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gh-148464: Add missing __ctype_le/be__ attributes for complex types in the ctype module #148485

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gh-148464: Add missing ``__ctype_le/be__`` attributes for complex typ…
skirpichev Apr 13, 2026
820c5d8
+ handle memory errors
skirpichev Apr 14, 2026
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43 changes: 43 additions & 0 deletions Lib/test/test_ctypes/test_byteswap.py
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Original file line number Diff line number Diff line change
@@ -1,4 +1,5 @@
import binascii
import ctypes
import math
import struct
import sys
Expand Down Expand Up @@ -165,6 +166,48 @@ def test_endian_double(self):
self.assertEqual(s.value, math.pi)
self.assertEqual(bin(struct.pack(">d", math.pi)), bin(s))

@unittest.skipUnless(hasattr(ctypes, 'c_float_complex'), "No complex types")
def test_endian_float_complex(self):
c_float_complex = ctypes.c_float_complex
if sys.byteorder == "little":
self.assertIs(c_float_complex.__ctype_le__, c_float_complex)
self.assertIs(c_float_complex.__ctype_be__.__ctype_le__,
c_float_complex)
else:
self.assertIs(c_float_complex.__ctype_be__, c_float_complex)
self.assertIs(c_float_complex.__ctype_le__.__ctype_be__,
c_float_complex)
s = c_float_complex(math.pi+1j)
self.assertEqual(bin(struct.pack("F", math.pi+1j)), bin(s))
self.assertAlmostEqual(s.value, math.pi+1j, places=6)
s = c_float_complex.__ctype_le__(math.pi+1j)
self.assertAlmostEqual(s.value, math.pi+1j, places=6)
self.assertEqual(bin(struct.pack("<F", math.pi+1j)), bin(s))
s = c_float_complex.__ctype_be__(math.pi+1j)
self.assertAlmostEqual(s.value, math.pi+1j, places=6)
self.assertEqual(bin(struct.pack(">F", math.pi+1j)), bin(s))

@unittest.skipUnless(hasattr(ctypes, 'c_double_complex'), "No complex types")
def test_endian_double_complex(self):
c_double_complex = ctypes.c_double_complex
if sys.byteorder == "little":
self.assertIs(c_double_complex.__ctype_le__, c_double_complex)
self.assertIs(c_double_complex.__ctype_be__.__ctype_le__,
c_double_complex)
else:
self.assertIs(c_double_complex.__ctype_be__, c_double_complex)
self.assertIs(c_double_complex.__ctype_le__.__ctype_be__,
c_double_complex)
s = c_double_complex(math.pi+1j)
self.assertEqual(bin(struct.pack("D", math.pi+1j)), bin(s))
self.assertAlmostEqual(s.value, math.pi+1j, places=6)
s = c_double_complex.__ctype_le__(math.pi+1j)
self.assertAlmostEqual(s.value, math.pi+1j, places=6)
self.assertEqual(bin(struct.pack("<D", math.pi+1j)), bin(s))
s = c_double_complex.__ctype_be__(math.pi+1j)
self.assertAlmostEqual(s.value, math.pi+1j, places=6)
self.assertEqual(bin(struct.pack(">D", math.pi+1j)), bin(s))

def test_endian_other(self):
self.assertIs(c_byte.__ctype_le__, c_byte)
self.assertIs(c_byte.__ctype_be__, c_byte)
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2026-04-13-06-22-27.gh-issue-148464.Bj_NZy.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Add missing ``__ctype_le/be__`` attributes for
:class:`~ctypes.c_float_complex` and :class:`~ctypes.c_double_complex`. Patch
by Sergey B Kirpichev.
21 changes: 20 additions & 1 deletion Modules/_ctypes/_ctypes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2267,7 +2267,22 @@ static PyObject *CreateSwappedType(ctypes_state *st, PyTypeObject *type,
return NULL;
}

stginfo->ffi_type_pointer = *fmt->pffi_type;
if (!fmt->pffi_type->elements) {
stginfo->ffi_type_pointer = *fmt->pffi_type;
}
else {
const size_t els_size = sizeof(fmt->pffi_type->elements);
stginfo->ffi_type_pointer.size = fmt->pffi_type->size;
stginfo->ffi_type_pointer.alignment = fmt->pffi_type->alignment;
stginfo->ffi_type_pointer.type = fmt->pffi_type->type;
stginfo->ffi_type_pointer.elements = PyMem_Malloc(els_size);
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@eendebakpt eendebakpt Apr 14, 2026

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According to https://www.chiark.greenend.org.uk/doc/libffi-dev/html/Structures.html the elements should be a NULL terminated list of pointers. With this allocation we are missing the NULL. According to Claude this is no problem for the current implementation, but it is a breach of contract and a latent bug.

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@skirpichev skirpichev Apr 14, 2026

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This is for primitive types (section above), not for structures.

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@encukou encukou Apr 14, 2026

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Could you put the duplicated code in a helper function, like fill_stginfo_from_pffi_type?

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@sunmy2019 sunmy2019 Apr 14, 2026

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This is for primitive types (section above), not for structures.

Could you elaborate more? I also think this could be a real problem.

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@sunmy2019 sunmy2019 Apr 14, 2026

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This is indeed a breakage of libffi's invariant. I opened #148573 for this.

if (!stginfo->ffi_type_pointer.elements) {
Py_DECREF(result);
return PyErr_NoMemory();
}
memcpy(stginfo->ffi_type_pointer.elements,
fmt->pffi_type->elements, els_size);
}
stginfo->align = fmt->pffi_type->alignment;
stginfo->length = 0;
stginfo->size = fmt->pffi_type->size;
Expand Down Expand Up @@ -2372,6 +2387,10 @@ PyCSimpleType_init(PyObject *self, PyObject *args, PyObject *kwds)
stginfo->ffi_type_pointer.alignment = fmt->pffi_type->alignment;
stginfo->ffi_type_pointer.type = fmt->pffi_type->type;
stginfo->ffi_type_pointer.elements = PyMem_Malloc(els_size);
if (!stginfo->ffi_type_pointer.elements) {
PyErr_NoMemory();
goto error;
}
memcpy(stginfo->ffi_type_pointer.elements,
fmt->pffi_type->elements, els_size);
}
Expand Down
54 changes: 54 additions & 0 deletions Modules/_ctypes/cfield.c
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Expand Up @@ -792,6 +792,32 @@ D_get(void *ptr, Py_ssize_t size)
return PyComplex_FromDoubles(x[0], x[1]);
}

static PyObject *
D_set_sw(void *ptr, PyObject *value, Py_ssize_t size)
{
assert(NUM_BITS(size) || (size == 2*sizeof(double)));
Py_complex c = PyComplex_AsCComplex(value);

if (c.real == -1 && PyErr_Occurred()) {
return NULL;
}
if (PyFloat_Pack8(c.real, ptr, PY_BIG_ENDIAN)
|| PyFloat_Pack8(c.imag, ptr + sizeof(double), PY_BIG_ENDIAN))
{
return NULL;
}
_RET(value);
}

static PyObject *
D_get_sw(void *ptr, Py_ssize_t size)
{
assert(NUM_BITS(size) || (size == 2*sizeof(double)));
return PyComplex_FromDoubles(PyFloat_Unpack8(ptr, PY_BIG_ENDIAN),
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@encukou encukou Apr 14, 2026

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Could you add error handling for the unpacks here and PyFloat_Unpack4 below?

if (x == -1.0 && PyErr_Occurred()) {

I'd be happier if ctypes didn't rely on an undocumented implementation detail here.

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@skirpichev skirpichev Apr 14, 2026

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Why undocumented? It's documented and widely used across the CPython codebase, e.g. in same file.

PyFloat_Unpack8(ptr + sizeof(double),
PY_BIG_ENDIAN));
}

/* F: float complex */
static PyObject *
F_set(void *ptr, PyObject *value, Py_ssize_t size)
Expand All @@ -817,6 +843,32 @@ F_get(void *ptr, Py_ssize_t size)
return PyComplex_FromDoubles(x[0], x[1]);
}

static PyObject *
F_set_sw(void *ptr, PyObject *value, Py_ssize_t size)
{
assert(NUM_BITS(size) || (size == 2*sizeof(float)));
Py_complex c = PyComplex_AsCComplex(value);

if (c.real == -1 && PyErr_Occurred()) {
return NULL;
}
if (PyFloat_Pack4(c.real, ptr, PY_BIG_ENDIAN)
|| PyFloat_Pack4(c.imag, ptr + sizeof(float), PY_BIG_ENDIAN))
{
return NULL;
}
_RET(value);
}

static PyObject *
F_get_sw(void *ptr, Py_ssize_t size)
{
assert(NUM_BITS(size) || (size == 2*sizeof(float)));
return PyComplex_FromDoubles(PyFloat_Unpack4(ptr, PY_BIG_ENDIAN),
PyFloat_Unpack4(ptr + sizeof(float),
PY_BIG_ENDIAN));
}

/* G: long double complex */
static PyObject *
G_set(void *ptr, PyObject *value, Py_ssize_t size)
Expand Down Expand Up @@ -1602,7 +1654,9 @@ for base_code, base_c_type in [
#if defined(_Py_FFI_SUPPORT_C_COMPLEX)
if (Py_FFI_COMPLEX_AVAILABLE) {
TABLE_ENTRY(D, &ffi_type_complex_double);
TABLE_ENTRY_SW(D, &ffi_type_complex_double);
TABLE_ENTRY(F, &ffi_type_complex_float);
TABLE_ENTRY_SW(F, &ffi_type_complex_float);
TABLE_ENTRY(G, &ffi_type_complex_longdouble);
}
#endif
Expand Down
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