Regex oddity

[Larry2]

Hello, running this test :

// match_results::begin/end
// - using smatch, a standard alias of match_results<string::iterator>
#include <iostream>
#include <string>
#include <regex>

int main ()
{
  std::string s ("subject");
  std::smatch m;
  std::regex e ("(sub)(.*)");

  std::regex_match ( s, m, e );

  std::cout << "matches:" << std::endl;
  for (std::smatch::iterator it = m.begin(); it!=m.end(); ++it) {
	std::cout << *it << std::endl;
  }
  return 0;
}

On gcc 4.7.2 with c++11, it will return :

"subject"
"sub"

and the wrong one :
"bject"

Why is this b coming in ? I just copied and pasted the official code. Tried other languages and the third result should be "ject"

Something odd going on.

Any clue ?

Thanks,

Larry

[JLBorges]

Do not use std::regex with GCC's libstdc++.

See section 28 in
http://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html#status.iso.2011

Use boost regex instead (Replace std:: with boost::)

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

int main ()
{
  std::string s ("subject");
  boost::smatch m;
  boost::regex e ("(sub)(.*)");

  boost::regex_match ( s, m, e );

  std::cout << "matches:" << std::endl;
  for ( auto it = m.begin() ; it!=m.end() ; ++it )
      std::cout << *it << std::endl;
}

[Larry2]

Done and solved :D

Thanks !