How do I convert a boost::spirit::lex token's value from iterator_range to a string?

When I try to convert the value of a token from iterator_range, the lexer fails when attempting to read the next token. Here's the Tokens struct which holds the token definitions: (I don't think this is relevant but I'm including just in case.) ``` template <typename Lexer> struct Tokens : boost::spirit::lex::lexer<Lexer> { Tokens(); boost::spirit::lex::token_def<std::string> identifier; boost::spirit::lex::token_def<std::string> string; boost::spirit::lex::token_def<bool> boolean; boost::spirit::lex::token_def<double> real; boost::spirit::lex::token_def<> comment; boost::spirit::lex::token_def<> whitespace; }; template <typename Lexer> Tokens<Lexer>::Tokens() { // Define regex macros this->self.add_pattern ("LETTER", "[a-zA-Z_]") ("DIGIT", "[0-9]") ("INTEGER", "-?{DIGIT}+") ("FLOAT", "-?{DIGIT}*\\.{DIGIT}+"); // Define the tokens' regular expressions identifier = "{LETTER}({LETTER}|{DIGIT})*"; string = "\"[a-zA-Z_0-9]*\""; boolean = "true|false"; real = "{INTEGER}|{FLOAT}"; comment = "#[^\n\r\f\v]*$"; whitespace = "\x20\n\r\f\v\t+"; // Define tokens this->self = identifier | string | boolean | real | '{' | '}' | '<' | '>'; // Define tokens to be ignored this->self("WS") = whitespace | comment; } ``` Here's the definition of my token and lexer types: ``` typedef lex::lexertl::token<char const*> TokenType; typedef lex::lexertl::actor_lexer<TokenType> LexerType; ``` Here's the code I'm using for reading a token and converting it's value to a string. ``` Tokens<LexerType> tokens; std::string string = "9index"; char const* first = string.c_str(); char const* last = &first[string.size()]; LexerType::iterator_type token = tokens.begin(first, last); LexerType::iterator_type end = tokens.end(); //typedef boost::iterator_range<char const*> iterator_range; //const iterator_range& range = boost::get<iterator_range>(token->value()); //std::cout << std::string(range.begin(), range.end()) << std::endl; ++token; token_is_valid(*token); // Returns false ONLY if I uncomment the above code ``` The output of this code is "9" (it read the first number, leaving "index" in the stream). If I print out the value of string(first, last) at this point, it shows "ndex". For some reason the lexer is failing on that 'i' character? I've even tried using a std::stringstream to do the conversion, but this also causes the next token to be invalid: ``` std::stringstream out; out << token->value(); std::cout << out.str() << std::endl; ++token; token_is_valid(*token); // still fails ``` Finally, the next token IS valid if I simply send the token's value to cout: ``` std::cout << token->value() << std::endl; ++token; token_is_valid(*token); // success, what? ``` What am I missing about how iterator_range returned by token->value() works? Neither of the methods I used for converting it to a string appear to modify the integer_range or the lexer's input stream of characters. edit: I'm adding this here since a comment reply is too short to fully explain what happened. I figured it out. As sehe and drhirsch pointed out, the code in my original question was a sterilized version of what I'm actually doing. I'm testing the lexer using gtest unit tests with a test fixture class. As a member of that class, I have void scan(const std::string& str) which assigns the first and last iterators (data members of the fixture) from the given string. Problem is as soon as we exit this function the const std::string& str parameter is popped off the stack and no longer exists, invalidating these iterators even though they're data members of the fixture. Moral of the story: The object to which the iterators passed to lexer::begin() refer should exist as long as you expect to be reading tokens. I'd rather delete this question than document my silly mistake on the Internet, but to help the community I suppose I should leave it.