PCRE has exponential worst-case time.�� See for example

https://www.regular-expressions.info/catastrophic.html

but searching for PCRE exponential time or worst case

will find more.�� That's not the problem.�� The problem

is that it isn't *obvious* which regexps are safe and

that people are taught that regular expressions can be

matched in linear time, which is sort of the point of

them.�� But PCRE patterns *aren't* regular expressions.

On Wed, 6 Feb 2019 at 04:54, Pierce Ng <pierce@samadhiweb.com> wrote:

On Wed, Feb 06, 2019 at 12:26:00AM +1300, Richard O'Keefe wrote:
> Please DON'T move to PCRE.
> "Outside world standards"?�� There are so many.
> There are two important things to know about
> PCRE: (1) it is a popular open source regexp
> library for Perl-style regexps, (2) because of
> that, it is prone to truly horrendous performance
> problems.�� There are alternatives, such as re2,
> https://github.com/google/re2 ,
> which are not subject to PCRE's intrinsic
> performance pathologies.�� As it happens, re2
> supports *? +? and ??.

Can you share some examples of PCRE's bad performance?

Pierce