From dd95447b05eb2e86e0500d953f43213df028c19a Mon Sep 17 00:00:00 2001
From: Eli Zaretskii <eliz@gnu.org>
Date: Sat, 21 Jun 2025 11:53:24 +0300
Subject: [PATCH] Avoid segfault when profiling Lisp programs with threads

* src/eval.c (backtrace_top): Don't segfault if current_thread is
NULL.  (Bug#76970)
---
 src/eval.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/eval.c b/src/eval.c
index 46705dc4543..4c514001d9d 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -171,7 +171,7 @@ backtrace_top (void)
   /* This is so "xbacktrace" doesn't crash in pdumped Emacs if they
      invoke the command before init_eval_once_for_pdumper initializes
      specpdl machinery.  See also backtrace_p above.  */
-  if (!specpdl)
+  if (!current_thread || !specpdl)
     return NULL;
 
   union specbinding *pdl = specpdl_ptr - 1;