Hold atexit entries in PyRc rather than Arc

PyObjectRef is Send and Sync only under the threading feature, so an Arc over a callback entry trips clippy::arc_with_non_send_sync in builds without it, such as the wasm package. PyRc is Arc there and Rc otherwise. Assisted-by: Claude
youknowone · Aug 16, 2026 · Aug 14, 2026 · Aug 14, 2026 · Aug 14, 2026 · Aug 14, 2026
commit e3dcd8e9441ac0240d29d6de6db7c4db6cd39535
diff --git a/crates/vm/src/stdlib/atexit.rs b/crates/vm/src/stdlib/atexit.rs
@@ -3,16 +3,17 @@ pub(crate) use atexit::module_def;
 
 #[pymodule]
 mod atexit {
-    use crate::{AsObject, PyObjectRef, PyResult, VirtualMachine, function::FuncArgs};
-    use alloc::sync::Arc;
+    use crate::{
+        AsObject, PyObjectRef, PyResult, VirtualMachine, common::rc::PyRc, function::FuncArgs,
+    };
 
     #[pyfunction]
     fn register(func: PyObjectRef, args: FuncArgs, vm: &VirtualMachine) -> PyObjectRef {
         // Callbacks go in LIFO order (insert at front)
         vm.state
             .atexit_funcs
             .lock()
-            .insert(0, Arc::new((func.clone(), args)));
+            .insert(0, PyRc::new((func.clone(), args)));
         func
     }
 
@@ -49,7 +50,7 @@ mod atexit {
                 let mut funcs = vm.state.atexit_funcs.lock();
                 let mut j = (funcs.len() as isize - 1).min(i);
                 while j >= 0 {
-                    if Arc::ptr_eq(funcs.get(j as usize).unwrap(), &entry) {
+                    if PyRc::ptr_eq(funcs.get(j as usize).unwrap(), &entry) {
                         funcs.remove(j as usize);
                         i = j;
                         break;
@@ -73,7 +74,7 @@ mod atexit {
         let funcs: Vec<_> = core::mem::take(&mut *vm.state.atexit_funcs.lock());
         // Callbacks stored in LIFO order, iterate forward
         for entry in funcs {
-            let (func, args) = Arc::try_unwrap(entry).unwrap_or_else(|e| (*e).clone());
+            let (func, args) = PyRc::try_unwrap(entry).unwrap_or_else(|e| (*e).clone());
             if let Err(e) = func.call(args, vm) {
                 let exit = e.fast_isinstance(vm.ctx.exceptions.system_exit);
                 let msg = func

diff --git a/crates/vm/src/vm/mod.rs b/crates/vm/src/vm/mod.rs
@@ -44,7 +44,7 @@ use crate::{
     stdlib,
     warn::WarningsState,
 };
-use alloc::{borrow::Cow, collections::BTreeMap, sync::Arc};
+use alloc::{borrow::Cow, collections::BTreeMap};
 #[cfg(all(not(unix), feature = "threading"))]
 use core::ptr::NonNull;
 #[cfg(feature = "threading")]
@@ -762,7 +762,7 @@ pub struct PyGlobalState {
     /// Registered `atexit` callbacks, newest first. Shared ownership so
     /// `atexit.unregister` can keep the entry it is comparing alive while the
     /// list is unlocked, and still recognize it afterwards by identity.
-    pub atexit_funcs: PyMutex<Vec<Arc<(PyObjectRef, FuncArgs)>>>,
+    pub atexit_funcs: PyMutex<Vec<PyRc<(PyObjectRef, FuncArgs)>>>,
     pub codec_registry: CodecsRegistry,
     pub finalizing: AtomicBool,
     pub warnings: WarningsState,