From 8fc1a444fa82ffaf5751cc87bd0ab470ee0cf307 Mon Sep 17 00:00:00 2001
From: Pip Cet <pipcet@protonmail.com>
Date: Sat, 12 Jul 2025 10:22:01 +0000
Subject: [PATCH] Avoid crashes when profiling multi-threaded Lisp (bug#76970)

* src/eval.c (backtrace_p): Check 'current_thread' before
dereferencing it.

(cherry picked from commit fce86c7e9523b9b6c29241ae9d1dea340f0d849c)
---
 src/eval.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/eval.c b/src/eval.c
index 2e96c584524..b606990a297 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -159,7 +159,11 @@ set_backtrace_debug_on_exit (union specbinding *pdl, bool doe)
 
 bool
 backtrace_p (union specbinding *pdl)
-{ return specpdl ? pdl >= specpdl : false; }
+{
+  if (current_thread && specpdl && pdl)
+    return pdl >= specpdl;
+  return false;
+}
 
 static bool
 backtrace_thread_p (struct thread_state *tstate, union specbinding *pdl)
-- 
2.39.5