From 56fc4e1a70f199ba93ce7b799bafe8532deb7bdb Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Fri, 17 Nov 2023 15:16:15 +0100
Subject: [PATCH] Add comment about _Py_IMMORTAL_REFCNT in Py_INCREF()

---
 Include/object.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Include/object.h b/Include/object.h
index 3a9e44849213f37..f5da8386626fc02 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -758,6 +758,7 @@ static inline Py_ALWAYS_INLINE void Py_INCREF(PyObject *op)
     uint32_t local = _Py_atomic_load_uint32_relaxed(&op->ob_ref_local);
     uint32_t new_local = local + 1;
     if (new_local == 0) {
+        // local is equal to _Py_IMMORTAL_REFCNT: do nothing
         return;
     }
     if (_Py_IsOwnedByCurrentThread(op)) {
@@ -771,6 +772,8 @@ static inline Py_ALWAYS_INLINE void Py_INCREF(PyObject *op)
     PY_UINT32_T cur_refcnt = op->ob_refcnt_split[PY_BIG_ENDIAN];
     PY_UINT32_T new_refcnt = cur_refcnt + 1;
     if (new_refcnt == 0) {
+        // cur_refcnt is equal to _Py_IMMORTAL_REFCNT: the object is immortal,
+        // do nothing
         return;
     }
     op->ob_refcnt_split[PY_BIG_ENDIAN] = new_refcnt;