"""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 ctypes
from ctypes import Structure, Union
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):
def _maybe_skip():
# `_pack_` enables MSVC-style packing, but keeps platform-specific
# alignments.
# The C code we generate for GCC/clang currently uses
# `__attribute__((ms_struct))`, which activates MSVC layout *and*
# alignments, that is, sizeof(basic type) == alignment(basic type).
# On a Pentium, int64 is 32-bit aligned, so the two won't match.
# The expected behavior is instead tested in
# StructureTestCase.test_packed, over in test_structures.py.
if sizeof(c_int64) != alignment(c_int64):
raise unittest.SkipTest('cannot test on this platform')
_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):
if _maybe_skip := getattr(cls, '_maybe_skip', None):
_maybe_skip()
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
""")
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