Add eventfd select test case

tiran · tiran · commit c0e9b4bf85b7 · 2020-11-13T11:27:56.000+01:00
Signed-off-by: Christian Heimes &lt;christian@python.org&gt;
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
@@ -60,6 +60,11 @@
 except ImportError:
     INT_MAX = PY_SSIZE_T_MAX = sys.maxsize
 
+try:
+    import select
+except ImportError:
+    select = None
+
 from test.support.script_helper import assert_python_ok
 from test.support import unix_shell
 from test.support.os_helper import FakePath
@@ -3589,6 +3594,31 @@ def test_eventfd_semaphore(self):
         with self.assertRaises(BlockingIOError):
             os.eventfd_read(fd)
 
+    @unittest.skipUnless(
+        hasattr(select, "select"), reason="test needs select.select"
+    )
+    def test_eventfd_select(self):
+        flags = os.EFD_CLOEXEC | os.EFD_NONBLOCK
+        fd = os.eventfd(0, flags)
+        self.assertNotEqual(fd, -1)
+        self.addCleanup(os.close, fd)
+
+        # counter is zero, only writeable
+        rfd, wfd, xfd = select.select([fd], [fd], [fd], 0)
+        self.assertEqual((rfd, wfd, xfd), ([], [fd], []))
+
+        # counter is non-zero, read and writeable
+        os.eventfd_write(fd, 23)
+        rfd, wfd, xfd = select.select([fd], [fd], [fd], 0)
+        self.assertEqual((rfd, wfd, xfd), ([fd], [fd], []))
+        self.assertEqual(os.eventfd_read(fd), 23)
+
+        # counter at max, only readable
+        os.eventfd_write(fd, (2**64) - 2)
+        rfd, wfd, xfd = select.select([fd], [fd], [fd], 0)
+        self.assertEqual((rfd, wfd, xfd), ([fd], [], []))
+        os.eventfd_read(fd)
+
 
 class OSErrorTests(unittest.TestCase):
     def setUp(self):
