[ruby-core:24190] Re: [Bug #1740] ruby regexp 100% usage cpu.

Excerpts from rubymine message of Tue Jul 07 17:38:10 +0300 2009:
> reg =
> %r{<.*?div\s*class\s*=\s*.entry.*?>[^<]*<.*?img\s*src\s*=\s*.([^"|']*).*?>[^<]*<
> .*?p\s*class\s*=\s*.date.*?>}im
> #del = %r{<(?!p|div|img)[^>]*>}i
>
> My ruby process use 100% cpu for long time and on linux exit normaly, on
> freebsd no exit %-(.
> I'm submited another bug for freebsd
> http://www.freebsd.org/cgi/query-pr.cgi?pr=136384 but this is for freebsd only. 
> 
> This templates writes another man for perl and i'm must use here.

Firstly, Ruby regexps are not PCRE, so you must have some
leeway constructing the regexp. You cannot (necessarily)
just drop the Perl version in and expect it to work, or
work the same.

Secondly, you should be using something like Nokogiri or
hpricot rather than "parsing" the HTML yourself. For example
your div matcher will fail if the attribute is quoted.

Thirdly, it has "pathological" written all over it. You
should refactor the regexp to try to get some small case
that is reproducible to illustrate the actual problem to
see if it is something that should be fixed.

I am pretty sure there was another thread about really bad
regexp performance in a pathological case a while back, if
you want to search the archives.


Eero
--
Magic is insufficiently advanced technology.