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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David Bateman                                David.Bateman at motorola.com
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