Question

I’m trying to use some code that I wrote on another computer that splits a string into tokens. This code compiles fine. The code also works as intended on some other computers. I’ve managed to reduce the code down to the following:

#include <string>
#include <boost/regex.hpp>

typedef std::vector<std::string> token_t ;

token_t generate_tokens(std::string raw_input){ 
//this function breaks a input string into tokens. So test 100 goes to 2 tokens "test" and "100".

    boost::regex re_splitter("\\s+"); //this uses the regex \s+ to find whitespace. The + finds one or more whitespace characters.

    boost::sregex_token_iterator iter(raw_input.begin(), raw_input.end(), re_splitter, -1);
    //this breaks the string using the regex re_splitter to split into tokens when that is found. 
    boost::sregex_token_iterator j; //This is actually in the Boost examples, j is the equivalent of end. Yes this did also seem weird to me at first...

    token_t token_vector;
    unsigned int count = 0;
    while(iter != j)
    {
        token_vector.push_back(*iter);
        std::cout << *iter++ << std::endl;
        ++count;
    }
    return token_vector;
}

int main(){
    std::string in;
    int amount = -1;

    std::cout << "action: ";
    std::getline(std::cin, in);

    boost::regex EXPR("^test \\d*(\\.\\d{1,2})?$");
    bool format_matches = boost::regex_match(in, EXPR);

    token_t tokens = generate_tokens(in);

    if(format_matches){
        amount = atoi(tokens.at(1).c_str());
    }
    std::cout << "amount: " << amount << "\n";
    return 0;
}

This compiles without errors or warnings using: g++ -Wall test.cpp -lboost_regex
but when used at runtime providing the input test 100 the program fails.

action: test 100

a.out: /usr/local/include/boost/smart_ptr/shared_ptr.hpp:412: typename boost::detail::shared_ptr_traits::reference boost::shared_ptr::operator*() const [with T = boost::regex_traits_wrapper > >]: Assertion `px != 0′ failed.

Aborted

I’m completely lost as to what is going on here. Is this a bug in in my code or in the library? Any advice for debugging this is greatly appreciated!

Answer 1

Since you’re not using shared_ptr in your code, and I can see no other stuff that looks wrong AND it works on other machines, I’d say it’s probably a bug in Boost.Regex.

I bet the other machines have other versions of boost installed?

If I had to guess I’d try changing the std::cout << *iter++ << std::endl; line first. -> std::cout << *iter << std::endl; ++iter;.

And yeah, run it in a debugger like Swiss suggested, and see where the assertion is triggered.