Rewrite code for 3.13.

Author: serhiy-storchaka

Include/internal/pycore_typeobject.h

@@ -199,6 +199,7 @@ extern PyObject * _PyType_GetMRO(PyTypeObject *type);
 extern PyObject* _PyType_GetSubclasses(PyTypeObject *);
 extern int _PyType_HasSubclasses(PyTypeObject *);
 PyAPI_FUNC(PyObject *) _PyType_GetModuleByDef2(PyTypeObject *, PyTypeObject *, PyModuleDef *);
+PyAPI_FUNC(PyObject *) _PyType_GetModuleByDef3(PyTypeObject *, PyTypeObject *, PyTypeObject *, PyModuleDef *);
 
 // PyType_Ready() must be called if _PyType_IsReady() is false.
 // See also the Py_TPFLAGS_READY flag.

Modules/_decimal/_decimal.c

@@ -143,19 +143,10 @@ find_state_left_or_right(PyObject *left, PyObject *right)
 static inline decimal_state *
 find_state_ternary(PyObject *left, PyObject *right, PyObject *modulus)
 {
-    PyTypeObject *base;
-    if (PyType_GetBaseByToken(Py_TYPE(left), &dec_spec, &base) != 1) {
-        assert(!PyErr_Occurred());
-        if (PyType_GetBaseByToken(Py_TYPE(right), &dec_spec, &base) != 1) {
-            assert(!PyErr_Occurred());
-            PyType_GetBaseByToken(Py_TYPE(modulus), &dec_spec, &base);
-        }
-    }
-    assert(base != NULL);
-    void *state = _PyType_GetModuleState(base);
-    assert(state != NULL);
-    Py_DECREF(base);
-    return (decimal_state *)state;
+    PyObject *mod = _PyType_GetModuleByDef3(Py_TYPE(left), Py_TYPE(right), Py_TYPE(modulus),
+                                            &_decimal_module);
+    assert(mod != NULL);
+    return get_module_state(mod);
 }
 
 

Objects/typeobject.c

@@ -5038,6 +5038,26 @@ _PyType_GetModuleByDef2(PyTypeObject *left, PyTypeObject *right,
     return module;
 }
 
+PyObject *
+_PyType_GetModuleByDef3(PyTypeObject *left, PyTypeObject *right, PyTypeObject *third,
+                        PyModuleDef *def)
+{
+    PyObject *module = get_module_by_def(left, def);
+    if (module == NULL) {
+        module = get_module_by_def(right, def);
+        if (module == NULL) {
+            module = get_module_by_def(third, def);
+            if (module == NULL) {
+                PyErr_Format(
+                    PyExc_TypeError,
+                    "PyType_GetModuleByDef: No superclass of '%s', '%s' nor '%s' has "
+                    "the given module", left->tp_name, right->tp_name, third->tp_name);
+            }
+        }
+    }
+    return module;
+}
+
 void *
 PyObject_GetTypeData(PyObject *obj, PyTypeObject *cls)
 {