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bpo-42972: Fully implement GC protocol for functools keywrapper and partial types #26363

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Merged
vstinner merged 11 commits into from
May 28, 2021
Merged

bpo-42972: Fully implement GC protocol for functools keywrapper and partial types #26363

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8ef6e98
bpo-42972: Fully implement GC protocol for functools types
May 25, 2021
6d7cdaf
Address review
May 26, 2021
a15b49f
Address review: visit node type for each strong ref
May 27, 2021
0c8df1f
Address review: visit members in correct order
May 27, 2021
f9ac4c5
Address review: revert Py_CLEAR change in lru_list_elem_dealloc
May 27, 2021
fc39917
Revert LRU cache element optimisation
May 27, 2021
07f2182
Address review: revert redundant slot removal
May 27, 2021
0861788
Address review: use tp_free
May 27, 2021
7c2f750
Revert lru list elem clear fn
May 27, 2021
6313247
Revert "Revert LRU cache element optimisation"
May 28, 2021
1539195
Restore lru_cache_tp_traverse
May 28, 2021
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66 changes: 41 additions & 25 deletions Modules/_functoolsmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -147,18 +147,37 @@ partial_new(PyTypeObject *type, PyObject *args, PyObject *kw)
return (PyObject *)pto;
}

static int
partial_clear(partialobject *pto)
{
Py_CLEAR(pto->fn);
Py_CLEAR(pto->args);
Py_CLEAR(pto->kw);
Py_CLEAR(pto->dict);
return 0;
}

static int
partial_traverse(partialobject *pto, visitproc visit, void *arg)
{
Py_VISIT(pto->fn);
Py_VISIT(pto->args);
Py_VISIT(pto->kw);
Py_VISIT(pto->dict);
Py_VISIT(Py_TYPE(pto));
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@vstinner vstinner May 27, 2021

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I would prefer to always start by visiting the type in all traverse functions. So same remark for other traverse functions.

I like to look into partialobject structure and visit them by their definition order. Technically, ob_type is the first one :-D

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@erlend-aasland erlend-aasland May 27, 2021

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Sure, I'll apply to all remaining PR's :)

return 0;
}

static void
partial_dealloc(partialobject *pto)
{
PyTypeObject *tp = Py_TYPE(pto);
/* bpo-31095: UnTrack is needed before calling any callbacks */
PyObject_GC_UnTrack(pto);
if (pto->weakreflist != NULL)
if (pto->weakreflist != NULL) {
PyObject_ClearWeakRefs((PyObject *) pto);
Py_XDECREF(pto->fn);
Py_XDECREF(pto->args);
Py_XDECREF(pto->kw);
Py_XDECREF(pto->dict);
}
(void)partial_clear(pto);
tp->tp_free(pto);
Py_DECREF(tp);
}
Expand Down Expand Up @@ -307,16 +326,6 @@ partial_call(partialobject *pto, PyObject *args, PyObject *kwargs)
return res;
}

static int
partial_traverse(partialobject *pto, visitproc visit, void *arg)
{
Py_VISIT(pto->fn);
Py_VISIT(pto->args);
Py_VISIT(pto->kw);
Py_VISIT(pto->dict);
return 0;
}

PyDoc_STRVAR(partial_doc,
"partial(func, *args, **keywords) - new function with partial application\n\
of the given arguments and keywords.\n");
Expand Down Expand Up @@ -469,11 +478,11 @@ static PyType_Slot partial_type_slots[] = {
{Py_tp_setattro, PyObject_GenericSetAttr},
{Py_tp_doc, (void *)partial_doc},
{Py_tp_traverse, partial_traverse},
{Py_tp_clear, partial_clear},
{Py_tp_methods, partial_methods},
{Py_tp_members, partial_memberlist},
{Py_tp_getset, partial_getsetlist},
{Py_tp_new, partial_new},
{Py_tp_free, PyObject_GC_Del},
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@vstinner vstinner May 27, 2021

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Would it be possible to keep it and maybe only change that in 3.11 (in a separated PR)? Type inheritance is more complex than what it looks. See https://bugs.python.org/issue43770 for examples of bad surprised that I got when trying to use the default implementation of tp_getattro and tp_setattro.

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@erlend-aasland erlend-aasland May 27, 2021

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Yep!

{0, 0}
};

Expand Down Expand Up @@ -506,8 +515,9 @@ static void
keyobject_dealloc(keyobject *ko)
{
PyTypeObject *tp = Py_TYPE(ko);
keyobject_clear(ko);
PyObject_Free(ko);
PyObject_GC_UnTrack(ko);
(void)keyobject_clear(ko);
PyObject_GC_Del(ko);
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@vstinner vstinner May 27, 2021

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IMO here it's ok to hardcode PyObject_GC_Del(), but in general I would suggest to call tp->tp_free(ko); in case tp_alloc/tp_free is overriden in a subclass. To make the code more consistent, I would suggest to always call tp_free in dealloc functions. What do you think?

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@erlend-aasland erlend-aasland May 27, 2021

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I agree :) Consistency FTW

Py_DECREF(tp);
}

Expand All @@ -516,6 +526,7 @@ keyobject_traverse(keyobject *ko, visitproc visit, void *arg)
{
Py_VISIT(ko->cmp);
Py_VISIT(ko->object);
Py_VISIT(Py_TYPE(ko));
return 0;
}

Expand Down Expand Up @@ -546,7 +557,8 @@ static PyType_Slot keyobject_type_slots[] = {
static PyType_Spec keyobject_type_spec = {
.name = "functools.KeyWrapper",
.basicsize = sizeof(keyobject),
.flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION,
.flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_DISALLOW_INSTANTIATION |
Py_TPFLAGS_HAVE_GC),
.slots = keyobject_type_slots
};

Expand All @@ -560,14 +572,15 @@ keyobject_call(keyobject *ko, PyObject *args, PyObject *kwds)
if (!PyArg_ParseTupleAndKeywords(args, kwds, "O:K", kwargs, &object))
return NULL;

result = PyObject_New(keyobject, Py_TYPE(ko));
result = PyObject_GC_New(keyobject, Py_TYPE(ko));
if (result == NULL) {
return NULL;
}
Py_INCREF(ko->cmp);
result->cmp = ko->cmp;
Py_INCREF(object);
result->object = object;
PyObject_GC_Track(result);
return (PyObject *)result;
}

Expand Down Expand Up @@ -621,12 +634,13 @@ functools_cmp_to_key(PyObject *self, PyObject *args, PyObject *kwds)
return NULL;

state = get_functools_state(self);
object = PyObject_New(keyobject, state->keyobject_type);
object = PyObject_GC_New(keyobject, state->keyobject_type);
if (!object)
return NULL;
Py_INCREF(cmp);
object->cmp = cmp;
object->object = NULL;
PyObject_GC_Track(object);
return (PyObject *)object;
}

Expand Down Expand Up @@ -752,9 +766,9 @@ static void
lru_list_elem_dealloc(lru_list_elem *link)
{
PyTypeObject *tp = Py_TYPE(link);
Py_XDECREF(link->key);
Py_XDECREF(link->result);
PyObject_Free(link);
Py_CLEAR(link->key);
Py_CLEAR(link->result);
tp->tp_free(link);
Py_DECREF(tp);
}

Expand Down Expand Up @@ -1260,7 +1274,7 @@ lru_cache_dealloc(lru_cache_object *obj)
PyObject_ClearWeakRefs((PyObject*)obj);
}

lru_cache_tp_clear(obj);
(void)lru_cache_tp_clear(obj);
tp->tp_free(obj);
Py_DECREF(tp);
}
Expand Down Expand Up @@ -1332,6 +1346,7 @@ lru_cache_tp_traverse(lru_cache_object *self, visitproc visit, void *arg)
lru_list_elem *next = link->next;
Py_VISIT(link->key);
Py_VISIT(link->result);
Py_VISIT(Py_TYPE(link));
link = next;
}
Py_VISIT(self->func);
Expand All @@ -1340,6 +1355,7 @@ lru_cache_tp_traverse(lru_cache_object *self, visitproc visit, void *arg)
Py_VISIT(self->lru_list_elem_type);
Py_VISIT(self->cache_info_type);
Py_VISIT(self->dict);
Py_VISIT(Py_TYPE(self));
return 0;
}

Expand Down