gh-112358: Fix Python 3.12 regression with subclassing struct.Struct. (#112424)

Revert commit c8c0afc713 (PR #94532),
which moved `struct.Struct` initialisation from `Struct.__init__` to `Struct.__new__`.
This caused issues with code in the wild that subclasses `struct.Struct`.
This commit is contained in:
Mark Dickinson 2023-11-26 14:29:52 +00:00 committed by GitHub
parent 3faf8e586d
commit 9fe60340d7
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
4 changed files with 52 additions and 48 deletions

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@ -700,20 +700,6 @@ class StructTest(unittest.TestCase):
with self.assertRaises(TypeError):
cls.x = 1
@support.cpython_only
def test__struct_Struct__new__initialized(self):
# See https://github.com/python/cpython/issues/78724
s = struct.Struct.__new__(struct.Struct, "b")
s.unpack_from(b"abcd")
@support.cpython_only
def test__struct_Struct_subclassing(self):
class Bob(struct.Struct):
pass
s = Bob("b")
s.unpack_from(b"abcd")
def test_issue35714(self):
# Embedded null characters should not be allowed in format strings.
@ -774,6 +760,15 @@ class StructTest(unittest.TestCase):
test_error_propagation('N')
test_error_propagation('n')
def test_struct_subclass_instantiation(self):
# Regression test for https://github.com/python/cpython/issues/112358
class MyStruct(struct.Struct):
def __init__(self):
super().__init__('>h')
my_struct = MyStruct()
self.assertEqual(my_struct.pack(12345), b'\x30\x39')
def test_repr(self):
s = struct.Struct('=i2H')
self.assertEqual(repr(s), f'Struct({s.format!r})')

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@ -0,0 +1,2 @@
Revert change to :class:`struct.Struct` initialization that broke some cases
of subclassing.

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@ -1553,9 +1553,28 @@ prepare_s(PyStructObject *self)
return -1;
}
static PyObject *
s_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
PyObject *self;
assert(type != NULL);
allocfunc alloc_func = PyType_GetSlot(type, Py_tp_alloc);
assert(alloc_func != NULL);
self = alloc_func(type, 0);
if (self != NULL) {
PyStructObject *s = (PyStructObject*)self;
s->s_format = Py_NewRef(Py_None);
s->s_codes = NULL;
s->s_size = -1;
s->s_len = -1;
}
return self;
}
/*[clinic input]
@classmethod
Struct.__new__
Struct.__init__
format: object
@ -1567,24 +1586,16 @@ the format string.
See help(struct) for more on format strings.
[clinic start generated code]*/
static PyObject *
Struct_impl(PyTypeObject *type, PyObject *format)
/*[clinic end generated code: output=49468b044e334308 input=8b91868eb1df0e28]*/
static int
Struct___init___impl(PyStructObject *self, PyObject *format)
/*[clinic end generated code: output=b8e80862444e92d0 input=192a4575a3dde802]*/
{
allocfunc alloc = PyType_GetSlot(type, Py_tp_alloc);
assert(alloc != NULL);
PyStructObject *self = (PyStructObject *)alloc(type, 0);
if (self == NULL) {
return NULL;
}
int ret = 0;
if (PyUnicode_Check(format)) {
format = PyUnicode_AsASCIIString(format);
if (format == NULL) {
Py_DECREF(self);
return NULL;
}
if (format == NULL)
return -1;
}
else {
Py_INCREF(format);
@ -1592,24 +1603,19 @@ Struct_impl(PyTypeObject *type, PyObject *format)
if (!PyBytes_Check(format)) {
Py_DECREF(format);
Py_DECREF(self);
PyErr_Format(PyExc_TypeError,
"Struct() argument 1 must be a str or bytes object, "
"not %.200s",
_PyType_Name(Py_TYPE(format)));
return NULL;
return -1;
}
self->s_format = format;
Py_SETREF(self->s_format, format);
if (prepare_s(self) < 0) {
Py_DECREF(self);
return NULL;
}
return (PyObject *)self;
ret = prepare_s(self);
return ret;
}
static int
s_clear(PyStructObject *s)
{
@ -2219,8 +2225,9 @@ static PyType_Slot PyStructType_slots[] = {
{Py_tp_methods, s_methods},
{Py_tp_members, s_members},
{Py_tp_getset, s_getsetlist},
{Py_tp_new, Struct},
{Py_tp_init, Struct___init__},
{Py_tp_alloc, PyType_GenericAlloc},
{Py_tp_new, s_new},
{Py_tp_free, PyObject_GC_Del},
{0, 0},
};

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@ -9,7 +9,7 @@ preserve
#include "pycore_abstract.h" // _PyNumber_Index()
#include "pycore_modsupport.h" // _PyArg_UnpackKeywords()
PyDoc_STRVAR(Struct__doc__,
PyDoc_STRVAR(Struct___init____doc__,
"Struct(format)\n"
"--\n"
"\n"
@ -20,13 +20,13 @@ PyDoc_STRVAR(Struct__doc__,
"\n"
"See help(struct) for more on format strings.");
static PyObject *
Struct_impl(PyTypeObject *type, PyObject *format);
static int
Struct___init___impl(PyStructObject *self, PyObject *format);
static PyObject *
Struct(PyTypeObject *type, PyObject *args, PyObject *kwargs)
static int
Struct___init__(PyObject *self, PyObject *args, PyObject *kwargs)
{
PyObject *return_value = NULL;
int return_value = -1;
#if defined(Py_BUILD_CORE) && !defined(Py_BUILD_CORE_MODULE)
#define NUM_KEYWORDS 1
@ -62,7 +62,7 @@ Struct(PyTypeObject *type, PyObject *args, PyObject *kwargs)
goto exit;
}
format = fastargs[0];
return_value = Struct_impl(type, format);
return_value = Struct___init___impl((PyStructObject *)self, format);
exit:
return return_value;
@ -436,4 +436,4 @@ exit:
return return_value;
}
/*[clinic end generated code: output=6a20e87f9b298b14 input=a9049054013a1b77]*/
/*[clinic end generated code: output=67bd299e5d72fee0 input=a9049054013a1b77]*/