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Issue 2235: __hash__ is once again inherited by default, but inheritance can be blocked explicitly so that collections.Hashable remains meaningful

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Nick Coghlan 2008-07-15 14:27:37 +00:00
parent 9ace15ca25
commit 53663a695e
14 changed files with 134 additions and 134 deletions
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68
Objects/typeobject.c
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@ -3648,27 +3648,6 @@ inherit_special(PyTypeObject *type, PyTypeObject *base)
type->tp_flags |= Py_TPFLAGS_DICT_SUBCLASS;
}
static char *hash_name_op[] = {
"__eq__",
"__cmp__",
"__hash__",
NULL
};
static int
overrides_hash(PyTypeObject *type)
{
char **p;
PyObject *dict = type->tp_dict;
assert(dict != NULL);
for (p = hash_name_op; *p; p++) {
if (PyDict_GetItemString(dict, *p) != NULL)
return 1;
}
return 0;
}
static void
inherit_slots(PyTypeObject *type, PyTypeObject *base)
{
@ -3802,8 +3781,7 @@ inherit_slots(PyTypeObject *type, PyTypeObject *base)
if (type->tp_flags & base->tp_flags & Py_TPFLAGS_HAVE_RICHCOMPARE) {
if (type->tp_compare == NULL &&
type->tp_richcompare == NULL &&
type->tp_hash == NULL &&
!overrides_hash(type))
type->tp_hash == NULL)
{
type->tp_compare = base->tp_compare;
type->tp_richcompare = base->tp_richcompare;
@ -3984,18 +3962,6 @@ PyType_Ready(PyTypeObject *type)
}
}
/* Hack for tp_hash and __hash__.
If after all that, tp_hash is still NULL, and __hash__ is not in
tp_dict, set tp_dict['__hash__'] equal to None.
This signals that __hash__ is not inherited.
*/
if (type->tp_hash == NULL &&
PyDict_GetItemString(type->tp_dict, "__hash__") == NULL &&
PyDict_SetItemString(type->tp_dict, "__hash__", Py_None) < 0)
{
goto error;
}
/* Some more special stuff */
base = type->tp_base;
if (base != NULL) {
@ -5280,10 +5246,8 @@ slot_tp_hash(PyObject *self)
func = lookup_method(self, "__cmp__", &cmp_str);
}
if (func != NULL) {
PyErr_Format(PyExc_TypeError, "unhashable type: '%.200s'",
self->ob_type->tp_name);
Py_DECREF(func);
return -1;
return PyObject_HashNotImplemented(self);
}
PyErr_Clear();
h = _Py_HashPointer((void *)self);
@ -6034,6 +5998,13 @@ update_one_slot(PyTypeObject *type, slotdef *p)
sanity checks. I'll buy the first person to
point out a bug in this reasoning a beer. */
}
else if (descr == Py_None &&
strcmp(p->name, "__hash__") == 0) {
/* We specifically allow __hash__ to be set to None
to prevent inheritance of the default
implementation from object.__hash__ */
specific = PyObject_HashNotImplemented;
}
else {
use_generic = 1;
generic = p->function;
@ -6247,12 +6218,21 @@ add_operators(PyTypeObject *type)
continue;
if (PyDict_GetItem(dict, p->name_strobj))
continue;
descr = PyDescr_NewWrapper(type, p, *ptr);
if (descr == NULL)
return -1;
if (PyDict_SetItem(dict, p->name_strobj, descr) < 0)
return -1;
Py_DECREF(descr);
if (*ptr == PyObject_HashNotImplemented) {
/* Classes may prevent the inheritance of the tp_hash
slot by storing PyObject_HashNotImplemented in it. Make it
visible as a None value for the __hash__ attribute. */
if (PyDict_SetItem(dict, p->name_strobj, Py_None) < 0)
return -1;
}
else {
descr = PyDescr_NewWrapper(type, p, *ptr);
if (descr == NULL)
return -1;
if (PyDict_SetItem(dict, p->name_strobj, descr) < 0)
return -1;
Py_DECREF(descr);
}
}
if (type->tp_new != NULL) {
if (add_tp_new_wrapper(type) < 0)