diff options
| -rw-r--r-- | Lib/test/test_builtin.py | 17 | ||||
| -rw-r--r-- | Misc/NEWS | 6 | ||||
| -rw-r--r-- | Objects/stringobject.c | 34 | ||||
| -rw-r--r-- | Python/bltinmodule.c | 5 |
4 files changed, 40 insertions, 22 deletions
diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py index bc5afdc..8e3a925 100644 --- a/Lib/test/test_builtin.py +++ b/Lib/test/test_builtin.py @@ -608,6 +608,23 @@ class BuiltinTest(unittest.TestCase): s2 = s.swapcase().swapcase() self.assert_(intern(s2) is s) + # Subclasses of string can't be interned, because they + # provide too much opportunity for insane things to happen. + # We don't want them in the interned dict and if they aren't + # actually interned, we don't want to create the appearance + # that they are by allowing intern() to succeeed. + class S(str): + def __hash__(self): + return 123 + + self.assertRaises(TypeError, intern, S("abc")) + + # It's still safe to pass these strings to routines that + # call intern internally, e.g. PyObject_SetAttr(). + s = S("abc") + setattr(s, s, s) + self.assertEqual(getattr(s, s), s) + def test_iter(self): self.assertRaises(TypeError, iter) self.assertRaises(TypeError, iter, 42, 42) @@ -12,6 +12,12 @@ What's New in Python 2.4 alpha 3? Core and builtins ----------------- +Subclasses of string can no longer be interned. The semantics of +interning were not clear here -- a subclass could be mutable, for +example -- and had bugs. Explicitly interning a subclass of string +via intern() will raise a TypeError. Internal operations that attempt +to intern a string subclass will have no effect. + Extension modules ----------------- diff --git a/Objects/stringobject.c b/Objects/stringobject.c index 29562a9..f29929b 100644 --- a/Objects/stringobject.c +++ b/Objects/stringobject.c @@ -4313,6 +4313,10 @@ PyString_InternInPlace(PyObject **p) PyObject *t; if (s == NULL || !PyString_Check(s)) Py_FatalError("PyString_InternInPlace: strings only please!"); + /* If it's a string subclass, we don't really know what putting + it in the interned dict might do. */ + if (!PyString_CheckExact(s)) + return; if (PyString_CHECK_INTERNED(s)) return; if (interned == NULL) { @@ -4322,36 +4326,22 @@ PyString_InternInPlace(PyObject **p) return; } } - if ((t = PyDict_GetItem(interned, (PyObject *)s)) != NULL) { + t = PyDict_GetItem(interned, (PyObject *)s); + if (t) { Py_INCREF(t); Py_DECREF(*p); *p = t; return; } - /* Ensure that only true string objects appear in the intern dict */ - if (!PyString_CheckExact(s)) { - t = PyString_FromStringAndSize(PyString_AS_STRING(s), - PyString_GET_SIZE(s)); - if (t == NULL) { - PyErr_Clear(); - return; - } - } else { - t = (PyObject*) s; - Py_INCREF(t); - } - if (PyDict_SetItem(interned, t, t) == 0) { - /* The two references in interned are not counted by - refcnt. The string deallocator will take care of this */ - ((PyObject *)t)->ob_refcnt-=2; - PyString_CHECK_INTERNED(t) = SSTATE_INTERNED_MORTAL; - Py_DECREF(*p); - *p = t; + if (PyDict_SetItem(interned, s, s) < 0) { + PyErr_Clear(); return; } - Py_DECREF(t); - PyErr_Clear(); + /* The two references in interned are not counted by refcnt. + The string deallocator will take care of this */ + (*p)->ob_refcnt -= 2; + PyString_CHECK_INTERNED(s) = SSTATE_INTERNED_MORTAL; } void diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c index 8ff733c..04fcf59 100644 --- a/Python/bltinmodule.c +++ b/Python/bltinmodule.c @@ -1035,6 +1035,11 @@ builtin_intern(PyObject *self, PyObject *args) PyObject *s; if (!PyArg_ParseTuple(args, "S:intern", &s)) return NULL; + if (!PyString_CheckExact(s)) { + PyErr_SetString(PyExc_TypeError, + "can't intern subclass of string"); + return NULL; + } Py_INCREF(s); PyString_InternInPlace(&s); return s; |