AMDG The following regular expression seems to cover all the cases: boost::regex min_max_regex( "((^\\s*#\\s*undef\\s*\\b(min|max)\\b)|" //#undef min/max "(\\b(min|max)\\b\\s*\\())|" //min/max(... "(\"[^\"]*\")|" //character array literals "(\'[^\']*\')|" //character literals "(/\\*.*?\\*/)|" // /**/ comments "(//.*?$)", // // comments boost::regex::normal ); There is an error iff match_results[1].matched is true. All that is required is to use regex_search instead of regex_iterator and to skip to the end of each match before continuing. In Christ, Steven Watanabe