github.com/python/mypy/issues/18698
github.com/python/mypy/pull/18699
github.com/python/mypy/commit/0808624

From 0808624c67331f52c2d503ad8afe4f1087b0371c Mon Sep 17 00:00:00 2001
From: "Michael R. Crusoe" <1330696+mr-c@users.noreply.github.com>
Date: Tue, 18 Feb 2025 00:45:37 +0100
Subject: [PATCH] pythoncapi_compat: don't define Py_NULL if it is already
 defined (#18699)

Fixes: #18698

This is a naive fix for the gcc 15 error when compiling for Python 3.12
---
 mypyc/lib-rt/pythoncapi_compat.h |    2 ++
 1 file changed, 2 insertions(+)

Index: mypy-1.14.1/mypyc/lib-rt/pythoncapi_compat.h
===================================================================
--- mypy-1.14.1.orig/mypyc/lib-rt/pythoncapi_compat.h	2024-12-30 15:26:58.000000000 +0100
+++ mypy-1.14.1/mypyc/lib-rt/pythoncapi_compat.h	2025-05-05 16:10:16.167068167 +0200
@@ -30,6 +30,7 @@
 #  define _Py_CAST(type, expr) ((type)(expr))
 #endif
 
+#ifndef _Py_NULL
 // Static inline functions should use _Py_NULL rather than using directly NULL
 // to prevent C++ compiler warnings. On C23 and newer and on C++11 and newer,
 // _Py_NULL is defined as nullptr.
@@ -39,6 +40,7 @@
 #else
 #  define _Py_NULL NULL
 #endif
+#endif
 
 // Cast argument to PyObject* type.
 #ifndef _PyObject_CAST