2.14 hang with zero-length match (using look-ahead)

[powerman]

~ $ mkdir tmp/ack
~ $ cd tmp/ack/
~/tmp/ack $ echo 'say "This is a test";' > test.pl
~/tmp/ack $ ack test 
test.pl
1:say "This is a test";
~/tmp/ack $ ack '(?=test)'
test.pl
----- HERE IT HANGS! Press Ctrl-C -----
^C
~/tmp/ack $ ack '(?=test).*'
test.pl
1:say "This is a test";

The real use-case was when I was looking for combination of several words which should be in same line but in unknown order, like:

ack '(?=.*word1)(?=.*word2)'

[hoelzro]

Thanks for the report! This issue has already been reported as #542, and has been fixed in the dev branch.