cpython/Objects/enumobject.c
Brandt Bucher 226a012d1c
bpo-42536: GC track recycled tuples (GH-23623)
Several built-in and standard library types now ensure that their internal result tuples are always tracked by the garbage collector:

- collections.OrderedDict.items
- dict.items
- enumerate
- functools.reduce
- itertools.combinations
- itertools.combinations_with_replacement
- itertools.permutations
- itertools.product
- itertools.zip_longest
- zip

Previously, they could have become untracked by a prior garbage collection.
2020-12-04 19:45:57 -08:00

480 lines
15 KiB
C

/* enumerate object */
#include "Python.h"
#include "pycore_long.h" // _PyLong_GetOne()
#include "pycore_object.h" // _PyObject_GC_TRACK()
#include "clinic/enumobject.c.h"
/*[clinic input]
class enumerate "enumobject *" "&PyEnum_Type"
class reversed "reversedobject *" "&PyReversed_Type"
[clinic start generated code]*/
/*[clinic end generated code: output=da39a3ee5e6b4b0d input=d2dfdf1a88c88975]*/
typedef struct {
PyObject_HEAD
Py_ssize_t en_index; /* current index of enumeration */
PyObject* en_sit; /* secondary iterator of enumeration */
PyObject* en_result; /* result tuple */
PyObject* en_longindex; /* index for sequences >= PY_SSIZE_T_MAX */
} enumobject;
/*[clinic input]
@classmethod
enumerate.__new__ as enum_new
iterable: object
an object supporting iteration
start: object = 0
Return an enumerate object.
The enumerate object yields pairs containing a count (from start, which
defaults to zero) and a value yielded by the iterable argument.
enumerate is useful for obtaining an indexed list:
(0, seq[0]), (1, seq[1]), (2, seq[2]), ...
[clinic start generated code]*/
static PyObject *
enum_new_impl(PyTypeObject *type, PyObject *iterable, PyObject *start)
/*[clinic end generated code: output=e95e6e439f812c10 input=782e4911efcb8acf]*/
{
enumobject *en;
en = (enumobject *)type->tp_alloc(type, 0);
if (en == NULL)
return NULL;
if (start != NULL) {
start = PyNumber_Index(start);
if (start == NULL) {
Py_DECREF(en);
return NULL;
}
assert(PyLong_Check(start));
en->en_index = PyLong_AsSsize_t(start);
if (en->en_index == -1 && PyErr_Occurred()) {
PyErr_Clear();
en->en_index = PY_SSIZE_T_MAX;
en->en_longindex = start;
} else {
en->en_longindex = NULL;
Py_DECREF(start);
}
} else {
en->en_index = 0;
en->en_longindex = NULL;
}
en->en_sit = PyObject_GetIter(iterable);
if (en->en_sit == NULL) {
Py_DECREF(en);
return NULL;
}
en->en_result = PyTuple_Pack(2, Py_None, Py_None);
if (en->en_result == NULL) {
Py_DECREF(en);
return NULL;
}
return (PyObject *)en;
}
static void
enum_dealloc(enumobject *en)
{
PyObject_GC_UnTrack(en);
Py_XDECREF(en->en_sit);
Py_XDECREF(en->en_result);
Py_XDECREF(en->en_longindex);
Py_TYPE(en)->tp_free(en);
}
static int
enum_traverse(enumobject *en, visitproc visit, void *arg)
{
Py_VISIT(en->en_sit);
Py_VISIT(en->en_result);
Py_VISIT(en->en_longindex);
return 0;
}
static PyObject *
enum_next_long(enumobject *en, PyObject* next_item)
{
PyObject *result = en->en_result;
PyObject *next_index;
PyObject *stepped_up;
PyObject *old_index;
PyObject *old_item;
if (en->en_longindex == NULL) {
en->en_longindex = PyLong_FromSsize_t(PY_SSIZE_T_MAX);
if (en->en_longindex == NULL) {
Py_DECREF(next_item);
return NULL;
}
}
next_index = en->en_longindex;
assert(next_index != NULL);
stepped_up = PyNumber_Add(next_index, _PyLong_GetOne());
if (stepped_up == NULL) {
Py_DECREF(next_item);
return NULL;
}
en->en_longindex = stepped_up;
if (Py_REFCNT(result) == 1) {
Py_INCREF(result);
old_index = PyTuple_GET_ITEM(result, 0);
old_item = PyTuple_GET_ITEM(result, 1);
PyTuple_SET_ITEM(result, 0, next_index);
PyTuple_SET_ITEM(result, 1, next_item);
Py_DECREF(old_index);
Py_DECREF(old_item);
// bpo-42536: The GC may have untracked this result tuple. Since we're
// recycling it, make sure it's tracked again:
if (!_PyObject_GC_IS_TRACKED(result)) {
_PyObject_GC_TRACK(result);
}
return result;
}
result = PyTuple_New(2);
if (result == NULL) {
Py_DECREF(next_index);
Py_DECREF(next_item);
return NULL;
}
PyTuple_SET_ITEM(result, 0, next_index);
PyTuple_SET_ITEM(result, 1, next_item);
return result;
}
static PyObject *
enum_next(enumobject *en)
{
PyObject *next_index;
PyObject *next_item;
PyObject *result = en->en_result;
PyObject *it = en->en_sit;
PyObject *old_index;
PyObject *old_item;
next_item = (*Py_TYPE(it)->tp_iternext)(it);
if (next_item == NULL)
return NULL;
if (en->en_index == PY_SSIZE_T_MAX)
return enum_next_long(en, next_item);
next_index = PyLong_FromSsize_t(en->en_index);
if (next_index == NULL) {
Py_DECREF(next_item);
return NULL;
}
en->en_index++;
if (Py_REFCNT(result) == 1) {
Py_INCREF(result);
old_index = PyTuple_GET_ITEM(result, 0);
old_item = PyTuple_GET_ITEM(result, 1);
PyTuple_SET_ITEM(result, 0, next_index);
PyTuple_SET_ITEM(result, 1, next_item);
Py_DECREF(old_index);
Py_DECREF(old_item);
// bpo-42536: The GC may have untracked this result tuple. Since we're
// recycling it, make sure it's tracked again:
if (!_PyObject_GC_IS_TRACKED(result)) {
_PyObject_GC_TRACK(result);
}
return result;
}
result = PyTuple_New(2);
if (result == NULL) {
Py_DECREF(next_index);
Py_DECREF(next_item);
return NULL;
}
PyTuple_SET_ITEM(result, 0, next_index);
PyTuple_SET_ITEM(result, 1, next_item);
return result;
}
static PyObject *
enum_reduce(enumobject *en, PyObject *Py_UNUSED(ignored))
{
if (en->en_longindex != NULL)
return Py_BuildValue("O(OO)", Py_TYPE(en), en->en_sit, en->en_longindex);
else
return Py_BuildValue("O(On)", Py_TYPE(en), en->en_sit, en->en_index);
}
PyDoc_STRVAR(reduce_doc, "Return state information for pickling.");
static PyMethodDef enum_methods[] = {
{"__reduce__", (PyCFunction)enum_reduce, METH_NOARGS, reduce_doc},
{"__class_getitem__", (PyCFunction)Py_GenericAlias,
METH_O|METH_CLASS, PyDoc_STR("See PEP 585")},
{NULL, NULL} /* sentinel */
};
PyTypeObject PyEnum_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
"enumerate", /* tp_name */
sizeof(enumobject), /* tp_basicsize */
0, /* tp_itemsize */
/* methods */
(destructor)enum_dealloc, /* tp_dealloc */
0, /* tp_vectorcall_offset */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_as_async */
0, /* tp_repr */
0, /* tp_as_number */
0, /* tp_as_sequence */
0, /* tp_as_mapping */
0, /* tp_hash */
0, /* tp_call */
0, /* tp_str */
PyObject_GenericGetAttr, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
Py_TPFLAGS_BASETYPE, /* tp_flags */
enum_new__doc__, /* tp_doc */
(traverseproc)enum_traverse, /* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
PyObject_SelfIter, /* tp_iter */
(iternextfunc)enum_next, /* tp_iternext */
enum_methods, /* tp_methods */
0, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
PyType_GenericAlloc, /* tp_alloc */
enum_new, /* tp_new */
PyObject_GC_Del, /* tp_free */
};
/* Reversed Object ***************************************************************/
typedef struct {
PyObject_HEAD
Py_ssize_t index;
PyObject* seq;
} reversedobject;
/*[clinic input]
@classmethod
reversed.__new__ as reversed_new
sequence as seq: object
/
Return a reverse iterator over the values of the given sequence.
[clinic start generated code]*/
static PyObject *
reversed_new_impl(PyTypeObject *type, PyObject *seq)
/*[clinic end generated code: output=f7854cc1df26f570 input=aeb720361e5e3f1d]*/
{
Py_ssize_t n;
PyObject *reversed_meth;
reversedobject *ro;
_Py_IDENTIFIER(__reversed__);
reversed_meth = _PyObject_LookupSpecial(seq, &PyId___reversed__);
if (reversed_meth == Py_None) {
Py_DECREF(reversed_meth);
PyErr_Format(PyExc_TypeError,
"'%.200s' object is not reversible",
Py_TYPE(seq)->tp_name);
return NULL;
}
if (reversed_meth != NULL) {
PyObject *res = _PyObject_CallNoArg(reversed_meth);
Py_DECREF(reversed_meth);
return res;
}
else if (PyErr_Occurred())
return NULL;
if (!PySequence_Check(seq)) {
PyErr_Format(PyExc_TypeError,
"'%.200s' object is not reversible",
Py_TYPE(seq)->tp_name);
return NULL;
}
n = PySequence_Size(seq);
if (n == -1)
return NULL;
ro = (reversedobject *)type->tp_alloc(type, 0);
if (ro == NULL)
return NULL;
ro->index = n-1;
Py_INCREF(seq);
ro->seq = seq;
return (PyObject *)ro;
}
static PyObject *
reversed_vectorcall(PyObject *type, PyObject * const*args,
size_t nargsf, PyObject *kwnames)
{
assert(PyType_Check(type));
if (!_PyArg_NoKwnames("reversed", kwnames)) {
return NULL;
}
Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
if (!_PyArg_CheckPositional("reversed", nargs, 1, 1)) {
return NULL;
}
return reversed_new_impl((PyTypeObject *)type, args[0]);
}
static void
reversed_dealloc(reversedobject *ro)
{
PyObject_GC_UnTrack(ro);
Py_XDECREF(ro->seq);
Py_TYPE(ro)->tp_free(ro);
}
static int
reversed_traverse(reversedobject *ro, visitproc visit, void *arg)
{
Py_VISIT(ro->seq);
return 0;
}
static PyObject *
reversed_next(reversedobject *ro)
{
PyObject *item;
Py_ssize_t index = ro->index;
if (index >= 0) {
item = PySequence_GetItem(ro->seq, index);
if (item != NULL) {
ro->index--;
return item;
}
if (PyErr_ExceptionMatches(PyExc_IndexError) ||
PyErr_ExceptionMatches(PyExc_StopIteration))
PyErr_Clear();
}
ro->index = -1;
Py_CLEAR(ro->seq);
return NULL;
}
static PyObject *
reversed_len(reversedobject *ro, PyObject *Py_UNUSED(ignored))
{
Py_ssize_t position, seqsize;
if (ro->seq == NULL)
return PyLong_FromLong(0);
seqsize = PySequence_Size(ro->seq);
if (seqsize == -1)
return NULL;
position = ro->index + 1;
return PyLong_FromSsize_t((seqsize < position) ? 0 : position);
}
PyDoc_STRVAR(length_hint_doc, "Private method returning an estimate of len(list(it)).");
static PyObject *
reversed_reduce(reversedobject *ro, PyObject *Py_UNUSED(ignored))
{
if (ro->seq)
return Py_BuildValue("O(O)n", Py_TYPE(ro), ro->seq, ro->index);
else
return Py_BuildValue("O(())", Py_TYPE(ro));
}
static PyObject *
reversed_setstate(reversedobject *ro, PyObject *state)
{
Py_ssize_t index = PyLong_AsSsize_t(state);
if (index == -1 && PyErr_Occurred())
return NULL;
if (ro->seq != 0) {
Py_ssize_t n = PySequence_Size(ro->seq);
if (n < 0)
return NULL;
if (index < -1)
index = -1;
else if (index > n-1)
index = n-1;
ro->index = index;
}
Py_RETURN_NONE;
}
PyDoc_STRVAR(setstate_doc, "Set state information for unpickling.");
static PyMethodDef reversediter_methods[] = {
{"__length_hint__", (PyCFunction)reversed_len, METH_NOARGS, length_hint_doc},
{"__reduce__", (PyCFunction)reversed_reduce, METH_NOARGS, reduce_doc},
{"__setstate__", (PyCFunction)reversed_setstate, METH_O, setstate_doc},
{NULL, NULL} /* sentinel */
};
PyTypeObject PyReversed_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
"reversed", /* tp_name */
sizeof(reversedobject), /* tp_basicsize */
0, /* tp_itemsize */
/* methods */
(destructor)reversed_dealloc, /* tp_dealloc */
0, /* tp_vectorcall_offset */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_as_async */
0, /* tp_repr */
0, /* tp_as_number */
0, /* tp_as_sequence */
0, /* tp_as_mapping */
0, /* tp_hash */
0, /* tp_call */
0, /* tp_str */
PyObject_GenericGetAttr, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
Py_TPFLAGS_BASETYPE, /* tp_flags */
reversed_new__doc__, /* tp_doc */
(traverseproc)reversed_traverse,/* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
PyObject_SelfIter, /* tp_iter */
(iternextfunc)reversed_next, /* tp_iternext */
reversediter_methods, /* tp_methods */
0, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
PyType_GenericAlloc, /* tp_alloc */
reversed_new, /* tp_new */
PyObject_GC_Del, /* tp_free */
.tp_vectorcall = (vectorcallfunc)reversed_vectorcall,
};