The use of `PyStackRef_AsPyObjectBorrow` makes it hard to track ownership of references, making analysis of escaping calls too difficult

The problem with PyStackRef_AsPyObjectBorrow is that it is not clear whether the reference is owned by the stack ref or the pointer.

Borrowing references across calls is fine but in less structured code, it is error prone and very hard to analyze.

The solution is change most, ideally all, uses of PyStackRef_AsPyObjectBorrow to PyStackRef_AsPyObjectSteal so that the ownership of the reference is clear.
E.g.

        inst(UNARY_NEGATIVE, (value -- res)) {
            PyObject *val_o = PyStackRef_AsPyObjectBorrow(value);
            PyObject *res_o = PyNumber_Negative(val_o);
            PyStackRef_CLOSE(value);
            ERROR_IF(res_o == NULL, error);
            res = PyStackRef_FromPyObjectSteal(res_o);
        }

would become:

        inst(UNARY_NEGATIVE, (value -- res)) {
            PyObject *val_o = PyStackRef_AsPyObjectSteal(value);
            PyObject *res_o = PyNumber_Negative(val_o);
            Py_DECREF(val_o);
            ERROR_IF(res_o == NULL, error);
            res = PyStackRef_FromPyObjectSteal(res_o);
        }

This ensures that during the escaping call to PyNumber_Negative, the reference to the value a PyObject *, so will not be reclaimed by the garbage collector.

Linked PRs

• gh-122037

Cerca nel codice sorgente di CPython gli usi di PyStackRef_AsPyObjectBorrow e rivedi i pattern di ownership di PyStackRef_AsPyObjectSteal e PyStackRef_CLOSE mostrati nell’issue. Determina quali usi attraversano chiamate in cui i riferimenti possono fuoriuscire, quindi verifica che i riferimenti pertinenti rimangano validi e che l’ownership sia esplicito; confronta il lavoro con la PR collegata gh-122037.