Issue #10576: Add a progress callback to gcmodule

1 files changed, 135 insertions, 1 deletions

diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
index 19313db796..caf5a3d0f9 100644
--- a/Lib/test/test_gc.py
+++ b/Lib/test/test_gc.py
@@ -32,6 +32,20 @@ class GC_Detector(object):
         # gc collects it.
         self.wr = weakref.ref(C1055820(666), it_happened)
 
+class Uncollectable(object):
+    """Create a reference cycle with multiple __del__ methods.
+
+    An object in a reference cycle will never have zero references,
+    and so must be garbage collected.  If one or more objects in the
+    cycle have __del__ methods, the gc refuses to guess an order,
+    and leaves the cycle uncollected."""
+    def __init__(self, partner=None):
+        if partner is None:
+            self.partner = Uncollectable(partner=self)
+        else:
+            self.partner = partner
+    def __del__(self):
+        pass
 
 ### Tests
 ###############################################################################
@@ -528,6 +542,126 @@ class GCTests(unittest.TestCase):
         self.assertNotIn(b"uncollectable objects at shutdown", stderr)
 
 
+class GCCallbackTests(unittest.TestCase):
+    def setUp(self):
+        # Save gc state and disable it.
+        self.enabled = gc.isenabled()
+        gc.disable()
+        self.debug = gc.get_debug()
+        gc.set_debug(0)
+        gc.callbacks.append(self.cb1)
+        gc.callbacks.append(self.cb2)
+
+    def tearDown(self):
+        # Restore gc state
+        del self.visit
+        gc.callbacks.remove(self.cb1)
+        gc.callbacks.remove(self.cb2)
+        gc.set_debug(self.debug)
+        if self.enabled:
+            gc.enable()
+        # destroy any uncollectables
+        gc.collect()
+        for obj in gc.garbage:
+            if isinstance(obj, Uncollectable):
+                obj.partner = None
+        del gc.garbage[:]
+        gc.collect()
+
+    othergarbage = []
+    def preclean(self):
+        # Remove all fluff from the system.  Invoke this function
+        # manually rather than through self.setUp() for maximum
+        # safety.
+        self.visit = []
+        gc.collect()
+        garbage, gc.garbage[:] = gc.garbage[:], []
+        self.othergarbage.append(garbage)
+        self.visit = []
+
+    def cb1(self, phase, info):
+        self.visit.append((1, phase, dict(info)))
+
+    def cb2(self, phase, info):
+        self.visit.append((2, phase, dict(info)))
+        if phase == "stop" and hasattr(self, "cleanup"):
+            # Clean Uncollectable from garbage
+            uc = [e for e in gc.garbage if isinstance(e, Uncollectable)]
+            gc.garbage[:] = [e for e in gc.garbage
+                             if not isinstance(e, Uncollectable)]
+            for e in uc:
+                e.partner = None
+
+    def testCollect(self):
+        self.preclean()
+        gc.collect()
+        # Algorithmically verify the contents of self.visit
+        # because it is long and tortuous.
+
+        # Count the number of visits to each callback
+        n = [v[0] for v in self.visit]
+        n1 = [i for i in n if i == 1]
+        n2 = [i for i in n if i == 2]
+        self.assertEqual(n1, [1]*2)
+        self.assertEqual(n2, [2]*2)
+
+        # Count that we got the right number of start and stop callbacks.
+        n = [v[1] for v in self.visit]
+        n1 = [i for i in n if i == "start"]
+        n2 = [i for i in n if i == "stop"]
+        self.assertEqual(n1, ["start"]*2)
+        self.assertEqual(n2, ["stop"]*2)
+
+        # 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)
+
+    def testCollectGen(self):
+        self.preclean()
+        gc.collect(2)
+        for v in self.visit:
+            info = v[2]
+            self.assertEqual(info["generation"], 2)
+
+    def testCollectGarbage(self):
+        self.preclean()
+        # Each of these cause four objects to be garbage: Two
+        # Uncolectables and their instance dicts.
+        Uncollectable()
+        Uncollectable()
+        C1055820(666)
+        gc.collect()
+        for v in self.visit:
+            if v[1] != "stop":
+                continue
+            info = v[2]
+            self.assertEqual(info["collected"], 2)
+            self.assertEqual(info["uncollectable"], 8)
+
+        # We should now have the Uncollectables in gc.garbage
+        self.assertEqual(len(gc.garbage), 4)
+        for e in gc.garbage:
+            self.assertIsInstance(e, Uncollectable)
+
+        # Now, let our callback handle the Uncollectable instances
+        self.cleanup=True
+        self.visit = []
+        gc.garbage[:] = []
+        gc.collect()
+        for v in self.visit:
+            if v[1] != "stop":
+                continue
+            info = v[2]
+            self.assertEqual(info["collected"], 0)
+            self.assertEqual(info["uncollectable"], 4)
+
+        # Uncollectables should be gone
+        self.assertEqual(len(gc.garbage), 0)
+
+
 class GCTogglingTests(unittest.TestCase):
     def setUp(self):
         gc.enable()
@@ -681,7 +815,7 @@ def test_main():
 
     try:
         gc.collect() # Delete 2nd generation garbage
-        run_unittest(GCTests, GCTogglingTests)
+        run_unittest(GCTests, GCTogglingTests, GCCallbackTests)
     finally:
         gc.set_debug(debug)
         # test gc.enable() even if GC is disabled by default