Re: [Boost-users] regexp: New problem with trailing - in character class

From: John Maddock (john_at_[hidden])
Date: 2005-10-31 06:08:15

> I've been using Boost regexp library forever, and it's great. But I just
> grabbed 1.33.0 (trying to get it to compile on 64-bit Windows), and I'm
> getting an error I never got before: it refuses to allow this regular
> expression:
>
>  [a-z-]
>
> which is supposed to mean "a lower case letter or a dash". Previous
> versions of Boost regexp allowed this, and grep allows it, and version
> 1.33.0 does allow this one:
>
>  [-a-z]
>
> Is this a deliberate restriction? It's causing me lots of problems,
> because my application has a lot of existing regular expressions which
> use this syntax.

Confirmed as a bug, here's the patch going into cvs for 1.33.1:

Index: boost/regex/v4/basic_regex_parser.hpp
===================================================================
RCS file: /cvsroot/boost/boost/boost/regex/v4/basic_regex_parser.hpp,v
retrieving revision 1.9.2.4
diff -u -r1.9.2.4 basic_regex_parser.hpp
--- boost/regex/v4/basic_regex_parser.hpp       16 Oct 2005 
18:12:58 -00001.9.2.
4
+++ boost/regex/v4/basic_regex_parser.hpp       31 Oct 2005 11:07:09 -0000
@@ -1220,6 +1220,17 @@
          char_set.add_range(start_range, end_range);
          if(this->m_traits.syntax_type(*m_position) == 
regex_constants::syntax_dash)
          {
+                          if(m_end == ++m_position)
+                          {
+                                  fail(regex_constants::error_brack, 
m_position - m_base);
+                                  return;
+                          }
+                          if(this->m_traits.syntax_type(*m_position) == 
regex_constants::syntax_close_set)
+                          {
+               // trailing - :
+               --m_position;
+               return;
+                          }
             fail(regex_constants::error_range, m_position - m_base);
             return;
          }

John.