8000 bpo-42972: Fully implement GC protocol for functools LRU cache by erlend-aasland · Pull Request #26423 · python/cpython · GitHub
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bpo-42972: Fully implement GC protocol for functools LRU cache #26423

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Merged
merged 1 commit into from
May 28, 2021
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bpo-42972: Fully implement GC protocol for functools LRU cache #26423

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6 changes: 4 additions & 2 deletions Modules/_functoolsmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1240,8 +1240,8 @@ static int
lru_cache_tp_clear(lru_cache_object *self)
{
lru_list_elem *list = lru_cache_unlink_list(self);
Py_CLEAR(self->func);
Py_CLEAR(self->cache);
Py_CLEAR(self->func);
Py_CLEAR(self->kwd_mark);
Py_CLEAR(self->lru_list_elem_type);
Py_CLEAR(self->cache_info_type);
Expand Down Expand Up @@ -1327,15 +1327,17 @@ lru_cache_deepcopy(PyObject *self, PyObject *unused)
static int
lru_cache_tp_traverse(lru_cache_object *self, visitproc visit, void *arg)
{
Py_VISIT(Py_TYPE(self));
lru_list_elem *link = self->root.next;
while (link != &self->root) {
lru_list_elem *next = link->next;
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Please add a comment (with a reference to bpo-42972) somewhere (here may be good place) to explain why the link type doesn't implement the GC protocol.

I understand that the code works as if the GC protocol is implemented, but the code is inlined.

Py_VISIT(link->key);
Py_VISIT(link->result);
Py_VISIT(Py_TYPE(link));
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nitpick: I suggest to visit the type first, to visit object members in their definition order.

I'm not sure that I get the rationale why the link type doesn't implement the GC protocol but is "exposed" by this Py_VISIT() call in gc.get_objects(). I'm not sure that it's a good idea to visit the type.

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@erlend-aasland erlend-aasland May 28, 2021 •
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nitpick: I suggest to visit the type first, to visit object members in their definition order.

Sorry, I was a little bit too fast there. We can fix it later if needed.

link = next;
}
Py_VISIT(self->func);
Py_VISIT(self->cache);
Py_VISIT(self->func);
Py_VISIT(self->kwd_mark);
Py_VISIT(self->lru_list_elem_type);
Py_VISIT(self->cache_info_type);
Expand Down
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