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authorTim Peters <tim.peters@gmail.com>2002-11-12 22:08:10 (GMT)
committerTim Peters <tim.peters@gmail.com>2002-11-12 22:08:10 (GMT)
commitb9099c3df495d4bf0090d7a751325343852b61db (patch)
tree02605a750bc4b07c663d01ee61cc75755ab26c67 /Objects/listobject.c
parent4b9ed2f346921353b34a99332d9efd6ddce3a28b (diff)
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SF patch 637176: list.sort crasher
Armin Rigo's Draconian but effective fix for SF bug 453523: list.sort crasher slightly fiddled to catch more cases of list mutation. The dreaded internal "immutable list type" is gone! OTOH, if you look at a list *while* it's being sorted now, it will appear to be empty. Better than a core dump.
Diffstat (limited to 'Objects/listobject.c')
-rw-r--r--Objects/listobject.c125
1 files changed, 29 insertions, 96 deletions
diff --git a/Objects/listobject.c b/Objects/listobject.c
index bee284d..3e3b4d7 100644
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -1634,8 +1634,6 @@ merge_compute_minrun(int n)
return n + r;
}
-static PyTypeObject immutable_list_type;
-
/* An adaptive, stable, natural mergesort. See listsort.txt.
* Returns Py_None on success, NULL on error. Even in case of error, the
* list will be some permutation of its input state (nothing is lost or
@@ -1648,7 +1646,9 @@ listsort(PyListObject *self, PyObject *args)
PyObject **lo, **hi;
int nremaining;
int minrun;
- PyTypeObject *savetype;
+ int saved_ob_size;
+ PyObject **saved_ob_item;
+ PyObject **empty_ob_item;
PyObject *compare = NULL;
PyObject *result = NULL; /* guilty until proved innocent */
@@ -1659,17 +1659,24 @@ listsort(PyListObject *self, PyObject *args)
}
merge_init(&ms, compare);
- savetype = self->ob_type;
- self->ob_type = &immutable_list_type;
+ /* The list is temporarily made empty, so that mutations performed
+ * by comparison functions can't affect the slice of memory we're
+ * sorting (allowing mutations during sorting is a core-dump
+ * factory, since ob_item may change).
+ */
+ saved_ob_size = self->ob_size;
+ saved_ob_item = self->ob_item;
+ self->ob_size = 0;
+ self->ob_item = empty_ob_item = PyMem_NEW(PyObject *, 0);
- nremaining = self->ob_size;
+ nremaining = saved_ob_size;
if (nremaining < 2)
goto succeed;
/* March over the array once, left to right, finding natural runs,
* and extending short natural runs to minrun elements.
*/
- lo = self->ob_item;
+ lo = saved_ob_item;
hi = lo + nremaining;
minrun = merge_compute_minrun(nremaining);
do {
@@ -1706,13 +1713,25 @@ listsort(PyListObject *self, PyObject *args)
if (merge_force_collapse(&ms) < 0)
goto fail;
assert(ms.n == 1);
- assert(ms.pending[0].base == self->ob_item);
- assert(ms.pending[0].len == self->ob_size);
+ assert(ms.pending[0].base == saved_ob_item);
+ assert(ms.pending[0].len == saved_ob_size);
succeed:
result = Py_None;
fail:
- self->ob_type = savetype;
+ if (self->ob_item != empty_ob_item || self->ob_size) {
+ /* The user mucked with the list during the sort. */
+ (void)list_ass_slice(self, 0, self->ob_size, (PyObject *)NULL);
+ if (result != NULL) {
+ PyErr_SetString(PyExc_ValueError,
+ "list modified during sort");
+ result = NULL;
+ }
+ }
+ if (self->ob_item == empty_ob_item)
+ PyMem_FREE(empty_ob_item);
+ self->ob_size = saved_ob_size;
+ self->ob_item = saved_ob_item;
merge_freemem(&ms);
Py_XINCREF(result);
return result;
@@ -2328,92 +2347,6 @@ PyTypeObject PyList_Type = {
};
-/* During a sort, we really can't have anyone modifying the list; it could
- cause core dumps. Thus, we substitute a dummy type that raises an
- explanatory exception when a modifying operation is used. Caveat:
- comparisons may behave differently; but I guess it's a bad idea anyway to
- compare a list that's being sorted... */
-
-static PyObject *
-immutable_list_op(void)
-{
- PyErr_SetString(PyExc_TypeError,
- "a list cannot be modified while it is being sorted");
- return NULL;
-}
-
-static PyMethodDef immutable_list_methods[] = {
- {"append", (PyCFunction)immutable_list_op, METH_VARARGS},
- {"insert", (PyCFunction)immutable_list_op, METH_VARARGS},
- {"extend", (PyCFunction)immutable_list_op, METH_O},
- {"pop", (PyCFunction)immutable_list_op, METH_VARARGS},
- {"remove", (PyCFunction)immutable_list_op, METH_VARARGS},
- {"index", (PyCFunction)listindex, METH_O},
- {"count", (PyCFunction)listcount, METH_O},
- {"reverse", (PyCFunction)immutable_list_op, METH_VARARGS},
- {"sort", (PyCFunction)immutable_list_op, METH_VARARGS},
- {NULL, NULL} /* sentinel */
-};
-
-static int
-immutable_list_ass(void)
-{
- immutable_list_op();
- return -1;
-}
-
-static PySequenceMethods immutable_list_as_sequence = {
- (inquiry)list_length, /* sq_length */
- (binaryfunc)list_concat, /* sq_concat */
- (intargfunc)list_repeat, /* sq_repeat */
- (intargfunc)list_item, /* sq_item */
- (intintargfunc)list_slice, /* sq_slice */
- (intobjargproc)immutable_list_ass, /* sq_ass_item */
- (intintobjargproc)immutable_list_ass, /* sq_ass_slice */
- (objobjproc)list_contains, /* sq_contains */
-};
-
-static PyTypeObject immutable_list_type = {
- PyObject_HEAD_INIT(&PyType_Type)
- 0,
- "list (immutable, during sort)",
- sizeof(PyListObject),
- 0,
- 0, /* Cannot happen */ /* tp_dealloc */
- (printfunc)list_print, /* tp_print */
- 0, /* tp_getattr */
- 0, /* tp_setattr */
- 0, /* Won't be called */ /* tp_compare */
- (reprfunc)list_repr, /* tp_repr */
- 0, /* tp_as_number */
- &immutable_list_as_sequence, /* tp_as_sequence */
- 0, /* tp_as_mapping */
- list_nohash, /* tp_hash */
- 0, /* tp_call */
- 0, /* tp_str */
- PyObject_GenericGetAttr, /* tp_getattro */
- 0, /* tp_setattro */
- 0, /* tp_as_buffer */
- Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
- list_doc, /* tp_doc */
- (traverseproc)list_traverse, /* tp_traverse */
- 0, /* tp_clear */
- list_richcompare, /* tp_richcompare */
- 0, /* tp_weaklistoffset */
- 0, /* tp_iter */
- 0, /* tp_iternext */
- immutable_list_methods, /* tp_methods */
- 0, /* tp_members */
- 0, /* tp_getset */
- 0, /* tp_base */
- 0, /* tp_dict */
- 0, /* tp_descr_get */
- 0, /* tp_descr_set */
- 0, /* tp_init */
- /* NOTE: This is *not* the standard list_type struct! */
-};
-
-
/*********************** List Iterator **************************/
typedef struct {