Vim positive lookbehind bug?

Question

Enter this in a file:

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA

Hello
A

Hello
B

And then search for this using /:

\(Hello\n\)\@<=A

On my version of Vim (7.4, included patches: 1-582), the A underneath Hello is matched as expected, B is not, but also the 446th A on the first line is matched.

There is also some weird behaviour with this, if I make the line longer with more As, the 632nd A is highlighted. If I introduce 16 spaces at the beginning of the line, the 447th and the 632nd characters on the line are matched.

My question is, does this affect anyone else, and is it really a bug or is my search erroneous?

score 4 · Accepted Answer · answered Feb 12 '15 at 17:00

4

Yes, this looks like a bug. I can reproduce with Vim 7.4.608, but only with the default :set regexpengine=0 automatic selection.

To avoid the problem, you can either change the global option, or explicitly specify an engine inside the pattern:

\%#=1\(Hello\n\)\@<=A
\%#=2\(Hello\n\)\@<=A

Please report this bug, either to the vim_dev mailing list, or its issue tracker.

answered Feb 12 '15 at 17:00

Ingo Karkat

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I've reported it, your suggestion works so it must be an easy fix, there is something wrong with the automatic regexp engine selector – texasflood Feb 12 '15 at 17:24
Have you sent this to the mailing list? I haven't seen your post yet. – Ingo Karkat Feb 13 '15 at 07:50
Yup, thank you very much! For the record, [here it is](https://groups.google.com/d/msg/vim_dev/aDti801-7qo/3lsDUEEmVFEJ). – Ingo Karkat Feb 13 '15 at 15:52

Vim positive lookbehind bug?

1 Answers1