GeezerVison is showing github.com — Improve object traversal for heap types and mro by youknowone · Pull Request #6976 · RustPython/RustPython
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youknowone
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Feb 3, 2026
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- Fix heap type instance traversal to include type reference (enables correct cycle detection for instance ↔ type references)
- Enable mro traversal in PyType (was previously disabled)
Summary by CodeRabbit
- Refactor
- Improved garbage collection traversal for type objects to ensure proper memory management of type hierarchies and heap-allocated types.
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- Fix heap type instance traversal to include type reference
(enables correct cycle detection for instance ↔ type references)
- Enable mro traversal in PyType (was previously disabled)
coderabbitai
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commented
Feb 3, 2026
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edited
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📝 Walkthrough
Walkthrough
This PR enhances garbage collection tracing in the RustPython VM by re-enabling MRO traversal in PyType and adding explicit heap-type reference tracing in PyInner object traversal. These changes ensure complete marking of type relationships during GC cycles.
Changes
| Cohort / File(s) |
Summary |
GC Traversal Enablement
crates/vm/src/builtins/type.rs |
Re-enabled MRO traversal in PyType's traverse implementation by uncommenting self.mro.traverse(tracer_fn), ensuring all MRO entries are visited during GC tracing. |
Heap Type Reference Tracing
crates/vm/src/object/traverse_object.rs |
Added explicit tracing of heap-type references in both PyInner and PyInner paths. When a type is a heap type, the type object is now converted to PyObject and traced before dict/slots traversal continues. |
Estimated code review effort
🎯 3 (Moderate) | ⏱️ ~22 minutes
Possibly related PRs
Poem
🐰 Hop, hop, the MRO flows,
No more gaps in traces that the garbage knows,
Heap types shine with reference bright,
GC cycles now collect all in sight! ✨
🚥 Pre-merge checks | ✅ 2 | ❌ 1
❌ Failed checks (1 warning)
| Check name |
Status |
Explanation |
Resolution |
| Docstring Coverage |
⚠️ Warning |
Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%. |
Write docstrings for the functions missing them to satisfy the coverage threshold. |
✅ Passed checks (2 passed)
| Check name |
Status |
Explanation |
| Description Check |
✅ Passed |
Check skipped - CodeRabbit’s high-level summary is enabled. |
| Title check |
✅ Passed |
The title 'Improve object traversal for heap types and mro' directly and accurately summarizes the main changes: enabling MRO traversal in PyType and improving heap type instance traversal to include type references. |
✏️ Tip: You can configure your own custom pre-merge checks in the settings.
✨ Finishing touches
🧪 Generate unit tests (beta)
- Create PR with unit tests
- Post copyable unit tests in a comment
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youknowone
added a commit
that referenced
this pull request
Sep 16, 2026
- Fix heap type instance traversal to include type reference
(enables correct cycle detection for instance ↔ type references)
- Enable mro traversal in PyType (was previously disabled)
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