Re: [Boost-bugs] [Boost C++ Libraries] #2340: Regex : Invalid preceding regular expression problem

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #2340: Regex : Invalid preceding regular expression problem
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2008-09-18 16:15:36

#2340: Regex : Invalid preceding regular expression problem
--------------------------------+-------------------------------------------
  Reporter:  jcombe_at_[hidden]  |       Owner:  johnmaddock
      Type:  Bugs               |      Status:  closed     
 Milestone:  To Be Determined   |   Component:  regex      
   Version:  Boost 1.36.0       |    Severity:  Problem    
Resolution:  wontfix            |    Keywords:  regex      
--------------------------------+-------------------------------------------
Changes (by johnmaddock):

  * status:  new => closed
  * resolution:  => wontfix

Comment:

 In a strict sense this is a bug (in the sense that Perl accepts it and we
 don't), but the problematic part of the original regular expression is
 meaningless:

 \b?

 means "maybe match a word boundary, or maybe don't bother", so either way
 it consumes zero characters and will *always* succeed.  The alternative
 form (which is also an error in Boost.Regex):

 \b+

 Is also rather meaningless and exactly equivalent to

 \b

 My gut feeling at present, is that these almost always represent errors in
 the regular expression, and are generally best diagnosed as such.  But...
 please do reopen if you can think of a legitimate use case :-)

 HTH, John.

-- 
Ticket URL: <http://svn.boost.org/trac/boost/ticket/2340#comment:1>
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