Replace unsafe pointer cast with AtomicPtr in PyCode

[youknowone]

Thanks @jaens

Summary by CodeRabbit

• Refactor
  • Switched the internal synchronization approach for source path handling. This preserves existing behavior while reducing internal overhead and simplifying access semantics; no user-facing functionality changes.

[coderabbitai]

📝 Walkthrough

Walkthrough

Replaced a mutex-based field with an atomic pointer: PyCode.source_path now uses AtomicPtr<PyStrInterned>. Constructors and accessors were updated to store/load raw pointers with Ordering::Relaxed, relying on interned strings never being deallocated.

Changes

Cohort / File(s)	Summary
PyCode source_path change crates/vm/src/builtins/code.rs	Replaced PyMutex<&'static PyStrInterned> with AtomicPtr<PyStrInterned>; updated constructor, source_path() accessor, and set_source_path() to use atomic load/store (Ordering::Relaxed). Adjusted imports (added AtomicPtr, Ordering) and removed mutex usage for this field.
Manifest Cargo.toml	Minor changes to manifest lines (+14/-7) included in this diff (no code-level semantics altered here).

Sequence Diagram(s)

(omitted — changes are localized and do not introduce multi-component control flow requiring a sequence diagram)

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly related PRs

• Replace unsafe pointer cast with PyMutex in PyCode #7055 — Introduced a PyMutex-wrapped source_path for PyCode; this PR directly replaces that mutex-based approach with an AtomicPtr.

Poem

🐰 I swapped the lock for atomic cheer,
A pointer hops, no crowding near.
Relaxed it dances, light and spry,
Interned strings watch from on high. ✨

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% 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 accurately describes the main change: replacing a synchronization primitive (PyMutex) with AtomicPtr for the PyCode.source_path field, which is the core modification in the changeset.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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No actionable comments were generated in the recent review. 🎉

🧹 Recent nitpick comments

crates/vm/src/builtins/code.rs (1)

349-359: Ordering::Relaxed is sufficient here, and the unsafe is sound.

Since the pointed-to PyStrInterned is immutable and 'static (interned strings are never deallocated), there's no dependent data requiring acquire/release synchronization. The only invariant is atomicity of the pointer swap, which Relaxed provides.

One minor observation: there's no doc-comment on set_source_path explaining why this is safe to call concurrently (i.e., the 'static + immutable invariant). Consider adding a brief // SAFETY: comment matching the one on source_path().

Suggested safety comment

     pub fn set_source_path(&self, new: &'static PyStrInterned) {
+        // SAFETY: interned strings are never deallocated, so the pointer remains valid
         self.source_path.store(
             new as *const PyStrInterned as *mut PyStrInterned,
             Ordering::Relaxed,
         );
     }

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@crates/vm/src/builtins/code.rs`:
- Line 22: The file contains an unused import of PyMutex (the line "use
rustpython_common::lock::PyMutex;") which should be removed; locate the use
statement referencing PyMutex in this module (e.g., the import line in code.rs)
and delete it so there are no unused imports or compile warnings/errors related
to PyMutex.