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In the free-threaded build, threads advancing the same dict iterator each read `di_dict` as a borrowed reference, so concurrently exhausting it could run `di->di_dict = NULL; Py_DECREF(d)` more than once and free the dict while other threads were still using it. Reversed iterators were also affected: they dropped the reference while holding the dict's critical section. In the free-threaded build, keep the iterator's reference to the dict until the iterator is deallocated (as list and tuple iterators do) and mark exhaustion by setting `di_pos` to -1.
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In the free-threaded build, threads advancing the same dict iterator each read
di_dictas a borrowed reference, so concurrently exhausting it could rundi->di_dict = NULL; Py_DECREF(d)more than once and free the dict while other threads were still using it. Reversed iterators were also affected: they dropped the reference while holding the dict's critical section.In the free-threaded build, keep the iterator's reference to the dict until the iterator is deallocated (as list and tuple iterators do) and mark exhaustion by setting
di_posto -1.