fix memory leak in cyclic object graphs, add non_root_count

[shruti2522]

added non_root_count to fix OOM memory leak occuring in the collector

[Copilot]

🟡 Changes recommended

One or more issues must be addressed before approval.

Once you've addressed the issues Copilot identified, you can request another Copilot review.

Pull request overview

Adds non-root reference counting to improve cycle collection in the branded mark-sweep collector.

Changes:

• Adds non-root counting and root classification.
• Adds traversal support for Gc references.
• Adjusts null trace handling.

File summaries

File	Description
oscars/src/collectors/mark_sweep_branded/trace.rs	Updated as part of this pull request.
oscars/src/collectors/mark_sweep_branded/mod.rs	Updated as part of this pull request.
oscars/src/collectors/mark_sweep_branded/gc.rs	Updated as part of this pull request.
oscars/src/collectors/mark_sweep_branded/gc_box.rs	Updated as part of this pull request.

Review details

Suppressed comments (1)

oscars/src/collectors/mark_sweep_branded/mod.rs:178

• The new liveness pass has no regression test for the failure mode named by this PR: the branded tests cover isolated allocations, roots, and ephemerons, but not two GC objects that point to each other. Add a test that creates a cycle and verifies it is reclaimed (for example through finalization or weak validity), including the container-nesting case this pass must support.

                gc_box.non_root_count.set(0);

• Files reviewed: 4/4 changed files
• Comments generated: 2
• Review effort level: Lite

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.