Re: [O] Stackoverflow in regexp matcher

[Peter Neilson]

On Wed, 03 Feb 2016 06:19:43 -0500, Nicolas Goaziou  
<address@hidden> wrote:

> "Loris Bennett" <address@hidden> writes:
>
> >   re-search-forward("^[^%]*\\\\usepackage.*{biblatex}" nil t)
>
> This is a pathological regexp. [^%] is anything but a percent sign, so
> it can contain newline characters. Basically [^%]* can match an entire
> buffer if it doesn't contain any %.
>
> I think the regexp used in `reftex-using-biblatex-p' should be
>
>   "^[^%\n]*\\\\usepackage.*{biblatex}"

Here's a link about the extreme difficulty of detecting pathological  
regular expressions:

https://mail.python.org/pipermail/python-dev/2003-May/035916.html

The author analyses the exponential not-found situation for (x+x+)+y and  
then suggests that for larger expressions, "... no more than 1 programmer  
in 1000 has even a vague idea how to start looking for such problems."