Subject: Re: bug#26193: [0-9] versus [[:digit:]]

From: Paul Eggert <[email-masked]>
Date: Wed, 22 Mar 2017 11:01:43 -0700

On 03/22/2017 05:44 AM, John P. Linderman wrote:
> That puts the runtimes on equal footing:
>
In my measurements, P[0-9] is still a tiny bit slower if one is using 
glibc regex, due to a performance problem in glibc. You can work around 
it by configuring --with-included-regex. It's probably not worth 
worrying about, though.

By the way, using LC_ALL=C should help avoid performance problems like 
these in the future, if all you're doing is something where single-byte 
pattern matching suffices.