How to properly catch std and boost exceptions

std::exception has a member function called what() that returns a const char* that might explain what happened. If you want to log it (guessing that LOG_FATAL wraps printf somehow) you can do:

catch(std::exception const&  ex)
{
    LOG_FATAL("Can't init settings. %s", ex.what());
}

For boost::exception though you can use boost::get_error_info to find out more about it.

probably WAY too late in answering... but

        <...snip...>
        catch (const boost::exception& e)
        {
            std::string diag = diagnostic_information(e);
            // display your error message here, then do whatever you need to, e.g.        
            LOG_FATAL("Can't init settings. %s", diag);
        }
        <...snip...>