Christian, If I put an unknown --option on the command line, I get an exception with an "unknown option" message, just as you would expect. If I omit --limit from the command line, then it gets defaulted to 1, just as it should. However, if I put --limit on the command line with an illegal value, say a string or a negative number rather than an unsigned int, then there is no exception message, even though I am catching std::exception& and (...) and printing a message for both. Instead, Dr Watson is called, apparently without triggering a C++ exception. Merrill