Issue #12105: Add O_CLOEXEC to the os module.
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 0e9ac75..9c2cac3 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -9,6 +9,7 @@
 import sys
 import time
 import os
+import fcntl
 import pwd
 import shutil
 import stat
@@ -307,6 +308,12 @@
                 fp1.close()
                 fp2.close()
 
+    @unittest.skipUnless(hasattr(os, 'O_CLOEXEC'), "needs os.O_CLOEXEC")
+    def test_oscloexec(self):
+        fd = os.open(support.TESTFN, os.O_RDONLY|os.O_CLOEXEC)
+        self.addCleanup(os.close, fd)
+        self.assertTrue(fcntl.fcntl(fd, fcntl.F_GETFD) & fcntl.FD_CLOEXEC)
+
     def test_osexlock(self):
         if hasattr(posix, "O_EXLOCK"):
             fd = os.open(support.TESTFN,