multiprocessing.Queue.empty() returns False after all producers have exited on Windows 3.13.3 #140331
Description
On Windows 11 with CPython 3.13.3 official installer, Queue.empty() incorrectly returns False when the producer process has already terminated, allowing a later-started consumer to successfully get() all buffered items. This contradicts the documented behaviour that empty() is only reliable while producers are alive.
To Reproduce
Save as clean_test.py:
Python
from multiprocessing import Process, Queue
def x(q):
for i in range(4):
q.put(i)
def y(q):
cnt = 0
while True:
if q.empty():
break
q.get()
cnt += 1
print('实际 get 次数：', cnt)
if __name__ == '__main__':
q = Queue()
p1 = Process(target=x, args=(q,))
p2 = Process(target=y, args=(q,))
p1.start()
p1.join() # producer already dead
p2.start()
p2.join()
Run:
powershell
python clean_test.py
Expected behaviour
Should print 实际 get 次数： 0 (consumer sees empty queue).
Actual behaviour
Prints 实际 get 次数： 4 (consumer successfully gets all items).
Environment
OS: Windows 11 (build 22631)
Python: 3.13.3 (tags/v3.13.3:6280bb5, Apr 8 2025, 14:47:33) [MSC v.1943 64 bit (AMD64)]
Installer: official python.org x64 exe
File SHA-256: 4D8746575FF5D9062D159EB0C382589DBFEC56C942D23DA57E44CF1920312D57
Additional context
The same script always outputs 0 on Linux (CPython 3.11-3.13) and on Windows 10 with 3.11.
Appears to be Windows-specific and version-specific (3.13.3).