Why does this C++11 std::regex example throw a regex_error exception?

28,519

Thanks for the hint. Had no idea the regex code in g++ was incomplete.

In the meantime, guess we'll have to refer to this old StackOverflow question:

C++: what regex library should I use?

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Stéphane
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Stéphane

Linux, Ubuntu, C++ developer. https://www.linkedin.com/in/scharette http://www.ccoderun.ca/

Updated on July 09, 2022

Comments

  • Stéphane
    Stéphane almost 2 years

    Trying to learn how to use the new std::regex in C++11. But the example I tried is throwing a regex_error exception I don't understand. Here is my sample code:

    #include <iostream>
    #include <regex>
    
    int main()
    {
        std::string str = "xyzabc1xyzabc2xyzabc3abc4xyz";
        std::regex re( "(abc[1234])" ); // <-- this line throws a C++ exception
    
        // also tried to do this:
        // std::regex re( "(abc[1234])", std::regex::optimize | std::regex::extended );
    
        while ( true )
        {
            std::cout << "searching in " << str << std::endl;
            std::smatch match;
            std::regex_search( str, match, re );
            if ( match.empty() )
            {
                std::cout << "...no more matches" << std::endl;
                break;
            }
            for ( auto x : match )
            {
                std::cout << "found: " << x << std::endl;
            }
            str = match.suffix().str();
        }
        return 0;
    }
    

    I compile and run like this:

    g++ -g -std=c++11 test.cpp
    ./a.out
    terminate called after throwing an instance of 'std::regex_error'
      what():  regex_error
    

    Looking at the backtrace in gdb, I see the exception thrown is regex_constants::error_brack.

  • ACyclic
    ACyclic over 9 years
    First gcc support is in gcc 4.9 : stackoverflow.com/questions/23474121/…