closes issue29167: fix race condition in (Int)Flag
diff --git a/Lib/enum.py b/Lib/enum.py
index e79b038..056400d 100644
--- a/Lib/enum.py
+++ b/Lib/enum.py
@@ -690,7 +690,9 @@
pseudo_member = object.__new__(cls)
pseudo_member._name_ = None
pseudo_member._value_ = value
- cls._value2member_map_[value] = pseudo_member
+ # use setdefault in case another thread already created a composite
+ # with this value
+ pseudo_member = cls._value2member_map_.setdefault(value, pseudo_member)
return pseudo_member
def __contains__(self, other):
@@ -785,7 +787,9 @@
pseudo_member = int.__new__(cls, value)
pseudo_member._name_ = None
pseudo_member._value_ = value
- cls._value2member_map_[value] = pseudo_member
+ # use setdefault in case another thread already created a composite
+ # with this value
+ pseudo_member = cls._value2member_map_.setdefault(value, pseudo_member)
return pseudo_member
def __or__(self, other):
@@ -835,18 +839,21 @@
# _decompose is only called if the value is not named
not_covered = value
negative = value < 0
+ # issue29167: wrap accesses to _value2member_map_ in a list to avoid race
+ # conditions between iterating over it and having more psuedo-
+ # members added to it
if negative:
# only check for named flags
flags_to_check = [
(m, v)
- for v, m in flag._value2member_map_.items()
+ for v, m in list(flag._value2member_map_.items())
if m.name is not None
]
else:
# check for named flags and powers-of-two flags
flags_to_check = [
(m, v)
- for v, m in flag._value2member_map_.items()
+ for v, m in list(flag._value2member_map_.items())
if m.name is not None or _power_of_two(v)
]
members = []
diff --git a/Lib/test/test_enum.py b/Lib/test/test_enum.py
index e97ef94..13a89fc 100644
--- a/Lib/test/test_enum.py
+++ b/Lib/test/test_enum.py
@@ -7,6 +7,11 @@
from io import StringIO
from pickle import dumps, loads, PicklingError, HIGHEST_PROTOCOL
from test import support
+try:
+ import threading
+except ImportError:
+ threading = None
+
# for pickle tests
try:
@@ -1983,6 +1988,45 @@
d = 6
self.assertEqual(repr(Bizarre(7)), '<Bizarre.d|c|b: 7>')
+ @unittest.skipUnless(threading, 'Threading required for this test.')
+ @support.reap_threads
+ def test_unique_composite(self):
+ # override __eq__ to be identity only
+ class TestFlag(Flag):
+ one = auto()
+ two = auto()
+ three = auto()
+ four = auto()
+ five = auto()
+ six = auto()
+ seven = auto()
+ eight = auto()
+ def __eq__(self, other):
+ return self is other
+ def __hash__(self):
+ return hash(self._value_)
+ # have multiple threads competing to complete the composite members
+ seen = set()
+ failed = False
+ def cycle_enum():
+ nonlocal failed
+ try:
+ for i in range(256):
+ seen.add(TestFlag(i))
+ except Exception:
+ failed = True
+ threads = [
+ threading.Thread(target=cycle_enum)
+ for _ in range(8)
+ ]
+ with support.start_threads(threads):
+ pass
+ # check that only 248 members were created
+ self.assertFalse(
+ failed,
+ 'at least one thread failed while creating composite members')
+ self.assertEqual(256, len(seen), 'too many composite members created')
+
class TestIntFlag(unittest.TestCase):
"""Tests of the IntFlags."""
@@ -2275,6 +2319,46 @@
for f in Open:
self.assertEqual(bool(f.value), bool(f))
+ @unittest.skipUnless(threading, 'Threading required for this test.')
+ @support.reap_threads
+ def test_unique_composite(self):
+ # override __eq__ to be identity only
+ class TestFlag(IntFlag):
+ one = auto()
+ two = auto()
+ three = auto()
+ four = auto()
+ five = auto()
+ six = auto()
+ seven = auto()
+ eight = auto()
+ def __eq__(self, other):
+ return self is other
+ def __hash__(self):
+ return hash(self._value_)
+ # have multiple threads competing to complete the composite members
+ seen = set()
+ failed = False
+ def cycle_enum():
+ nonlocal failed
+ try:
+ for i in range(256):
+ seen.add(TestFlag(i))
+ except Exception:
+ failed = True
+ threads = [
+ threading.Thread(target=cycle_enum)
+ for _ in range(8)
+ ]
+ with support.start_threads(threads):
+ pass
+ # check that only 248 members were created
+ self.assertFalse(
+ failed,
+ 'at least one thread failed while creating composite members')
+ self.assertEqual(256, len(seen), 'too many composite members created')
+
+
class TestUnique(unittest.TestCase):
def test_unique_clean(self):
@@ -2484,7 +2568,8 @@
class TestIntEnumConvert(unittest.TestCase):
def test_convert_value_lookup_priority(self):
test_type = enum.IntEnum._convert(
- 'UnittestConvert', 'test.test_enum',
+ 'UnittestConvert',
+ ('test.test_enum', '__main__')[__name__=='__main__'],
filter=lambda x: x.startswith('CONVERT_TEST_'))
# We don't want the reverse lookup value to vary when there are
# multiple possible names for a given value. It should always
@@ -2493,7 +2578,8 @@
def test_convert(self):
test_type = enum.IntEnum._convert(
- 'UnittestConvert', 'test.test_enum',
+ 'UnittestConvert',
+ ('test.test_enum', '__main__')[__name__=='__main__'],
filter=lambda x: x.startswith('CONVERT_TEST_'))
# Ensure that test_type has all of the desired names and values.
self.assertEqual(test_type.CONVERT_TEST_NAME_F,