# PR-3.7 — Integrate GC Cycle at Safepoint (`FRAME_SYNC`)

### Briefing

The GC must only run at safepoints. This PR connects the mark-sweep collector to the VM’s safepoint logic, primarily at `FRAME_SYNC`.

### Target

* Trigger GC cycles only at safepoints.
* Keep execution deterministic.

### Work items

* Identify safepoint handling code in the VM.
* Add logic:

  * If allocation threshold exceeded, run GC at `FRAME_SYNC`.
* Ensure GC does not run in arbitrary instruction contexts.

### Acceptance checklist

* [ ] GC runs only at safepoints.
* [ ] No GC during arbitrary instruction execution.
* [ ] VM remains deterministic.
* [ ] `cargo test` passes.

### Tests

* Add a test where allocations trigger GC only at `FRAME_SYNC`.

### Junie instructions

**You MAY:**

* Hook GC invocation into safepoint handling.

**You MUST NOT:**

* Trigger GC at random points.
* Add background or concurrent GC.

**If unclear:**

* Ask before modifying safepoint semantics.

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# PR-3.8 — GC Smoke and Stress Tests

### Briefing

We need confidence that the GC behaves correctly under simple and stressed conditions.

### Target

* Add deterministic smoke and stress tests for the GC.

### Work items

* Add tests:

  * Simple allocation and collection cycle.
  * Many short-lived objects.
  * Cyclic references.
* Ensure tests are deterministic.

### Acceptance checklist

* [ ] Smoke tests pass.
* [ ] Stress tests pass.
* [ ] No nondeterministic failures.
* [ ] `cargo test` passes.

### Tests

* New GC-specific tests.

### Junie instructions

**You MAY:**

* Add deterministic tests.

**You MUST NOT:**

* Introduce random or timing-dependent tests.
* Modify GC semantics to satisfy tests.

**If unclear:**

* Ask before changing test scenarios.