From a4709e525f5bc3a1719b33f52377cccb2af70278 Mon Sep 17 00:00:00 2001
From: Sergey Miryanov <sergey.miryanov@gmail.com>
Date: Wed, 22 Oct 2025 18:14:25 +0500
Subject: [PATCH] GH-139193: Fix dump_stack when PYTHON_LLTRACE=4 (GH-139384)

---
 Include/internal/pycore_stackref.h | 6 ++++++
 Python/ceval.c                     | 4 ++++
 2 files changed, 10 insertions(+)

diff --git a/Include/internal/pycore_stackref.h b/Include/internal/pycore_stackref.h
index 062834368bcd..efe9fb3b6c7c 100644
--- a/Include/internal/pycore_stackref.h
+++ b/Include/internal/pycore_stackref.h
@@ -296,6 +296,12 @@ PyStackRef_IsError(_PyStackRef ref)
     return ref.bits == Py_TAG_INVALID;
 }
 
+static inline bool
+PyStackRef_IsMalformed(_PyStackRef ref)
+{
+    return (ref.bits & Py_TAG_BITS) == Py_TAG_INVALID;
+}
+
 static inline bool
 PyStackRef_IsValid(_PyStackRef ref)
 {
diff --git a/Python/ceval.c b/Python/ceval.c
index f48f412fab83..defd084db9a4 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -160,6 +160,10 @@ dump_item(_PyStackRef item)
         printf("<NULL>");
         return;
     }
+    if (PyStackRef_IsMalformed(item)) {
+        printf("<INVALID>");
+        return;
+    }
     if (PyStackRef_IsTaggedInt(item)) {
         printf("%" PRId64, (int64_t)PyStackRef_UntagInt(item));
         return;
-- 
2.47.3