From fa80b209a2a3f166b34cff12a8d8c36a99fa16d2 Mon Sep 17 00:00:00 2001
From: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Date: Mon, 19 Oct 2026 12:34:30 -0700
Subject: [PATCH] gh-159739: Check character formatting allocation failure

Propagate the error from PyUnicode_FromOrdinal() before using the
result.

Backport to 3.15 and 3.14. On 3.14, the equivalent code is in
Python/formatter_unicode.c.
---
 .../2026-10-19-19-33-35.gh-issue-159739.173d49.rst             | 2 ++
 Objects/unicode_formatter.c                                    | 3 +++
 2 files changed, 5 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-10-19-19-33-35.gh-issue-159739.173d49.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-10-19-19-33-35.gh-issue-159739.173d49.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-10-19-19-33-35.gh-issue-159739.173d49.rst
new file mode 100644
index 000000000000000..a552d06ff7bb898
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-10-19-19-33-35.gh-issue-159739.173d49.rst
@@ -0,0 +1,2 @@
+Avoid a crash if formatting an integer with the ``c`` presentation type runs
+out of memory.
diff --git a/Objects/unicode_formatter.c b/Objects/unicode_formatter.c
index 8cbc774584fa685..7f0e0584f3813f3 100644
--- a/Objects/unicode_formatter.c
+++ b/Objects/unicode_formatter.c
@@ -1258,6 +1258,9 @@ format_long_internal(PyObject *value, const InternalFormatSpec *format,
             goto done;
         }
         tmp = PyUnicode_FromOrdinal(x);
+        if (tmp == NULL) {
+            goto done;
+        }
         inumeric_chars = 0;
         n_digits = 1;
         maxchar = Py_MAX(maxchar, (Py_UCS4)x);