Index: multiple_sources.cpp
===================================================================
--- multiple_sources.cpp	(Revision 58289)
+++ multiple_sources.cpp	(Arbeitskopie)
@@ -27,7 +27,6 @@
 {
     try {
         int opt;
-        string config_file;
     
         // Declare a group of options that will be 
         // allowed only on command line
@@ -35,7 +34,7 @@
         generic.add_options()
             ("version,v", "print version string")
             ("help", "produce help message")
-            ("config,c", po::value<string>(&config_file)->default_value("multiple_sources.cfg"),
+            ("config,c", po::value<string>()->default_value("multiple_sources.cfg"),
                   "name of a file of a configuration.")
             ;
     
@@ -44,10 +43,10 @@
         // config file
         po::options_description config("Configuration");
         config.add_options()
-            ("optimization", po::value<int>(&opt)->default_value(10), 
+            ("optimization", po::value<int>(&opt)->default_value(10)->required(), 
                   "optimization level")
             ("include-path,I", 
-                 po::value< vector<string> >()->composing(), 
+                 po::value< vector<string> >()->composing()->required(), 
                  "include path")
             ;
 
@@ -74,8 +73,8 @@
         po::variables_map vm;
         store(po::command_line_parser(ac, av).
               options(cmdline_options).positional(p).run(), vm);
-        notify(vm);
-        
+
+        string config_file = vm["config"].as< string >();
         ifstream ifs(config_file.c_str());
         if (!ifs)
         {