CALL_LIST_APPEND specialization can make no progress #141367
Description
Bug report
Bug description:
CALL_LIST_APPEND requires self to be a PyList_CheckExact in bytecodes.c. However, the specialize.c doesn't check that. This means there's a possible discrepancy between what we specialize for and what we deopt.
The fix is to check that self is a list. It should be as simple as
diff --git a/Python/specialize.c b/Python/specialize.c
index a1c5dedd615..5b44432b8b7 100644
--- a/Python/specialize.c
+++ b/Python/specialize.c
@@ -2041,8 +2041,12 @@ specialize_method_descriptor(PyMethodDescrObject *descr, _Py_CODEUNIT *instr,
bool pop = (next.op.code == POP_TOP);
int oparg = instr->op.arg;
if ((PyObject *)descr == list_append && oparg == 1 && pop) {
- specialize(instr, CALL_LIST_APPEND);
- return 0;
+ PyThreadState *tstate = PyThreadState_GET();
+ PyObject *self = PyStackRef_AsPyObjectBorrow(tstate->current_frame->stackpointer[-2]);
+ if (PyList_CheckExact(self)) {
+ specialize(instr, CALL_LIST_APPEND);
+ return 0;
+ }
}
specialize(instr, CALL_METHOD_DESCRIPTOR_O);
return 0;The test case should be in test_opcache.py, and test something like
class MyList(list): pass
x = MyList()
for _ in range(spec_counter):
x.append(1)and ensure that the append is not specialized to CALL_LIST_APPEND.
@efimov-mikhail can I let you take up this issue please? I'm pretty sure 3.14 is affected too.
CPython versions tested on:
CPython main branch, 3.15, 3.14
Operating systems tested on:
No response