Fix compilation using WITH_OLD_KEEPALIVE

Closes #3250. Thanks to Stefan Bigler

ChangeLog.txt

@@ -14,6 +14,7 @@ Broker:
   Closes #3238.
 - Fix reporting of client disconnections being incorrectly attributed to "out
   of memory". Closes #3253.
+- Fix compilation when using `WITH_OLD_KEEPALIVE`. Closes #3250.
 
 Client library:
 - Fix C++ symbols being removed when compiled with link time optimisation.

src/CMakeLists.txt

@@ -113,6 +113,12 @@ if (WITH_PERSISTENCE)
 	add_definitions("-DWITH_PERSISTENCE")
 endif (WITH_PERSISTENCE)
 
+option(WITH_OLD_KEEPALIVE
+	"Use legacy keepalive check mechanism?" OFF)
+if (WITH_OLD_KEEPALIVE)
+	add_definitions("-DWITH_OLD_KEEPALIVE")
+endif (WITH_OLD_KEEPALIVE)
+
 option(WITH_SYS_TREE
 	"Include $SYS tree support?" ON)
 if (WITH_SYS_TREE)

src/keepalive.c

@@ -146,15 +146,7 @@ void keepalive__check(void)
 void keepalive__check(void)
 {
 	struct mosquitto *context, *ctxt_tmp;
-	time_t timeout;
 
-	if(db.contexts_by_sock){
-		timeout = (last_keepalive_check + 5 - db.now_s);
-		if(timeout <= 0){
-			timeout = 5;
-		}
-		loop__update_next_event(timeout*1000);
-	}
 	if(last_keepalive_check + 5 <= db.now_s){
 		last_keepalive_check = db.now_s;