RustPython · youknowone · Jun 26, 2026
diff --git a/.cspell.dict/rust-more.txt b/.cspell.dict/rust-more.txt
@@ -13,6 +13,7 @@ bstr
 byteorder
 byteset
 caseless
+cdpt
 chrono
 consts
 cranelift

diff --git a/Cargo.lock b/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
@@ -49,7 +49,7 @@
 flamescope = { version = "0.1.2", optional = true }

 rustls = { workspace = true, optional = true }
 rustls-graviola = { workspace = true, optional = true }

 [target.'cfg(windows)'.dependencies]
 libc = { workspace = true }
@@ -201,6 +201,7 @@
 bstr = "1"
 bzip2 = "0.6"
 chrono = { version = "0.4.44", default-features = false, features = ["clock", "std"] }
+cdpt = "0.1.0"
 console_error_panic_hook = "0.1"
 constant_time_eq = "0.5"
 cranelift = "0.132.0"

diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
@@ -236,7 +236,6 @@ def test_function(self):
         # is 3 because it includes f's code object.
         self.assertIn(gc.collect(), (2, 3))
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON; - weakref clear ordering differs from 3.15+
     def test_function_tp_clear_leaves_consistent_state(self):
         # https://github.com/python/cpython/issues/91636
         code = """if 1:
@@ -831,7 +830,6 @@ def __del__(self):
         rc, out, err = assert_python_ok(TESTFN)
         self.assertEqual(out.strip(), b'__del__ called')
 
-    @unittest.expectedFailure  # TODO: RUSTPYTHON
     def test_get_stats(self):
         stats = gc.get_stats()
         self.assertEqual(len(stats), 3)

diff --git a/crates/vm/Cargo.toml b/crates/vm/Cargo.toml
@@ -90,6 +90,7 @@ writeable = { workspace = true }
 exitcode = { workspace = true }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
+cdpt = { workspace = true }
 rustyline = { workspace = true }
 which = { workspace = true }
 widestring = { workspace = true }

diff --git a/crates/vm/src/gc_state.rs b/crates/vm/src/gc_state.rs
@@ -136,6 +136,21 @@ impl GcGeneration {
 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
 struct GcPtr(NonNull<PyObject>);
 
+fn clear_weakrefs_and_invoke_callbacks(objects: &[PyObjectRef]) {
+    let mut all_callbacks = Vec::new();
+    for obj_ref in objects {
+        let callbacks = obj_ref.gc_clear_weakrefs_collect_callbacks();
+        all_callbacks.extend(callbacks);
+    }
+    for (wr, cb) in all_callbacks {
+        if let Some(Err(e)) = crate::vm::thread::with_vm(&cb, |vm| cb.call((wr.clone(),), vm)) {
+            crate::vm::thread::with_vm(&cb, |vm| {
+                vm.run_unraisable(e.clone(), Some("weakref callback".to_owned()), cb.clone());
+            });
+        }
+    }
+}
+
 /// Global GC state
 pub struct GcState {
     /// 3 generations (0 = youngest, 2 = oldest)
@@ -398,6 +413,11 @@ impl GcState {
             _ => std::time::Instant::now(),
         };
 
+        // Keep a CDPT guard during collection, following origin/gc's
+        // coarse-grained guarded collection experiment.
+        #[cfg(not(target_arch = "wasm32"))]
+        let _cdpt_guard = cdpt::pin();
+
         // Memory barrier to ensure visibility of all reference count updates
         // from other threads before we start analyzing the object graph.
         core::sync::atomic::fence(Ordering::SeqCst);
@@ -602,20 +622,10 @@ impl GcState {
             })
             .collect();
 
-        // 6c: Clear existing weakrefs BEFORE calling __del__
-        let mut all_callbacks: Vec<(crate::PyRef<crate::object::PyWeak>, crate::PyObjectRef)> =
-            Vec::new();
-        for obj_ref in &unreachable_refs {
-            let callbacks = obj_ref.gc_clear_weakrefs_collect_callbacks();
-            all_callbacks.extend(callbacks);
-        }
-        for (wr, cb) in all_callbacks {
-            if let Some(Err(e)) = crate::vm::thread::with_vm(&cb, |vm| cb.call((wr.clone(),), vm)) {
-                crate::vm::thread::with_vm(&cb, |vm| {
-                    vm.run_unraisable(e.clone(), Some("weakref callback".to_owned()), cb.clone());
-                });
-            }
-        }
+        // 6c: Clear weakrefs that existed before finalizers. This prevents a
+        // later tp_clear side effect from observing callback-free weakrefs to
+        // garbage in this generation.
+        clear_weakrefs_and_invoke_callbacks(&unreachable_refs);
 
         // 6d: Call __del__ on unreachable objects (skip already-finalized).
         // try_call_finalizer() internally checks gc_finalized() and sets it,
@@ -624,6 +634,11 @@ impl GcState {
             obj_ref.try_call_finalizer();
         }
 
+        // 6e: Clear weakrefs after finalizers, but before tp_clear. Finalizers
+        // can create weakrefs to other unreachable objects, and those must not
+        // reveal an object while its clear function is running.
+        clear_weakrefs_and_invoke_callbacks(&unreachable_refs);
+
         // Detect resurrection
         let mut resurrected_set: HashSet<GcPtr> = HashSet::new();
         let unreachable_set: HashSet<GcPtr> = unreachable.iter().copied().collect();

diff --git a/crates/vm/src/object/core.rs b/crates/vm/src/object/core.rs
@@ -1770,7 +1770,8 @@ impl PyObject {
     }
 
     /// Clear weakrefs but collect callbacks instead of calling them.
-    /// This is used by GC to ensure ALL weakrefs are cleared BEFORE any callbacks run.
+    /// GC uses this while handling a garbage set so callbacks run only after all
+    /// weakrefs in the current pass have been invalidated.
     /// Returns collected callbacks as (PyRef<PyWeak>, callback) pairs.
     // = handle_weakrefs
     pub fn gc_clear_weakrefs_collect_callbacks(&self) -> Vec<(PyRef<PyWeak>, PyObjectRef)> {

diff --git a/crates/vm/src/stdlib/gc.rs b/crates/vm/src/stdlib/gc.rs
@@ -142,8 +142,6 @@ mod gc {
                 vm.ctx.new_int(stat.uncollectable).into(),
                 vm,
             )?;
-            dict.set_item("candidates", vm.ctx.new_int(stat.candidates).into(), vm)?;
-            dict.set_item("duration", vm.ctx.new_float(stat.duration).into(), vm)?;
             result.push(dict.into());
         }
-Original file line number
+Diff line change
@@ Expand Up / @@ -13,6 +13,7 @@ bstr @@
     byteorder
     byteset
     caseless
+    cdpt
     chrono
     consts
     cranelift
@@ Expand Down @@