Fix ResourceWarning in test_shared_memory_SharedMemoryManager_reuses_resource_tracker

Author: pitrou

Lib/test/_test_multiprocessing.py

@@ -17,6 +17,7 @@
 import socket
 import random
 import logging
+import subprocess
 import struct
 import operator
 import pickle
@@ -3769,7 +3770,6 @@ def test_shared_memory_SharedMemoryServer_ignores_sigint(self):
     def test_shared_memory_SharedMemoryManager_reuses_resource_tracker(self):
         # bpo-36867: test that a SharedMemoryManager uses the
         # same resource_tracker process as its parent.
-        import subprocess
         cmd = '''if 1:
             from multiprocessing.managers import SharedMemoryManager
 
@@ -3779,16 +3779,13 @@ def test_shared_memory_SharedMemoryManager_reuses_resource_tracker(self):
             sl = smm.ShareableList(range(10))
             smm.shutdown()
         '''
-        p = subprocess.Popen([sys.executable, '-E', '-c', cmd],
-                             stderr=subprocess.PIPE)
-        p.wait()
+        rc, out, err = test.support.script_helper.assert_python_ok('-c', cmd)
 
         # Before bpo-36867 was fixed, a SharedMemoryManager not using the same
         # resource_tracker process as its parent would make the parent's
         # tracker complain about sl being leaked even though smm.shutdown()
         # properly released sl.
-        stderr = p.stderr.read().strip().decode()
-        self.assertNotRegex(stderr, "resource_tracker")
+        self.assertFalse(err)
 
     def test_shared_memory_SharedMemoryManager_basics(self):
         smm1 = multiprocessing.managers.SharedMemoryManager()
@@ -3929,8 +3926,6 @@ def test_shared_memory_ShareableList_pickling(self):
         sl.shm.close()
 
     def test_shared_memory_cleaned_after_process_termination(self):
-        import subprocess
-        from multiprocessing import shared_memory
         cmd = '''if 1:
             import os, time, sys
             from multiprocessing import shared_memory
@@ -3941,18 +3936,24 @@ def test_shared_memory_cleaned_after_process_termination(self):
             sys.stdout.flush()
             time.sleep(100)
         '''
-        p = subprocess.Popen([sys.executable, '-E', '-c', cmd],
-                             stdout=subprocess.PIPE)
-        name = p.stdout.readline().strip().decode()
+        with subprocess.Popen([sys.executable, '-E', '-c', cmd],
+                              stdout=subprocess.PIPE,
+                              stderr=subprocess.PIPE) as p:
+            name = p.stdout.readline().strip().decode()
 
-        # killing abruptly processes holding reference to a shared memory
-        # segment should not leak the given memory segment.
-        p.terminate()
-        p.wait()
-        time.sleep(1.0)  # wait for the OS to collect the segment
+            # killing abruptly processes holding reference to a shared memory
+            # segment should not leak the given memory segment.
+            p.terminate()
+            p.wait()
+            time.sleep(1.0)  # wait for the OS to collect the segment
 
-        with self.assertRaises(FileNotFoundError):
-            smm = shared_memory.SharedMemory(name, create=False)
+            # The shared memory file was deleted.
+            with self.assertRaises(FileNotFoundError):
+                smm = shared_memory.SharedMemory(name, create=False)
+            # A warning was emitted by the subprocess' own resource_tracker.
+            err = p.stderr.read().decode()
+            self.assertIn("resource_tracker: There appear to be 1 leaked "
+                          "shared_memory objects to clean up at shutdown", err)
 
 #
 #
@@ -4585,7 +4586,7 @@ def run_in_child(cls):
         print(json.dumps(flags))
 
     def test_flags(self):
-        import json, subprocess
+        import json
         # start child process using unusual flags
         prog = ('from test._test_multiprocessing import TestFlags; ' +
                 'TestFlags.run_in_child()')
@@ -4891,7 +4892,6 @@ def test_resource_tracker(self):
         #
         # Check that killing process does not leak named semaphores
         #
-        import subprocess
         cmd = '''if 1:
             import time, os, tempfile
             import multiprocessing as mp