gh-127946: Use a critical section for `CFuncPtr` attributes (GH-128109)

1 files changed, 19 insertions, 1 deletions

diff --git a/Lib/test/test_ctypes/test_cfuncs.py b/Lib/test/test_ctypes/test_cfuncs.py
index 48330c4..e0c1246 100644
--- a/Lib/test/test_ctypes/test_cfuncs.py
+++ b/Lib/test/test_ctypes/test_cfuncs.py
@@ -5,7 +5,8 @@ from ctypes import (CDLL,
                     c_short, c_ushort, c_int, c_uint,
                     c_long, c_ulong, c_longlong, c_ulonglong,
                     c_float, c_double, c_longdouble)
-from test.support import import_helper
+from test import support
+from test.support import import_helper, threading_helper
 _ctypes_test = import_helper.import_module("_ctypes_test")
 
 
@@ -191,6 +192,23 @@ class CFunctions(unittest.TestCase):
         self.assertEqual(self._dll.tv_i(-42), None)
         self.assertEqual(self.S(), -42)
 
+    @threading_helper.requires_working_threading()
+    @support.requires_resource("cpu")
+    @unittest.skipUnless(support.Py_GIL_DISABLED, "only meaningful on free-threading")
+    def test_thread_safety(self):
+        from threading import Thread
+
+        def concurrent():
+            for _ in range(100):
+                self._dll.tf_b.restype = c_byte
+                self._dll.tf_b.argtypes = (c_byte,)
+
+        with threading_helper.catch_threading_exception() as exc:
+            with threading_helper.start_threads((Thread(target=concurrent) for _ in range(10))):
+                pass
+
+            self.assertIsNone(exc.exc_value)
+
 
 # The following repeats the above tests with stdcall functions (where
 # they are available)