From 54a358a3d0e149484284a7823773d28cb95f4f4e Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Mon, 27 Oct 2025 12:59:56 +0100
Subject: [PATCH] gh-140487: Fix Py_RETURN_NOTIMPLEMENTED in limited C API 3.11
 (GH-140636)

Py_RETURN_NONE, Py_RETURN_TRUE and Py_RETURN_FALSE have already been
fixed by commit 9258f3da9175134d03f2c8c7c7eed223802ad945 (issue gh-134989).

(cherry picked from commit c6364775236e3c634c3393c7f50fece50611245f)
---
 Include/object.h                                         | 9 +++++++--
 .../C API/2025-10-26-16-45-06.gh-issue-140487.fGOqss.rst | 2 ++
 2 files changed, 9 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/C API/2025-10-26-16-45-06.gh-issue-140487.fGOqss.rst

diff --git a/Include/object.h b/Include/object.h
index 0266d25230a2b4..e59f78789844e7 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -1130,8 +1130,13 @@ PyAPI_DATA(PyObject) _Py_NotImplementedStruct; /* Don't use this directly */
 #  define Py_NotImplemented (&_Py_NotImplementedStruct)
 #endif
 
-/* Macro for returning Py_NotImplemented from a function */
-#define Py_RETURN_NOTIMPLEMENTED return Py_NotImplemented
+/* Macro for returning Py_NotImplemented from a function. Only treat
+ * Py_NotImplemented as immortal in the limited C API 3.12 and newer. */
+#if defined(Py_LIMITED_API) && Py_LIMITED_API+0 < 0x030c0000
+#  define Py_RETURN_NOTIMPLEMENTED return Py_NewRef(Py_NotImplemented)
+#else
+#  define Py_RETURN_NOTIMPLEMENTED return Py_NotImplemented
+#endif
 
 /* Rich comparison opcodes */
 #define Py_LT 0
diff --git a/Misc/NEWS.d/next/C API/2025-10-26-16-45-06.gh-issue-140487.fGOqss.rst b/Misc/NEWS.d/next/C API/2025-10-26-16-45-06.gh-issue-140487.fGOqss.rst
new file mode 100644
index 00000000000000..16b0d9d4084ba0
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2025-10-26-16-45-06.gh-issue-140487.fGOqss.rst	
@@ -0,0 +1,2 @@
+Fix :c:macro:`Py_RETURN_NOTIMPLEMENTED` in limited C API 3.11 and older:
+don't treat ``Py_NotImplemented`` as immortal. Patch by Victor Stinner.