GNU bug report logs - #17373
24.3.50; match data is incorrect if there are too many groups

Previous Next

Full log

Message #8 received at 17373 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: 17373 <at> debbugs.gnu.org
Subject: Re: 24.3.50; match data is incorrect if there are too many groups
Date: Sun, 18 May 2014 22:47:33 -0700

Yes, unfortunately Emacs currently has a limit of at most 256 groups of 
match data: one for the entire pattern, and 255 for parenthesized 
subpatterns.  If you go over the limit, the excess matches are silently 
discarded.  I don't see this limitation documented anywhere; it should 
be.  Or better yet, the limitation should be removed.

The limitation is wired into the representation of the 'start_memory' 
code in compiled regular expressions: this code has a one-byte operand. 
 As far as I know, the limitation is specific to Emacs, and is not 
present in the Gnulib or glibc versions of the regexp matcher.

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.