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Make weak references subclassable:
- weakref.ref and weakref.ReferenceType will become aliases for each other - weakref.ref will be a modern, new-style class with proper __new__ and __init__ methods - weakref.WeakValueDictionary will have a lighter memory footprint, using a new weakref.ref subclass to associate the key with the value, allowing us to have only a single object of overhead for each dictionary entry (currently, there are 3 objects of overhead per entry: a weakref to the value, a weakref to the dictionary, and a function object used as a weakref callback; the weakref to the dictionary could be avoided without this change) - a new macro, PyWeakref_CheckRefExact(), will be added - PyWeakref_CheckRef() will check for subclasses of weakref.ref This closes SF patch #983019.
This commit is contained in:
Fred Drake
parent
813914049d
commit
0a4dd390bf
8 changed files with 338 additions and 109 deletions
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@ -19,6 +19,15 @@ _PyWeakref_GetWeakrefCount(PyWeakReference *head)
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}
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static void
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init_weakref(PyWeakReference *self, PyObject *ob, PyObject *callback)
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{
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self->hash = -1;
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self->wr_object = ob;
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Py_XINCREF(callback);
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self->wr_callback = callback;
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}
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static PyWeakReference *
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new_weakref(PyObject *ob, PyObject *callback)
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{
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@ -26,10 +35,7 @@ new_weakref(PyObject *ob, PyObject *callback)
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result = PyObject_GC_New(PyWeakReference, &_PyWeakref_RefType);
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if (result) {
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result->hash = -1;
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result->wr_object = ob;
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Py_XINCREF(callback);
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result->wr_callback = callback;
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init_weakref(result, ob, callback);
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PyObject_GC_Track(result);
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}
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return result;
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@ -92,11 +98,11 @@ _PyWeakref_ClearRef(PyWeakReference *self)
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}
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static void
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weakref_dealloc(PyWeakReference *self)
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weakref_dealloc(PyObject *self)
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{
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PyObject_GC_UnTrack((PyObject *)self);
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clear_weakref(self);
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PyObject_GC_Del(self);
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PyObject_GC_UnTrack(self);
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clear_weakref((PyWeakReference *) self);
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self->ob_type->tp_free(self);
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}
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@ -193,6 +199,134 @@ weakref_richcompare(PyWeakReference* self, PyWeakReference* other, int op)
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PyWeakref_GET_OBJECT(other), op);
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}
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/* Given the head of an object's list of weak references, extract the
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* two callback-less refs (ref and proxy). Used to determine if the
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* shared references exist and to determine the back link for newly
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* inserted references.
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*/
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static void
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get_basic_refs(PyWeakReference *head,
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PyWeakReference **refp, PyWeakReference **proxyp)
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{
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*refp = NULL;
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*proxyp = NULL;
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if (head != NULL && head->wr_callback == NULL) {
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/* We need to be careful that the "basic refs" aren't
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subclasses of the main types. That complicates this a
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little. */
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if (PyWeakref_CheckRefExact(head)) {
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*refp = head;
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head = head->wr_next;
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}
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if (head != NULL
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&& head->wr_callback == NULL
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&& PyWeakref_CheckProxy(head)) {
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*proxyp = head;
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/* head = head->wr_next; */
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}
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}
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}
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/* Insert 'newref' in the list after 'prev'. Both must be non-NULL. */
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static void
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insert_after(PyWeakReference *newref, PyWeakReference *prev)
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{
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newref->wr_prev = prev;
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newref->wr_next = prev->wr_next;
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if (prev->wr_next != NULL)
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prev->wr_next->wr_prev = newref;
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prev->wr_next = newref;
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}
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/* Insert 'newref' at the head of the list; 'list' points to the variable
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* that stores the head.
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*/
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static void
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insert_head(PyWeakReference *newref, PyWeakReference **list)
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{
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PyWeakReference *next = *list;
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newref->wr_prev = NULL;
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newref->wr_next = next;
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if (next != NULL)
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next->wr_prev = newref;
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*list = newref;
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}
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static int
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parse_weakref_init_args(char *funcname, PyObject *args, PyObject *kwargs,
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PyObject **obp, PyObject **callbackp)
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{
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/* XXX Should check that kwargs == NULL or is empty. */
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return PyArg_UnpackTuple(args, funcname, 1, 2, obp, callbackp);
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}
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static PyObject *
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weakref___new__(PyTypeObject *type, PyObject *args, PyObject *kwargs)
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{
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PyWeakReference *self = NULL;
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PyObject *ob, *callback = NULL;
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if (parse_weakref_init_args("__new__", args, kwargs, &ob, &callback)) {
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PyWeakReference *ref, *proxy;
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PyWeakReference **list;
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if (!PyType_SUPPORTS_WEAKREFS(ob->ob_type)) {
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PyErr_Format(PyExc_TypeError,
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"cannot create weak reference to '%s' object",
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ob->ob_type->tp_name);
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return NULL;
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}
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if (callback == Py_None)
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callback = NULL;
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list = GET_WEAKREFS_LISTPTR(ob);
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get_basic_refs(*list, &ref, &proxy);
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if (callback == NULL && type == &_PyWeakref_RefType) {
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if (ref != NULL) {
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/* We can re-use an existing reference. */
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Py_INCREF(ref);
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return (PyObject *)ref;
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}
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}
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/* We have to create a new reference. */
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/* Note: the tp_alloc() can trigger cyclic GC, so the weakref
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list on ob can be mutated. This means that the ref and
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proxy pointers we got back earlier may have been collected,
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so we need to compute these values again before we use
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them. */
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self = (PyWeakReference *) (type->tp_alloc(type, 0));
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if (self != NULL) {
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init_weakref(self, ob, callback);
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if (callback == NULL && type == &_PyWeakref_RefType) {
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insert_head(self, list);
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}
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else {
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PyWeakReference *prev;
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get_basic_refs(*list, &ref, &proxy);
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prev = (proxy == NULL) ? ref : proxy;
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if (prev == NULL)
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insert_head(self, list);
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else
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insert_after(self, prev);
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}
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}
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}
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return (PyObject *)self;
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}
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static int
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weakref___init__(PyObject *self, PyObject *args, PyObject *kwargs)
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{
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PyObject *tmp;
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if (parse_weakref_init_args("__init__", args, kwargs, &tmp, &tmp))
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return 0;
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else
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return 1;
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}
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PyTypeObject
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_PyWeakref_RefType = {
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@ -201,7 +335,7 @@ _PyWeakref_RefType = {
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"weakref",
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sizeof(PyWeakReference),
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0,
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(destructor)weakref_dealloc,/*tp_dealloc*/
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weakref_dealloc, /*tp_dealloc*/
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0, /*tp_print*/
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0, /*tp_getattr*/
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0, /*tp_setattr*/
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@ -210,18 +344,33 @@ _PyWeakref_RefType = {
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0, /*tp_as_number*/
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0, /*tp_as_sequence*/
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0, /*tp_as_mapping*/
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(hashfunc)weakref_hash, /*tp_hash*/
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(hashfunc)weakref_hash, /*tp_hash*/
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(ternaryfunc)weakref_call, /*tp_call*/
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0, /*tp_str*/
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0, /*tp_getattro*/
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0, /*tp_setattro*/
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0, /*tp_as_buffer*/
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_RICHCOMPARE,
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_RICHCOMPARE
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| Py_TPFLAGS_BASETYPE, /*tp_flags*/
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0, /*tp_doc*/
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(traverseproc)gc_traverse, /*tp_traverse*/
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(inquiry)gc_clear, /*tp_clear*/
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(richcmpfunc)weakref_richcompare, /*tp_richcompare*/
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0, /*tp_weaklistoffset*/
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0, /*tp_weaklistoffset*/
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0, /*tp_iter*/
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0, /*tp_iternext*/
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0, /*tp_methods*/
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0, /*tp_members*/
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0, /*tp_getset*/
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0, /*tp_base*/
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0, /*tp_dict*/
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0, /*tp_descr_get*/
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0, /*tp_descr_set*/
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0, /*tp_dictoffset*/
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(initproc)weakref___init__, /*tp_init*/
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PyType_GenericAlloc, /*tp_alloc*/
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weakref___new__, /*tp_new*/
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PyObject_GC_Del, /*tp_free*/
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};
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@ -363,6 +512,15 @@ proxy_nonzero(PyWeakReference *proxy)
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return 1;
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}
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static void
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proxy_dealloc(PyWeakReference *self)
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{
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if (self->wr_callback != NULL)
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PyObject_GC_UnTrack((PyObject *)self);
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clear_weakref(self);
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PyObject_GC_Del(self);
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}
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/* sequence slots */
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static PyObject *
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@ -496,7 +654,7 @@ _PyWeakref_ProxyType = {
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sizeof(PyWeakReference),
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0,
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/* methods */
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(destructor)weakref_dealloc, /* tp_dealloc */
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(destructor)proxy_dealloc, /* tp_dealloc */
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0, /* tp_print */
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0, /* tp_getattr */
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0, /* tp_setattr */
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@ -531,7 +689,7 @@ _PyWeakref_CallableProxyType = {
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sizeof(PyWeakReference),
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0,
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/* methods */
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(destructor)weakref_dealloc, /* tp_dealloc */
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(destructor)proxy_dealloc, /* tp_dealloc */
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0, /* tp_print */
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0, /* tp_getattr */
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0, /* tp_setattr */
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@ -558,56 +716,6 @@ _PyWeakref_CallableProxyType = {
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};
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/* Given the head of an object's list of weak references, extract the
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* two callback-less refs (ref and proxy). Used to determine if the
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* shared references exist and to determine the back link for newly
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* inserted references.
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*/
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static void
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get_basic_refs(PyWeakReference *head,
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PyWeakReference **refp, PyWeakReference **proxyp)
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{
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*refp = NULL;
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*proxyp = NULL;
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if (head != NULL && head->wr_callback == NULL) {
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if (head->ob_type == &_PyWeakref_RefType) {
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*refp = head;
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head = head->wr_next;
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}
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if (head != NULL && head->wr_callback == NULL) {
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*proxyp = head;
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head = head->wr_next;
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}
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}
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}
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/* Insert 'newref' in the list after 'prev'. Both must be non-NULL. */
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static void
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insert_after(PyWeakReference *newref, PyWeakReference *prev)
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{
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newref->wr_prev = prev;
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newref->wr_next = prev->wr_next;
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if (prev->wr_next != NULL)
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prev->wr_next->wr_prev = newref;
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prev->wr_next = newref;
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}
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/* Insert 'newref' at the head of the list; 'list' points to the variable
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* that stores the head.
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*/
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static void
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insert_head(PyWeakReference *newref, PyWeakReference **list)
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{
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PyWeakReference *next = *list;
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newref->wr_prev = NULL;
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newref->wr_next = next;
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if (next != NULL)
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next->wr_prev = newref;
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*list = newref;
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}
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PyObject *
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PyWeakref_NewRef(PyObject *ob, PyObject *callback)
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@ -769,8 +877,10 @@ PyObject_ClearWeakRefs(PyObject *object)
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current->wr_callback = NULL;
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clear_weakref(current);
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handle_callback(current, callback);
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Py_DECREF(callback);
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if (callback != NULL) {
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handle_callback(current, callback);
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Py_DECREF(callback);
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}
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}
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else {
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PyObject *tuple = PyTuple_New(count * 2);
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@ -787,10 +897,12 @@ PyObject_ClearWeakRefs(PyObject *object)
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current = next;
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}
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for (i = 0; i < count; ++i) {
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PyObject *current = PyTuple_GET_ITEM(tuple, i * 2);
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PyObject *callback = PyTuple_GET_ITEM(tuple, i * 2 + 1);
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handle_callback((PyWeakReference *)current, callback);
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if (callback != NULL) {
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PyObject *current = PyTuple_GET_ITEM(tuple, i * 2);
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handle_callback((PyWeakReference *)current, callback);
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}
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}
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Py_DECREF(tuple);
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}
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