8000 gh-105733: Deprecate ctypes SetPointerType() and ARRAY() by vstinner · Pull Request #105734 · python/cpython · GitHub
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gh-105733: Deprecate ctypes SetPointerType() and ARRAY() #105734

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merged 1 commit into from
Jun 13, 2023
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gh-105733: Deprecate ctypes SetPointerType() and ARRAY() #105734

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6 changes: 6 additions & 0 deletions Doc/whatsnew/3.13.rst
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Expand Up @@ -140,6 +140,12 @@ Deprecated
Use the ``'w'`` format code instead.
(contributed by Hugo van Kemenade in :gh:`80480`)

* :mod:`ctypes`: Deprecate undocumented :func:`!ctypes.SetPointerType`
and :func:`!ctypes.ARRAY` functions.
Replace ``ctypes.SetPointerType(item_type, size)`` with ``item_type * size``.
(Contributed by Victor Stinner in :gh:`105733`.)


Removed
=======

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6 changes: 4 additions & 2 deletions Lib/ctypes/__init__.py
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Expand Up @@ -302,8 +302,9 @@ def create_unicode_buffer(init, size=None):
raise TypeError(init)


# XXX Deprecated
def SetPointerType(pointer, cls):
import warnings
warnings._deprecated("ctypes.SetPointerType", remove=(3, 15))
if _pointer_type_cache.get(cls, None) is not None:
raise RuntimeError("This type already exists in the cache")
if id(pointer) not in _pointer_type_cache:
Expand All @@ -312,8 +313,9 @@ def SetPointerType(pointer, cls):
_pointer_type_cache[cls] = pointer
del _pointer_type_cache[id(pointer)]

# XXX Deprecated
def ARRAY(typ, len):
import warnings
warnings._deprecated("ctypes.ARRAY", remove=(3, 15))
return typ * len
Comment on lines 316 to 319
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Do you think there's a high expected maintenance overhead or security risk here?

Per PEP 387:

If the expected maintenance overhead and security risk of the deprecated behavior is small (e.g. an old function is reimplemented in terms of a new, more general one), it can stay indefinitely (or until the situation changes).

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it's not a big maintenance burden nor a securty issue, why do you ask?

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I ask to see if there's a special reason for remove=(3, 15), or if it can be relaxed.

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What do you propose? To postpone the removal to Python 3.16?

On PyPI top 8,000 projects (at 2024-03-16), I found only 2 projects using ctypes.ARRAY. I search for regex ctypes.ARRAY|\<ARRAY\> (and excluded unrelated lines).

  • astroid (3.1.0)
  • pwntools (4.12.0)

It's about two lines:

astroid-3.1.0.tar.gz: astroid-3.1.0/tests/brain/test_ctypes.py: ctypes.ARRAY(3, 2)
pwntools-4.12.0.tar.gz: pwntools-4.12.0/pwnlib/adb/bootloader.py: imgarray = ctypes.ARRAY(img_info, self.num_images)

Before the function was only deprecated with a comment:

# XXX Deprecated
def ARRAY(typ, len):
    return typ * len

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I'll propose to follow the part of PEP 387 I quoted above. Alternatively, since this does break known projects, to soft-deprecate instead.

But I plan to propose that in the beta period, right now I'm only gathering info. Thanks for the answer!


################################################################
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19 changes: 17 additions & 2 deletions Lib/test/test_ctypes/test_arrays.py
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@@ -1,7 +1,9 @@
import unittest
from test.support import bigmemtest, _2G
import ctypes
import sys
import unittest
import warnings
from ctypes import *
from test.support import bigmemtest, _2G

from test.test_ctypes import need_symbol

Expand All @@ -10,6 +12,14 @@
formats = c_byte, c_ubyte, c_short, c_ushort, c_int, c_uint, \
c_long, c_ulonglong, c_float, c_double, c_longdouble


def ARRAY(*args):
# ignore DeprecationWarning in tests
with warnings.catch_warnings():
warnings.simplefilter('ignore', DeprecationWarning)
return ctypes.ARRAY(*args)


class ArrayTestCase(unittest.TestCase):
def test_simple(self):
# create classes holding simple numeric types, and check
Expand Down Expand Up @@ -234,5 +244,10 @@ def test_bpo36504_signed_int_overflow(self):
def test_large_array(self, size):
c_char * size

def test_deprecation(self):
with self.assertWarns(DeprecationWarning):
CharArray = ctypes.ARRAY(c_char, 3)


if __name__ == '__main__':
unittest.main()
23 changes: 18 additions & 5 deletions Lib/test/test_ctypes/test_incomplete.py
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@@ -1,20 +1,28 @@
import ctypes
import unittest
import warnings
from ctypes import *

################################################################
#
# The incomplete pointer example from the tutorial
#

class MyTestCase(unittest.TestCase):
class TestSetPointerType(unittest.TestCase):

def tearDown(self):
# to not leak references, we must clean _pointer_type_cache
ctypes._reset_cache()

def test_incomplete_example(self):
lpcell = POINTER("cell")
class cell(Structure):
_fields_ = [("name", c_char_p),
("next", lpcell)]

SetPointerType(lpcell, cell)
with warnings.catch_warnings():
warnings.simplefilter('ignore', DeprecationWarning)
ctypes.SetPointerType(lpcell, cell)

c1 = cell()
c1.name = b"foo"
Expand All @@ -32,9 +40,14 @@ class cell(Structure):
p = p.next[0]
self.assertEqual(result, [b"foo", b"bar"] * 4)

# to not leak references, we must clean _pointer_type_cache
from ctypes import _pointer_type_cache
del _pointer_type_cache[cell]
def test_deprecation(self):
lpcell = POINTER("cell")
class cell(Structure):
_fields_ = [("name", c_char_p),
("next", lpcell)]

with self.assertWarns(DeprecationWarning):
ctypes.SetPointerType(lpcell, cell)

################################################################

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2023-06-13-19-38-12.gh-issue-105733.WOp0mG.rst
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@@ -0,0 +1,2 @@
:mod:`ctypes`: Deprecate undocumented :func:`!ctypes.SetPointerType` and
:func:`!ctypes.ARRAY` functions. Patch by Victor Stinner.
0