http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58576
Bug ID: 58576 Summary: std::regex_match() reports mismatched braces on a valid regex Product: gcc Version: 4.8.1 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: galens at capaccess dot org Created attachment 30929 --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30929&action=edit Archive containing the g++ -v -save-temps compile log, the generated .ii file and the original .cpp with the minimum-to-reproduce test case. I attempted to use a regex to validate qualified hostnames. However, when I used the regex from this thread ( http://stackoverflow.com/questions/1418423/the-hostname-regex ), with or without replacing the [0-9A-Za-z] with [:alnum:] (and properly escaping the backslashes), I get a regex_error exception thrown on std::regex_match() call, with a regex_constants::error_brack as the reported code(). Using: An unmodified copy of gcc 4.8.1 20130603 from the Fedora 19 primary repository (rpm ver: 4.8.1-1.fc19 ) (I use 4-spaces-per-tab in my source code, which isn't relevant for the code, but might make hand-tracing of Parens, Braces, and Brackets I did in comments more understandable.) (And, yes, I know replacing [0-9A-Za-z] with [:alnum:] isn't a legitimate change WRT domain name validity, unless I force a 'C' locale. It was just easier to read when hunting down this issue.)