mirror of https://github.com/python/cpython
Issue #17936: Fix O(n**2) behaviour when adding or removing many subclasses of a given type.
This commit is contained in:
Antoine Pitrou
parent
dc6b933d23
commit
84745ab464
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@ -10,6 +10,9 @@ Projected release date: 2013-11-24
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Core and Builtins
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-----------------
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- Issue #17936: Fix O(n**2) behaviour when adding or removing many subclasses
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of a given type.
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- Issue #19428: zipimport now handles errors when reading truncated or invalid
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ZIP archive.
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@ -101,16 +101,17 @@ PyType_Modified(PyTypeObject *type)
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needed.
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*/
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PyObject *raw, *ref;
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Py_ssize_t i, n;
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Py_ssize_t i;
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if (!PyType_HasFeature(type, Py_TPFLAGS_VALID_VERSION_TAG))
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return;
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raw = type->tp_subclasses;
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if (raw != NULL) {
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n = PyList_GET_SIZE(raw);
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for (i = 0; i < n; i++) {
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ref = PyList_GET_ITEM(raw, i);
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assert(PyDict_CheckExact(raw));
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i = 0;
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while (PyDict_Next(raw, &i, NULL, &ref)) {
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assert(PyWeakref_CheckRef(ref));
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ref = PyWeakref_GET_OBJECT(ref);
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if (ref != Py_None) {
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PyType_Modified((PyTypeObject *)ref);
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@ -435,6 +436,7 @@ static int mro_internal(PyTypeObject *);
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static int compatible_for_assignment(PyTypeObject *, PyTypeObject *, char *);
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static int add_subclass(PyTypeObject*, PyTypeObject*);
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static void remove_subclass(PyTypeObject *, PyTypeObject *);
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static void remove_all_subclasses(PyTypeObject *type, PyObject *bases);
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static void update_all_slots(PyTypeObject *);
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typedef int (*update_callback)(PyTypeObject *, void *);
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@ -448,15 +450,15 @@ mro_subclasses(PyTypeObject *type, PyObject* temp)
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{
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PyTypeObject *subclass;
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PyObject *ref, *subclasses, *old_mro;
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Py_ssize_t i, n;
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Py_ssize_t i;
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subclasses = type->tp_subclasses;
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if (subclasses == NULL)
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return 0;
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assert(PyList_Check(subclasses));
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n = PyList_GET_SIZE(subclasses);
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for (i = 0; i < n; i++) {
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ref = PyList_GET_ITEM(subclasses, i);
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assert(PyDict_CheckExact(subclasses));
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i = 0;
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while (PyDict_Next(subclasses, &i, NULL, &ref)) {
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assert(PyWeakref_CheckRef(ref));
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subclass = (PyTypeObject *)PyWeakref_GET_OBJECT(ref);
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assert(subclass != NULL);
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@ -575,13 +577,7 @@ type_set_bases(PyTypeObject *type, PyObject *value, void *context)
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/* for now, sod that: just remove from all old_bases,
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add to all new_bases */
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for (i = PyTuple_GET_SIZE(old_bases) - 1; i >= 0; i--) {
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ob = PyTuple_GET_ITEM(old_bases, i);
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if (PyType_Check(ob)) {
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remove_subclass(
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(PyTypeObject*)ob, type);
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}
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}
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remove_all_subclasses(type, old_bases);
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for (i = PyTuple_GET_SIZE(value) - 1; i >= 0; i--) {
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ob = PyTuple_GET_ITEM(value, i);
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@ -2733,10 +2729,14 @@ static void
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type_dealloc(PyTypeObject *type)
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{
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PyHeapTypeObject *et;
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PyObject *tp, *val, *tb;
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/* Assert this is a heap-allocated type object */
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assert(type->tp_flags & Py_TPFLAGS_HEAPTYPE);
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_PyObject_GC_UNTRACK(type);
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PyErr_Fetch(&tp, &val, &tb);
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remove_all_subclasses(type, type->tp_bases);
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PyErr_Restore(tp, val, tb);
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PyObject_ClearWeakRefs((PyObject *)type);
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et = (PyHeapTypeObject *)type;
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Py_XDECREF(type->tp_base);
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@ -2761,7 +2761,7 @@ static PyObject *
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type_subclasses(PyTypeObject *type, PyObject *args_ignored)
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{
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PyObject *list, *raw, *ref;
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Py_ssize_t i, n;
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Py_ssize_t i;
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list = PyList_New(0);
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if (list == NULL)
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@ -2769,10 +2769,9 @@ type_subclasses(PyTypeObject *type, PyObject *args_ignored)
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raw = type->tp_subclasses;
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if (raw == NULL)
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return list;
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assert(PyList_Check(raw));
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n = PyList_GET_SIZE(raw);
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for (i = 0; i < n; i++) {
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ref = PyList_GET_ITEM(raw, i);
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assert(PyDict_CheckExact(raw));
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i = 0;
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while (PyDict_Next(raw, &i, NULL, &ref)) {
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assert(PyWeakref_CheckRef(ref));
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ref = PyWeakref_GET_OBJECT(ref);
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if (ref != Py_None) {
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@ -2961,8 +2960,8 @@ type_clear(PyTypeObject *type)
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class's dict; the cycle will be broken that way.
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tp_subclasses:
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A list of weak references can't be part of a cycle; and
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lists have their own tp_clear.
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A dict of weak references can't be part of a cycle; and
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dicts have their own tp_clear.
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slots (in PyHeapTypeObject):
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A tuple of strings can't be part of a cycle.
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@ -4353,51 +4352,57 @@ PyType_Ready(PyTypeObject *type)
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static int
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add_subclass(PyTypeObject *base, PyTypeObject *type)
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{
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Py_ssize_t i;
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int result;
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PyObject *list, *ref, *newobj;
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int result = -1;
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PyObject *dict, *key, *newobj;
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list = base->tp_subclasses;
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if (list == NULL) {
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base->tp_subclasses = list = PyList_New(0);
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if (list == NULL)
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dict = base->tp_subclasses;
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if (dict == NULL) {
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base->tp_subclasses = dict = PyDict_New();
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if (dict == NULL)
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return -1;
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}
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assert(PyList_Check(list));
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assert(PyDict_CheckExact(dict));
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key = PyLong_FromVoidPtr((void *) type);
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if (key == NULL)
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return -1;
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newobj = PyWeakref_NewRef((PyObject *)type, NULL);
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if (newobj == NULL)
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return -1;
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i = PyList_GET_SIZE(list);
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while (--i >= 0) {
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ref = PyList_GET_ITEM(list, i);
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assert(PyWeakref_CheckRef(ref));
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if (PyWeakref_GET_OBJECT(ref) == Py_None)
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return PyList_SetItem(list, i, newobj);
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}
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result = PyList_Append(list, newobj);
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if (newobj != NULL) {
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result = PyDict_SetItem(dict, key, newobj);
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Py_DECREF(newobj);
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}
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Py_DECREF(key);
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return result;
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}
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static void
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remove_subclass(PyTypeObject *base, PyTypeObject *type)
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{
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Py_ssize_t i;
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PyObject *list, *ref;
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PyObject *dict, *key;
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list = base->tp_subclasses;
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if (list == NULL) {
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dict = base->tp_subclasses;
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if (dict == NULL) {
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return;
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}
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assert(PyList_Check(list));
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i = PyList_GET_SIZE(list);
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while (--i >= 0) {
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ref = PyList_GET_ITEM(list, i);
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assert(PyWeakref_CheckRef(ref));
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if (PyWeakref_GET_OBJECT(ref) == (PyObject*)type) {
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/* this can't fail, right? */
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PySequence_DelItem(list, i);
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return;
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assert(PyDict_CheckExact(dict));
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key = PyLong_FromVoidPtr((void *) type);
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if (key == NULL || PyDict_DelItem(dict, key)) {
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/* This can happen if the type initialization errored out before
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the base subclasses were updated (e.g. a non-str __qualname__
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was passed in the type dict). */
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PyErr_Clear();
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}
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Py_XDECREF(key);
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}
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static void
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remove_all_subclasses(PyTypeObject *type, PyObject *bases)
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{
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if (bases) {
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Py_ssize_t i;
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for (i = 0; i < PyTuple_GET_SIZE(bases); i++) {
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PyObject *base = PyTuple_GET_ITEM(bases, i);
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if (PyType_Check(base))
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remove_subclass((PyTypeObject*) base, type);
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}
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}
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}
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@ -6173,15 +6178,14 @@ recurse_down_subclasses(PyTypeObject *type, PyObject *name,
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{
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PyTypeObject *subclass;
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PyObject *ref, *subclasses, *dict;
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Py_ssize_t i, n;
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Py_ssize_t i;
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subclasses = type->tp_subclasses;
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if (subclasses == NULL)
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return 0;
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assert(PyList_Check(subclasses));
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n = PyList_GET_SIZE(subclasses);
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for (i = 0; i < n; i++) {
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ref = PyList_GET_ITEM(subclasses, i);
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assert(PyDict_CheckExact(subclasses));
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i = 0;
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while (PyDict_Next(subclasses, &i, NULL, &ref)) {
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assert(PyWeakref_CheckRef(ref));
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subclass = (PyTypeObject *)PyWeakref_GET_OBJECT(ref);
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assert(subclass != NULL);
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