bug in regex 3.31 (boost 1.28)?

I sent this originally to James Maddock, but realized this is probably a better place to post it. At work we've been testing out regex (nice work BTW) in some of our code, and appear to have found a bug. We ran into it parsing HTML, and I've written a test C++ app to reproduce it. In the program below, the output should be the same for both searches as far as I can tell, but it's not. I don't know if it's some interaction with the quote character or something like that. We attempted to use other quantifiers (after '?', we tried '*', '{0,1}', ["]?) to no avail. I'm confident this is not user error. The extra grouping is annoying (in "goodPatternStr"), but is an acceptable workaround. The strange thing is that a non-capturing group doesn't fix it. Ideas? --Mark Ping -------------------------------------------------------------------------------------- output: input: ]*name=\"?([^> \"]*)[^>]*value=\"?([^> \"]*)"; const char* goodPatternStr = "]*name=(\"?)([^> \"]*)[^>]*value=\"?([^> \"]*)"; // ^^^^^ //note that the only difference between bad and good is that "good" //has grouping around the optional " after 'name=' // //In both versions of the matches, the second group is matched. //Only the first group has this problem. boost::match_resultsstd::string::const_iterator what; std::string in = "