[Bug 198552] awk unmatched right parenthesis in regular expressions

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=198552

            Bug ID: 198552
           Summary: awk unmatched right parenthesis in regular expressions
           Product: Base System
           Version: 9.3-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Many People
          Priority: ---
         Component: bin
          Assignee: freebsd-bugs at FreeBSD.org
          Reporter: weeks at iastate.edu

Created attachment 154253
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=154253&action=edit
Patch to awk 20121220 b.c

awk version 20121220 disallows the use of an unmatched right parenthesis in
regular expressions:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
$ awk 'BEGIN { print match("...)", ")") }'
awk: illegal primary in regular expression ) at
 source line number 1
 context is
        BEGIN { print match("...)", >>>  ")") <<<
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

The unmatched right parenthesis should be allowed in this context, as
POSIX.1-2008
(http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_04_03)
states the following in section 9.4.3 (ERE Special Characters):

"The <right-parenthesis> shall be special when matched with a preceding
<left-parenthesis>, both outside a bracket expression."

and in section 9.5.1 (BRE/ERE Grammar Lexical Conventions)
(http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html#tag_09_05_01),
the description of the "SPEC_CHAR" token contains the following exception:

"The close-parenthesis shall be considered special in this context only if
matched with a preceding open-parenthesis."

I contacted Mr. BWK, who agreed that it was a bug. I then attempted to fix it
using the attached patch, which I submitted to BWK, but didn't get a response.
Consequently, don't have high hopes for this issue being fixed upstream, but
I'm submitting this bug report so that it is documented somewhere.

-- 
Nathan Weeks
IT Specialist
USDA-ARS Corn Insects and Crop Genetics Research Unit
Crop Genome Informatics Laboratory
Iowa State University
http://weeks.public.iastate.edu/

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