From 64814182976aa7af18e419a46e7279be8965d365 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: Handle module filename encoding errors

Propagate UTF-8 conversion errors before copying the module filename.

Backport to 3.15 and 3.14.
---
 .../2026-10-19-19-33-35.gh-issue-159739.09590b.rst            | 1 +
 Objects/moduleobject.c                                        | 4 ++++
 2 files changed, 5 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2026-10-19-19-33-35.gh-issue-159739.09590b.rst

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2026-10-19-19-33-35.gh-issue-159739.09590b.rst b/Misc/NEWS.d/next/Core_and_Builtins/2026-10-19-19-33-35.gh-issue-159739.09590b.rst
new file mode 100644
index 00000000000000..3231be417aa80e
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2026-10-19-19-33-35.gh-issue-159739.09590b.rst
@@ -0,0 +1 @@
+Avoid a crash when a module filename cannot be encoded as UTF-8.
diff --git a/Objects/moduleobject.c b/Objects/moduleobject.c
index 7a5d14c538391d..7c842f3ed8b196 100644
--- a/Objects/moduleobject.c
+++ b/Objects/moduleobject.c
@@ -992,6 +992,10 @@ _PyModule_GetFilenameUTF8(PyObject *mod, char *buffer, Py_ssize_t maxlen)
     }
     else {
         const char *filename = PyUnicode_AsUTF8AndSize(filenameobj, &size);
+        if (filename == NULL) {
+            Py_DECREF(filenameobj);
+            return -1;
+        }
         assert(size >= 0);
         if (size > maxlen) {
             size = -1;