bug#36167: [PATCH] Replace manually crafted hex regexes with [[:xdigit:]]

[Paul Eggert]

On 6/11/19 10:04 AM, Eli Zaretskii wrote:
> Where did the question about non-ASCII
> digits come from, given this text?

It came from POSIX, where [:xdigit:] and [:digit:] might match other 
characters. Similarly, in POSIX [a-f] might match characters other than 
'a', 'b', 'c', 'd', 'e', 'f'. We don't need to worry about this in 
Emacs, since Emacs regexps don't have that particular misfeature of POSIX.

I'm on the fence about replacing 0-9A-Fa-f with [:xdigit:], as I can see 
both sides of the argument. If Mattias is dubious, then perhaps we 
should leave the regexps alone - he's had more experience than the rest 
of us when it comes to scanning for dubious regexp constructions.