gh-97588: Failing tests to demonstrate the issue

Lib/test/test_ctypes/test_bitfields.py

@@ -3,6 +3,7 @@
 from test import support
 import unittest
 import os
+import sys
 
 import _ctypes_test
 
@@ -236,6 +237,79 @@ class X(Structure):
         else:
             self.assertEqual(sizeof(X), sizeof(c_int) * 2)
 
+    @unittest.skipIf(sys.platform == 'win32', "Doesn't fail on Windows")
+    @unittest.expectedFailure  # gh-97588
+    def test_mixed_5(self):
+        class X(Structure):
+            _fields_ = [
+                ('A', c_uint, 1),
+                ('B', c_ushort, 16)]
+        a = X()
+        a.A = 0
+        a.B = 1
+        self.assertEqual(1, a.B)
+
+    @unittest.skipIf(sys.platform == 'win32', "Doesn't fail on Windows")
+    @unittest.expectedFailure  # gh-97588
+    def test_mixed_6(self):
+        class X(Structure):
+            _fields_ = [
+                ('A', c_ulonglong, 1),
+                ('B', c_uint, 32)]
+        a = X()
+        a.A = 0
+        a.B = 1
+        self.assertEqual(1, a.B)
+
+    @unittest.skipIf(sys.platform == 'win32', "Doesn't fail on Windows")
+    @unittest.expectedFailure  # gh-97588
+    def test_mixed_7(self):
+        class X(Structure):
+            _fields_ = [
+                ("A", c_uint),
+                ('B', c_uint, 20),
+                ('C', c_ulonglong, 24)]
+        self.assertEqual(16, sizeof(X))
+
+    @unittest.skipIf(sys.platform == 'win32', "Doesn't fail on Windows")
+    @unittest.expectedFailure  # gh-97588
+    def test_mixed_8(self):
+        class Foo(Structure):
+            _fields_ = [
+                ("A", c_uint),
+                ("B", c_uint, 32),
+                ("C", c_ulonglong, 1),
+                ]
+
+        class Bar(Structure):
+            _fields_ = [
+                ("A", c_uint),
+                ("B", c_uint),
+                ("C", c_ulonglong, 1),
+                ]
+        self.assertEqual(sizeof(Foo), sizeof(Bar))
+
+    @unittest.skipIf(sys.platform == 'win32', "Doesn't fail on Windows")
+    @unittest.expectedFailure  # gh-97588
+    def test_mixed_9(self):
+        class X(Structure):
+            _fields_ = [
+                ("A", c_uint8),
+                ("B", c_uint, 1),
+                ]
+        self.assertEqual(4, sizeof(X))
+
+    @unittest.skipIf(sys.platform == 'win32', "Doesn't fail on Windows")
+    @unittest.expectedFailure  # gh-97588
+    def test_mixed_10(self):
+        class X(Structure):
+            _fields_ = [
+                ("A", c_uint32, 1),
+                ("B", c_uint64, 1),
+                ]
+        self.assertEqual(8, alignment(X))
+        self.assertEqual(8, sizeof(X))
+
     def test_anon_bitfields(self):
         # anonymous bit-fields gave a strange error message
         class X(Structure):

Misc/NEWS.d/next/C API/2022-09-30-07-16-00.gh-issue-97588.yQFteB.rst

@@ -0,0 +1 @@
+Add failing tests to document problems with ctypes structs.