[dlunch]

Garbage collection

• Add optional consumer-provided ExternalRoots to Jvm::new.
• Make push_native_frame(args) return a scoped NativeFrame guard that roots object arguments and releases local references on drop; remove manual Jvm::pop_frame.
• Track reachability by object identity, retain active monitor owners and waiters, and keep synchronized method arguments and results rooted across suspension.
• Return collection failures through anyhow::Result without sweeping after root discovery or tracing fails; translate Java GC entry-point failures to InternalError.
• Extend GC tests and existing synchronization fixtures to cover external roots, frame lifetimes, cyclic references, and collection during monitor operations.

Member resolution

• Check the requested static or instance kind first, preserving declaring-class lookup order and incompatible-kind errors.

Verification

• cargo fmt --all
• cargo clippy --workspace --all-targets --locked --offline -- -D warnings
• cargo clippy --target wasm32-unknown-unknown --locked --offline -- -D warnings
• cargo test --workspace --locked --offline --quiet: 581 passed, 2 ignored.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-25T00:35:47.252497Z	b0fac61	New commits

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[codecov]

Codecov Report

❌ Patch coverage is 94.28571% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.79%. Comparing base (00a2734) to head (b0fac61).

Files with missing lines	Patch %	Lines
jvm/src/jvm.rs	91.76%	7 Missing ⚠️
rustjava-runtime/src/classes/java/lang/runtime.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #227      +/-   ##
==========================================
+ Coverage   87.78%   87.79%   +0.01%     
==========================================
  Files         311      311              
  Lines       47092    47155      +63     
==========================================
+ Hits        41338    41401      +63     
  Misses       5754     5754              

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[Copilot]

🔵 Needs a closer look

It reworks core GC reachability, monitor concurrency, and synchronized-method execution ordering—high-risk areas where subtle lifetime or race regressions warrant final human review despite passing tests.

No open issues 🎉

What changed in this PR

This PR hardens the native JVM's garbage collector against collecting host-visible references and tightens member resolution. On the GC side it adds a consumer-provided ExternalRoots trait plus scoped NativeFrame guards so that host references, synchronized-method arguments/results, and active monitor objects stay rooted across suspension points; reachability is now tracked by object identity (fixing cyclic-reference handling) and collection failures surface through anyhow::Result instead of panicking, with Java System.gc()/Runtime.gc() translating failures to InternalError. On the resolution side, field/method lookup now tries the caller's requested static/instance kind first while preserving JVMS declaring-class order and incompatible-kind errors.

Changes:

• GC roots now include ExternalRoots, active monitors (Monitor::is_active), and NativeFrame-scoped host references; collect_garbage/determine_garbage return anyhow::Result and key reachability on ClassInstance::identity().
• Synchronized-method execution acquires the monitor after pushing the Java frame and uses pop_frame_with_result, keeping arguments/results rooted while waiting for the monitor; MonitorWait tracks active_waits and releases it on Drop.
• resolve_field/resolve_method gained an expected_static preference; broad test/fixture additions cover external roots, frame lifetimes, cycles, and GC during monitor operations.

File	Description
jvm/​src/​external_roots.rs	New ExternalRoots trait for consumer-provided root discovery.
jvm/​src/​jvm.rs	NativeFrame guard, native_frame/pop_frame_with_result, external-root + monitor rooting, expected_static resolution, reordered synchronized-method flow.
jvm/​src/​garbage_collector.rs	Identity-based reachability and anyhow::Result error propagation instead of unwrap.
jvm/​src/​monitor.rs	active_waits counter, is_active, MonitorWait Drop, and &mut listener await.
jvm/​src/​lib.rs	Re-exports ExternalRoots and NativeFrame.
rustjava-runtime/​src/​classes/​java/​lang/​{system,runtime}.rs	Translate GC failure to InternalError.
jvm/​tests/​test_garbage_collection.rs, jvm/​tests/​test_string.rs	New/updated GC tests (external roots, frames, monitors, cycles).
test-data/​src/​{MonitorSemantics,ThreadInterruption}.java	Add System.gc() to exercise collection during monitor operations.
test-utils/​src/​lib.rs, src/​lib.rs, rustjava-runtime/​tests/​.../​test_class.rs	Re-export get_bootstrap_class_loader and pass new Jvm::new argument.

_{Review effort: Balanced}