From: vyacheslav@kononenko.net   
      
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   I hit an issue with using boost::regex_match()   
      
   boost::regex reg( ".*" );   
   std::string function();   
   boost::smatch what;   
   if( boost::regex_match( function(), what, reg ) )   
       std::cout << what[0].str() << std::endl;   
      
   This code seems to have UB, as boost::smatch from boost-regex stores   
   positions in original string and use them for str() method. But the   
   problem is that temporary of std::string destroyed as soon as   
   boost::regex_match() terminates.   
      
   Bad thing this issue is not easy to diagnose as passing temporary of   
   std::string to const reference is completely legit, and to understand   
   that there is issue with such issue you have to dig into implementation.   
      
   I believe following code has the same problem:   
      
   boost::regex reg( ".*" );   
   boost::smatch what;   
   if( boost::regex_match( std::string( "abc" ), what, reg ) )   
       std::cout << what[0].str() << std::endl;   
      
   std::regex_match has the same signature when match is passed. Does it   
   have similar issue?   
      
   details can be found at http://stackoverflow.com/questions/15213   
   62/passing-temporary-stdstring-to-boostregex-match/15214343#15214343   
      
      
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