Issue #7105: weak dict iterators are fragile because of unpredictable GC runs
Backport the fix from pyton 3.x for this issue.
diff --git a/Lib/test/test_weakref.py b/Lib/test/test_weakref.py
index b70230f..40e1473 100644
--- a/Lib/test/test_weakref.py
+++ b/Lib/test/test_weakref.py
@@ -4,6 +4,8 @@
import UserList
import weakref
import operator
+import contextlib
+import copy
from test import test_support
@@ -903,7 +905,7 @@
def check_len_cycles(self, dict_type, cons):
N = 20
items = [RefCycle() for i in range(N)]
- dct = dict_type(cons(o) for o in items)
+ dct = dict_type(cons(i, o) for i, o in enumerate(items))
# Keep an iterator alive
it = dct.iteritems()
try:
@@ -913,18 +915,23 @@
del items
gc.collect()
n1 = len(dct)
+ list(it)
del it
gc.collect()
n2 = len(dct)
- # one item may be kept alive inside the iterator
- self.assertIn(n1, (0, 1))
+ # iteration should prevent garbage collection here
+ # Note that this is a test on an implementation detail. The requirement
+ # is only to provide stable iteration, not that the size of the container
+ # stay fixed.
+ self.assertEqual(n1, 20)
+ #self.assertIn(n1, (0, 1))
self.assertEqual(n2, 0)
def test_weak_keyed_len_cycles(self):
- self.check_len_cycles(weakref.WeakKeyDictionary, lambda k: (k, 1))
+ self.check_len_cycles(weakref.WeakKeyDictionary, lambda n, k: (k, n))
def test_weak_valued_len_cycles(self):
- self.check_len_cycles(weakref.WeakValueDictionary, lambda k: (1, k))
+ self.check_len_cycles(weakref.WeakValueDictionary, lambda n, k: (n, k))
def check_len_race(self, dict_type, cons):
# Extended sanity checks for len() in the face of cyclic collection
@@ -1090,6 +1097,86 @@
self.assertEqual(len(values), 0,
"itervalues() did not touch all values")
+ def check_weak_destroy_while_iterating(self, dict, objects, iter_name):
+ n = len(dict)
+ it = iter(getattr(dict, iter_name)())
+ next(it) # Trigger internal iteration
+ # Destroy an object
+ del objects[-1]
+ gc.collect() # just in case
+ # We have removed either the first consumed object, or another one
+ self.assertIn(len(list(it)), [len(objects), len(objects) - 1])
+ del it
+ # The removal has been committed
+ self.assertEqual(len(dict), n - 1)
+
+ def check_weak_destroy_and_mutate_while_iterating(self, dict, testcontext):
+ # Check that we can explicitly mutate the weak dict without
+ # interfering with delayed removal.
+ # `testcontext` should create an iterator, destroy one of the
+ # weakref'ed objects and then return a new key/value pair corresponding
+ # to the destroyed object.
+ with testcontext() as (k, v):
+ self.assertFalse(k in dict)
+ with testcontext() as (k, v):
+ self.assertRaises(KeyError, dict.__delitem__, k)
+ self.assertFalse(k in dict)
+ with testcontext() as (k, v):
+ self.assertRaises(KeyError, dict.pop, k)
+ self.assertFalse(k in dict)
+ with testcontext() as (k, v):
+ dict[k] = v
+ self.assertEqual(dict[k], v)
+ ddict = copy.copy(dict)
+ with testcontext() as (k, v):
+ dict.update(ddict)
+ self.assertEqual(dict, ddict)
+ with testcontext() as (k, v):
+ dict.clear()
+ self.assertEqual(len(dict), 0)
+
+ def test_weak_keys_destroy_while_iterating(self):
+ # Issue #7105: iterators shouldn't crash when a key is implicitly removed
+ dict, objects = self.make_weak_keyed_dict()
+ self.check_weak_destroy_while_iterating(dict, objects, 'iterkeys')
+ self.check_weak_destroy_while_iterating(dict, objects, 'iteritems')
+ self.check_weak_destroy_while_iterating(dict, objects, 'itervalues')
+ self.check_weak_destroy_while_iterating(dict, objects, 'iterkeyrefs')
+ dict, objects = self.make_weak_keyed_dict()
+ @contextlib.contextmanager
+ def testcontext():
+ try:
+ it = iter(dict.iteritems())
+ next(it)
+ # Schedule a key/value for removal and recreate it
+ v = objects.pop().arg
+ gc.collect() # just in case
+ yield Object(v), v
+ finally:
+ it = None # should commit all removals
+ self.check_weak_destroy_and_mutate_while_iterating(dict, testcontext)
+
+ def test_weak_values_destroy_while_iterating(self):
+ # Issue #7105: iterators shouldn't crash when a key is implicitly removed
+ dict, objects = self.make_weak_valued_dict()
+ self.check_weak_destroy_while_iterating(dict, objects, 'iterkeys')
+ self.check_weak_destroy_while_iterating(dict, objects, 'iteritems')
+ self.check_weak_destroy_while_iterating(dict, objects, 'itervalues')
+ self.check_weak_destroy_while_iterating(dict, objects, 'itervaluerefs')
+ dict, objects = self.make_weak_valued_dict()
+ @contextlib.contextmanager
+ def testcontext():
+ try:
+ it = iter(dict.iteritems())
+ next(it)
+ # Schedule a key/value for removal and recreate it
+ k = objects.pop().arg
+ gc.collect() # just in case
+ yield k, Object(k)
+ finally:
+ it = None # should commit all removals
+ self.check_weak_destroy_and_mutate_while_iterating(dict, testcontext)
+
def test_make_weak_keyed_dict_from_dict(self):
o = Object(3)
dict = weakref.WeakKeyDictionary({o:364})
diff --git a/Lib/test/test_weakset.py b/Lib/test/test_weakset.py
index fb9e8d7..6b34a8d 100644
--- a/Lib/test/test_weakset.py
+++ b/Lib/test/test_weakset.py
@@ -11,6 +11,7 @@
import collections
import gc
import contextlib
+from UserString import UserString as ustr
class Foo:
@@ -448,6 +449,54 @@
self.assertGreaterEqual(n2, 0)
self.assertLessEqual(n2, n1)
+ def test_weak_destroy_while_iterating(self):
+ # Issue #7105: iterators shouldn't crash when a key is implicitly removed
+ # Create new items to be sure no-one else holds a reference
+ items = [ustr(c) for c in ('a', 'b', 'c')]
+ s = WeakSet(items)
+ it = iter(s)
+ next(it) # Trigger internal iteration
+ # Destroy an item
+ del items[-1]
+ gc.collect() # just in case
+ # We have removed either the first consumed items, or another one
+ self.assertIn(len(list(it)), [len(items), len(items) - 1])
+ del it
+ # The removal has been committed
+ self.assertEqual(len(s), len(items))
+
+ def test_weak_destroy_and_mutate_while_iterating(self):
+ # Issue #7105: iterators shouldn't crash when a key is implicitly removed
+ items = [ustr(c) for c in string.ascii_letters]
+ s = WeakSet(items)
+ @contextlib.contextmanager
+ def testcontext():
+ try:
+ it = iter(s)
+ next(it)
+ # Schedule an item for removal and recreate it
+ u = ustr(str(items.pop()))
+ gc.collect() # just in case
+ yield u
+ finally:
+ it = None # should commit all removals
+
+ with testcontext() as u:
+ self.assertFalse(u in s)
+ with testcontext() as u:
+ self.assertRaises(KeyError, s.remove, u)
+ self.assertFalse(u in s)
+ with testcontext() as u:
+ s.add(u)
+ self.assertTrue(u in s)
+ t = s.copy()
+ with testcontext() as u:
+ s.update(t)
+ self.assertEqual(len(s), len(t))
+ with testcontext() as u:
+ s.clear()
+ self.assertEqual(len(s), 0)
+
def test_main(verbose=None):
test_support.run_unittest(TestWeakSet)