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gh-119127: Fix _functools.Placeholder singleton #124601

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Merged
merged 1 commit into from
Sep 26, 2024
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gh-119127: Fix _functools.Placeholder singleton #124601

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48 changes: 35 additions & 13 deletions Modules/_functoolsmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -26,7 +26,7 @@ typedef struct _functools_state {
/* this object is used delimit args and keywords in the cache keys */
PyObject *kwd_mark;
PyTypeObject *placeholder_type;
PyObject *placeholder;
PyObject *placeholder; // strong reference (singleton)
PyTypeObject *partial_type;
PyTypeObject *keyobject_type;
PyTypeObject *lru_list_elem_type;
Expand Down Expand Up @@ -76,13 +76,12 @@ static PyMethodDef placeholder_methods[] = {
};

static void
placeholder_dealloc(PyObject* placeholder)
placeholder_dealloc(PyObject* self)
{
/* This should never get called, but we also don't want to SEGV if
* we accidentally decref Placeholder out of existence. Instead,
* since Placeholder is an immortal object, re-set the reference count.
*/
_Py_SetImmortal(placeholder);
PyObject_GC_UnTrack(self);
PyTypeObject *tp = Py_TYPE(self);
tp->tp_free((PyObject*)self);
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@Eclips4 Eclips4 Sep 26, 2024 •
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Suggested change
tp->tp_free((PyObject*)self);
tp->tp_free(self);

nit: there's no need to casting it to PyObject * since it's already a PyObject *

Py_DECREF(tp);
}

static PyObject *
Expand All @@ -93,10 +92,26 @@ placeholder_new(PyTypeObject *type, PyObject *args, PyObject *kwargs)
return NULL;
}
_functools_state *state = get_functools_state_by_type(type);
if (state->placeholder != NULL) {
return Py_NewRef(state->placeholder);
}

PyObject *placeholder = PyType_GenericNew(type, NULL, NULL);
if (placeholder == NULL) {
return NULL;
}

if (state->placeholder == NULL) {
state->placeholder = PyType_GenericNew(type, NULL, NULL);
state->placeholder = Py_NewRef(placeholder);
}
return state->placeholder;
return placeholder;
}

static int
placeholder_traverse(PyObject *self, visitproc visit, void *arg)
{
Py_VISIT(Py_TYPE(self));
return 0;
}

static PyType_Slot placeholder_type_slots[] = {
Expand All @@ -105,13 +120,14 @@ static PyType_Slot placeholder_type_slots[] = {
{Py_tp_doc, (void *)placeholder_doc},
{Py_tp_methods, placeholder_methods},
{Py_tp_new, placeholder_new},
{Py_tp_traverse, placeholder_traverse},
{0, 0}
};

static PyType_Spec placeholder_type_spec = {
.name = "functools._PlaceholderType",
.basicsize = sizeof(placeholderobject),
.flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE,
.flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_IMMUTABLETYPE | Py_TPFLAGS_HAVE_GC,
.slots = placeholder_type_slots
};

Expand Down Expand Up @@ -1717,13 +1733,17 @@ _functools_exec(PyObject *module)
if (PyModule_AddType(module, state->placeholder_type) < 0) {
return -1;
}
state->placeholder = PyObject_CallNoArgs((PyObject *)state->placeholder_type);
if (state->placeholder == NULL) {

PyObject *placeholder = PyObject_CallNoArgs((PyObject *)state->placeholder_type);
if (placeholder == NULL) {
return -1;
}
if (PyModule_AddObject(module, "Placeholder", state->placeholder) < 0) {
if (PyModule_AddObjectRef(module, "Placeholder", placeholder) < 0) {
Py_DECREF(placeholder);
return -1;
}
Py_DECREF(placeholder);

state->partial_type = (PyTypeObject *)PyType_FromModuleAndSpec(module,
&partial_type_spec, NULL);
if (state->partial_type == NULL) {
Expand Down Expand Up @@ -1769,6 +1789,7 @@ _functools_traverse(PyObject *module, visitproc visit, void *arg)
_functools_state *state = get_functools_state(module);
Py_VISIT(state->kwd_mark);
Py_VISIT(state->placeholder_type);
Py_VISIT(state->placeholder);
Py_VISIT(state->partial_type);
Py_VISIT(state->keyobject_type);
Py_VISIT(state->lru_list_elem_type);
Expand All @@ -1781,6 +1802,7 @@ _functools_clear(PyObject *module)
_functools_state *state = get_functools_state(module);
Py_CLEAR(state->kwd_mark);
Py_CLEAR(state->placeholder_type);
Py_CLEAR(state->placeholder);
Py_CLEAR(state->partial_type);
Py_CLEAR(state->keyobject_type);
Py_CLEAR(state->lru_list_elem_type);
Expand Down
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