From 574b080d69b2b968cfe871bc7cfe8fdf930fbc2e Mon Sep 17 00:00:00 2001
From: Daniel-Constantin Mierla <miconda@gmail.com>
Date: Tue, 5 Nov 2019 13:47:53 +0100
Subject: [PATCH] core: slow timer - warning message if callback function is
 null

---
 src/core/timer.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/src/core/timer.c b/src/core/timer.c
index 1bcd036fda1..f6b60ec3df0 100644
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -1101,7 +1101,19 @@ void slow_timer_main()
 #endif
 				SET_RUNNING_SLOW(tl);
 				UNLOCK_SLOW_TIMER_LIST();
-					ret=tl->f(*ticks, tl, tl->data);
+					if(likely(tl->f)) {
+						ret=tl->f(*ticks, tl, tl->data);
+					} else {
+						ret =0;
+#ifdef TIMER_DEBUG
+						LM_WARN("null timer callback for %p (%s:%u - %s(...))\n",
+								tl, (tl->add_file)?tl->add_file:"unknown",
+								tl->add_line,
+								(tl->add_func)?tl->add_func:"unknown");
+#else
+						LM_WARN("null callback function for %p\n", tl);
+#endif
+					}
 					/* reset the configuration group handles */
 					cfg_reset_all();
 					if (ret==0){