https://github.com/python/cpython/commit/678b8e165646e72a2f39f017ad237210d3d481ef
commit: 678b8e165646e72a2f39f017ad237210d3d481ef
branch: main
author: sobolevn <m...@sobolevn.me>
committer: sobolevn <m...@sobolevn.me>
date: 2025-04-18T17:32:28+03:00
summary:
gh-132673: Fix `ctypes.Structure` with `_align_=0` (#132676)
Co-authored-by: Bénédikt Tran <10796600+picn...@users.noreply.github.com>
files:
A Misc/NEWS.d/next/Library/2025-04-18-14-34-43.gh-issue-132673.0sliCv.rst
M Lib/ctypes/_layout.py
M Lib/test/test_ctypes/test_aligned_structures.py
diff --git a/Lib/ctypes/_layout.py b/Lib/ctypes/_layout.py
index beb3b86414c010..0719e72cfed312 100644
--- a/Lib/ctypes/_layout.py
+++ b/Lib/ctypes/_layout.py
@@ -84,7 +84,7 @@ def get_layout(cls, input_fields, is_struct, base):
raise ValueError('_align_ must be a non-negative integer')
elif align == 0:
# Setting `_align_ = 0` amounts to using the default alignment
- align == 1
+ align = 1
if base:
align = max(ctypes.alignment(base), align)
diff --git a/Lib/test/test_ctypes/test_aligned_structures.py
b/Lib/test/test_ctypes/test_aligned_structures.py
index 26d24f31b29f7b..0c563ab80559a6 100644
--- a/Lib/test/test_ctypes/test_aligned_structures.py
+++ b/Lib/test/test_ctypes/test_aligned_structures.py
@@ -1,7 +1,7 @@
from ctypes import (
c_char, c_uint32, c_uint16, c_ubyte, c_byte, alignment, sizeof,
BigEndianStructure, LittleEndianStructure,
- BigEndianUnion, LittleEndianUnion,
+ BigEndianUnion, LittleEndianUnion, Structure,
)
import struct
import unittest
@@ -69,6 +69,41 @@ class Main(base):
self.assertEqual(Main.z.offset, 8)
self.assertEqual(main.z, 7)
+ def test_negative_align(self):
+ for base in (Structure, LittleEndianStructure, BigEndianStructure):
+ with (
+ self.subTest(base=base),
+ self.assertRaisesRegex(
+ ValueError,
+ '_align_ must be a non-negative integer',
+ )
+ ):
+ class MyStructure(base):
+ _align_ = -1
+ _fields_ = []
+
+ def test_zero_align_no_fields(self):
+ for base in (Structure, LittleEndianStructure, BigEndianStructure):
+ with self.subTest(base=base):
+ class MyStructure(base):
+ _align_ = 0
+ _fields_ = []
+
+ self.assertEqual(alignment(MyStructure), 1)
+ self.assertEqual(alignment(MyStructure()), 1)
+
+ def test_zero_align_with_fields(self):
+ for base in (Structure, LittleEndianStructure, BigEndianStructure):
+ with self.subTest(base=base):
+ class MyStructure(base):
+ _align_ = 0
+ _fields_ = [
+ ("x", c_ubyte),
+ ]
+
+ self.assertEqual(alignment(MyStructure), 1)
+ self.assertEqual(alignment(MyStructure()), 1)
+
def test_oversized_structure(self):
data = bytearray(b"\0" * 8)
for base in (LittleEndianStructure, BigEndianStructure):
diff --git
a/Misc/NEWS.d/next/Library/2025-04-18-14-34-43.gh-issue-132673.0sliCv.rst
b/Misc/NEWS.d/next/Library/2025-04-18-14-34-43.gh-issue-132673.0sliCv.rst
new file mode 100644
index 00000000000000..4d5a26caf0ea90
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-04-18-14-34-43.gh-issue-132673.0sliCv.rst
@@ -0,0 +1,2 @@
+Fix :exc:`AssertionError` raised on :class:`ctypes.Structure` with
+``_align_ = 0`` and ``_fields_ = []``.
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