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gh-145272: Fix data race when accessing func_code in PyFunctionObject#145534

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gh-145272: Fix data race when accessing func_code in PyFunctionObject #145534

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d926271
gh-142572: Fix data race when accessing func_code in PyFunctionObject
Krishna-web-hub Mar 5, 2026
7b10320
Fix data race on func_code in free-threaded Python
Krishna-web-hub Mar 6, 2026
e703995
Fixing the issues
Krishna-web-hub Mar 6, 2026
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8 changes: 6 additions & 2 deletions Include/cpython/funcobject.h
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Expand Up@@ -88,10 +88,14 @@ PyAPI_FUNC(int) PyFunction_SetAnnotations(PyObject *, PyObject *);
/* Static inline functions for direct access to these values.
Type checks are *not* done, so use with care. */
static inline PyObject* PyFunction_GET_CODE(PyObject *func) {
return _PyFunction_CAST(func)->func_code;
PyFunctionObject *op = _PyFunction_CAST(func);
#ifdef Py_GIL_DISABLED
return (PyObject *)_Py_atomic_load_ptr(&op->func_code);

@picnixzpicnixzMar 7, 2026

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Aren't all attributes of function objects subject to this issue then?

#else
return op->func_code;
#endif
}
#define PyFunction_GET_CODE(func) PyFunction_GET_CODE(_PyObject_CAST(func))
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static inline PyObject* PyFunction_GET_GLOBALS(PyObject *func) {
return _PyFunction_CAST(func)->func_globals;
}
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-03-05-12-01-44.gh-issue-145272.MeSSbg.rst
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@@ -0,0 +1 @@
Fixing race condition in PyFunctionObject.func_code

@picnixzpicnixzMar 7, 2026

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I think we should be less precise in terms of implementation and rather mention __func__.__code__ directly.

10 changes: 7 additions & 3 deletions Objects/funcobject.c
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Expand Up@@ -631,7 +631,8 @@ func_get_code(PyObject *self, void *Py_UNUSED(ignored))
return NULL;
}

return Py_NewRef(op->func_code);
PyCodeObject *code = _Py_atomic_load_ptr(&op->func_code);
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return Py_NewRef(code);
Comment on lines +634 to +635

@da-woodsda-woodsMar 7, 2026

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This isn't right.

code might have been deallocated by the time you do Py_NewRef

}

static int
Expand DownExpand Up@@ -664,7 +665,7 @@ func_set_code(PyObject *self, PyObject *value, void *Py_UNUSED(ignored))
return -1;
}

PyObject *func_code = PyFunction_GET_CODE(op);
PyCodeObject *func_code = (PyCodeObject *)PyFunction_GET_CODE(op);

@picnixzpicnixzMar 7, 2026

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Why this change?

int old_flags = ((PyCodeObject *)func_code)->co_flags;
int new_flags = ((PyCodeObject *)value)->co_flags;
int mask = CO_GENERATOR | CO_COROUTINE | CO_ASYNC_GENERATOR;
Expand All@@ -679,7 +680,10 @@ func_set_code(PyObject *self, PyObject *value, void *Py_UNUSED(ignored))

handle_func_event(PyFunction_EVENT_MODIFY_CODE, op, value);
_PyFunction_ClearVersion(op);
Py_XSETREF(op->func_code, Py_NewRef(value));
PyCodeObject *new = (PyCodeObject *)Py_NewRef(value);

@picnixzpicnixzMar 7, 2026

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This should be GIL_DISABLED-guarded

@picnixzpicnixzMar 7, 2026

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Also, don't we have a FT-helper alterantive to Py_XSETREF?

PyCodeObject *old =
(PyCodeObject *)_Py_atomic_exchange_ptr(&op->func_code, new);
Py_XDECREF(old);
return 0;
}

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