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[3.9] bpo-44707: Fix an undefined behavior of the null pointer arithmetic (GH-27292) #27443

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Merged
merged 1 commit into from
Jul 29, 2021
Merged

[3.9] bpo-44707: Fix an undefined behavior of the null pointer arithmetic (GH-27292) #27443

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11 changes: 9 additions & 2 deletions Objects/listobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -165,9 +165,10 @@ PyList_New(Py_ssize_t size)
static PyObject *
list_new_prealloc(Py_ssize_t size)
{
assert(size > 0);
PyListObject *op = (PyListObject *) PyList_New(0);
if (size == 0 || op == NULL) {
return (PyObject *) op;
if (op == NULL) {
return NULL;
}
assert(op->ob_item == NULL);
op->ob_item = PyMem_New(PyObject *, size);
Expand Down Expand Up @@ -446,6 +447,9 @@ list_slice(PyListObject *a, Py_ssize_t ilow, Py_ssize_t ihigh)
PyObject **src, **dest;
Py_ssize_t i, len;
len = ihigh - ilow;
if (len <= 0) {
return PyList_New(0);
}
np = (PyListObject *) list_new_prealloc(len);
if (np == NULL)
return NULL;
Expand Down Expand Up @@ -500,6 +504,9 @@ list_concat(PyListObject *a, PyObject *bb)
if (Py_SIZE(a) > PY_SSIZE_T_MAX - Py_SIZE(b))
return PyErr_NoMemory();
size = Py_SIZE(a) + Py_SIZE(b);
if (size == 0) {
return PyList_New(0);
}
np = (PyListObject *) list_new_prealloc(size);
if (np == NULL) {
return NULL;
Expand Down