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gh-132835: Add defensive NULL checks in mro resolution #134763

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gh-132835: Add defensive NULL checks in mro resolution #134763

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28521e9
Add defensive NULL checks in mro resolution
emmatyping May 27, 2025
c305485
Rename mro_hierarchy to indicate it should be used with complete types
emmatyping May 27, 2025
5109a35
Merge branch 'main' into check-mro-lookup-not-null
emmatyping Jun 1, 2025
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8 changes: 7 additions & 1 deletion Objects/typeobject.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1652,6 +1652,7 @@ mro_hierarchy(PyTypeObject *type, PyObject *temp)
return res;
}
PyObject *new_mro = lookup_tp_mro(type);
assert(new_mro != NULL);

PyObject *tuple;
if (old_mro != NULL) {
Expand Down Expand Up @@ -3274,6 +3275,7 @@ mro_implementation_unlocked(PyTypeObject *type)
*/
PyTypeObject *base = _PyType_CAST(PyTuple_GET_ITEM(bases, 0));
PyObject *base_mro = lookup_tp_mro(base);
assert(base_mro != NULL);
Py_ssize_t k = PyTuple_GET_SIZE(base_mro);
PyObject *result = PyTuple_New(k + 1);
if (result == NULL) {
Expand Down Expand Up @@ -3308,9 +3310,12 @@ mro_implementation_unlocked(PyTypeObject *type)
return NULL;
}

PyObject *mro_to_merge;
for (Py_ssize_t i = 0; i < n; i++) {
PyTypeObject *base = _PyType_CAST(PyTuple_GET_ITEM(bases, i));
to_merge[i] = lookup_tp_mro(base);
mro_to_merge = lookup_tp_mro(base);
assert(mro_to_merge != NULL);
to_merge[i] = mro_to_merge;
}
to_merge[n] = bases;

Expand Down Expand Up @@ -8598,6 +8603,7 @@ type_ready_inherit(PyTypeObject *type)

// Inherit slots
PyObject *mro = lookup_tp_mro(type);
assert(mro != NULL);
Py_ssize_t n = PyTuple_GET_SIZE(mro);
for (Py_ssize_t i = 1; i < n; i++) {
PyObject *b = PyTuple_GET_ITEM(mro, i);
Expand Down
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