bpo-36279: Ensure os.wait3() rusage is initialized (GH-15111)

Co-Authored-By: David Wilson <dw@botanicus.net>

1 files changed, 18 insertions, 0 deletions

diff --git a/Lib/test/test_wait3.py b/Lib/test/test_wait3.py
index eb51b2c..3825451 100644
--- a/Lib/test/test_wait3.py
+++ b/Lib/test/test_wait3.py
@@ -2,6 +2,8 @@
 """
 
 import os
+import subprocess
+import sys
 import time
 import unittest
 from test.fork_wait import ForkWait
@@ -31,6 +33,22 @@ class Wait3Test(ForkWait):
         self.assertEqual(status, 0, "cause = %d, exit = %d" % (status&0xff, status>>8))
         self.assertTrue(rusage)
 
+    def test_wait3_rusage_initialized(self):
+        # Ensure a successful wait3() call where no child was ready to report
+        # its exit status does not return uninitialized memory in the rusage
+        # structure. See bpo-36279.
+        args = [sys.executable, '-c', 'import sys; sys.stdin.read()']
+        proc = subprocess.Popen(args, stdin=subprocess.PIPE)
+        try:
+            pid, status, rusage = os.wait3(os.WNOHANG)
+            self.assertEqual(0, pid)
+            self.assertEqual(0, status)
+            self.assertEqual(0, sum(rusage))
+        finally:
+            proc.stdin.close()
+            proc.wait()
+
+
 def tearDownModule():
     reap_children()