[imapfilter-devel]imapfilter 0.8.3 & glibc-2.2.93/RH8.0 & regexps

[Lefteris Chatzibarbas]

On Wed, Oct 02, 2002 at 01:53:12PM +0300, Lari Hotari wrote:
> Hi!
> 
> I just upgraded to RH8.0, which uses glibc 2.2.93 . The regular
> expression syntax has changed, so imapfilter doesn't work properly.
> 
> The problems are in using the "|" operator in regular expressions.
> 
> for example (line 84 in file.c):
>        "^([[:blank:]]*\n|#.*\n)$",
> should be fixed as:
>        "^([[:blank:]]*\n)|(#.*\n)$",
> 
> The default grouping has somehow changed. All of the regular expressions
> should be checked.
>
> [...]

This is strange... because the first ERE [0], is equivalent to:

  match "^[[:blank:]]*\n$" or "^#.*\n$"

while the second:

  match "^[[:blank:]]*\n" or "#.*\n$"
  
This is according to the IEEE Std 1003.1-2001 [1] specification, where is
defined that concatenation has higher order of precedence than alternation,
meaning that "ab|cd" matches "ab" or "cd" rather than "abd" or "acd".
That's the way the glibc-2.2.5, *BSD libc, Perl's regular expressions,
etc. work.

Apart from that, I don't think it is a very good idea to "debug" a program
based on a CVS snapshot(?) of a library...


[0] Extender Regular Expression
[1] POSIX.1-2001