[Boost-bugs] [Boost C++ Libraries] #2157: Xpressive end-of-line match broken

Subject: [Boost-bugs] [Boost C++ Libraries] #2157: Xpressive end-of-line match broken
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2008-07-30 21:52:51

#2157: Xpressive end-of-line match broken
--------------------------------------------------+-------------------------
 Reporter:  Simon Steele <s.steele_at_[hidden]>  |       Owner:  eric_niebler
     Type:  Bugs                                  |      Status:  new         
Milestone:  Boost 1.36.0                          |   Component:  xpressive   
  Version:  Boost 1.35.0                          |    Severity:  Problem     
 Keywords:                                        |  
--------------------------------------------------+-------------------------
 End of line matching inside a string is broken, simple example:

 Subject: abc\ndef\nghi
 Regex: ^.+$

 I'm looking for "abc". The following xpressive-based code has odd results:

 string text(argv[1]);
 sregex rex = sregex::compile(text, regex_constants::not_dot_newline);

 smatch match;
 string subject("abc\ndef\nghi");
 if (regex_search(subject.begin(), subject.end(), match, rex,
 regex_constants::match_default))
 {
    std::cout << "Match at: " << match.position(0) << " length: " <<
 match.length(0);
 }

 ^.+$: Match at: 8 length: 3
 $: Match at: 4 length: 0
 .$: Match at: 10 length: 1

 These definitely aren't right, it appears that the only place where
 end-of-line is matching is at end-of-string. Things get even stranger if I
 try to use Windows or Mac style end-of-line styles. If I use boost::regex
 instead then I get these results:

 ^.+$: Match at: 0 length: 3
 $: Match at: 3 length: 0
 .$: Match at: 2 length: 1

 These are the results I'd expect. It appears in Xpressive that the
 check in assert_line_base::is_line_break is broken, the following
 line:

 if(traits_cast<Traits>(state).isctype(ch, this->newline_))

 checks the previous character to see if it's a line break. I believe
 this should check the current character:

 if(traits_cast<Traits>(state).isctype(*state.cur_, this->newline_))

 This then gets me sane results:

 ^.+$: Match at: 0 length: 3
 $: Match at: 3 length: 0
 .$: Match at: 2 length: 1

 [note: Eric says that this patch is probably not correct as it causes
 regression failures]

-- 
Ticket URL: <http://svn.boost.org/trac/boost/ticket/2157>
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