>>>>> "C" == Christian Kaiser <bchk / gmx.de> writes:

C> which was very tempting to assume that problem...

 This is this case

svg% ruby -rjj -e '/[\b]/.dump'
Regexp /[\b]/
  0   cclass \010 (1)
  1   end
Optimize MAP_SEARCH \010 (1)
svg% 


C> BTW: Do you have any idea how to fix the bug from my first mail
C> ("upper=-1...")?

 I have, but the author of Oniguruma will give you a better patch.

 I was not able to reproduce your first problem (RegEx strings > 16 KB)
 with 1.9


Guy Decoux