entirely. Good alternatives are CTRE (https://github.com/hanickadot/compile-time-regular-expressio...) which parses the regex and instantiates the automaton entirely at compile-time, or Google's re2 (https://github.com/google/re2) if you need to generate regular expressions at run-time.

Even boost.regex on which std::regex is originally based, performs better because they can afford to break ABI.