boost::program_options - does it do an exact string matching for command line options?

Question

There seems to be a problem the way boost::program_options's options_description matching is done.

int main(int argc, char* argv[])
{
    boost::program_options::options_description desc("CmdLine utility");
    desc.add_options()
        ("hel", "hel message")
        ("help", "produce help message")
        ("helps","helps message")       
    ;
    boost::program_options::variables_map vm;
    boost::program_options::store(boost::program_options::parse_command_line(argc, argv,desc), vm);
    boost::program_options::notify(vm);

    if(vm.count("help")) {
        std::cout << desc << std::endl;
    }
    if(vm.count("helps")) {
        std::cout << "helps..." << std::endl;
    }
    if(vm.count("hel")) {
        std::cout << "hel..." << std::endl;
    }
    return 0;
}

Output -

C:\code>cmd.exe --helps
helps...
C:\code>cmd.exe --help
helps...
C:\code>cmd.exe --hel
helps...

The output changes if I change the order in which options are added using add_options() call. Also it looks like program_options does not do a complete command string matching, so even if you enter a substring of the option, it will consider it as a valid option without doing a complete string comparison. If this is a boost::program_options feature, is there any way to force it to do exact string matching rather than doing it with substring matching ? (I am using Boost version 1.42)

Answer 1

By default, program_option has allow_guessing style bit on, so a substring match is sufficient. The behaviour you observe, where an option is matching a prefix of the command line, even when there's a different option that matches fully, is a bug. It's fixed in 1.45.