject the merge.
Deliverables
- Stack-shape validator and branch fixtures
Rollout and recovery
Keep runtime stack checks even after static validation.
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.