RustPython · youknowone · Mar 5, 2026 · Mar 5, 2026 · Mar 5, 2026 · Mar 5, 2026
diff --git a/Lib/test/_test_gc_fast_cycles.py b/Lib/test/_test_gc_fast_cycles.py
@@ -0,0 +1,48 @@
+# Run by test_gc.
+from test import support
+import _testinternalcapi
+import gc
+import unittest
+
+class IncrementalGCTests(unittest.TestCase):
+
+    # Use small increments to emulate longer running process in a shorter time
+    @support.gc_threshold(200, 10)
+    def test_incremental_gc_handles_fast_cycle_creation(self):
+
+        class LinkedList:
+
+            #Use slots to reduce number of implicit objects
+            __slots__ = "next", "prev", "surprise"
+
+            def __init__(self, next=None, prev=None):
+                self.next = next
+                if next is not None:
+                    next.prev = self
+                self.prev = prev
+                if prev is not None:
+                    prev.next = self
+
+        def make_ll(depth):
+            head = LinkedList()
+            for i in range(depth):
+                head = LinkedList(head, head.prev)
+            return head
+
+        head = make_ll(1000)
+
+        assert(gc.isenabled())
+        olds = []
+        initial_heap_size = _testinternalcapi.get_tracked_heap_size()
+        for i in range(20_000):
+            newhead = make_ll(20)
+            newhead.surprise = head
+            olds.append(newhead)
+            if len(olds) == 20:
+                new_objects = _testinternalcapi.get_tracked_heap_size() - initial_heap_size
+                self.assertLess(new_objects, 27_000, f"Heap growing. Reached limit after {i} iterations")
+                del olds[:]
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
@@ -236,6 +236,8 @@ def test_function(self):
         # is 3 because it includes f's code object.
         self.assertIn(gc.collect(), (2, 3))
 
+    # TODO: RUSTPYTHON - weakref clear ordering differs from 3.15+
+    @unittest.expectedFailure
     def test_function_tp_clear_leaves_consistent_state(self):
         # https://github.com/python/cpython/issues/91636
         code = """if 1:
@@ -262,9 +264,11 @@ class Cyclic(tuple):
             #    finalizer.
             def __del__(self):
 
-                # 5. Create a weakref to `func` now. If we had created
-                #    it earlier, it would have been cleared by the
-                #    garbage collector before calling the finalizers.
+                # 5. Create a weakref to `func` now. In previous
+                #    versions of Python, this would avoid having it
+                #    cleared by the garbage collector before calling
+                #    the finalizers.  Now, weakrefs get cleared after
+                #    calling finalizers.
                 self[1].ref = weakref.ref(self[0])
 
                 # 6. Drop the global reference to `latefin`. The only
@@ -293,16 +297,42 @@ def func():
         #    which will find `cyc` and `func` as garbage.
         gc.collect()
 
-        # 9. Previously, this would crash because `func_qualname`
-        #    had been NULL-ed out by func_clear().
+        # 9. Previously, this would crash because the weakref
+        #    created in the finalizer revealed the function after
+        #    `tp_clear` was called and `func_qualname`
+        #    had been NULL-ed out by func_clear().  Now, we clear
+        #    weakrefs to unreachable objects before calling `tp_clear`
+        #    but after calling finalizers.
         print(f"{func=}")
         """
-        # We're mostly just checking that this doesn't crash.
         rc, stdout, stderr = assert_python_ok("-c", code)
         self.assertEqual(rc, 0)
-        self.assertRegex(stdout, rb"""\A\s*func=<function  at \S+>\s*\z""")
+        # The `func` global is None because the weakref was cleared.
+        self.assertRegex(stdout, rb"""\A\s*func=None""")
         self.assertFalse(stderr)
 
+    # TODO: RUSTPYTHON - _datetime module not available
+    @unittest.expectedFailure
+    def test_datetime_weakref_cycle(self):
+        # https://github.com/python/cpython/issues/132413
+        # If the weakref used by the datetime extension gets cleared by the GC (due to being
+        # in an unreachable cycle) then datetime functions would crash (get_module_state()
+        # was returning a NULL pointer).  This bug is fixed by clearing weakrefs without
+        # callbacks *after* running finalizers.
+        code = """if 1:
+        import _datetime
+        class C:
+            def __del__(self):
+                print('__del__ called')
+                _datetime.timedelta(days=1)  # crash?
+
+        l = [C()]
+        l.append(l)
+        """
+        rc, stdout, stderr = assert_python_ok("-c", code)
+        self.assertEqual(rc, 0)
+        self.assertEqual(stdout.strip(), b'__del__ called')
+
     @refcount_test
     def test_frame(self):
         def f():
@@ -652,9 +682,8 @@ def callback(ignored):
         gc.collect()
         self.assertEqual(len(ouch), 2)  # else the callbacks didn't run
         for x in ouch:
-            # If the callback resurrected one of these guys, the instance
-            # would be damaged, with an empty __dict__.
-            self.assertEqual(x, None)
+            # The weakref should be cleared before executing the callback.
+            self.assertIsNone(x)
 
     def test_bug21435(self):
         # This is a poor test - its only virtue is that it happened to
@@ -821,11 +850,15 @@ def test_get_stats(self):
         self.assertEqual(len(stats), 3)
         for st in stats:
             self.assertIsInstance(st, dict)
-            self.assertEqual(set(st),
-                             {"collected", "collections", "uncollectable"})
+            self.assertEqual(
+                set(st),
+                {"collected", "collections", "uncollectable", "candidates", "duration"}
+            )
             self.assertGreaterEqual(st["collected"], 0)
             self.assertGreaterEqual(st["collections"], 0)
             self.assertGreaterEqual(st["uncollectable"], 0)
+            self.assertGreaterEqual(st["candidates"], 0)
+            self.assertGreaterEqual(st["duration"], 0)
         # Check that collection counts are incremented correctly
         if gc.isenabled():
             self.addCleanup(gc.enable)
@@ -836,11 +869,25 @@ def test_get_stats(self):
         self.assertEqual(new[0]["collections"], old[0]["collections"] + 1)
         self.assertEqual(new[1]["collections"], old[1]["collections"])
         self.assertEqual(new[2]["collections"], old[2]["collections"])
+        self.assertGreater(new[0]["duration"], old[0]["duration"])
+        self.assertEqual(new[1]["duration"], old[1]["duration"])
+        self.assertEqual(new[2]["duration"], old[2]["duration"])
+        for stat in ["collected", "uncollectable", "candidates"]:
+            self.assertGreaterEqual(new[0][stat], old[0][stat])
+            self.assertEqual(new[1][stat], old[1][stat])
+            self.assertEqual(new[2][stat], old[2][stat])
         gc.collect(2)
-        new = gc.get_stats()
-        self.assertEqual(new[0]["collections"], old[0]["collections"] + 1)
+        old, new = new, gc.get_stats()
+        self.assertEqual(new[0]["collections"], old[0]["collections"])
         self.assertEqual(new[1]["collections"], old[1]["collections"])
         self.assertEqual(new[2]["collections"], old[2]["collections"] + 1)
+        self.assertEqual(new[0]["duration"], old[0]["duration"])
+        self.assertEqual(new[1]["duration"], old[1]["duration"])
+        self.assertGreater(new[2]["duration"], old[2]["duration"])
+        for stat in ["collected", "uncollectable", "candidates"]:
+            self.assertEqual(new[0][stat], old[0][stat])
+            self.assertEqual(new[1][stat], old[1][stat])
+            self.assertGreaterEqual(new[2][stat], old[2][stat])
 
     def test_freeze(self):
         gc.freeze()
@@ -1156,6 +1203,37 @@ def test_something(self):
         """)
         assert_python_ok("-c", source)
 
+    def test_do_not_cleanup_type_subclasses_before_finalization(self):
+        #  See https://github.com/python/cpython/issues/135552
+        # If we cleanup weakrefs for tp_subclasses before calling
+        # the finalizer (__del__) then the line `fail = BaseNode.next.next`
+        # should fail because we are trying to access a subclass
+        # attribute. But subclass type cache was not properly invalidated.
+        code = """
+            class BaseNode:
+                def __del__(self):
+                    BaseNode.next = BaseNode.next.next
+                    fail = BaseNode.next.next
+
+            class Node(BaseNode):
+                pass
+
+            BaseNode.next = Node()
+            BaseNode.next.next = Node()
+        """
+        # this test checks garbage collection while interp
+        # finalization
+        assert_python_ok("-c", textwrap.dedent(code))
+
+        code_inside_function = textwrap.dedent(F"""
+            def test():
+                {textwrap.indent(code, '    ')}
+
+            test()
+        """)
+        # this test checks regular garbage collection
+        assert_python_ok("-c", code_inside_function)
+
 
     @unittest.skipUnless(Py_GIL_DISABLED, "requires free-threaded GC")
     @unittest.skipIf(_testinternalcapi is None, "requires _testinternalcapi")
@@ -1260,9 +1338,11 @@ def test_collect(self):
         # Check that we got the right info dict for all callbacks
         for v in self.visit:
             info = v[2]
-            self.assertTrue("generation" in info)
-            self.assertTrue("collected" in info)
-            self.assertTrue("uncollectable" in info)
+            self.assertIn("generation", info)
+            self.assertIn("collected", info)
+            self.assertIn("uncollectable", info)
+            self.assertIn("candidates", info)
+            self.assertIn("duration", info)
 
     def test_collect_generation(self):
         self.preclean()
@@ -1450,6 +1530,7 @@ def callback(ignored):
             self.assertEqual(x, None)
 
     @gc_threshold(1000, 0, 0)
+    @unittest.skipIf(Py_GIL_DISABLED, "requires GC generations or increments")
     def test_bug1055820d(self):
         # Corresponds to temp2d.py in the bug report.  This is very much like
         # test_bug1055820c, but uses a __del__ method instead of a weakref

diff --git a/Lib/test/test_symtable.py b/Lib/test/test_symtable.py
@@ -561,7 +561,6 @@ def get_identifiers_recursive(self, st, res):
         for ch in st.get_children():
             self.get_identifiers_recursive(ch, res)
 
-    @unittest.expectedFailure # TODO: RUSTPYTHON; AssertionError: 2 != 1
     def test_loopvar_in_only_one_scope(self):
         # ensure that the loop variable appears only once in the symtable
         comps = [

diff --git a/crates/codegen/src/symboltable.rs b/crates/codegen/src/symboltable.rs
@@ -2037,20 +2037,13 @@ impl SymbolTableBuilder {
             self.line_index_start(range),
         );
 
-        // Mark non-generator comprehensions as inlined (PEP 709)
-        // inline_comp = entry->ste_comprehension && !entry->ste_generator && !ste->ste_can_see_class_scope
-        // We check is_generator and can_see_class_scope of parent
-        let parent_can_see_class = self
-            .tables
-            .get(self.tables.len().saturating_sub(2))
-            .map(|t| t.can_see_class_scope)
-            .unwrap_or(false);
-        if !is_generator
-            && !parent_can_see_class
-            && let Some(table) = self.tables.last_mut()
-        {
-            table.comp_inlined = true;
-        }
+        // PEP 709: inlined comprehensions are not yet implemented in the
+        // compiler (is_inlined_comprehension_context always returns false),
+        // so do NOT mark comp_inlined here.  Setting it would cause the
+        // symbol-table analyzer to merge comprehension-local symbols into
+        // the parent scope, while the compiler still emits a separate code
+        // object — leading to the merged symbols being missing from the
+        // comprehension's own symbol table lookup.
 
         // Register the passed argument to the generator function as the name ".0"
         self.register_name(".0", SymbolUsage::Parameter, range)?;

diff --git a/crates/stdlib/src/_asyncio.rs b/crates/stdlib/src/_asyncio.rs
@@ -499,7 +499,8 @@ pub(crate) mod _asyncio {
         }
 
         fn make_cancelled_error_impl(&self, vm: &VirtualMachine) -> PyBaseExceptionRef {
-            if let Some(exc) = self.fut_cancelled_exc.read().clone()
+            // If a saved CancelledError exists, take it (clearing the stored reference)
+            if let Some(exc) = self.fut_cancelled_exc.write().take()
                 && let Ok(exc) = exc.downcast::<PyBaseException>()
             {
                 return exc;
@@ -508,12 +509,10 @@ pub(crate) mod _asyncio {
             let msg = self.fut_cancel_msg.read().clone();
             let args = if let Some(m) = msg { vec![m] } else { vec![] };
 
-            let exc = match get_cancelled_error_type(vm) {
+            match get_cancelled_error_type(vm) {
                 Ok(cancelled_error) => vm.new_exception(cancelled_error, args),
                 Err(_) => vm.new_runtime_error("cancelled"),
-            };
-            *self.fut_cancelled_exc.write() = Some(exc.clone().into());
-            exc
+            }
         }
 
         fn schedule_callbacks(zelf: &PyRef<Self>, vm: &VirtualMachine) -> PyResult<()> {
@@ -1309,7 +1308,8 @@ pub(crate) mod _asyncio {
         }
 
         fn make_cancelled_error_impl(&self, vm: &VirtualMachine) -> PyBaseExceptionRef {
-            if let Some(exc) = self.base.fut_cancelled_exc.read().clone()
+            // If a saved CancelledError exists, take it (clearing the stored reference)
+            if let Some(exc) = self.base.fut_cancelled_exc.write().take()
                 && let Ok(exc) = exc.downcast::<PyBaseException>()
             {
                 return exc;
@@ -1318,12 +1318,10 @@ pub(crate) mod _asyncio {
             let msg = self.base.fut_cancel_msg.read().clone();
             let args = if let Some(m) = msg { vec![m] } else { vec![] };
 
-            let exc = match get_cancelled_error_type(vm) {
+            match get_cancelled_error_type(vm) {
                 Ok(cancelled_error) => vm.new_exception(cancelled_error, args),
                 Err(_) => vm.new_runtime_error("cancelled"),
-            };
-            *self.base.fut_cancelled_exc.write() = Some(exc.clone().into());
-            exc
+            }
         }
 
         #[pymethod]

diff --git a/crates/stdlib/src/socket.rs b/crates/stdlib/src/socket.rs
@@ -1384,13 +1384,20 @@ mod _socket {
 
     impl DefaultConstructor for PySocket {}
 
+    #[derive(FromArgs)]
+    pub struct SocketInitArgs {
+        #[pyarg(any, optional)]
+        family: OptionalArg<i32>,
+        #[pyarg(any, optional)]
+        r#type: OptionalArg<i32>,
+        #[pyarg(any, optional)]
+        proto: OptionalArg<i32>,
+        #[pyarg(any, optional)]
+        fileno: OptionalOption<PyObjectRef>,
+    }
+
     impl Initializer for PySocket {
-        type Args = (
-            OptionalArg<i32>,
-            OptionalArg<i32>,
-            OptionalArg<i32>,
-            OptionalOption<PyObjectRef>,
-        );
+        type Args = SocketInitArgs;
 
         fn init(zelf: PyRef<Self>, args: Self::Args, vm: &VirtualMachine) -> PyResult<()> {
             Self::_init(zelf, args, vm).map_err(|e| e.into_pyexception(vm))
@@ -1414,13 +1421,14 @@ mod _socket {
     impl PySocket {
         fn _init(
             zelf: PyRef<Self>,
-            (family, socket_kind, proto, fileno): <Self as Initializer>::Args,
+            args: <Self as Initializer>::Args,
             vm: &VirtualMachine,
         ) -> Result<(), IoOrPyException> {
-            let mut family = family.unwrap_or(-1);
-            let mut socket_kind = socket_kind.unwrap_or(-1);
-            let mut proto = proto.unwrap_or(-1);
+            let mut family = args.family.unwrap_or(-1);
+            let mut socket_kind = args.r#type.unwrap_or(-1);
+            let mut proto = args.proto.unwrap_or(-1);
 
+            let fileno = args.fileno;
             let sock;
 
             // On Windows, fileno can be bytes from socket.share() for fromshare()