Part one: I spent yesterday trying to use a char * to set the default for a string option: opts.add_option("config", "Set the config file to examine", po::value<string>()->default_value("newconfig")); The result was a segmentation fault or illegal instruction during the destruction of my opts class (a wrapper that has several options_descriptions and a positional_options_description; there are methods like the add_option() above that allow various options to be set, in general they put the value_semantic argument last, but otherwise pass arguments directly through). So today I realized that passing a char * to something expecting a std:string might be asking for trouble. So I tried this: string DefaultConfig("newconfig"); opts.add_option("config", "Set the config file to examine", po::value<string>()->default_value(DefaultConfig)); That didn't work any better. Moving the string to global scope didn't help, nor did making it static. So, how do I set the default for a string option? Part two: I want to set up a boolean option (its existence returns true, and if it is not there it returns false). This is done using bool_switch(), I see. However I end up with a segmentation fault if I use this following line: opts.add_option("bool", "testing boolean", po::bool_switch()); The fault occurs, again, when opts' destructor is running. If I leave out the bool_switch() (ie. don't set a value semantic) I get no such error, although the behaviour is not as I'd like it. So, how do I use bool_switch()? What am I missing here? It is possible I'm having trouble with all occurences of po::value<>, as I haven't used it elsewhere yet (I'm adding stuff gradually)... Take care, Liam -- Liam Routt Ph: (03) 8344-1315 Research Programmer caligari@cs.mu.oz.au Computer Science, Melbourne University (or liam@routt.net)