Re: strange regexp behavior

[David Bateman]

Thomas Weber wrote:
> On Thu, Sep 18, 2008 at 11:34:55AM +0200, David Bateman wrote:
>   
> > Thomas Weber wrote:
> >     
> > > I'm currently discussing this with PCRE developers on their list,  
> > > http://lists.exim.org/lurker/message/20080915.202357.7f71f452.en.html
> > >
> > > I already learned that this innocent looking pattern is a bad citizen :)
> > >   
> > >       
> > Ok, tell us what happens with this thread.
> >     
>
> Patch attached; I've included a user-visible warning, because Phil Hazel
> (pcre's author) suggested that a regexp triggering such a problem should
> be rephrased.
>
> Maybe calling OCTAVE_QUIT in the added while-loop would be sensible as
> well.
>
> Patch is against 3.0.2, I had trouble compiling current tip. 
>
>         
Looking at the patch it looks ok to me, however maybe

while (matches == PCRE_ERROR_MATCHLIMIT)
 {
    pe.match_limit *= 10;
   matches = pcre_exec(re, &pe, buffer.c_str(),
    buffer.length(), idx,
    (idx ? PCRE_NOTBOL : 0),
    ovector, (subpatterns+1)*3);
  }

should be written as

#define PCRE_MATCHLIMIT_MAX 10
int i = 0;
while (matches == PCRE_ERROR_MATCHLIMIT && i++ < PCRE_MATCHLIMIT_MAX)
 {
    pe.match_limit *= 10;
   matches = pcre_exec(re, &pe, buffer.c_str(),
    buffer.length(), idx,
    (idx ? PCRE_NOTBOL : 0),
    ovector, (subpatterns+1)*3);
  }

to avoid a truly infinite recursion in the pattern string. The max limit 
might need adjusting.. What issues did you have copiling with the tip?

Regards
David


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