C++ regex not understanding

Question

The following outputs ">Hut" where I expect it to output "Hut". I know that .* is greedy but > must be matched and it is outside of the capture group so why is it in my submatch?

#include <string>
#include <regex>
#include <iostream>

using namespace std;

int main() {
        regex my_r(".*>(.*)");
        string temp(R"~(cols="64">Hut)~");
        smatch m;
        if (regex_match(temp, m, my_r)) {
                cout << m[1] << endl;
        }
}

Answer 1

This is a bug in libstdc++'s implementation. Watch these:

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

int main() {
    {
        using namespace std;
        regex my_r("(.*)(6)(.*)");
        smatch m;
        if (regex_match(std::string{"123456789"}, m, my_r)) {
            std::cout << m.length(1) << ", "
                      << m.length(2) << ", "
                      << m.length(3) << std::endl;
        }
    }

    {
        using namespace boost;
        regex my_r("(.*)(6)(.*)");
        smatch m;
        if (regex_match(std::string{"123456789"}, m, my_r)) {
            std::cout << m.length(1) << ", "
                      << m.length(2) << ", "
                      << m.length(3) << std::endl;

        }
    }

    return 0;
}

If you compile with gcc, the first one (libstdc++) returns the totally wrong result 9, -2, 4 and the second one (boost's implementation) returns 5, 1, 3 as expected.

If you compile with clang + libc++, your code works fine.

(Note that libstdc++'s regex implementation is only "partially supported", as described in http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52719.)