The problem was caused by a lazy repeat looping forever, growing the backtracking stack. Greedy repeats were OK.
2020.7.14
Git issue 377: request: \h for horizontal space
Added \h as an alias to [[:blank:]].
2020.6.7
Git issue 376: Is the \L option as efficient as it can be?
Switched StringSet to use fallback method due to inefficiencies in the engine. Needs more investigation.
2020.5.14
Git issue 372: Regression from 2020.4.4 -> 2020.5.7 in non-fuzzy matching pattern
Changed the 'state' member that's tested in is_repeat_guarded for a fuzzy match. The previously-used member wasn't initialised in a non-fuzzy match. The new test is a better one to use anyway.
2020.5.13
Git issue 371: Specifying character set when fuzzy-matching allows characters not in the set
fuzzy_ext_match and fuzzy_ext_match_group_fld didn't support sets!
2020.5.7
Git issue 370: Confusions about Fuzzy matching behavior (prob a bug?)