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gh-97588: Align ctypes struct layout to GCC/MSVC (GH-97702)

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Structure layout, and especially bitfields, sometimes resulted in clearly
wrong behaviour like overlapping fields. This fixes

Co-authored-by: Gregory P. Smith <gps@python.org>
Co-authored-by: Petr Viktorin <encukou@gmail.com>
This commit is contained in:
Matthias Görgens 2024-05-29 18:02:53 +08:00 committed by GitHub
parent c1e9647107
commit 18c1a8d3a8
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GPG Key ID: B5690EEEBB952194
17 changed files with 3282 additions and 184 deletions
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43
Doc/library/ctypes.rst
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@ -661,14 +661,18 @@ for debugging because they can provide useful information::
guaranteed by the library to work in the general case. Unions and
structures with bit-fields should always be passed to functions by pointer.
Structure/union alignment and byte order
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Structure/union layout, alignment and byte order
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
By default, Structure and Union fields are laid out in the same way the C
compiler does it. It is possible to override this behavior entirely by specifying a
:attr:`~Structure._layout_` class attribute in the subclass definition; see
the attribute documentation for details.
It is possible to specify the maximum alignment for the fields by setting
the :attr:`~Structure._pack_` class attribute to a positive integer.
This matches what ``#pragma pack(n)`` does in MSVC.
By default, Structure and Union fields are aligned in the same way the C
compiler does it. It is possible to override this behavior by specifying a
:attr:`~Structure._pack_` class attribute in the subclass definition.
This must be set to a positive integer and specifies the maximum alignment for the fields.
This is what ``#pragma pack(n)`` also does in MSVC.
It is also possible to set a minimum alignment for how the subclass itself is packed in the
same way ``#pragma align(n)`` works in MSVC.
This can be achieved by specifying a ::attr:`~Structure._align_` class attribute
@ -2540,6 +2544,31 @@ fields, or any other data types containing pointer type fields.
the structure when being packed or unpacked to/from memory.
Setting this attribute to 0 is the same as not setting it at all.
.. attribute:: _layout_
An optional string naming the struct/union layout. It can currently
be set to:
- ``"ms"``: the layout used by the Microsoft compiler (MSVC).
On GCC and Clang, this layout can be selected with
``__attribute__((ms_struct))``.
- ``"gcc-sysv"``: the layout used by GCC with the System V or “SysV-like”
data model, as used on Linux and macOS.
With this layout, :attr:`~Structure._pack_` must be unset or zero.
If not set explicitly, ``ctypes`` will use a default that
matches the platform conventions. This default may change in future
Python releases (for example, when a new platform gains official support,
or when a difference between similar platforms is found).
Currently the default will be:
- On Windows: ``"ms"``
- When :attr:`~Structure._pack_` is specified: ``"ms"``
- Otherwise: ``"gcc-sysv"``
:attr:`!_layout_` must already be defined when
:attr:`~Structure._fields_` is assigned, otherwise it will have no effect.
.. attribute:: _anonymous_
An optional sequence that lists the names of unnamed (anonymous) fields.

12
Doc/whatsnew/3.13.rst
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@ -656,6 +656,18 @@ copy
any user classes which define the :meth:`!__replace__` method.
(Contributed by Serhiy Storchaka in :gh:`108751`.)
ctypes
------
* The layout of :ref:`bit fields <ctypes-bit-fields-in-structures-unions>` in
:class:`~ctypes.Structure` and :class:`~ctypes.Union` was improved to better
match platform defaults (GCC/Clang or MSC). In particular, fields no longer
overlap.
(Contributed by Matthias Görgens in :gh:`97702`.)
* A :attr:`ctypes.Structure._layout_` class attribute can be set
to help match a non-default ABI.
(Contributed by Petr Viktorin in :gh:`97702`.)
dbm
---

1
Include/internal/pycore_global_objects_fini_generated.h generated
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@ -767,6 +767,7 @@ _PyStaticObjects_CheckRefcnt(PyInterpreterState *interp) {
_PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(_initializing));
_PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(_io));
_PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(_is_text_encoding));
_PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(_layout_));
_PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(_length_));
_PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(_limbo));
_PyStaticObject_CheckRefcnt((PyObject *)&_Py_ID(_lock_unlock_module));

1
Include/internal/pycore_global_strings.h
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@ -256,6 +256,7 @@ struct _Py_global_strings {
STRUCT_FOR_ID(_initializing)
STRUCT_FOR_ID(_io)
STRUCT_FOR_ID(_is_text_encoding)
STRUCT_FOR_ID(_layout_)
STRUCT_FOR_ID(_length_)
STRUCT_FOR_ID(_limbo)
STRUCT_FOR_ID(_lock_unlock_module)

1
Include/internal/pycore_runtime_init_generated.h generated
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@ -765,6 +765,7 @@ extern "C" {
INIT_ID(_initializing), \
INIT_ID(_io), \
INIT_ID(_is_text_encoding), \
INIT_ID(_layout_), \
INIT_ID(_length_), \
INIT_ID(_limbo), \
INIT_ID(_lock_unlock_module), \

3
Include/internal/pycore_unicodeobject_generated.h generated
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@ -609,6 +609,9 @@ _PyUnicode_InitStaticStrings(PyInterpreterState *interp) {
string = &_Py_ID(_is_text_encoding);
assert(_PyUnicode_CheckConsistency(string, 1));
_PyUnicode_InternInPlace(interp, &string);
string = &_Py_ID(_layout_);
assert(_PyUnicode_CheckConsistency(string, 1));
_PyUnicode_InternInPlace(interp, &string);
string = &_Py_ID(_length_);
assert(_PyUnicode_CheckConsistency(string, 1));
_PyUnicode_InternInPlace(interp, &string);

317
Lib/test/test_ctypes/test_bitfields.py
View File

@ -1,9 +1,10 @@
import os
import sys
import unittest
from ctypes import (CDLL, Structure, sizeof, POINTER, byref, alignment,
LittleEndianStructure, BigEndianStructure,
c_byte, c_ubyte, c_char, c_char_p, c_void_p, c_wchar,
c_uint32, c_uint64,
c_uint8, c_uint16, c_uint32, c_uint64,
c_short, c_ushort, c_int, c_uint, c_long, c_ulong, c_longlong, c_ulonglong)
from test import support
from test.support import import_helper
@ -33,27 +34,88 @@ func = CDLL(_ctypes_test.__file__).unpack_bitfields
func.argtypes = POINTER(BITS), c_char
class BITS_msvc(Structure):
_layout_ = "ms"
_fields_ = [("A", c_int, 1),
("B", c_int, 2),
("C", c_int, 3),
("D", c_int, 4),
("E", c_int, 5),
("F", c_int, 6),
("G", c_int, 7),
("H", c_int, 8),
("I", c_int, 9),
("M", c_short, 1),
("N", c_short, 2),
("O", c_short, 3),
("P", c_short, 4),
("Q", c_short, 5),
("R", c_short, 6),
("S", c_short, 7)]
try:
func_msvc = CDLL(_ctypes_test.__file__).unpack_bitfields_msvc
except AttributeError as err:
# The MSVC struct must be available on Windows; it's optional elsewhere
if support.MS_WINDOWS:
raise err
func_msvc = None
else:
func_msvc.argtypes = POINTER(BITS_msvc), c_char
class C_Test(unittest.TestCase):
def test_ints(self):
for i in range(512):
for name in "ABCDEFGHI":
b = BITS()
setattr(b, name, i)
self.assertEqual(getattr(b, name), func(byref(b), name.encode('ascii')))
with self.subTest(i=i, name=name):
b = BITS()
setattr(b, name, i)
self.assertEqual(
getattr(b, name),
func(byref(b), (name.encode('ascii'))))
# bpo-46913: _ctypes/cfield.c h_get() has an undefined behavior
@support.skip_if_sanitizer(ub=True)
def test_shorts(self):
b = BITS()
name = "M"
# See Modules/_ctypes/_ctypes_test.c for where the magic 999 comes from.
if func(byref(b), name.encode('ascii')) == 999:
# unpack_bitfields and unpack_bitfields_msvc in
# Modules/_ctypes/_ctypes_test.c return 999 to indicate
# an invalid name. 'M' is only valid, if signed short bitfields
# are supported by the C compiler.
self.skipTest("Compiler does not support signed short bitfields")
for i in range(256):
for name in "MNOPQRS":
b = BITS()
setattr(b, name, i)
self.assertEqual(getattr(b, name), func(byref(b), name.encode('ascii')))
with self.subTest(i=i, name=name):
b = BITS()
setattr(b, name, i)
self.assertEqual(
getattr(b, name),
func(byref(b), (name.encode('ascii'))))
@unittest.skipUnless(func_msvc, "need MSVC or __attribute__((ms_struct))")
def test_shorts_msvc_mode(self):
b = BITS_msvc()
name = "M"
# See Modules/_ctypes/_ctypes_test.c for where the magic 999 comes from.
if func_msvc(byref(b), name.encode('ascii')) == 999:
# unpack_bitfields and unpack_bitfields_msvc in
# Modules/_ctypes/_ctypes_test.c return 999 to indicate
# an invalid name. 'M' is only valid, if signed short bitfields
# are supported by the C compiler.
self.skipTest("Compiler does not support signed short bitfields")
for i in range(256):
for name in "MNOPQRS":
with self.subTest(i=i, name=name):
b = BITS_msvc()
setattr(b, name, i)
self.assertEqual(
getattr(b, name),
func_msvc(byref(b), name.encode('ascii')))
signed_int_types = (c_byte, c_short, c_int, c_long, c_longlong)
@ -87,35 +149,41 @@ class BitFieldTest(unittest.TestCase):
def test_signed(self):
for c_typ in signed_int_types:
class X(Structure):
_fields_ = [("dummy", c_typ),
("a", c_typ, 3),
("b", c_typ, 3),
("c", c_typ, 1)]
self.assertEqual(sizeof(X), sizeof(c_typ)*2)
with self.subTest(c_typ):
if sizeof(c_typ) != alignment(c_typ):
self.skipTest('assumes size=alignment')
class X(Structure):
_fields_ = [("dummy", c_typ),
("a", c_typ, 3),
("b", c_typ, 3),
("c", c_typ, 1)]
self.assertEqual(sizeof(X), sizeof(c_typ)*2)
x = X()
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, 0, 0, 0))
x.a = -1
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, -1, 0, 0))
x.a, x.b = 0, -1
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, 0, -1, 0))
x = X()
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, 0, 0, 0))
x.a = -1
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, -1, 0, 0))
x.a, x.b = 0, -1
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, 0, -1, 0))
def test_unsigned(self):
for c_typ in unsigned_int_types:
class X(Structure):
_fields_ = [("a", c_typ, 3),
("b", c_typ, 3),
("c", c_typ, 1)]
self.assertEqual(sizeof(X), sizeof(c_typ))
with self.subTest(c_typ):
if sizeof(c_typ) != alignment(c_typ):
self.skipTest('assumes size=alignment')
class X(Structure):
_fields_ = [("a", c_typ, 3),
("b", c_typ, 3),
("c", c_typ, 1)]
self.assertEqual(sizeof(X), sizeof(c_typ))
x = X()
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, 0, 0, 0))
x.a = -1
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, 7, 0, 0))
x.a, x.b = 0, -1
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, 0, 7, 0))
x = X()
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, 0, 0, 0))
x.a = -1
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, 7, 0, 0))
x.a, x.b = 0, -1
self.assertEqual((c_typ, x.a, x.b, x.c), (c_typ, 0, 7, 0))
def fail_fields(self, *fields):
return self.get_except(type(Structure), "X", (),
@ -149,22 +217,28 @@ class BitFieldTest(unittest.TestCase):
def test_single_bitfield_size(self):
for c_typ in int_types:
result = self.fail_fields(("a", c_typ, -1))
self.assertEqual(result, (ValueError, 'number of bits invalid for bit field'))
with self.subTest(c_typ):
if sizeof(c_typ) != alignment(c_typ):
self.skipTest('assumes size=alignment')
result = self.fail_fields(("a", c_typ, -1))
self.assertEqual(result, (ValueError,
"number of bits invalid for bit field 'a'"))
result = self.fail_fields(("a", c_typ, 0))
self.assertEqual(result, (ValueError, 'number of bits invalid for bit field'))
result = self.fail_fields(("a", c_typ, 0))
self.assertEqual(result, (ValueError,
"number of bits invalid for bit field 'a'"))
class X(Structure):
_fields_ = [("a", c_typ, 1)]
self.assertEqual(sizeof(X), sizeof(c_typ))
class X(Structure):
_fields_ = [("a", c_typ, 1)]
self.assertEqual(sizeof(X), sizeof(c_typ))
class X(Structure):
_fields_ = [("a", c_typ, sizeof(c_typ)*8)]
self.assertEqual(sizeof(X), sizeof(c_typ))
class X(Structure):
_fields_ = [("a", c_typ, sizeof(c_typ)*8)]
self.assertEqual(sizeof(X), sizeof(c_typ))
result = self.fail_fields(("a", c_typ, sizeof(c_typ)*8 + 1))
self.assertEqual(result, (ValueError, 'number of bits invalid for bit field'))
result = self.fail_fields(("a", c_typ, sizeof(c_typ)*8 + 1))
self.assertEqual(result, (ValueError,
"number of bits invalid for bit field 'a'"))
def test_multi_bitfields_size(self):
class X(Structure):
@ -236,6 +310,161 @@ class BitFieldTest(unittest.TestCase):
else:
self.assertEqual(sizeof(X), sizeof(c_int) * 2)
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)
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(sizeof(c_uint64) != alignment(c_uint64),
'assumes size=alignment')
def test_mixed_7(self):
class X(Structure):
_fields_ = [
("A", c_uint32),
('B', c_uint32, 20),
('C', c_uint64, 24)]
self.assertEqual(16, sizeof(X))
def test_mixed_8(self):
class Foo(Structure):
_fields_ = [
("A", c_uint32),
("B", c_uint32, 32),
("C", c_ulonglong, 1),
]
class Bar(Structure):
_fields_ = [
("A", c_uint32),
("B", c_uint32),
("C", c_ulonglong, 1),
]
self.assertEqual(sizeof(Foo), sizeof(Bar))
def test_mixed_9(self):
class X(Structure):
_fields_ = [
("A", c_uint8),
("B", c_uint32, 1),
]
if sys.platform == 'win32':
self.assertEqual(8, sizeof(X))
else:
self.assertEqual(4, sizeof(X))
@unittest.skipIf(sizeof(c_uint64) != alignment(c_uint64),
'assumes size=alignment')
def test_mixed_10(self):
class X(Structure):
_fields_ = [
("A", c_uint32, 1),
("B", c_uint64, 1),
]
if sys.platform == 'win32':
self.assertEqual(8, alignment(X))
self.assertEqual(16, sizeof(X))
else:
self.assertEqual(8, alignment(X))
self.assertEqual(8, sizeof(X))
def test_gh_95496(self):
for field_width in range(1, 33):
class TestStruct(Structure):
_fields_ = [
("Field1", c_uint32, field_width),
("Field2", c_uint8, 8)
]
cmd = TestStruct()
cmd.Field2 = 1
self.assertEqual(1, cmd.Field2)
def test_gh_84039(self):
class Bad(Structure):
_pack_ = 1
_fields_ = [
("a0", c_uint8, 1),
("a1", c_uint8, 1),
("a2", c_uint8, 1),
("a3", c_uint8, 1),
("a4", c_uint8, 1),
("a5", c_uint8, 1),
("a6", c_uint8, 1),
("a7", c_uint8, 1),
("b0", c_uint16, 4),
("b1", c_uint16, 12),
]
class GoodA(Structure):
_pack_ = 1
_fields_ = [
("a0", c_uint8, 1),
("a1", c_uint8, 1),
("a2", c_uint8, 1),
("a3", c_uint8, 1),
("a4", c_uint8, 1),
("a5", c_uint8, 1),
("a6", c_uint8, 1),
("a7", c_uint8, 1),
]
class Good(Structure):
_pack_ = 1
_fields_ = [
("a", GoodA),
("b0", c_uint16, 4),
("b1", c_uint16, 12),
]
self.assertEqual(3, sizeof(Bad))
self.assertEqual(3, sizeof(Good))
def test_gh_73939(self):
class MyStructure(Structure):
_pack_ = 1
_fields_ = [
("P", c_uint16),
("L", c_uint16, 9),
("Pro", c_uint16, 1),
("G", c_uint16, 1),
("IB", c_uint16, 1),
("IR", c_uint16, 1),
("R", c_uint16, 3),
("T", c_uint32, 10),
("C", c_uint32, 20),
("R2", c_uint32, 2)
]
self.assertEqual(8, sizeof(MyStructure))
def test_gh_86098(self):
class X(Structure):
_fields_ = [
("a", c_uint8, 8),
("b", c_uint8, 8),
("c", c_uint32, 16)
]
if sys.platform == 'win32':
self.assertEqual(8, sizeof(X))
else:
self.assertEqual(4, sizeof(X))
def test_anon_bitfields(self):
# anonymous bit-fields gave a strange error message
class X(Structure):

718
Lib/test/test_ctypes/test_generated_structs.py Normal file
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@ -0,0 +1,718 @@
"""Test CTypes structs, unions, bitfields against C equivalents.
The types here are auto-converted to C source at
`Modules/_ctypes/_ctypes_test_generated.c.h`, which is compiled into
_ctypes_test.
Run this module to regenerate the files:
./python Lib/test/test_ctypes/test_generated_structs.py > Modules/_ctypes/_ctypes_test_generated.c.h
"""
import unittest
from test.support import import_helper
import re
from dataclasses import dataclass
from functools import cached_property
import sys
import ctypes
from ctypes import Structure, Union, _SimpleCData
from ctypes import sizeof, alignment, pointer, string_at
_ctypes_test = import_helper.import_module("_ctypes_test")
# ctypes erases the difference between `c_int` and e.g.`c_int16`.
# To keep it, we'll use custom subclasses with the C name stashed in `_c_name`:
class c_bool(ctypes.c_bool):
_c_name = '_Bool'
# To do it for all the other types, use some metaprogramming:
for c_name, ctypes_name in {
'signed char': 'c_byte',
'short': 'c_short',
'int': 'c_int',
'long': 'c_long',
'long long': 'c_longlong',
'unsigned char': 'c_ubyte',
'unsigned short': 'c_ushort',
'unsigned int': 'c_uint',
'unsigned long': 'c_ulong',
'unsigned long long': 'c_ulonglong',
**{f'{u}int{n}_t': f'c_{u}int{n}'
for u in ('', 'u')
for n in (8, 16, 32, 64)}
}.items():
ctype = getattr(ctypes, ctypes_name)
newtype = type(ctypes_name, (ctype,), {'_c_name': c_name})
globals()[ctypes_name] = newtype
# Register structs and unions to test
TESTCASES = {}
def register(name=None, set_name=False):
def decorator(cls, name=name):
if name is None:
name = cls.__name__
assert name.isascii() # will be used in _PyUnicode_EqualToASCIIString
assert name.isidentifier() # will be used as a C identifier
assert name not in TESTCASES
TESTCASES[name] = cls
if set_name:
cls.__name__ = name
return cls
return decorator
@register()
class SingleInt(Structure):
_fields_ = [('a', c_int)]
@register()
class SingleInt_Union(Union):
_fields_ = [('a', c_int)]
@register()
class SingleU32(Structure):
_fields_ = [('a', c_uint32)]
@register()
class SimpleStruct(Structure):
_fields_ = [('x', c_int32), ('y', c_int8), ('z', c_uint16)]
@register()
class SimpleUnion(Union):
_fields_ = [('x', c_int32), ('y', c_int8), ('z', c_uint16)]
@register()
class ManyTypes(Structure):
_fields_ = [
('i8', c_int8), ('u8', c_uint8),
('i16', c_int16), ('u16', c_uint16),
('i32', c_int32), ('u32', c_uint32),
('i64', c_int64), ('u64', c_uint64),
]
@register()
class ManyTypesU(Union):
_fields_ = [
('i8', c_int8), ('u8', c_uint8),
('i16', c_int16), ('u16', c_uint16),
('i32', c_int32), ('u32', c_uint32),
('i64', c_int64), ('u64', c_uint64),
]
@register()
class Nested(Structure):
_fields_ = [
('a', SimpleStruct), ('b', SimpleUnion), ('anon', SimpleStruct),
]
_anonymous_ = ['anon']
@register()
class Packed1(Structure):
_fields_ = [('a', c_int8), ('b', c_int64)]
_pack_ = 1
@register()
class Packed2(Structure):
_fields_ = [('a', c_int8), ('b', c_int64)]
_pack_ = 2
@register()
class Packed3(Structure):
_fields_ = [('a', c_int8), ('b', c_int64)]
_pack_ = 4
@register()
class Packed4(Structure):
_fields_ = [('a', c_int8), ('b', c_int64)]
_pack_ = 8
@register()
class X86_32EdgeCase(Structure):
# On a Pentium, long long (int64) is 32-bit aligned,
# so these are packed tightly.
_fields_ = [('a', c_int32), ('b', c_int64), ('c', c_int32)]
@register()
class MSBitFieldExample(Structure):
# From https://learn.microsoft.com/en-us/cpp/c-language/c-bit-fields
_fields_ = [
('a', c_uint, 4),
('b', c_uint, 5),
('c', c_uint, 7)]
@register()
class MSStraddlingExample(Structure):
# From https://learn.microsoft.com/en-us/cpp/c-language/c-bit-fields
_fields_ = [
('first', c_uint, 9),
('second', c_uint, 7),
('may_straddle', c_uint, 30),
('last', c_uint, 18)]
@register()
class IntBits(Structure):
_fields_ = [("A", c_int, 1),
("B", c_int, 2),
("C", c_int, 3),
("D", c_int, 4),
("E", c_int, 5),
("F", c_int, 6),
("G", c_int, 7),
("H", c_int, 8),
("I", c_int, 9)]
@register()
class Bits(Structure):
_fields_ = [*IntBits._fields_,
("M", c_short, 1),
("N", c_short, 2),
("O", c_short, 3),
("P", c_short, 4),
("Q", c_short, 5),
("R", c_short, 6),
("S", c_short, 7)]
@register()
class IntBits_MSVC(Structure):
_layout_ = "ms"
_fields_ = [("A", c_int, 1),
("B", c_int, 2),
("C", c_int, 3),
("D", c_int, 4),
("E", c_int, 5),
("F", c_int, 6),
("G", c_int, 7),
("H", c_int, 8),
("I", c_int, 9)]
@register()
class Bits_MSVC(Structure):
_layout_ = "ms"
_fields_ = [*IntBits_MSVC._fields_,
("M", c_short, 1),
("N", c_short, 2),
("O", c_short, 3),
("P", c_short, 4),
("Q", c_short, 5),
("R", c_short, 6),
("S", c_short, 7)]
# Skipped for now -- we don't always match the alignment
#@register()
class IntBits_Union(Union):
_fields_ = [("A", c_int, 1),
("B", c_int, 2),
("C", c_int, 3),
("D", c_int, 4),
("E", c_int, 5),
("F", c_int, 6),
("G", c_int, 7),
("H", c_int, 8),
("I", c_int, 9)]
# Skipped for now -- we don't always match the alignment
#@register()
class BitsUnion(Union):
_fields_ = [*IntBits_Union._fields_,
("M", c_short, 1),
("N", c_short, 2),
("O", c_short, 3),
("P", c_short, 4),
("Q", c_short, 5),
("R", c_short, 6),
("S", c_short, 7)]
@register()
class I64Bits(Structure):
_fields_ = [("a", c_int64, 1),
("b", c_int64, 62),
("c", c_int64, 1)]
@register()
class U64Bits(Structure):
_fields_ = [("a", c_uint64, 1),
("b", c_uint64, 62),
("c", c_uint64, 1)]
for n in 8, 16, 32, 64:
for signedness in '', 'u':
ctype = globals()[f'c_{signedness}int{n}']
@register(f'Struct331_{signedness}{n}', set_name=True)
class _cls(Structure):
_fields_ = [("a", ctype, 3),
("b", ctype, 3),
("c", ctype, 1)]
@register(f'Struct1x1_{signedness}{n}', set_name=True)
class _cls(Structure):
_fields_ = [("a", ctype, 1),
("b", ctype, n-2),
("c", ctype, 1)]
@register(f'Struct1nx1_{signedness}{n}', set_name=True)
class _cls(Structure):
_fields_ = [("a", ctype, 1),
("full", ctype),
("b", ctype, n-2),
("c", ctype, 1)]
@register(f'Struct3xx_{signedness}{n}', set_name=True)
class _cls(Structure):
_fields_ = [("a", ctype, 3),
("b", ctype, n-2),
("c", ctype, n-2)]
@register()
class Mixed1(Structure):
_fields_ = [("a", c_byte, 4),
("b", c_int, 4)]
@register()
class Mixed2(Structure):
_fields_ = [("a", c_byte, 4),
("b", c_int32, 32)]
@register()
class Mixed3(Structure):
_fields_ = [("a", c_byte, 4),
("b", c_ubyte, 4)]
@register()
class Mixed4(Structure):
_fields_ = [("a", c_short, 4),
("b", c_short, 4),
("c", c_int, 24),
("d", c_short, 4),
("e", c_short, 4),
("f", c_int, 24)]
@register()
class Mixed5(Structure):
_fields_ = [('A', c_uint, 1),
('B', c_ushort, 16)]
@register()
class Mixed6(Structure):
_fields_ = [('A', c_ulonglong, 1),
('B', c_uint, 32)]
@register()
class Mixed7(Structure):
_fields_ = [("A", c_uint32),
('B', c_uint32, 20),
('C', c_uint64, 24)]
@register()
class Mixed8_a(Structure):
_fields_ = [("A", c_uint32),
("B", c_uint32, 32),
("C", c_ulonglong, 1)]
@register()
class Mixed8_b(Structure):
_fields_ = [("A", c_uint32),
("B", c_uint32),
("C", c_ulonglong, 1)]
@register()
class Mixed9(Structure):
_fields_ = [("A", c_uint8),
("B", c_uint32, 1)]
@register()
class Mixed10(Structure):
_fields_ = [("A", c_uint32, 1),
("B", c_uint64, 1)]
@register()
class Example_gh_95496(Structure):
_fields_ = [("A", c_uint32, 1),
("B", c_uint64, 1)]
@register()
class Example_gh_84039_bad(Structure):
_pack_ = 1
_fields_ = [("a0", c_uint8, 1),
("a1", c_uint8, 1),
("a2", c_uint8, 1),
("a3", c_uint8, 1),
("a4", c_uint8, 1),
("a5", c_uint8, 1),
("a6", c_uint8, 1),
("a7", c_uint8, 1),
("b0", c_uint16, 4),
("b1", c_uint16, 12)]
@register()
class Example_gh_84039_good_a(Structure):
_pack_ = 1
_fields_ = [("a0", c_uint8, 1),
("a1", c_uint8, 1),
("a2", c_uint8, 1),
("a3", c_uint8, 1),
("a4", c_uint8, 1),
("a5", c_uint8, 1),
("a6", c_uint8, 1),
("a7", c_uint8, 1)]
@register()
class Example_gh_84039_good(Structure):
_pack_ = 1
_fields_ = [("a", Example_gh_84039_good_a),
("b0", c_uint16, 4),
("b1", c_uint16, 12)]
@register()
class Example_gh_73939(Structure):
_pack_ = 1
_fields_ = [("P", c_uint16),
("L", c_uint16, 9),
("Pro", c_uint16, 1),
("G", c_uint16, 1),
("IB", c_uint16, 1),
("IR", c_uint16, 1),
("R", c_uint16, 3),
("T", c_uint32, 10),
("C", c_uint32, 20),
("R2", c_uint32, 2)]
@register()
class Example_gh_86098(Structure):
_fields_ = [("a", c_uint8, 8),
("b", c_uint8, 8),
("c", c_uint32, 16)]
@register()
class Example_gh_86098_pack(Structure):
_pack_ = 1
_fields_ = [("a", c_uint8, 8),
("b", c_uint8, 8),
("c", c_uint32, 16)]
@register()
class AnonBitfields(Structure):
class X(Structure):
_fields_ = [("a", c_byte, 4),
("b", c_ubyte, 4)]
_anonymous_ = ["_"]
_fields_ = [("_", X), ('y', c_byte)]
class GeneratedTest(unittest.TestCase):
def test_generated_data(self):
"""Check that a ctypes struct/union matches its C equivalent.
This compares with data from get_generated_test_data(), a list of:
- name (str)
- size (int)
- alignment (int)
- for each field, three snapshots of memory, as bytes:
- memory after the field is set to -1
- memory after the field is set to 1
- memory after the field is set to 0
or:
- None
- reason to skip the test (str)
This does depend on the C compiler keeping padding bits zero.
Common compilers seem to do so.
"""
for name, cls in TESTCASES.items():
with self.subTest(name=name):
expected = iter(_ctypes_test.get_generated_test_data(name))
expected_name = next(expected)
if expected_name is None:
self.skipTest(next(expected))
self.assertEqual(name, expected_name)
self.assertEqual(sizeof(cls), next(expected))
with self.subTest('alignment'):
self.assertEqual(alignment(cls), next(expected))
obj = cls()
ptr = pointer(obj)
for field in iterfields(cls):
for value in -1, 1, 0:
with self.subTest(field=field.full_name, value=value):
field.set_to(obj, value)
py_mem = string_at(ptr, sizeof(obj))
c_mem = next(expected)
if py_mem != c_mem:
# Generate a helpful failure message
lines, requires = dump_ctype(cls)
m = "\n".join([str(field), 'in:', *lines])
self.assertEqual(py_mem.hex(), c_mem.hex(), m)
# The rest of this file is generating C code from a ctypes type.
# This is only meant for (and tested with) the known inputs in this file!
def c_str_repr(string):
"""Return a string as a C literal"""
return '"' + re.sub('([\"\'\\\\\n])', r'\\\1', string) + '"'
def dump_simple_ctype(tp, variable_name='', semi=''):
"""Get C type name or declaration of a scalar type
variable_name: if given, declare the given variable
semi: a semicolon, and/or bitfield specification to tack on to the end
"""
length = getattr(tp, '_length_', None)
if length is not None:
return f'{dump_simple_ctype(tp._type_, variable_name)}[{length}]{semi}'
assert not issubclass(tp, (Structure, Union))
return f'{tp._c_name}{maybe_space(variable_name)}{semi}'
def dump_ctype(tp, struct_or_union_tag='', variable_name='', semi=''):
"""Get C type name or declaration of a ctype
struct_or_union_tag: name of the struct or union
variable_name: if given, declare the given variable
semi: a semicolon, and/or bitfield specification to tack on to the end
"""
requires = set()
if issubclass(tp, (Structure, Union)):
attributes = []
pushes = []
pops = []
pack = getattr(tp, '_pack_', None)
if pack is not None:
pushes.append(f'#pragma pack(push, {pack})')
pops.append(f'#pragma pack(pop)')
layout = getattr(tp, '_layout_', None)
if layout == 'ms' or pack:
# The 'ms_struct' attribute only works on x86 and PowerPC
requires.add(
'defined(MS_WIN32) || ('
'(defined(__x86_64__) || defined(__i386__) || defined(__ppc64__)) && ('
'defined(__GNUC__) || defined(__clang__)))'
)
attributes.append('ms_struct')
if attributes:
a = f' GCC_ATTR({", ".join(attributes)})'
else:
a = ''
lines = [f'{struct_or_union(tp)}{a}{maybe_space(struct_or_union_tag)} ' +'{']
for fielddesc in tp._fields_:
f_name, f_tp, f_bits = unpack_field_desc(*fielddesc)
if f_name in getattr(tp, '_anonymous_', ()):
f_name = ''
if f_bits is None:
subsemi = ';'
else:
if f_tp not in (c_int, c_uint):
# XLC can reportedly only handle int & unsigned int
# bitfields (the only types required by C spec)
requires.add('!defined(__xlc__)')
subsemi = f' :{f_bits};'
sub_lines, sub_requires = dump_ctype(
f_tp, variable_name=f_name, semi=subsemi)
requires.update(sub_requires)
for line in sub_lines:
lines.append(' ' + line)
lines.append(f'}}{maybe_space(variable_name)}{semi}')
return [*pushes, *lines, *reversed(pops)], requires
else:
return [dump_simple_ctype(tp, variable_name, semi)], requires
def struct_or_union(cls):
if issubclass(cls, Structure):
return 'struct'
if issubclass(cls, Union):
return 'union'
raise TypeError(cls)
def maybe_space(string):
if string:
return ' ' + string
return string
def unpack_field_desc(f_name, f_tp, f_bits=None):
"""Unpack a _fields_ entry into a (name, type, bits) triple"""
return f_name, f_tp, f_bits
@dataclass
class FieldInfo:
"""Information about a (possibly nested) struct/union field"""
name: str
tp: type
bits: int | None # number if this is a bit field
parent_type: type
parent: 'FieldInfo' #| None
@cached_property
def attr_path(self):
"""Attribute names to get at the value of this field"""
if self.name in getattr(self.parent_type, '_anonymous_', ()):
selfpath = ()
else:
selfpath = (self.name,)
if self.parent:
return (*self.parent.attr_path, *selfpath)
else:
return selfpath
@cached_property
def full_name(self):
"""Attribute names to get at the value of this field"""
return '.'.join(self.attr_path)
def set_to(self, obj, new):
"""Set the field on a given Structure/Union instance"""
for attr_name in self.attr_path[:-1]:
obj = getattr(obj, attr_name)
setattr(obj, self.attr_path[-1], new)
@cached_property
def root(self):
if self.parent is None:
return self
else:
return self.parent
@cached_property
def descriptor(self):
return getattr(self.parent_type, self.name)
def __repr__(self):
qname = f'{self.root.parent_type.__name__}.{self.full_name}'
try:
desc = self.descriptor
except AttributeError:
desc = '???'
return f'<{type(self).__name__} for {qname}: {desc}>'
def iterfields(tp, parent=None):
"""Get *leaf* fields of a structure or union, as FieldInfo"""
try:
fields = tp._fields_
except AttributeError:
yield parent
else:
for fielddesc in fields:
f_name, f_tp, f_bits = unpack_field_desc(*fielddesc)
sub = FieldInfo(f_name, f_tp, f_bits, tp, parent)
yield from iterfields(f_tp, sub)
if __name__ == '__main__':
# Dump C source to stdout
def output(string):
print(re.compile(r'^ +$', re.MULTILINE).sub('', string).lstrip('\n'))
output("""
/* Generated by Lib/test/test_ctypes/test_generated_structs.py */
// Append VALUE to the result.
#define APPEND(ITEM) { \\
PyObject *item = ITEM; \\
if (!item) { \\
Py_DECREF(result); \\
return NULL; \\
} \\
int rv = PyList_Append(result, item); \\
Py_DECREF(item); \\
if (rv < 0) { \\
Py_DECREF(result); \\
return NULL; \\
} \\
}
// Set TARGET, and append a snapshot of `value`'s
// memory to the result.
#define SET_AND_APPEND(TYPE, TARGET, VAL) { \\
TYPE v = VAL; \\
TARGET = v; \\
APPEND(PyBytes_FromStringAndSize( \\
(char*)&value, sizeof(value))); \\
}
// Set a field to -1, 1 and 0; append a snapshot of the memory
// after each of the operations.
#define TEST_FIELD(TYPE, TARGET) { \\
SET_AND_APPEND(TYPE, TARGET, -1) \\
SET_AND_APPEND(TYPE, TARGET, 1) \\
SET_AND_APPEND(TYPE, TARGET, 0) \\
}
#if defined(__GNUC__) || defined(__clang__)
#define GCC_ATTR(X) __attribute__((X))
#else
#define GCC_ATTR(X) /* */
#endif
static PyObject *
get_generated_test_data(PyObject *self, PyObject *name)
{
if (!PyUnicode_Check(name)) {
PyErr_SetString(PyExc_TypeError, "need a string");
return NULL;
}
PyObject *result = PyList_New(0);
if (!result) {
return NULL;
}
""")
for name, cls in TESTCASES.items():
output("""
if (PyUnicode_CompareWithASCIIString(name, %s) == 0) {
""" % c_str_repr(name))
lines, requires = dump_ctype(cls, struct_or_union_tag=name, semi=';')
if requires:
output(f"""
#if {" && ".join(f'({r})' for r in sorted(requires))}
""")
for line in lines:
output(' ' + line)
typename = f'{struct_or_union(cls)} {name}'
output(f"""
{typename} value = {{0}};
APPEND(PyUnicode_FromString({c_str_repr(name)}));
APPEND(PyLong_FromLong(sizeof({typename})));
APPEND(PyLong_FromLong(_Alignof({typename})));
""".rstrip())
for field in iterfields(cls):
f_tp = dump_simple_ctype(field.tp)
output(f"""\
TEST_FIELD({f_tp}, value.{field.full_name});
""".rstrip())
if requires:
output(f"""
#else
APPEND(Py_NewRef(Py_None));
APPEND(PyUnicode_FromString("skipped on this compiler"));
#endif
""")
output("""
return result;
}
""")
output("""
Py_DECREF(result);
PyErr_Format(PyExc_ValueError, "unknown testcase %R", name);
return NULL;
}
#undef GCC_ATTR
#undef TEST_FIELD
#undef SET_AND_APPEND
#undef APPEND
""")

1
Makefile.pre.in
View File

@ -3106,6 +3106,7 @@ MODULE_PYEXPAT_DEPS=@LIBEXPAT_INTERNAL@
MODULE_UNICODEDATA_DEPS=$(srcdir)/Modules/unicodedata_db.h $(srcdir)/Modules/unicodename_db.h
MODULE__BLAKE2_DEPS=$(srcdir)/Modules/_blake2/impl/blake2-config.h $(srcdir)/Modules/_blake2/impl/blake2-impl.h $(srcdir)/Modules/_blake2/impl/blake2.h $(srcdir)/Modules/_blake2/impl/blake2b-load-sse2.h $(srcdir)/Modules/_blake2/impl/blake2b-load-sse41.h $(srcdir)/Modules/_blake2/impl/blake2b-ref.c $(srcdir)/Modules/_blake2/impl/blake2b-round.h $(srcdir)/Modules/_blake2/impl/blake2b.c $(srcdir)/Modules/_blake2/impl/blake2s-load-sse2.h $(srcdir)/Modules/_blake2/impl/blake2s-load-sse41.h $(srcdir)/Modules/_blake2/impl/blake2s-load-xop.h $(srcdir)/Modules/_blake2/impl/blake2s-ref.c $(srcdir)/Modules/_blake2/impl/blake2s-round.h $(srcdir)/Modules/_blake2/impl/blake2s.c $(srcdir)/Modules/_blake2/blake2module.h $(srcdir)/Modules/hashlib.h
MODULE__CTYPES_DEPS=$(srcdir)/Modules/_ctypes/ctypes.h
MODULE__CTYPES_TEST_DEPS=$(srcdir)/Modules/_ctypes/_ctypes_test_generated.c.h
MODULE__CTYPES_MALLOC_CLOSURE=@MODULE__CTYPES_MALLOC_CLOSURE@
MODULE__DECIMAL_DEPS=$(srcdir)/Modules/_decimal/docstrings.h @LIBMPDEC_INTERNAL@
MODULE__ELEMENTTREE_DEPS=$(srcdir)/Modules/pyexpat.c @LIBEXPAT_INTERNAL@

2
Misc/NEWS.d/next/C API/2022-10-01-09-56-27.gh-issue-97588.Gvg54o.rst Normal file
View File

@ -0,0 +1,2 @@
Fix creating bitfields in :mod:`ctypes` structures and unions. Fields
no longer overlap.

75
Modules/_ctypes/_ctypes_test.c
View File

@ -22,6 +22,8 @@
#define EXPORT(x) Py_EXPORTED_SYMBOL x
#include "_ctypes_test_generated.c.h"
/* some functions handy for testing */
EXPORT(int)
@ -343,6 +345,31 @@ _testfunc_bitfield_by_reference2(Test7 *in) {
return result;
}
typedef struct{
uint16_t A ;
uint16_t B : 9;
uint16_t C : 1;
uint16_t D : 1;
uint16_t E : 1;
uint16_t F : 1;
uint16_t G : 3;
uint32_t H : 10;
uint32_t I : 20;
uint32_t J : 2;
} Test9;
EXPORT(long)
_testfunc_bitfield_by_reference3(Test9 *in, long pos) {
long data[] = {in->A , in->B , in->C , in->D , in->E , in->F , in->G , in->H , in->I , in->J};
long data_length = (long) (sizeof(data)/sizeof(data[0]));
if(pos < 0)
return -1;
if(pos >= data_length)
return -1;
return data[pos];
}
typedef union {
signed int A: 1, B:2, C:3, D:2;
} Test8;
@ -704,7 +731,7 @@ struct BITS {
*/
#ifndef __xlc__
#define SIGNED_SHORT_BITFIELDS
short M: 1, N: 2, O: 3, P: 4, Q: 5, R: 6, S: 7;
signed short M: 1, N: 2, O: 3, P: 4, Q: 5, R: 6, S: 7;
#endif
};
@ -734,12 +761,58 @@ EXPORT(int) unpack_bitfields(struct BITS *bits, char name)
return 999;
}
#if (defined(MS_WIN32) || ((defined(__x86_64__) || defined(__i386__) || defined(__ppc64__)) && (defined(__GNUC__) || defined(__clang__))))
struct
#ifndef MS_WIN32
__attribute__ ((ms_struct))
#endif
BITS_msvc
{
signed int A: 1, B:2, C:3, D:4, E: 5, F: 6, G: 7, H: 8, I: 9;
/*
* The test case needs/uses "signed short" bitfields, but the
* IBM XLC compiler does not support this
*/
#ifndef __xlc__
#define SIGNED_SHORT_BITFIELDS
signed short M: 1, N: 2, O: 3, P: 4, Q: 5, R: 6, S: 7;
#endif
};
EXPORT(int) unpack_bitfields_msvc(struct BITS_msvc *bits, char name)
{
switch (name) {
case 'A': return bits->A;
case 'B': return bits->B;
case 'C': return bits->C;
case 'D': return bits->D;
case 'E': return bits->E;
case 'F': return bits->F;
case 'G': return bits->G;
case 'H': return bits->H;
case 'I': return bits->I;
#ifdef SIGNED_SHORT_BITFIELDS
case 'M': return bits->M;
case 'N': return bits->N;
case 'O': return bits->O;
case 'P': return bits->P;
case 'Q': return bits->Q;
case 'R': return bits->R;
case 'S': return bits->S;
#endif
}
return 999;
}
#endif
static PyMethodDef module_methods[] = {
/* {"get_last_tf_arg_s", get_last_tf_arg_s, METH_NOARGS},
{"get_last_tf_arg_u", get_last_tf_arg_u, METH_NOARGS},
*/
{"func_si", py_func_si, METH_VARARGS},
{"func", py_func, METH_NOARGS},
{"get_generated_test_data", get_generated_test_data, METH_O},
{ NULL, NULL, 0, NULL},
};

1885
Modules/_ctypes/_ctypes_test_generated.c.h Normal file
View File

File diff suppressed because it is too large Load Diff

339
Modules/_ctypes/cfield.c
View File

@ -31,40 +31,168 @@ static void pymem_destructor(PyObject *ptr)
PyCField_Type
*/
/*
* Expects the size, index and offset for the current field in *psize and
* *poffset, stores the total size so far in *psize, the offset for the next
* field in *poffset, the alignment requirements for the current field in
* *palign, and returns a field descriptor for this field.
*/
/*
* bitfields extension:
* bitsize != 0: this is a bit field.
* pbitofs points to the current bit offset, this will be updated.
* prev_desc points to the type of the previous bitfield, if any.
*/
static inline
Py_ssize_t round_down(Py_ssize_t numToRound, Py_ssize_t multiple)
{
assert(numToRound >= 0);
assert(multiple >= 0);
if (multiple == 0)
return numToRound;
return (numToRound / multiple) * multiple;
}
static inline
Py_ssize_t round_up(Py_ssize_t numToRound, Py_ssize_t multiple)
{
assert(numToRound >= 0);
assert(multiple >= 0);
if (multiple == 0)
return numToRound;
return ((numToRound + multiple - 1) / multiple) * multiple;
}
static inline
Py_ssize_t NUM_BITS(Py_ssize_t bitsize);
static inline
Py_ssize_t LOW_BIT(Py_ssize_t offset);
static inline
Py_ssize_t BUILD_SIZE(Py_ssize_t bitsize, Py_ssize_t offset);
/* PyCField_FromDesc creates and returns a struct/union field descriptor.
The function expects to be called repeatedly for all fields in a struct or
union. It uses helper functions PyCField_FromDesc_gcc and
PyCField_FromDesc_msvc to simulate the corresponding compilers.
GCC mode places fields one after another, bit by bit. But "each bit field must
fit within a single object of its specified type" (GCC manual, section 15.8
"Bit Field Packing"). When it doesn't, we insert a few bits of padding to
avoid that.
MSVC mode works similar except for bitfield packing. Adjacent bit-fields are
packed into the same 1-, 2-, or 4-byte allocation unit if the integral types
are the same size and if the next bit-field fits into the current allocation
unit without crossing the boundary imposed by the common alignment requirements
of the bit-fields.
See https://gcc.gnu.org/onlinedocs/gcc/x86-Options.html#index-mms-bitfields for details.
We do not support zero length bitfields. In fact we use bitsize != 0 elsewhere
to indicate a bitfield. Here, non-bitfields need bitsize set to size*8.
PyCField_FromDesc manages:
- *psize: the size of the structure / union so far.
- *poffset, *pbitofs: 8* (*poffset) + *pbitofs points to where the next field
would start.
- *palign: the alignment requirements of the last field we placed.
*/
static int
PyCField_FromDesc_gcc(Py_ssize_t bitsize, Py_ssize_t *pbitofs,
Py_ssize_t *psize, Py_ssize_t *poffset, Py_ssize_t *palign,
CFieldObject* self, StgInfo* info,
int is_bitfield
)
{
// We don't use poffset here, so clear it, if it has been set.
*pbitofs += *poffset * 8;
*poffset = 0;
*palign = info->align;
if (bitsize > 0) {
// Determine whether the bit field, if placed at the next free bit,
// fits within a single object of its specified type.
// That is: determine a "slot", sized & aligned for the specified type,
// which contains the bitfield's beginning:
Py_ssize_t slot_start_bit = round_down(*pbitofs, 8 * info->align);
Py_ssize_t slot_end_bit = slot_start_bit + 8 * info->size;
// And see if it also contains the bitfield's last bit:
Py_ssize_t field_end_bit = *pbitofs + bitsize;
if (field_end_bit > slot_end_bit) {
// It doesn't: add padding (bump up to the next alignment boundary)
*pbitofs = round_up(*pbitofs, 8*info->align);
}
}
assert(*poffset == 0);
self->offset = round_down(*pbitofs, 8*info->align) / 8;
if(is_bitfield) {
Py_ssize_t effective_bitsof = *pbitofs - 8 * self->offset;
self->size = BUILD_SIZE(bitsize, effective_bitsof);
assert(effective_bitsof <= info->size * 8);
} else {
self->size = info->size;
}
*pbitofs += bitsize;
*psize = round_up(*pbitofs, 8) / 8;
return 0;
}
static int
PyCField_FromDesc_msvc(
Py_ssize_t *pfield_size, Py_ssize_t bitsize,
Py_ssize_t *pbitofs, Py_ssize_t *psize, Py_ssize_t *poffset,
Py_ssize_t *palign, int pack,
CFieldObject* self, StgInfo* info,
int is_bitfield
)
{
if (pack) {
*palign = Py_MIN(pack, info->align);
} else {
*palign = info->align;
}
// *poffset points to end of current bitfield.
// *pbitofs is generally non-positive,
// and 8 * (*poffset) + *pbitofs points just behind
// the end of the last field we placed.
if (0 < *pbitofs + bitsize || 8 * info->size != *pfield_size) {
// Close the previous bitfield (if any).
// and start a new bitfield:
*poffset = round_up(*poffset, *palign);
*poffset += info->size;
*pfield_size = info->size * 8;
// Reminder: 8 * (*poffset) + *pbitofs points to where we would start a
// new field. Ie just behind where we placed the last field plus an
// allowance for alignment.
*pbitofs = - *pfield_size;
}
assert(8 * info->size == *pfield_size);
self->offset = *poffset - (*pfield_size) / 8;
if(is_bitfield) {
assert(0 <= (*pfield_size + *pbitofs));
assert((*pfield_size + *pbitofs) < info->size * 8);
self->size = BUILD_SIZE(bitsize, *pfield_size + *pbitofs);
} else {
self->size = info->size;
}
assert(*pfield_size + *pbitofs <= info->size * 8);
*pbitofs += bitsize;
*psize = *poffset;
return 0;
}
PyObject *
PyCField_FromDesc(ctypes_state *st, PyObject *desc, Py_ssize_t index,
Py_ssize_t *pfield_size, int bitsize, int *pbitofs,
Py_ssize_t *psize, Py_ssize_t *poffset, Py_ssize_t *palign,
int pack, int big_endian)
Py_ssize_t *pfield_size, Py_ssize_t bitsize,
Py_ssize_t *pbitofs, Py_ssize_t *psize, Py_ssize_t *poffset, Py_ssize_t *palign,
int pack, int big_endian, LayoutMode layout_mode)
{
CFieldObject *self;
PyObject *proto;
Py_ssize_t size, align;
SETFUNC setfunc = NULL;
GETFUNC getfunc = NULL;
int fieldtype;
#define NO_BITFIELD 0
#define NEW_BITFIELD 1
#define CONT_BITFIELD 2
#define EXPAND_BITFIELD 3
PyTypeObject *tp = st->PyCField_Type;
self = (CFieldObject *)tp->tp_alloc(tp, 0);
if (self == NULL)
CFieldObject* self = (CFieldObject *)tp->tp_alloc(tp, 0);
if (self == NULL) {
return NULL;
}
StgInfo *info;
if (PyStgInfo_FromType(st, desc, &info) < 0) {
Py_DECREF(self);
@ -77,44 +205,13 @@ PyCField_FromDesc(ctypes_state *st, PyObject *desc, Py_ssize_t index,
return NULL;
}
if (bitsize /* this is a bitfield request */
&& *pfield_size /* we have a bitfield open */
#ifdef MS_WIN32
/* MSVC, GCC with -mms-bitfields */
&& info->size * 8 == *pfield_size
#else
/* GCC */
&& info->size * 8 <= *pfield_size
#endif
&& (*pbitofs + bitsize) <= *pfield_size) {
/* continue bit field */
fieldtype = CONT_BITFIELD;
#ifndef MS_WIN32
} else if (bitsize /* this is a bitfield request */
&& *pfield_size /* we have a bitfield open */
&& info->size * 8 >= *pfield_size
&& (*pbitofs + bitsize) <= info->size * 8) {
/* expand bit field */
fieldtype = EXPAND_BITFIELD;
#endif
} else if (bitsize) {
/* start new bitfield */
fieldtype = NEW_BITFIELD;
*pbitofs = 0;
*pfield_size = info->size * 8;
} else {
/* not a bit field */
fieldtype = NO_BITFIELD;
*pbitofs = 0;
*pfield_size = 0;
}
size = info->size;
proto = desc;
PyObject* proto = desc;
/* Field descriptors for 'c_char * n' are be scpecial cased to
return a Python string instead of an Array object instance...
*/
SETFUNC setfunc = NULL;
GETFUNC getfunc = NULL;
if (PyCArrayTypeObject_Check(st, proto)) {
StgInfo *ainfo;
if (PyStgInfo_FromType(st, proto, &ainfo) < 0) {
@ -153,61 +250,43 @@ PyCField_FromDesc(ctypes_state *st, PyObject *desc, Py_ssize_t index,
self->proto = Py_NewRef(proto);
switch (fieldtype) {
case NEW_BITFIELD:
if (big_endian)
self->size = (bitsize << 16) + *pfield_size - *pbitofs - bitsize;
else
self->size = (bitsize << 16) + *pbitofs;
*pbitofs = bitsize;
/* fall through */
case NO_BITFIELD:
if (pack)
align = min(pack, info->align);
else
align = info->align;
if (align && *poffset % align) {
Py_ssize_t delta = align - (*poffset % align);
*psize += delta;
*poffset += delta;
}
if (bitsize == 0)
self->size = size;
*psize += size;
self->offset = *poffset;
*poffset += size;
*palign = align;
break;
case EXPAND_BITFIELD:
*poffset += info->size - *pfield_size/8;
*psize += info->size - *pfield_size/8;
*pfield_size = info->size * 8;
if (big_endian)
self->size = (bitsize << 16) + *pfield_size - *pbitofs - bitsize;
else
self->size = (bitsize << 16) + *pbitofs;
self->offset = *poffset - size; /* poffset is already updated for the NEXT field */
*pbitofs += bitsize;
break;
case CONT_BITFIELD:
if (big_endian)
self->size = (bitsize << 16) + *pfield_size - *pbitofs - bitsize;
else
self->size = (bitsize << 16) + *pbitofs;
self->offset = *poffset - size; /* poffset is already updated for the NEXT field */
*pbitofs += bitsize;
break;
int is_bitfield = !!bitsize;
if(!is_bitfield) {
assert(info->size >= 0);
// assert: no overflow;
assert((unsigned long long int) info->size
< (1ULL << (8*sizeof(Py_ssize_t)-1)) / 8);
bitsize = 8 * info->size;
// Caution: bitsize might still be 0 now.
}
assert(bitsize <= info->size * 8);
int result;
if (layout_mode == LAYOUT_MODE_MS) {
result = PyCField_FromDesc_msvc(
pfield_size, bitsize, pbitofs,
psize, poffset, palign,
pack,
self, info,
is_bitfield
);
} else {
assert(pack == 0);
result = PyCField_FromDesc_gcc(
bitsize, pbitofs,
psize, poffset, palign,
self, info,
is_bitfield
);
}
if (result < 0) {
Py_DECREF(self);
return NULL;
}
assert(!is_bitfield || (LOW_BIT(self->size) <= self->size * 8));
if(big_endian && is_bitfield) {
self->size = BUILD_SIZE(NUM_BITS(self->size), 8*info->size - LOW_BIT(self->size) - bitsize);
}
return (PyObject *)self;
}
@ -298,8 +377,8 @@ static PyObject *
PyCField_repr(CFieldObject *self)
{
PyObject *result;
Py_ssize_t bits = self->size >> 16;
Py_ssize_t size = self->size & 0xFFFF;
Py_ssize_t bits = NUM_BITS(self->size);
Py_ssize_t size = LOW_BIT(self->size);
const char *name;
name = ((PyTypeObject *)self->proto)->tp_name;
@ -396,8 +475,28 @@ get_ulonglong(PyObject *v, unsigned long long *p)
*/
/* how to decode the size field, for integer get/set functions */
#define LOW_BIT(x) ((x) & 0xFFFF)
#define NUM_BITS(x) ((x) >> 16)
static inline
Py_ssize_t LOW_BIT(Py_ssize_t offset) {
return offset & 0xFFFF;
}
static inline
Py_ssize_t NUM_BITS(Py_ssize_t bitsize) {
return bitsize >> 16;
}
static inline
Py_ssize_t BUILD_SIZE(Py_ssize_t bitsize, Py_ssize_t offset) {
assert(0 <= offset);
assert(offset <= 0xFFFF);
// We don't support zero length bitfields.
// And GET_BITFIELD uses NUM_BITS(size)==0,
// to figure out whether we are handling a bitfield.
assert(0 < bitsize);
Py_ssize_t result = (bitsize << 16) + offset;
assert(bitsize == NUM_BITS(result));
assert(offset == LOW_BIT(result));
return result;
}
/* Doesn't work if NUM_BITS(size) == 0, but it never happens in SET() call. */
#define BIT_MASK(type, size) (((((type)1 << (NUM_BITS(size) - 1)) - 1) << 1) + 1)

11
Modules/_ctypes/ctypes.h
View File

@ -210,12 +210,17 @@ extern int PyObject_stginfo(PyObject *self, Py_ssize_t *psize, Py_ssize_t *palig
extern struct fielddesc *_ctypes_get_fielddesc(const char *fmt);
typedef enum {
LAYOUT_MODE_MS,
LAYOUT_MODE_GCC_SYSV,
} LayoutMode;
extern PyObject *
PyCField_FromDesc(ctypes_state *st, PyObject *desc, Py_ssize_t index,
Py_ssize_t *pfield_size, int bitsize, int *pbitofs,
Py_ssize_t *psize, Py_ssize_t *poffset, Py_ssize_t *palign,
int pack, int is_big_endian);
Py_ssize_t *pfield_size, Py_ssize_t bitsize,
Py_ssize_t *pbitofs, Py_ssize_t *psize, Py_ssize_t *poffset,
Py_ssize_t *palign,
int pack, int is_big_endian, LayoutMode layout_mode);
extern PyObject *PyCData_AtAddress(ctypes_state *st, PyObject *type, void *buf);
extern PyObject *PyCData_FromBytes(ctypes_state *st, PyObject *type, char *data, Py_ssize_t length);

49
Modules/_ctypes/stgdict.c
View File

@ -243,7 +243,7 @@ PyCStructUnionType_update_stginfo(PyObject *type, PyObject *fields, int isStruct
Py_ssize_t len, offset, size, align, i;
Py_ssize_t union_size, total_align, aligned_size;
Py_ssize_t field_size = 0;
int bitofs;
Py_ssize_t bitofs = 0;
PyObject *tmp;
int pack;
int forced_alignment = 1;
@ -287,6 +287,38 @@ PyCStructUnionType_update_stginfo(PyObject *type, PyObject *fields, int isStruct
pack = 0;
}
#ifdef MS_WIN32
LayoutMode layout_mode = LAYOUT_MODE_MS;
#else
LayoutMode layout_mode = (pack > 0) ? LAYOUT_MODE_MS : LAYOUT_MODE_GCC_SYSV;
#endif
if (PyObject_GetOptionalAttr(type, &_Py_ID(_layout_), &tmp) < 0) {
return -1;
}
if (tmp) {
if (!PyUnicode_Check(tmp)) {
PyErr_SetString(PyExc_TypeError,
"_layout_ must be a string");
return -1;
}
if (PyUnicode_CompareWithASCIIString(tmp, "ms") == 0) {
layout_mode = LAYOUT_MODE_MS;
}
else if (PyUnicode_CompareWithASCIIString(tmp, "gcc-sysv") == 0) {
layout_mode = LAYOUT_MODE_GCC_SYSV;
if (pack > 0) {
PyErr_SetString(PyExc_ValueError,
"_pack_ is not compatible with _layout_=\"gcc-sysv\"");
return -1;
}
}
else {
PyErr_Format(PyExc_ValueError,
"unknown _layout_ %R", tmp);
return -1;
}
}
if (PyObject_GetOptionalAttr(type, &_Py_ID(_align_), &tmp) < 0) {
return -1;
}
@ -409,9 +441,9 @@ PyCStructUnionType_update_stginfo(PyObject *type, PyObject *fields, int isStruct
PyObject *name = NULL, *desc = NULL;
PyObject *pair = PySequence_GetItem(fields, i);
PyObject *prop;
int bitsize = 0;
Py_ssize_t bitsize = 0;
if (!pair || !PyArg_ParseTuple(pair, "UO|i", &name, &desc, &bitsize)) {
if (!pair || !PyArg_ParseTuple(pair, "UO|n", &name, &desc, &bitsize)) {
PyErr_SetString(PyExc_TypeError,
"'_fields_' must be a sequence of (name, C type) pairs");
Py_XDECREF(pair);
@ -465,8 +497,9 @@ PyCStructUnionType_update_stginfo(PyObject *type, PyObject *fields, int isStruct
return -1;
}
if (bitsize <= 0 || bitsize > info->size * 8) {
PyErr_SetString(PyExc_ValueError,
"number of bits invalid for bit field");
PyErr_Format(PyExc_ValueError,
"number of bits invalid for bit field %R",
name);
Py_DECREF(pair);
return -1;
}
@ -493,7 +526,7 @@ PyCStructUnionType_update_stginfo(PyObject *type, PyObject *fields, int isStruct
prop = PyCField_FromDesc(st, desc, i,
&field_size, bitsize, &bitofs,
&size, &offset, &align,
pack, big_endian);
pack, big_endian, layout_mode);
if (prop == NULL) {
Py_DECREF(pair);
return -1;
@ -541,13 +574,15 @@ PyCStructUnionType_update_stginfo(PyObject *type, PyObject *fields, int isStruct
return -1;
}
} else /* union */ {
field_size = 0;
size = 0;
bitofs = 0;
offset = 0;
align = 0;
prop = PyCField_FromDesc(st, desc, i,
&field_size, bitsize, &bitofs,
&size, &offset, &align,
pack, big_endian);
pack, big_endian, layout_mode);
if (prop == NULL) {
Py_DECREF(pair);
return -1;

3
PCbuild/_ctypes_test.vcxproj
View File

@ -94,6 +94,7 @@
</PropertyGroup>
<ItemGroup>
<ClInclude Include="..\Modules\_ctypes\_ctypes_test.h" />
<ClInclude Include="..\Modules\_ctypes\_ctypes_test_generated.c.h" />
</ItemGroup>
<ItemGroup>
<ClCompile Include="..\Modules\_ctypes\_ctypes_test.c" />
@ -109,4 +110,4 @@
<Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
<ImportGroup Label="ExtensionTargets">
</ImportGroup>
</Project>
</Project>

5
PCbuild/_ctypes_test.vcxproj.filters
View File

@ -15,6 +15,9 @@
<ClInclude Include="..\Modules\_ctypes\_ctypes_test.h">
<Filter>Header Files</Filter>
</ClInclude>
<ClInclude Include="..\Modules\_ctypes\_ctypes_test_generated.c.h">
<Filter>Header Files</Filter>
</ClInclude>
</ItemGroup>
<ItemGroup>
<ClCompile Include="..\Modules\_ctypes\_ctypes_test.c">
@ -26,4 +29,4 @@
<Filter>Resource Files</Filter>
</ResourceCompile>
</ItemGroup>
</Project>
</Project>