Reworked move_finalizer_reachable() to create two distinct lists:
externally unreachable objects with finalizers, and externally unreachable
objects without finalizers reachable from such objects. This allows us
to call has_finalizer() at most once per object, and so limit the pain of
nasty getattr hooks. This fixes the failing "boom 2" example Jeremy
posted (a non-printing variant of which is now part of test_gc), via never
triggering the nasty part of its __getattr__ method.
diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
index 5ec87b9..e225881 100644
--- a/Lib/test/test_gc.py
+++ b/Lib/test/test_gc.py
@@ -253,21 +253,21 @@
v = {1: v, 2: Ouch()}
gc.disable()
-class C:
+class Boom:
def __getattr__(self, someattribute):
del self.attr
raise AttributeError
def test_boom():
- a = C()
- b = C()
+ a = Boom()
+ b = Boom()
a.attr = b
b.attr = a
gc.collect()
garbagelen = len(gc.garbage)
del a, b
- # a<->b are in a trash cycle now. Collection will invoke C.__getattr__
+ # a<->b are in a trash cycle now. Collection will invoke Boom.__getattr__
# (to see whether a and b have __del__ methods), and __getattr__ deletes
# the internal "attr" attributes as a side effect. That causes the
# trash cycle to get reclaimed via refcounts falling to 0, thus mutating
@@ -276,6 +276,33 @@
expect(gc.collect(), 0, "boom")
expect(len(gc.garbage), garbagelen, "boom")
+class Boom2:
+ def __init__(self):
+ self.x = 0
+
+ def __getattr__(self, someattribute):
+ self.x += 1
+ if self.x > 1:
+ del self.attr
+ raise AttributeError
+
+def test_boom2():
+ a = Boom2()
+ b = Boom2()
+ a.attr = b
+ b.attr = a
+
+ gc.collect()
+ garbagelen = len(gc.garbage)
+ del a, b
+ # Much like test_boom(), except that __getattr__ doesn't break the
+ # cycle until the second time gc checks for __del__. As of 2.3b1,
+ # there isn't a second time, so this simply cleans up the trash cycle.
+ # We expect a, b, a.__dict__ and b.__dict__ (4 objects) to get reclaimed
+ # this way.
+ expect(gc.collect(), 4, "boom2")
+ expect(len(gc.garbage), garbagelen, "boom2")
+
def test_all():
gc.collect() # Delete 2nd generation garbage
run_test("lists", test_list)
@@ -295,6 +322,7 @@
run_test("saveall", test_saveall)
run_test("trashcan", test_trashcan)
run_test("boom", test_boom)
+ run_test("boom2", test_boom2)
def test():
if verbose: