On Sat, 27 Jul 2019, ND via Pcre-dev wrote: > It seems last code unit "c" is not detected and so start optimization don't > work: > > > PCRE2 version 10.34-RC1 2019-04-22 > /\Aabc/info,auto_callout > Capture group count = 0 > Max lookbehind = 1 > Compile options: auto_callout > Overall options: anchored auto_callout > First code unit = 'a' > Subject length lower bound = 3 > abx > --->abx > +0 ^ \A > +2 ^ a > +3 ^^ b > +4 ^ ^ c > No match
For an anchored pattern, the "must be present" code unit value is set only if it follows a variable length item in the pattern. This is a judgement that it will probably be faster in most cases and it will avoid the really bad case: suppose, instead of "abx" you have abxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx...very long string without "c" It can take a lot of time to search a long string (and in fact, for that reason, there is a limit to how much is searched, even when there is a value to search for). Much quicker to fail the match after just checking the first three characters. Philip -- Philip Hazel -- ## List details at https://lists.exim.org/mailman/listinfo/pcre-dev
