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gh-157526: Call __instancecheck__ and __subclasscheck__ without creating a bound method #157670

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gh-157526: Call __instancecheck__ and __subclasscheck__ without creating a bound method #157670

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79 changes: 47 additions & 32 deletions Objects/abstract.c
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@
#include "pycore_list.h" // _PyList_AppendTakeRef()
#include "pycore_long.h" // _PyLong_IsNegative()
#include "pycore_object.h" // _Py_CheckSlotResult()
#include "pycore_stackref.h" // _PyStackRef
#include "pycore_pybuffer.h" // _PyBuffer_ReleaseInInterpreterAndRawFree()
#include "pycore_pyerrors.h" // _PyErr_Occurred()
#include "pycore_pystate.h" // _PyThreadState_GET()
Expand Down Expand Up @@ -2635,6 +2636,40 @@ object_isinstance(PyObject *inst, PyObject *cls)
return retval;
}

static int
call_special_method(PyThreadState *tstate, PyObject *cls, PyObject *name,
const char *where, PyObject *arg, PyObject **res)
{
_PyCStackRef cref;
_PyThreadState_PushCStackRef(tstate, &cref);
_PyStackRef method_and_self[2] = {
PyStackRef_NULL, PyStackRef_FromPyObjectBorrow(cls)
};
int found = _PyObject_LookupSpecialMethod(name, method_and_self);
cref.ref = method_and_self[0];
if (found > 0) {
*res = NULL;
if (!_Py_EnterRecursiveCallTstate(tstate, where)) {
PyObject *method = PyStackRef_AsPyObjectBorrow(cref.ref);
PyObject *args[2] = {PyStackRef_AsPyObjectBorrow(method_and_self[1]), arg};
if (args[0] != NULL) {
/* Unbound method: prepend self. */
*res = PyObject_Vectorcall(method, args, 2, NULL);
}
else {
*res = PyObject_Vectorcall(method, args + 1, 1, NULL);
}
_Py_LeaveRecursiveCallTstate(tstate);
}
if (*res == NULL) {
found = -1;
}
}
PyStackRef_XCLOSE(method_and_self[1]);
_PyThreadState_PopCStackRef(tstate, &cref);
return found;
}

static int
object_recursive_isinstance(PyThreadState *tstate, PyObject *inst, PyObject *cls)
{
Expand Down Expand Up @@ -2672,26 +2707,16 @@ object_recursive_isinstance(PyThreadState *tstate, PyObject *inst, PyObject *cls
return r;
}

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

PyObject *res = PyObject_CallOneArg(checker, inst);
_Py_LeaveRecursiveCallTstate(tstate);
Py_DECREF(checker);

if (res == NULL) {
return -1;
}
PyObject *res;
int found = call_special_method(tstate, cls, &_Py_ID(__instancecheck__),
" in __instancecheck__", inst, &res);
if (found > 0) {
int ok = PyObject_IsTrue(res);
Py_DECREF(res);

return ok;
}
else if (_PyErr_Occurred(tstate)) {
else if (found < 0) {
return -1;
}

Expand Down Expand Up @@ -2731,8 +2756,6 @@ recursive_issubclass(PyObject *derived, PyObject *cls)
static int
object_issubclass(PyThreadState *tstate, PyObject *derived, PyObject *cls)
{
PyObject *checker;

/* We know what type's __subclasscheck__ does. */
if (PyType_CheckExact(cls)) {
/* Quick test for an exact match */
Expand Down Expand Up @@ -2763,23 +2786,15 @@ object_issubclass(PyThreadState *tstate, PyObject *derived, PyObject *cls)
return r;
}

checker = _PyObject_LookupSpecial(cls, &_Py_ID(__subclasscheck__));
if (checker != NULL) {
int ok = -1;
if (_Py_EnterRecursiveCallTstate(tstate, " in __subclasscheck__")) {
Py_DECREF(checker);
return ok;
}
PyObject *res = PyObject_CallOneArg(checker, derived);
_Py_LeaveRecursiveCallTstate(tstate);
Py_DECREF(checker);
if (res != NULL) {
ok = PyObject_IsTrue(res);
Py_DECREF(res);
}
PyObject *res;
int found = call_special_method(tstate, cls, &_Py_ID(__subclasscheck__),
" in __subclasscheck__", derived, &res);
if (found > 0) {
int ok = PyObject_IsTrue(res);
Py_DECREF(res);
return ok;
}
else if (_PyErr_Occurred(tstate)) {
else if (found < 0) {
return -1;
}

Expand Down
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