Refcount leak in `finalize_remove_modules()`

[hyongtao-code]

Bug report

Bug description:

There is a reference leak in finalize_remove_modules() (pylifecycle.c).

In the iterator-based cleanup path, PyIter_Next() returns a new reference
for key, but if PyObject_GetItem(modules, key) fails, the code continues
without DECREF'ing key.

The fix is to add Py_DECREF(key) before continue;.

Minimal fix:

PyObject *key;
while ((key = PyIter_Next(iterator))) {
    PyObject *value = PyObject_GetItem(modules, key);
    if (value == NULL) {
        PyErr_FormatUnraisable("Exception ignored while removing modules");
        Py_DECREF(key);      <--------------------here
        continue;
    }
    CLEAR_MODULE(key, value);
    Py_DECREF(value);
    Py_DECREF(key);
}
if (PyErr_Occurred()) {
    PyErr_FormatUnraisable("Exception ignored while removing modules");
}
Py_DECREF(iterator);

CPython versions tested on:

CPython main branch

Operating systems tested on:

Windows

Linked PRs

• gh-144307: fix refcount leak in finalize_remove_modules() #144308