lookbehind broken

[Matt Chesler]

Trying to troubleshoot unexpected behavior with haproxy, I discovered that lookbehind appears to be broken in version 1:8.31-2ubuntu2.3 of the libpcre3 package.

I have an haproxy rule to rewrite URL paths that do not begin with "build" or "static":

reqirep ^([^\ :]*)\ /(?!build|static).*\ (.*) \1\ /index.html\ \2

With the latest version of libpcre3 installed (1:8.31-2ubuntu2.3), this line matches all requests. If I downgrade to 1:8.31-2ubuntu2.2 and restart haproxy, the rule correctly matches only paths that do not start with "static" or "build".

$ lsb_release -rd
Description: Ubuntu 14.04.4 LTS
Release: 14.04

$ apt-cache policy libpcre3
libpcre3:
  Installed: 1:8.31-2ubuntu2.3
  Candidate: 1:8.31-2ubuntu2.3
  Version table:
 *** 1:8.31-2ubuntu2.3 0
        500 http://us-east-1.ec2.archive.ubuntu.com/ubuntu/ trusty-updates/main amd64 Packages
        100 /var/lib/dpkg/status
     1:8.31-2ubuntu2.2 0
        500 http://security.ubuntu.com/ubuntu/ trusty-security/main amd64 Packages
     1:8.31-2ubuntu2 0
        500 http://us-east-1.ec2.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages