Issue #21362: concurrent.futures does not validate that max_workers is proper
diff --git a/Lib/concurrent/futures/process.py b/Lib/concurrent/futures/process.py
index 07b5225..1299390 100644
--- a/Lib/concurrent/futures/process.py
+++ b/Lib/concurrent/futures/process.py
@@ -334,6 +334,9 @@
if max_workers is None:
self._max_workers = os.cpu_count() or 1
else:
+ if max_workers <= 0:
+ raise ValueError("max_workers must be greater than 0")
+
self._max_workers = max_workers
# Make the call queue slightly larger than the number of processes to
diff --git a/Lib/concurrent/futures/thread.py b/Lib/concurrent/futures/thread.py
index f9beb0f..8d6081c 100644
--- a/Lib/concurrent/futures/thread.py
+++ b/Lib/concurrent/futures/thread.py
@@ -87,6 +87,9 @@
max_workers: The maximum number of threads that can be used to
execute the given calls.
"""
+ if max_workers <= 0:
+ raise ValueError("max_workers must be greater than 0")
+
self._max_workers = max_workers
self._work_queue = queue.Queue()
self._threads = set()
diff --git a/Lib/test/test_concurrent_futures.py b/Lib/test/test_concurrent_futures.py
index c74b2ca..55254b5 100644
--- a/Lib/test/test_concurrent_futures.py
+++ b/Lib/test/test_concurrent_futures.py
@@ -425,6 +425,13 @@
self.assertTrue(collected,
"Stale reference not collected within timeout.")
+ def test_max_workers_negative(self):
+ for number in (0, -1):
+ with self.assertRaisesRegexp(ValueError,
+ "max_workers must be greater "
+ "than 0"):
+ self.executor_type(max_workers=number)
+
class ThreadPoolExecutorTest(ThreadPoolMixin, ExecutorTest, unittest.TestCase):
def test_map_submits_without_iteration(self):