From 29dc991bc6c2482212b00ec3f2b660e60ce262ec Mon Sep 17 00:00:00 2001 From: Yongtao Huang Date: Fri, 26 Dec 2025 01:08:43 +0800 Subject: [PATCH] gh-143164: Fix incorrect error message for ctypes bitfield overflow (GH-143165) (cherry picked from commit b9a48064306229287d7211e9510f578065e457fc) Co-authored-by: Yongtao Huang Signed-off-by: Yongtao Huang --- Lib/test/test_ctypes/test_struct_fields.py | 15 +++++++++++++++ ...2025-12-25-08-58-55.gh-issue-142164.XrFztf.rst | 1 + Modules/_ctypes/cfield.c | 4 ++-- 3 files changed, 18 insertions(+), 2 deletions(-) create mode 100644 Misc/NEWS.d/next/Library/2025-12-25-08-58-55.gh-issue-142164.XrFztf.rst diff --git a/Lib/test/test_ctypes/test_struct_fields.py b/Lib/test/test_ctypes/test_struct_fields.py index b50bbcbb65c423..dc26e26d8a9fb1 100644 --- a/Lib/test/test_ctypes/test_struct_fields.py +++ b/Lib/test/test_ctypes/test_struct_fields.py @@ -130,6 +130,21 @@ class S(Structure): self.check_struct(S) self.assertEqual(S.largeField.bit_size, size * 8) + def test_bitfield_overflow_error_message(self): + with self.assertRaisesRegex( + ValueError, + r"bit field 'x' overflows its type \(2 \+ 7 > 8\)", + ): + CField( + name="x", + type=c_byte, + byte_size=1, + byte_offset=0, + index=0, + _internal_use=True, + bit_size=7, + bit_offset=2, + ) # __set__ and __get__ should raise a TypeError in case their self # argument is not a ctype instance. diff --git a/Misc/NEWS.d/next/Library/2025-12-25-08-58-55.gh-issue-142164.XrFztf.rst b/Misc/NEWS.d/next/Library/2025-12-25-08-58-55.gh-issue-142164.XrFztf.rst new file mode 100644 index 00000000000000..e75270b9e94c03 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2025-12-25-08-58-55.gh-issue-142164.XrFztf.rst @@ -0,0 +1 @@ +Fix the ctypes bitfield overflow error message to report the correct offset and size calculation. diff --git a/Modules/_ctypes/cfield.c b/Modules/_ctypes/cfield.c index 662b57a5b825e2..e0d172fa435416 100644 --- a/Modules/_ctypes/cfield.c +++ b/Modules/_ctypes/cfield.c @@ -160,8 +160,8 @@ PyCField_new_impl(PyTypeObject *type, PyObject *name, PyObject *proto, if ((bitfield_size + bit_offset) > byte_size * 8) { PyErr_Format( PyExc_ValueError, - "bit field %R overflows its type (%zd + %zd >= %zd)", - name, bit_offset, byte_size*8); + "bit field %R overflows its type (%zd + %zd > %zd)", + name, bit_offset, bitfield_size, byte_size * 8); goto error; } }