PCRE-related segfault in grep 2.5.1

[Michael Henry]

Dear grep maintainers,

I believe I've found a bug in GNU grep 2.5.1 related to
Perl-compatible regular expressions.

Symptom
=================================
A segmentation fault is produced by GNU grep whenever
Perl-compatible regular expressions is turned on and a
negated character class is used that fails to match after
scanning a non-zero amount of text.

Reproducing the bug
=================================
 address@hidden ~]$ echo "No bug" | grep -P '[^a]'
 No bug
 address@hidden ~]$ echo "a" | grep -P '[^a]'
 Segmentation fault


Test environment
=================================

Tested using GNU grep 2.5.1 on my Fedora Core 2 and 3 boxes.
 address@hidden ~]$ grep --version
 grep (GNU grep) 2.5.1

 Copyright 1988, 1992-1999, 2000, 2001 Free Software Foundation, Inc.
 This is free software; see the source for copying conditions. There is NO
 warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR 
PURPOSE.

It appears to be a problem only with the Perl-compatible regular
expression mode (enabled by the -P option).

Thanks,
Michael Henry