Replace unsafe pointer cast with PyMutex in PyCode#7055

youknowone

Add source_path: PyMutex<&'static PyStrInterned> field to PyCode for interior mutability, replacing the UB-inducing #[allow(invalid_reference_casting)] + write_volatile pattern in update_code_filenames. Update all 12 read sites across the codebase to use the new source_path() method.

Summary by CodeRabbit

Refactor
- Improved thread-safety and safer handling of code object source paths across the runtime by replacing direct internal field access and in-place mutations with controlled accessors and setters, reducing unsafe mutations and standardizing path retrieval in traceback, import, and warning/reporting flows.

coderabbitai

📝 Walkthrough

Walkthrough

Encapsulate PyCode.source_path behind a PyMutex with getter/setter and replace direct field accesses across the VM to use the new methods; PyCode construction updated to use PyCode::new.

Changes

Cohort / File(s)	Summary
PyCode core `crates/vm/src/builtins/code.rs`	Added `PyMutex`-wrapped `source_path`, `PyCode::new`, and `source_path()` / `set_source_path()` accessors; updated repr, co_filename, and ReplaceArgs usage to call the new accessor/setter.
Traceback & error reporting `crates/vm/src/builtins/traceback.rs`, `crates/vm/src/exceptions.rs`, `crates/vm/src/frame.rs`, `crates/stdlib/src/faulthandler.rs`	Replaced direct `source_path` field access with `source_path()` calls when serializing or printing filenames in tracebacks and faulthandler output.
Import & stdlib updates `crates/vm/src/import.rs`, `crates/vm/src/stdlib/imp.rs`, `crates/vm/src/stdlib/io.rs`	Switched from field access to getter for `__file__`/filename handling; in imp.rs replaced unsafe direct mutation with `set_source_path(new_name)` and adjusted update traversal to use the public API.
VM construction & context `crates/vm/src/vm/context.rs`	Changed PyCode instantiation from literal struct to `PyCode::new(code)` in Context::new_code.
Warnings / runtime setup `crates/vm/src/warn.rs`	Replaced direct `source_path` field access with `source_path()` when setting up filenames for warnings.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Possibly related PRs

Update faulthandler to 3.14.2 #6949 — similar change converting faulthandler frame printing to use a source_path() getter.
Fix PyCode constructor/replace #6193 — related adjustments to PyCode construction/usage and access patterns.

Suggested reviewers

ShaharNaveh

Poem

🐰 A tiny mutex hugs the path so neat,
No tumble, no race, no hurried feet,
Getters whisper where raw fields slept,
Safe hops through code the rabbit kept. 🥕

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 68.42% 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 clearly and accurately summarizes the main objective of the PR: replacing unsafe pointer casting with PyMutex for interior mutability of PyCode's source_path field.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing touches

📝 Generate docstrings

🧪 Generate unit tests (beta)

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

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

_{Comment @coderabbitai help to get the list of available commands and usage tips.}

coderabbitai

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@crates/vm/src/builtins/code.rs`:
- Around line 337-351: Replace direct reads of the CodeObject field
"frame.code.source_path" with the PyCode accessor "frame.code.source_path()" so
the mutex-protected value from PyCode::source_path is used; search for
occurrences of "frame.code.source_path" in faulthandler.rs and update them to
call the accessor (leveraging the existing PyCode::source_path and
set_source_path methods).

Add `source_path: PyMutex<&'static PyStrInterned>` field to `PyCode` for interior mutability, replacing the UB-inducing `#[allow(invalid_reference_casting)]` + `write_volatile` pattern in `update_code_filenames`. Update all read sites across the codebase to use the new `source_path()` accessor method.

coderabbitai

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@crates/stdlib/src/faulthandler.rs`:
- Around line 254-256: dump_frame_from_raw is called from the signal handler
faulthandler_fatal_error but calls frame.code.source_path() which acquires a
PyMutex and can deadlock; make this signal-safe by avoiding any mutex
acquisition: either add a signal-safe cached string pointer on PyCode (e.g., an
atomic/AtomicPtr holding a nul-terminated C string updated outside signal
handlers and read here) and read that in dump_frame_from_raw, or replace the
call to source_path() with a non-blocking attempt (call try_lock() on the
PyCode/source_path mutex and if it fails print a fallback like "<unknown>" or
the raw pointer/address), updating references to Frame/ PyCode/ source_path
accordingly so dump_frame_from_raw never blocks in a signal context.

jaens

@youknowone doesn't PyMutex add quite a bit of memory overhead? The mutex functionality is not really even used here, as there are no non-atomic operations done inside the lock...

Since the lifetime is static anyway, I think something like atomic_ref should work (or AtomicPtr from std, though that would still require a bit of unsafe).

What the update code does is actually an atomic compare and exchange, I think.

youknowone

@jaens Thanks! That sounds right

youknowone marked this pull request as ready for review February 9, 2026 00:26

coderabbitai Bot reviewed Feb 9, 2026

View reviewed changes

youknowone force-pushed the pycode-path branch from 66eb96f to 5103e88 Compare February 9, 2026 03:57

coderabbitai Bot reviewed Feb 9, 2026

View reviewed changes

youknowone deleted the pycode-path branch February 9, 2026 05:01

coderabbitai Bot mentioned this pull request Feb 9, 2026

Replace unsafe pointer cast with AtomicPtr in PyCode #7063

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Replace unsafe pointer cast with PyMutex in PyCode#7055