Error recovering values from boost::unordered::unordered_map using std::string keys

Question

I'm storing in an unordered_map the results I get from a regex match. std::cout the sub matches m[1].str() and m[2].str() shows the pair key-value correctly.

Although when I store them in an unordered_map I always get an exception reporting that the key wasn't found.This is the code:

boost::unordered::unordered_map<std::string, std::string>
loadConfigFile(std::string pathToConfFile) throw(std::string){
    std::fstream fs;
    fs.open(pathToConfFile.c_str());
    if(!fs)
        throw std::string("Cannot read config file.");

    boost::unordered::unordered_map<std::string, std::string> variables;

    while(!fs.eof())
    {
        std::string line;
        std::getline(fs, line);
        //std::cout << line << std::endl;
        boost::regex e("^(.+)\\s*=\\s*(.+)");
        boost::smatch m; //This creates a boost::match_results
        if(boost::regex_match(line, m, e)){
            std::cout << m[1].str() << " " << m[2].str() << std::endl;
            variables[m[1].str()] = m[2].str();
        }
    }
    std::cout << variables.at(std::string("DEPOT_PATH")) << std::endl; //Here I get the exception

    return variables;
}

DEPOT_PATH is the name of a "variable" in a config file. std::cout << m[1].str() shows it perfectly, but not found in the unordered_map. Any ideas?

Answer 1

Most likely, the key you put in the unordered map contains whitespace (which you don't see when outputting it) and therefore is not found later.

In your regex ^(.+)\\s*=\\s*(.+), the first (.+) will greedily match as many characters as possible, including leading and trailing whitespace. The \\s* following it will always match an empty string. To prevent this, you can use (\\S+) for non-whitespace only, or use a non-greedy (.+?).

By the way, while (!fs.eof()) is wrong. Use while (std::getline(fs, line)) {...} instead.