bpo-31019: Fix multiprocessing.Process.is_alive() (#2875) (#2882)
multiprocessing.Process.is_alive() now removes the process from the
_children set if the process completed.
The change prevents leaking "dangling" processes.
(cherry picked from commit 2db64823c20538a6cfc6033661fab5711d2d4585)
diff --git a/Lib/multiprocessing/process.py b/Lib/multiprocessing/process.py
index 16c4e1e..11c8fca 100644
--- a/Lib/multiprocessing/process.py
+++ b/Lib/multiprocessing/process.py
@@ -156,10 +156,16 @@
if self is _current_process:
return True
assert self._parent_pid == os.getpid(), 'can only test a child process'
+
if self._popen is None:
return False
- self._popen.poll()
- return self._popen.returncode is None
+
+ returncode = self._popen.poll()
+ if returncode is None:
+ return True
+ else:
+ _current_process._children.discard(self)
+ return False
@property
def name(self):