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Revert "gh-46376: Return existing pointer when possible in ctypes (#1… (#108688) 

This reverts commit 08447b5deb.

Revert also _ctypes.c changes of the PyDict_ContainsString() change,
commit 6726626646.
This commit is contained in:
Victor Stinner 2023-09-04 11:21:47 +02:00 committed by GitHub
parent 44fc378b59
commit 5a79d2ae57
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3 changed files with 0 additions and 63 deletions
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27
Lib/test/test_ctypes/test_keeprefs.py
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@ -98,33 +98,6 @@ class PointerTestCase(unittest.TestCase):
x = pointer(i)
self.assertEqual(x._objects, {'1': i})
def test_pp_ownership(self):
d = c_int(123)
n = c_int(456)
p = pointer(d)
pp = pointer(p)
self.assertIs(pp._objects['1'], p)
self.assertIs(pp._objects['0']['1'], d)
pp.contents.contents = n
self.assertIs(pp._objects['1'], p)
self.assertIs(pp._objects['0']['1'], n)
self.assertIs(p._objects['1'], n)
self.assertEqual(len(p._objects), 1)
del d
del p
self.assertIs(pp._objects['0']['1'], n)
self.assertEqual(len(pp._objects), 2)
del n
self.assertEqual(len(pp._objects), 2)
class PointerToStructure(unittest.TestCase):
def test(self):

1
Misc/NEWS.d/next/Library/2023-07-24-01-21-16.gh-issue-46376.w-xuDL.rst
View File

@ -1 +0,0 @@
Prevent memory leak and use-after-free when using pointers to pointers with ctypes

35
Modules/_ctypes/_ctypes.c
View File

@ -5148,41 +5148,6 @@ Pointer_get_contents(CDataObject *self, void *closure)
stgdict = PyObject_stgdict((PyObject *)self);
assert(stgdict); /* Cannot be NULL for pointer instances */
PyObject *keep = GetKeepedObjects(self);
if (keep != NULL) {
// check if it's a pointer to a pointer:
// pointers will have '0' key in the _objects
int ptr_probe = PyDict_ContainsString(keep, "0");
if (ptr_probe < 0) {
return NULL;
}
if (ptr_probe) {
PyObject *item;
if (PyDict_GetItemStringRef(keep, "1", &item) < 0) {
return NULL;
}
if (item == NULL) {
PyErr_SetString(PyExc_ValueError,
"Unexpected NULL pointer in _objects");
return NULL;
}
#ifndef NDEBUG
CDataObject *ptr2ptr = (CDataObject *)item;
// Don't construct a new object,
// return existing one instead to preserve refcount.
// Double-check that we are returning the same thing.
assert(
*(void**) self->b_ptr == ptr2ptr->b_ptr ||
*(void**) self->b_value.c == ptr2ptr->b_ptr ||
*(void**) self->b_ptr == ptr2ptr->b_value.c ||
*(void**) self->b_value.c == ptr2ptr->b_value.c
);
#endif
return item;
}
}
return PyCData_FromBaseObj(stgdict->proto,
(PyObject *)self, 0,
*(void **)self->b_ptr);