Re: Support for '.*?' meaning leftmost-shortest per latest POSIX ERE spec

[Ed Morton]

I posted that question at bug-gnulib yesterday:

https://lists.gnu.org/archive/html/bug-gnulib/2024-08/msg00122.html

No response yet, I'll let you know if/when I hear anything.

    Ed.

On 8/20/2024 1:41 AM, arnold@skeeve.com wrote:
> It adds considerable complexity into the regexp matchers. Doing this is
> (way) beyond my capabilities.
>
> Please ask the Gnulib guys about it (and let me know what they say).
> As all of gawk, GNU grep and GNU sed use the routines from Gnulib,
> this feature won't be available until they add it.
>
> Arnold
>
> Ed Morton<mortoneccc@comcast.net>  wrote:
>
> > Thanks for the quick response, just curious - what makes it a bad
> > addition, is it extra complexity or worse performance or something else?
> >
> >       Ed.
> >
> > On 8/19/2024 8:26 AM,arnold@skeeve.com  wrote:
> > > Hi.
> > >
> > > I am aware of it.  Support for this feature can't happen unless and until
> > > GNU regex and GNU dfa, which are both part of Gnulib, support it.
> > > So you might consider asking on the bug-gnulib list what their plans
> > > are for it.
> > >
> > > EVEN if those libraries support this feature, I may not add it;
> > > I think this was a bad addition, and I'm quite certain that it's not on
> > > the radar screen for almost any other version of awk.
> > >
> > > Realistically, I wouldn't expect to see this appear any time soon.
> > >
> > > Arnold
> > >
> > > Ed Morton via "Bug reports only for gawk."<bug-gawk@gnu.org>   wrote:
> > >
> > > > Configuration Information [Automatically generated, do not change]:
> > > > Machine: x86_64
> > > > OS: cygwin
> > > > Compiler: gcc
> > > > Compilation CFLAGS: -ggdb -O2 -pipe -Wall -Werror=format-security
> > > > -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector-strong
> > > > --param=ssp-buffer-size=4
> > > > -fdebug-prefix-map=/cygdrive/d/a/scallywag/gawk/gawk-5.3.0-1.x86_64/build=/usr/src/debug/gawk-5.3.0-1
> > > > -fdebug-prefix-map=/cygdrive/d/a/scallywag/gawk/gawk-5.3.0-1.x86_64/src/gawk-5.3.0=/usr/src/debug/gawk-5.3.0-1
> > > > -DNDEBUG
> > > > uname output: CYGWIN_NT-10.0-22631 TournaMart_2023 3.5.3-1.x86_64
> > > > 2024-04-03 17:25 UTC x86_64 Cygwin
> > > > Machine Type: x86_64-pc-cygwin
> > > >
> > > > Gawk Version: 5.3.0
> > > >
> > > > Attestation 1:
> > > >        I have read
> > > > https://www.gnu.org/software/gawk/manual/html_node/Bugs.html.
> > > >        Yes
> > > >
> > > > Attestation 2:
> > > >        I have not modified the sources before building gawk.
> > > >        True
> > > >
> > > > Description:
> > > >        The latest POSIX ERE spec
> > > > (https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap09.html#tag_09_04_06)
> > > > says:
> > > >        ----
> > > >        Each of the duplication symbols ('+', '*', '?', and intervals) can
> > > > be suffixed by the repetition modifier '?' (<question-mark>), in which
> > > > case matching behavior for that repetition shall be changed from the
> > > > leftmost longest possible match to the leftmost shortest possible match,
> > > > including the null match (see A.9 Regular Expressions ). For example,
> > > > the ERE ".*c" matches up to and including the last character ('c') in
> > > > the string "abc abc", whereas the ERE ".*?c" matches up to and including
> > > > the first character 'c', the third character in the string.
> > > >        ----
> > > >        Gawk doesn't do that (yet) but I assume you're already aware of it
> > > > and so this is probably more of a "do you plan to support it and, if so,
> > > > what's the current target release?" than a real bug report.
> > > >
> > > > Repeat-By:
> > > >
> > > >        $ echo 'abc abc' | awk '{sub(/b.*c/,"")} 1'
> > > >        a
> > > >
> > > >        $ echo 'abc abc' | awk '{sub(/b.*?c/,"")} 1'
> > > >        a
> > > >
> > > >        "1" above is correct but "2" should output "a abc" per the new
> > > > POSIX spec.