From b012b84a8ef441fb53e1c7447caa1055a4164b1c Mon Sep 17 00:00:00 2001
From: dmiller <dmiller@e0a8ed71-7df4-0310-8962-fdc924857419>
Date: Fri, 17 Jun 2016 16:11:33 +0000
Subject: [PATCH] Avoid undefined behavior from calling front() on possibly
 empty std::list

---
 service_scan.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/service_scan.cc b/service_scan.cc
index c42431498..e61d65383 100644
--- a/service_scan.cc
+++ b/service_scan.cc
@@ -2264,7 +2264,7 @@ static int launchSomeServiceProbes(nsock_pool nsp, ServiceGroup *SG) {
     // Check that the service is still where we left it.
     // servicescan_connect_handler can call end_svcprobe before this point,
     // putting it into services_finished already.
-    if (SG->services_remaining.front() == svc) {
+    if (!SG->services_remaining.empty() && SG->services_remaining.front() == svc) {
       // Now remove it from the remaining service list
       SG->services_remaining.pop_front();
       // And add it to the in progress list