emacs-devel
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: performance/hang bug in regex.c


From: Richard M. Stallman
Subject: Re: performance/hang bug in regex.c
Date: Tue, 02 Sep 2008 22:41:28 -0400

    Regexps can be implemented in mainly 2 ways: backtracking or not.
    If you don't do backtracking, the above problem doesn't occur.
    But many/most regexp implementations use a backtracking algorithm
    because it's almost indispensable in order to handle backreferences.

    Emacs provides backreferences and doesn't bother to provide 2 regexp
    implementations (a backtracking one for regexps with backrefs and
    a non-backtracking one for all the others), so you get pathological
    behaviors for regexps such as the one above.  It's too bad, and I hope
    we can fix it at some point, but don't hold your breath,

This comes up often enough that maybe it should be explained in one
of the manuals.




reply via email to

[Prev in Thread] Current Thread [Next in Thread]