Issue #8275: Fix passing of callback arguments with ctypes under Win64.

Patch by Stan Mihai. Ok'ed by Georg.

Lib/ctypes/test/test_callbacks.py

@@ -200,6 +200,42 @@ class SampleCallbacksTestCase(unittest.TestCase):
 
             windll.user32.EnumWindows(EnumWindowsCallbackFunc, 0)
 
+    def test_callback_register_int(self):
+        # Issue #8275: buggy handling of callback args under Win64
+        # NOTE: should be run on release builds as well
+        dll = CDLL(_ctypes_test.__file__)
+        CALLBACK = CFUNCTYPE(c_int, c_int, c_int, c_int, c_int, c_int)
+        # All this function does is call the callback with its args squared
+        func = dll._testfunc_cbk_reg_int
+        func.argtypes = (c_int, c_int, c_int, c_int, c_int, CALLBACK)
+        func.restype = c_int
+
+        def callback(a, b, c, d, e):
+            return a + b + c + d + e
+
+        result = func(2, 3, 4, 5, 6, CALLBACK(callback))
+        self.assertEqual(result, callback(2*2, 3*3, 4*4, 5*5, 6*6))
+
+    def test_callback_register_double(self):
+        # Issue #8275: buggy handling of callback args under Win64
+        # NOTE: should be run on release builds as well
+        dll = CDLL(_ctypes_test.__file__)
+        CALLBACK = CFUNCTYPE(c_double, c_double, c_double, c_double,
+                             c_double, c_double)
+        # All this function does is call the callback with its args squared
+        func = dll._testfunc_cbk_reg_double
+        func.argtypes = (c_double, c_double, c_double,
+                         c_double, c_double, CALLBACK)
+        func.restype = c_double
+
+        def callback(a, b, c, d, e):
+            return a + b + c + d + e
+
+        result = func(1.1, 2.2, 3.3, 4.4, 5.5, CALLBACK(callback))
+        self.assertEqual(result,
+                         callback(1.1*1.1, 2.2*2.2, 3.3*3.3, 4.4*4.4, 5.5*5.5))
+
+
 ################################################################
 
 if __name__ == '__main__':