GNU bug report logs - #16046
Bug with Regexp Containing only a Character Class with a Caret

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From: Cameron Desautels <camdez <at> gmail.com>
To: 16046 <at> debbugs.gnu.org
Subject: bug#16046: Bug with Regexp Containing only a Character Class with a Caret (PATCH)
Date: Thu, 5 Dec 2013 13:26:58 -0600

[Message part 1 (text/plain, inline)]

After further experimentation, I suspect that "[^]" is simply not
a valid regular expression.  For instance, grep(1) gives the
following behavior:

    $ echo "^" | grep "[^]"
    grep: brackets ([ ]) not balanced

This suggests that the broken behavior is within
`regexp-opt-charset`.  I've attached a patch for that function.

Here are some test cases which reveal the behavior of the unpatched
and patched versions of the function (the only difference is the
handling of the "[^]" case):

    ;; Pre-patch
    (regexp-opt-charset (list ?^))          ; "[^]"
    (regexp-opt-charset (list ?^ ?a))       ; "[a^]"
    (regexp-opt-charset (list ?^ ?-))       ; "[-^]"
    (regexp-opt-charset (list ?^ ?\]))      ; "[]^]"
    (regexp-opt-charset (list ?^ ?- ?\]))   ; "[]^-]"

    ;; Post-patch
    (regexp-opt-charset (list ?^))          ; "\\^"
    (regexp-opt-charset (list ?^ ?a))       ; "[a^]"
    (regexp-opt-charset (list ?^ ?-))       ; "[-^]"
    (regexp-opt-charset (list ?^ ?\]))      ; "[]^]"
    (regexp-opt-charset (list ?^ ?- ?\]))   ; "[]^-]"

--
Cameron Desautels <camdez <at> gmail.com>

[regexp-opt.el.diff (text/plain, attachment)]

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