> re2 uses a DFA-based system instead that just doesn't support the kinds of regexes that catastrophically backtrack
There are certain fearures that are harder or impossible to implement with RE2's approach, but it's not true that it doesn't support the kind of regex that would catastrophically backtrack using a backtracking engine.
`(.*a)*b` would be a (silly) example of a regex that can catastrophically backtrack using backtracking engines and re2 supports it just fine without backtracking.
There are certain fearures that are harder or impossible to implement with RE2's approach, but it's not true that it doesn't support the kind of regex that would catastrophically backtrack using a backtracking engine.
`(.*a)*b` would be a (silly) example of a regex that can catastrophically backtrack using backtracking engines and re2 supports it just fine without backtracking.