Re: Possible regression in grep 3.10

[Paul Eggert]

On 2023-04-02 00:00, arnold@skeeve.com wrote:
> Maybe it's time to drop PCRE support from grep?

I doubt whether we could do that - it's a big change and I expect too 
many users depend on -P.

However, I still have qualms about the recent -P '\d' business, as \d 
currently means something different with grep -P than it does in Perl - 
or in Python and Java, for that matter.

The \d vs [0-9] issue has long been a source of trouble. See, for 
example the circa 2009 
<https://stackoverflow.com/questions/890686/should-i-use-d-or-0-9-to-match-digits-in-a-perl-regex>. 
That being said, Grep's current disagreement with Perl on this issue 
smells like even more trouble, as the Perl community has long settled on 
\d matching non-ASCII decimal digits, despite well-known issues with 
that <https://perldoc.perl.org/perlrecharclass#Digits>.

There's no perfect solution here. All things considered, though, perhaps 
it'd be better to go back to grep 3.9's behavior, which matches Perl's. 
Proposed patch attached. I have tested this with Ubuntu 22.10 but not 
with bleeding-edge PCRE2.

0001-grep-go-back-to-3.9-P-d-behavior.patch
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