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| author | Guido van Rossum <guido@python.org> | 2001-12-03 16:32:18 (GMT) |
|---|---|---|
| committer | Guido van Rossum <guido@python.org> | 2001-12-03 16:32:18 (GMT) |
| commit | dbb53d99189075522eecc87723292c85aee15388 (patch) | |
| tree | 1131490f1290ba22acf8505c9d1e7aa25308336b /Objects/listobject.c | |
| parent | cb33165ca2f8c1493b511bb7b38b44ede4211280 (diff) | |
| download | cpython-dbb53d99189075522eecc87723292c85aee15388.zip cpython-dbb53d99189075522eecc87723292c85aee15388.tar.gz cpython-dbb53d99189075522eecc87723292c85aee15388.tar.bz2 | |
Fix of SF bug #475877 (Mutable subtype instances are hashable).
Rather than tweaking the inheritance of type object slots (which turns
out to be too messy to try), this fix adds a __hash__ to the list and
dict types (the only mutable types I'm aware of) that explicitly
raises an error. This has the advantage that list.__hash__([]) also
raises an error (previously, this would invoke object.__hash__([]),
returning the argument's address); ditto for dict.__hash__.
The disadvantage for this fix is that 3rd party mutable types aren't
automatically fixed. This should be added to the rules for creating
subclassable extension types: if you don't want your object to be
hashable, add a tp_hash function that raises an exception.
Also, it's possible that I've forgotten about other mutable types for
which this should be done.
Diffstat (limited to 'Objects/listobject.c')
| -rw-r--r-- | Objects/listobject.c | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/Objects/listobject.c b/Objects/listobject.c index b05fe27..dbbc4a9 100644 --- a/Objects/listobject.c +++ b/Objects/listobject.c @@ -1617,6 +1617,13 @@ list_init(PyListObject *self, PyObject *args, PyObject *kw) return 0; } +static long +list_nohash(PyObject *self) +{ + PyErr_SetString(PyExc_TypeError, "list objects are unhashable"); + return -1; +} + static char append_doc[] = "L.append(object) -- append object to end"; static char extend_doc[] = @@ -1681,7 +1688,7 @@ PyTypeObject PyList_Type = { 0, /* tp_as_number */ &list_as_sequence, /* tp_as_sequence */ 0, /* tp_as_mapping */ - 0, /* tp_hash */ + list_nohash, /* tp_hash */ 0, /* tp_call */ 0, /* tp_str */ PyObject_GenericGetAttr, /* tp_getattro */ @@ -1771,7 +1778,7 @@ static PyTypeObject immutable_list_type = { 0, /* tp_as_number */ &immutable_list_as_sequence, /* tp_as_sequence */ 0, /* tp_as_mapping */ - 0, /* tp_hash */ + list_nohash, /* tp_hash */ 0, /* tp_call */ 0, /* tp_str */ PyObject_GenericGetAttr, /* tp_getattro */ |