8000 gh-126937: ctypes: fix TypeError when a field's size is >65535 bytes … · python/cpython@cef0a90 · GitHub
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gh-126937: ctypes: fix TypeError when a field's size is >65535 bytes (GH-126938)
 Co-authored-by: Peter Bierma <zintensitydev@gmail.com> Co-authored-by: Terry Jan Reedy <tjreedy@udel.edu> Co-authored-by: Petr Viktorin <encukou@gmail.com>
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‎Lib/test/test_ctypes/test_struct_fields.py

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@@ -1,4 +1,5 @@
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import unittest
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import sys
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from ctypes import Structure, Union, sizeof, c_char, c_int
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from ._support import (CField, Py_TPFLAGS_DISALLOW_INSTANTIATION,
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Py_TPFLAGS_IMMUTABLETYPE)
@@ -75,6 +76,28 @@ def __init_subclass__(cls, **kwargs):
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'ctypes state is not initialized'):
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class Subclass(BrokenStructure): ...
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def test_max_field_size_gh126937(self):
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# Classes for big structs should be created successfully.
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# (But they most likely can't be instantiated.)
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# Here we test the exact limit: the number of *bits* must fit
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# in Py_ssize_t.
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class X(self.cls):
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_fields_ = [('char', c_char),]
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max_field_size = sys.maxsize // 8
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class Y(self.cls):
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_fields_ = [('largeField', X * max_field_size)]
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class Z(self.cls):
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_fields_ = [('largeField', c_char * max_field_size)]
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with self.assertRaises(ValueError):
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class TooBig(self.cls):
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_fields_ = [('largeField', X * (max_field_size + 1))]
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with self.assertRaises(ValueError):
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class TooBig(self.cls):
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_fields_ = [('largeField', c_char * (max_field_size + 1))]
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# __set__ and __get__ should raise a TypeError in case their self
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# argument is not a ctype instance.
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def test___set__(self):

‎Misc/NEWS.d/next/Core_and_Builtins/2024-11-17-21-35-55.gh-issue-126937.qluVM0.rst

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Fix :exc:`TypeError` when a :class:`ctypes.Structure` has a field size
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that doesn't fit into an unsigned 16-bit integer.
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Instead, the maximum number of *bits* is :data:`sys.maxsize`.

‎Modules/_ctypes/cfield.c

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Original file line numberDiff line numberDiff line change
@@ -110,10 +110,16 @@ PyCField_new_impl(PyTypeObject *type, PyObject *name, PyObject *proto,
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goto error;
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}
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Py_ssize_t bit_size = NUM_BITS(size);
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if (bit_size) {
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if (bit_size_obj != Py_None) {
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#ifdef Py_DEBUG
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Py_ssize_t bit_size = NUM_BITS(size);
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assert(bit_size > 0);
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assert(bit_size <= info->size * 8);
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// Currently, the bit size is specified redundantly
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// in NUM_BITS(size) and bit_size_obj.
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// Verify that they match.
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assert(PyLong_AsSsize_t(bit_size_obj) == bit_size);
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#endif
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switch(info->ffi_type_pointer.type) {
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case FFI_TYPE_UINT8:
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case FFI_TYPE_UINT16:

‎Modules/_ctypes/stgdict.c

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Original file line numberDiff line numberDiff line change
@@ -292,7 +292,7 @@ PyCStructUnionType_update_stginfo(PyObject *type, PyObject *fields, int isStruct
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if (!tmp) {
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goto error;
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}
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Py_ssize_t total_align = PyLong_AsInt(tmp);
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Py_ssize_t total_align = PyLong_AsSsize_t(tmp);
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Py_DECREF(tmp);
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if (total_align < 0) {
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if (!PyErr_Occurred()) {
@@ -306,7 +306,7 @@ PyCStructUnionType_update_stginfo(PyObject *type, PyObject *fields, int isStruct
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if (!tmp) {
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goto error;
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}
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Py_ssize_t total_size = PyLong_AsInt(tmp);
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Py_ssize_t total_size = PyLong_AsSsize_t(tmp);
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Py_DECREF(tmp);
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if (total_size < 0) {
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if (!PyErr_Occurred()) {

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