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gh-153083: Defer GC tracking of an array to the end of construction. #153284

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gh-153083: Defer GC tracking of an array to the end of construction. #153284

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gh-153083: Defer GC tracking of an array to the end of construction.
corona10 Jul 7, 2026
4b499e9
Address code review
corona10 Jul 7, 2026
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3 changes: 2 additions & 1 deletion Include/internal/pycore_object.h
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Original file line number Diff line number Diff line change
Expand Up @@ -872,7 +872,8 @@ static inline int _PyType_SUPPORTS_WEAKREFS(PyTypeObject *type) {
return (type->tp_weaklistoffset != 0);
}

extern PyObject* _PyType_AllocNoTrack(PyTypeObject *type, Py_ssize_t nitems);
// Export for 'array' shared extension.
PyAPI_FUNC(PyObject*) _PyType_AllocNoTrack(PyTypeObject *type, Py_ssize_t nitems);

@vstinner vstinner Jul 7, 2026

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Suggested change
PyAPI_FUNC(PyObject*) _PyType_AllocNoTrack(PyTypeObject *type, Py_ssize_t nitems);
// Export for 'array' shared extension.
PyAPI_FUNC(PyObject*) _PyType_AllocNoTrack(PyTypeObject *type, Py_ssize_t nitems);

PyAPI_FUNC(PyObject *) _PyType_NewManagedObject(PyTypeObject *type);

extern PyTypeObject* _PyType_CalculateMetaclass(PyTypeObject *, PyObject *);
Expand Down
2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2026-07-08-01-47-15.gh-issue-153083.XbKZCp.rst
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@@ -0,0 +1,2 @@
Defer GC tracking of an :class:`array.array` to the end of its construction.
Patch by Donghee Na.
40 changes: 30 additions & 10 deletions Modules/arraymodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@
#include "pycore_floatobject.h" // _PY_FLOAT_BIG_ENDIAN
#include "pycore_modsupport.h" // _PyArg_NoKeywords()
#include "pycore_moduleobject.h" // _PyModule_GetState()
#include "pycore_object.h" // _PyObject_GC_TRACK()
#include "pycore_tuple.h" // _PyTuple_FromPairSteal
#include "pycore_weakref.h" // FT_CLEAR_WEAKREFS()

Expand Down Expand Up @@ -752,7 +753,8 @@ class array.array "arrayobject *" "ArrayType"
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=a5c29edf59f176a3]*/

static PyObject *
newarrayobject(PyTypeObject *type, Py_ssize_t size, const struct arraydescr *descr)
newarrayobject_untracked(PyTypeObject *type, Py_ssize_t size,
const struct arraydescr *descr)
{
arrayobject *op;
size_t nbytes;
Expand All @@ -767,7 +769,7 @@ newarrayobject(PyTypeObject *type, Py_ssize_t size, const struct arraydescr *des
return PyErr_NoMemory();
}
nbytes = size * descr->itemsize;
op = (arrayobject *) type->tp_alloc(type, 0);
op = (arrayobject *) _PyType_AllocNoTrack(type, 0);

@sergey-miryanov sergey-miryanov Jul 7, 2026

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Should we update tp_alloc slot?

if (op == NULL) {
return NULL;
}
Expand All @@ -789,6 +791,16 @@ newarrayobject(PyTypeObject *type, Py_ssize_t size, const struct arraydescr *des
return (PyObject *) op;
}

static PyObject *
newarrayobject(PyTypeObject *type, Py_ssize_t size, const struct arraydescr *descr)
{
PyObject *op = newarrayobject_untracked(type, size, descr);
if (op != NULL) {
_PyObject_GC_TRACK(op);
}
return op;
}

static PyObject *
getarrayitem(PyObject *op, Py_ssize_t i)
{
Expand Down Expand Up @@ -990,13 +1002,14 @@ array_slice(arrayobject *a, Py_ssize_t ilow, Py_ssize_t ihigh)
ihigh = ilow;
else if (ihigh > Py_SIZE(a))
ihigh = Py_SIZE(a);
np = (arrayobject *) newarrayobject(state->ArrayType, ihigh - ilow, a->ob_descr);
np = (arrayobject *) newarrayobject_untracked(state->ArrayType, ihigh - ilow, a->ob_descr);
if (np == NULL)
return NULL;
if (ihigh > ilow) {
memcpy(np->ob_item, a->ob_item + ilow * a->ob_descr->itemsize,
(ihigh-ilow) * a->ob_descr->itemsize);
}
_PyObject_GC_TRACK(np);
return (PyObject *)np;
}

Expand Down Expand Up @@ -1067,7 +1080,7 @@ array_concat(PyObject *op, PyObject *bb)
return PyErr_NoMemory();
}
size = Py_SIZE(a) + Py_SIZE(b);
np = (arrayobject *) newarrayobject(state->ArrayType, size, a->ob_descr);
np = (arrayobject *) newarrayobject_untracked(state->ArrayType, size, a->ob_descr);
if (np == NULL) {
return NULL;
}
Expand All @@ -1078,6 +1091,7 @@ array_concat(PyObject *op, PyObject *bb)
memcpy(np->ob_item + Py_SIZE(a)*a->ob_descr->itemsize,
b->ob_item, Py_SIZE(b)*b->ob_descr->itemsize);
}
_PyObject_GC_TRACK(np);
return (PyObject *)np;
#undef b
}
Expand All @@ -1095,16 +1109,19 @@ array_repeat(PyObject *op, Py_ssize_t n)
return PyErr_NoMemory();
}
Py_ssize_t size = array_length * n;
arrayobject* np = (arrayobject *) newarrayobject(state->ArrayType, size, a->ob_descr);
arrayobject* np = (arrayobject *) newarrayobject_untracked(state->ArrayType, size, a->ob_descr);
if (np == NULL)
return NULL;
if (size == 0)
if (size == 0) {
_PyObject_GC_TRACK(np);
return (PyObject *)np;
}

const Py_ssize_t oldbytes = array_length * a->ob_descr->itemsize;
const Py_ssize_t newbytes = oldbytes * n;
_PyBytes_RepeatBuffer(np->ob_item, newbytes, a->ob_item, oldbytes);

_PyObject_GC_TRACK(np);
return (PyObject *)np;
}

Expand Down Expand Up @@ -2666,17 +2683,17 @@ array_subscr(PyObject *op, PyObject *item)
return newarrayobject(state->ArrayType, 0, self->ob_descr);
}
else if (step == 1) {
PyObject *result = newarrayobject(state->ArrayType,
slicelength, self->ob_descr);
PyObject *result = newarrayobject_untracked(state->ArrayType, slicelength, self->ob_descr);
if (result == NULL)
return NULL;
memcpy(((arrayobject *)result)->ob_item,
self->ob_item + start * itemsize,
slicelength * itemsize);
_PyObject_GC_TRACK(result);
return result;
}
else {
result = newarrayobject(state->ArrayType, slicelength, self->ob_descr);
result = newarrayobject_untracked(state->ArrayType, slicelength, self->ob_descr);
if (!result) return NULL;

ar = (arrayobject*)result;
Expand All @@ -2688,6 +2705,7 @@ array_subscr(PyObject *op, PyObject *item)
itemsize);
}

_PyObject_GC_TRACK(result);
return result;
}
}
Expand Down Expand Up @@ -2973,7 +2991,7 @@ array_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
else
len = 0;

a = newarrayobject(type, len, descr);
a = newarrayobject_untracked(type, len, descr);
if (a == NULL) {
Py_XDECREF(it);
return NULL;
Expand Down Expand Up @@ -3039,6 +3057,8 @@ array_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
}
Py_DECREF(it);
}
// Track only once fully built.
_PyObject_GC_TRACK(a);
return a;
}
}
Expand Down
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