gh-140487: Fix Py_RETURN_NOTIMPLEMENTED in limited C API 3.11 (GH-140636)

vstinner · web-flow · commit c6364775236e · 2025-10-27T12:59:56.000+01:00
Py_RETURN_NONE, Py_RETURN_TRUE and Py_RETURN_FALSE have already been fixed by commit 9258f3d (issue gh-134989).
diff --git a/Include/object.h b/Include/object.h
@@ -695,8 +695,13 @@ 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
@@ -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.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+Fix :c:macro:`Py_RETURN_NOTIMPLEMENTED` in limited C API 3.11 and older:
	`2`	+don't treat ``Py_NotImplemented`` as immortal. Patch by Victor Stinner.