A few fixes

Makefile

@@ -2,7 +2,7 @@
 CFLAGS:=-lwayland
 LDFLAGS:=-lwayland-client
 wl_unlocker: unlocker.o session-lock.o
-	gcc $(LDFLAGS) unlocker.o session-lock.o -o wl_unlocker
+	gcc -o wl_unlocker unlocker.o session-lock.o $(LDFLAGS)
 
 unlocker.o: unlocker.c session-lock.h
 

unlocker.c

@@ -52,6 +52,10 @@ static void lock_finished_handler(void * data, struct ext_session_lock_v1 * lock
 int main(void) {
 	// get wl_display, the core object
 	wl = wl_display_connect(NULL);
+	if (wl == NULL) {
+		fprintf(stderr, "Cannot connect to compositor, no wayland?\n");
+		return 1;
+	}
 
 	// prepare listeners for wl_registry.global
 	struct wl_registry_listener reg_listener = {
@@ -89,7 +93,7 @@ int main(void) {
 		fprintf(stderr, "BUG!\n");
 		return 1;
 	} else if (lock_state == FINISHED) {
-		printf("Not locked.\n");
+		printf("Cannot get lock – either another lock is running or not lockable.\n");
 		// nothing to do, just destroy stuff
 		ext_session_lock_v1_destroy(lock);
 	} else if (lock_state == LOCKED) {