[bug #37737] Contained subexpressions don't follow POSIX

[РоманДонченко]

URL:
  <http://savannah.gnu.org/bugs/?37737>

                 Summary: Contained subexpressions don't follow POSIX
                 Project: grep
            Submitted by: rdonch
            Submitted on: Срд 14 Ноя 2012 21:26:45
                Category: None
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any

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Details:

Here's what POSIX says
<http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html>:

9.3.6 BREs Matching Multiple Characters

<...> The string matched by a contained subexpression shall be within the
string matched by the containing subexpression. If the containing
subexpression does not match, or if there is no match for the contained
subexpression within the string matched by the containing subexpression, then
back-reference expressions corresponding to the contained subexpression shall
not match. <...> For example, <...> the expression "\(a\(b\)*\)*\2" fails to
match 'abab' <...> .

And yet...

$ src/grep '\(a\(b\)*\)*\2' <<< 'abab'
abab

I'm guessing that it assumes that \1 covers character #3, but \2 covers
character #2, which is against the spec.





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