gh-101037: Fix potential memory underallocation for zeros of int subtypes (#101038)

This PR fixes object allocation in long_subtype_new to ensure that there's at least one digit in all cases, and makes sure that the value of that digit is copied over from the source long.

Needs backport to 3.11, but not any further: the change to require at least one digit was only introduced for Python 3.11.

Fixes #101037.
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Mark Dickinson 2023-01-21 10:23:59 +00:00 • committed by GitHub
parent 9e947675ae
commit 401fdf9c85
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3 changed files with 10 additions and 0 deletions

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@ -5638,6 +5638,11 @@ long_subtype_new(PyTypeObject *type, PyObject *x, PyObject *obase)
n = Py_SIZE(tmp);
if (n < 0)
n = -n;
/* Fast operations for single digit integers (including zero)
* assume that there is always at least one digit present. */
if (n == 0) {
n = 1;
}
newobj = (PyLongObject *)type->tp_alloc(type, n);
if (newobj == NULL) {
Py_DECREF(tmp);