From a2b0b3ca37398bef4e14d1c01ad049529a06937c Mon Sep 17 00:00:00 2001
From: Jukka Lehtosalo <jukka.lehtosalo@iki.fi>
Date: Tue, 27 May 2025 17:39:28 +0100
Subject: [PATCH] [mypyc] Add comment about incref/decref and free-threaded
 builds

---
 mypyc/lib-rt/mypyc_util.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mypyc/lib-rt/mypyc_util.h b/mypyc/lib-rt/mypyc_util.h
index 64bf025aec27..27a11ab9f581 100644
--- a/mypyc/lib-rt/mypyc_util.h
+++ b/mypyc/lib-rt/mypyc_util.h
@@ -38,6 +38,9 @@
 //
 // Py_INCREF and other CPython operations check for immortality. This
 // can be expensive when we know that an object cannot be immortal.
+//
+// This optimization cannot be performed in free-threaded mode so we
+// fall back to just calling the normal incref/decref operations.
 
 static inline void CPy_INCREF_NO_IMM(PyObject *op)
 {