Update 2025-04-24_11:44:19

venv/lib/python3.11/site-packages/greenlet/tests/test_gc.py

@@ -0,0 +1,86 @@
+import gc
+
+import weakref
+
+import greenlet
+
+
+from . import TestCase
+from .leakcheck import fails_leakcheck
+# These only work with greenlet gc support
+# which is no longer optional.
+assert greenlet.GREENLET_USE_GC
+
+class GCTests(TestCase):
+    def test_dead_circular_ref(self):
+        o = weakref.ref(greenlet.greenlet(greenlet.getcurrent).switch())
+        gc.collect()
+        if o() is not None:
+            import sys
+            print("O IS NOT NONE.", sys.getrefcount(o()))
+        self.assertIsNone(o())
+        self.assertFalse(gc.garbage, gc.garbage)
+
+    def test_circular_greenlet(self):
+        class circular_greenlet(greenlet.greenlet):
+            self = None
+        o = circular_greenlet()
+        o.self = o
+        o = weakref.ref(o)
+        gc.collect()
+        self.assertIsNone(o())
+        self.assertFalse(gc.garbage, gc.garbage)
+
+    def test_inactive_ref(self):
+        class inactive_greenlet(greenlet.greenlet):
+            def __init__(self):
+                greenlet.greenlet.__init__(self, run=self.run)
+
+            def run(self):
+                pass
+        o = inactive_greenlet()
+        o = weakref.ref(o)
+        gc.collect()
+        self.assertIsNone(o())
+        self.assertFalse(gc.garbage, gc.garbage)
+
+    @fails_leakcheck
+    def test_finalizer_crash(self):
+        # This test is designed to crash when active greenlets
+        # are made garbage collectable, until the underlying
+        # problem is resolved. How does it work:
+        # - order of object creation is important
+        # - array is created first, so it is moved to unreachable first
+        # - we create a cycle between a greenlet and this array
+        # - we create an object that participates in gc, is only
+        #   referenced by a greenlet, and would corrupt gc lists
+        #   on destruction, the easiest is to use an object with
+        #   a finalizer
+        # - because array is the first object in unreachable it is
+        #   cleared first, which causes all references to greenlet
+        #   to disappear and causes greenlet to be destroyed, but since
+        #   it is still live it causes a switch during gc, which causes
+        #   an object with finalizer to be destroyed, which causes stack
+        #   corruption and then a crash
+
+        class object_with_finalizer(object):
+            def __del__(self):
+                pass
+        array = []
+        parent = greenlet.getcurrent()
+        def greenlet_body():
+            greenlet.getcurrent().object = object_with_finalizer()
+            try:
+                parent.switch()
+            except greenlet.GreenletExit:
+                print("Got greenlet exit!")
+            finally:
+                del greenlet.getcurrent().object
+        g = greenlet.greenlet(greenlet_body)
+        g.array = array
+        array.append(g)
+        g.switch()
+        del array
+        del g
+        greenlet.getcurrent()
+        gc.collect()