missing return

exercises/06/vslc/vsl_programs/ps5-codegen1/function_call.vsl

@@ -6,4 +6,5 @@ end
 func main() 
 begin
     print 2 + add(40, 2) + 2
+    return 0
 end

exercises/06/vslc/vsl_programs/ps5-codegen1/helloworld.vsl

@@ -1,3 +1,4 @@
 func main() begin
     print "Hello, World!"
+    return 0
 end

exercises/06/vslc/vsl_programs/ps5-codegen1/shadow.vsl

@@ -21,4 +21,5 @@ func main() begin
         print a
     end
     print b
+    return 0
 end