From ee514323a553596ee2e937a8f8463eb741c09cb6 Mon Sep 17 00:00:00 2001
From: Mark Dickinson <dickinsm@gmail.com>
Date: Sat, 14 Jan 2023 17:01:49 +0000
Subject: [PATCH] gh-101037: Fix memory allocation for zeros of int subtypes

---
 .../2023-01-14-17-03-08.gh-issue-101037.9ATNuf.rst           | 2 ++
 Objects/longobject.c                                         | 5 +++++
 2 files changed, 7 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2023-01-14-17-03-08.gh-issue-101037.9ATNuf.rst

diff --git a/Misc/NEWS.d/next/Core and Builtins/2023-01-14-17-03-08.gh-issue-101037.9ATNuf.rst b/Misc/NEWS.d/next/Core and Builtins/2023-01-14-17-03-08.gh-issue-101037.9ATNuf.rst
new file mode 100644
index 000000000000000..a48756657a29d30
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2023-01-14-17-03-08.gh-issue-101037.9ATNuf.rst	
@@ -0,0 +1,2 @@
+Fix potential memory underallocation issue for instances of :class:`int`
+subclasses with value zero.
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 1db4ca418e066ec..51ac86961c99542 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -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);