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Replace unsafe pointer cast with AtomicPtr in PyCode #7063

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Merged
youknowone merged 1 commit into from
Feb 10, 2026
Merged

Replace unsafe pointer cast with AtomicPtr in PyCode #7063

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Replace unsafe pointer cast with AtomicPtr in PyCode 
Add `source_path: AtomicPtr<PyStrInterned>` field to `PyCode`
for interior mutability, replacing the UB-inducing
`#[allow(invalid_reference_casting)]` + `write_volatile` pattern
in `update_code_filenames`. Use atomic load/store instead of a
mutex since the operation is a simple pointer swap on a 'static
reference. Update all read sites to use `source_path()` accessor.
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@youknowone
youknowone committed Feb 10, 2026
commit 4dad3e0dbd92e3571948646f17df90328c236eeb
21 changes: 14 additions & 7 deletions crates/vm/src/builtins/code.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,10 +12,13 @@ use crate::{
types::{Constructor, Representable},
};
use alloc::fmt;
use core::{borrow::Borrow, ops::Deref};
use core::{
borrow::Borrow,
ops::Deref,
sync::atomic::{AtomicPtr, Ordering},
};
use malachite_bigint::BigInt;
use num_traits::Zero;
use rustpython_common::lock::PyMutex;
use rustpython_compiler_core::{OneIndexed, bytecode::CodeUnits, bytecode::PyCodeLocationInfoKind};

/// State for iterating through code address ranges
Expand Down Expand Up @@ -324,7 +327,7 @@ impl<B: AsRef<[u8]>> IntoCodeObject for frozen::FrozenCodeObject<B> {
#[pyclass(module = false, name = "code")]
pub struct PyCode {
pub code: CodeObject,
source_path: PyMutex<&'static PyStrInterned>,
source_path: AtomicPtr<PyStrInterned>,
}

impl Deref for PyCode {
Expand All @@ -336,19 +339,23 @@ impl Deref for PyCode {

impl PyCode {
pub fn new(code: CodeObject) -> Self {
let sp = code.source_path;
let sp = code.source_path as *const PyStrInterned as *mut PyStrInterned;
Self {
code,
source_path: PyMutex::new(sp),
source_path: AtomicPtr::new(sp),
}
}

pub fn source_path(&self) -> &'static PyStrInterned {
*self.source_path.lock()
// SAFETY: always points to a valid &'static PyStrInterned (interned strings are never deallocated)
unsafe { &*self.source_path.load(Ordering::Relaxed) }
}

pub fn set_source_path(&self, new: &'static PyStrInterned) {
*self.source_path.lock() = new;
self.source_path.store(
new as *const PyStrInterned as *mut PyStrInterned,
Ordering::Relaxed,
);
}
pub fn from_pyc_path(path: &std::path::Path, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
let name = match path.file_stem() {
Expand Down
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