Add extra test and fix documentation typo

monkeyman192 · monkeyman192 · commit a7bc0fef39ea · 2024-02-02T16:17:17.000+11:00
diff --git a/Doc/library/ctypes.rst b/Doc/library/ctypes.rst
@@ -2540,7 +2540,7 @@ fields, or any other data types containing pointer type fields.
 
    .. attribute:: _align_
 
-      An optional small interger that allows overriding the alignment of
+      An optional small integer that allows overriding the alignment of
       the structure when being packed or unpacked to/from memory.
       Setting this attribute to 0 is the same as not setting it at all.
 
diff --git a/Lib/test/test_ctypes/test_aligned_structures.py b/Lib/test/test_ctypes/test_aligned_structures.py
@@ -245,6 +245,42 @@ class Main(SubUnion):
             self.assertEqual(main.unsigned, 0xD6)
             self.assertEqual(main.signed, -42)
 
+    def test_aligned_packed_structures(self):
+        for sbase, e in (
+            (LittleEndianStructure, "<"),
+            (BigEndianStructure, ">"),
+        ):
+            data = bytearray(struct.pack(f"{e}B2H4xB", 1, 2, 3, 4))
+
+            class Inner(sbase):
+                _align_ = 8
+                _fields_ = [
+                    ("x", c_uint16),
+                    ("y", c_uint16),
+                ]
+
+            class Main(sbase):
+                _pack_ = 1
+                _fields_ = [
+                    ("a", c_ubyte),
+                    ("b", Inner),
+                    ("c", c_ubyte),
+                ]
+
+            main = Main.from_buffer(data)
+            self.assertEqual(sizeof(main), 10)
+            self.assertEqual(Main.b.offset, 1)
+            # Alignment == 8 because _pack_ wins out.
+            self.assertEqual(alignment(main.b), 8)
+            # Size is still 8 though since inside this Structure, it will have
+            # effect.
+            self.assertEqual(sizeof(main.b), 8)
+            self.assertEqual(Main.c.offset, 9)
+            self.assertEqual(main.a, 1)
+            self.assertEqual(main.b.x, 2)
+            self.assertEqual(main.b.y, 3)
+            self.assertEqual(main.c, 4)
+
 
 if __name__ == '__main__':
     unittest.main()
