The answers given there cite denial of service attacks as the big threat. When I wrote the regexp matcher that comes buried inside of GNU Arch, I was careful t

The answers given there cite denial of service attacks as the big threat. When I wrote the regexp matcher that comes buried inside of GNU Arch, I was careful to ensure that client programs could limit both amount of memory and the amount of time used to attempt a match. If the matcher runs into the memory unit, it trades time for space and simply runs more slowly. If it runs for too long, programs can just stop the match and free everything up. Of course, on many normal, non-malicious patterns, the matcher is simply fast and memory efficient. That matcher also supports matching text that is not contiguous in memory. For example, if your text is split up into lots of separate strings (as in a DOM), this matcher can treat those as if they were all one long string.