[tools] gen_settings: error if a handler but no module attribute is s…

…pecified

previously it just silently ignored the handler, which is really really bad!

sw/tools/gen_settings.ml

@@ -81,9 +81,14 @@ let print_dl_settings = fun settings ->
       let v = ExtXml.attrib s "var" in
       begin
         try
-          let h = ExtXml.attrib s "handler" and
-              m =  ExtXml.attrib s "module" in
-          lprintf "case %d: %s_%s( _value ); _value = %s; break;\\\n" !idx (Filename.basename m) h v
+          let h = ExtXml.attrib s "handler" in
+          begin
+            try
+              let m =  ExtXml.attrib s "module" in
+              lprintf "case %d: %s_%s( _value ); _value = %s; break;\\\n" !idx (Filename.basename m) h v
+            with
+                ExtXml.Error e -> prerr_endline (sprintf "Error: You need to specify the module attribute for setting %s to use the handler %s" v h); exit 1
+          end;
         with
             ExtXml.Error e -> lprintf "case %d: %s = _value; break;\\\n" !idx v
       end;