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bpo-2534: Restore PyObject_IsInstance() comment #18345

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Merged
vstinner merged 1 commit into from
Feb 4, 2020
Merged

bpo-2534: Restore PyObject_IsInstance() comment #18345

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40 changes: 23 additions & 17 deletions Objects/abstract.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2423,7 +2423,7 @@ check_class(PyObject *cls, const char *error)
}

static int
recursive_isinstance(PyObject *inst, PyObject *cls)
object_isinstance(PyObject *inst, PyObject *cls)
{
PyObject *icls;
int retval;
Expand Down Expand Up @@ -2461,67 +2461,73 @@ recursive_isinstance(PyObject *inst, PyObject *cls)
}

static int
object_isinstance(PyThreadState *tstate, PyObject *inst, PyObject *cls)
object_recursive_isinstance(PyThreadState *tstate, PyObject *inst, PyObject *cls)
{
_Py_IDENTIFIER(__instancecheck__);
PyObject *checker;

/* Quick test for an exact match */
if (Py_TYPE(inst) == (PyTypeObject *)cls)
if (Py_TYPE(inst) == (PyTypeObject *)cls) {
return 1;
}

/* We know what type's __instancecheck__ does. */
if (PyType_CheckExact(cls)) {
return recursive_isinstance(inst, cls);
return object_isinstance(inst, cls);
}

if (PyTuple_Check(cls)) {
/* Not a general sequence -- that opens up the road to
recursion and stack overflow. */
if (_Py_EnterRecursiveCall(tstate, " in __instancecheck__")) {
return -1;
}
Py_ssize_t n = PyTuple_GET_SIZE(cls);
int r = 0;
for (Py_ssize_t i = 0; i < n; ++i) {
PyObject *item = PyTuple_GET_ITEM(cls, i);
r = object_isinstance(tstate, inst, item);
if (r != 0)
r = object_recursive_isinstance(tstate, inst, item);
if (r != 0) {
/* either found it, or got an error */
break;
}
}
_Py_LeaveRecursiveCall(tstate);
return r;
}

checker = _PyObject_LookupSpecial(cls, &PyId___instancecheck__);
PyObject *checker = _PyObject_LookupSpecial(cls, &PyId___instancecheck__);
if (checker != NULL) {
int ok = -1;
if (_Py_EnterRecursiveCall(tstate, " in __instancecheck__")) {
Py_DECREF(checker);
return ok;
return -1;
}

PyObject *res = _PyObject_CallOneArg(checker, inst);
_Py_LeaveRecursiveCall(tstate);
Py_DECREF(checker);
if (res != NULL) {
ok = PyObject_IsTrue(res);
Py_DECREF(res);

if (res == NULL) {
return -1;
}
int ok = PyObject_IsTrue(res);
Py_DECREF(res);

return ok;
}
else if (_PyErr_Occurred(tstate)) {
return -1;
}

/* Probably never reached anymore. */
return recursive_isinstance(inst, cls);
/* cls has no __instancecheck__() method */
return object_isinstance(inst, cls);
}


int
PyObject_IsInstance(PyObject *inst, PyObject *cls)
{
PyThreadState *tstate = _PyThreadState_GET();
return object_isinstance(tstate, inst, cls);
return object_recursive_isinstance(tstate, inst, cls);
}


Expand Down Expand Up @@ -2611,7 +2617,7 @@ PyObject_IsSubclass(PyObject *derived, PyObject *cls)
int
_PyObject_RealIsInstance(PyObject *inst, PyObject *cls)
{
return recursive_isinstance(inst, cls);
return object_isinstance(inst, cls);
}

int
Expand Down