Issue #18904: test_socket: add inheritance tests using fcntl and FD_CLOEXEC

Lib/test/test_socket.py

@@ -26,6 +26,10 @@ try:
     import multiprocessing
 except ImportError:
     multiprocessing = False
+try:
+    import fcntl
+except ImportError:
+    fcntl = None
 
 HOST = support.HOST
 MSG = 'Michael Gilfix was here\u1234\r\n'.encode('utf-8') ## test unicode string and carriage return
@@ -4804,6 +4808,32 @@ class InheritanceTest(unittest.TestCase):
             sock.set_inheritable(False)
             self.assertEqual(sock.get_inheritable(), False)
 
+    if fcntl:
+        def test_get_inheritable_cloexec(self):
+            sock = socket.socket()
+            with sock:
+                fd = sock.fileno()
+                self.assertEqual(sock.get_inheritable(), False)
+
+                # clear FD_CLOEXEC flag
+                flags = fcntl.fcntl(fd, fcntl.F_GETFD)
+                flags &= ~fcntl.FD_CLOEXEC
+                fcntl.fcntl(fd, fcntl.F_SETFD, flags)
+
+                self.assertEqual(sock.get_inheritable(), True)
+
+        def test_set_inheritable_cloexec(self):
+            sock = socket.socket()
+            with sock:
+                fd = sock.fileno()
+                self.assertEqual(fcntl.fcntl(fd, fcntl.F_GETFD) & fcntl.FD_CLOEXEC,
+                                 fcntl.FD_CLOEXEC)
+
+                sock.set_inheritable(True)
+                self.assertEqual(fcntl.fcntl(fd, fcntl.F_GETFD) & fcntl.FD_CLOEXEC,
+                                 0)
+
+
     @unittest.skipUnless(hasattr(socket, "socketpair"),
                          "need socket.socketpair()")
     def test_socketpair(self):