bug#19420: intermittent segfault using grep -P

[J.P. Hendrix]

When using the following command, *most* of the time I get a 
Segmentation fault (10 out of 16 times):

€ cat grepTxt | grep -P 'b(?:(?!tom).)+'
Segmentation fault (core dumped)

This happens with the  grep version that came with my Linux installation:

€ grep -V
grep (GNU grep) 2.16

I am on:

NAME="Ubuntu"
VERSION="14.04.1 LTS, Trusty Tahr"

But also compiled grep from sources 
(http://ftp.gnu.org/gnu/grep/grep-2.21.tar.xz) with the same problem.

libpcre3:amd64; libpcre3:i386; libpcre3-dev:amd64; libpcrecpp0:amd64 are 
all 1:8.31-2ubuntu2

I tried to reduce the regex and the text as much as possible to still 
reproduce the issue most of the time, unfortunately the text is still 
16893 bytes long. As I don't know if it is OK to attach such a long 
file, I put it on pastebin, but will expire in a month.

http://pastebin.com/download.php?i=jsHskMAA

Please advise.

Kind regards,

JP