Aidan Kehoe writes: > > 21.4 doesn’t have the problem; it found its way in between the > releases of 21.5.18 and 21.5.19, which from the mentions of regex.c in > src/ChangeLog implicates Ben. Nothing obvious strikes me from > eyeballing the diff between the two, so it may be another file. Dunno about that, but here's a few more test cases: (string-match "[\x7f\x80-\x9f]" "\x80") => nil (string-match "[\x80-\x9f]" "\x80") => 0 (string-match "[\x7f\x80-\x9e]" "\x80") => 0 (string-match "[\x7f\x80\x9f]" "\x80") => 0

(string-match "[\x7e\x80-\x9f]" "\x80") => 0 (string-match "[\x7f\x81-\x9f]" "\x81") => 0 I would guess this has something to do with \x7f and \x80 being special cases among the Mule leading bytes.