This Week on perl5-porters (16-22 June 2003)

This Week on perl5-porters (16-22 June 2003)
  This week, there was fewer threads than usual, but they were larger, so
  the volume of mail exchanged on p5p remained more or less constant.
  Here's the high signal-to-noise ratio summary for this week.

Algorimic Complexity Attack
  You might remember that last month, Scott Crosby reported (as bug
  #22371) a way to produce colliding hash keys. Once fed into a hash,
  these may severely degrade performance of element lookup, and thus be
  used as a basis for DoS attacks. Jarkko proposed a way to protect hash
  tables against this : instead of using 0 as initial value for the
  computation of the hash value, as it is now, use some pseudo-random
  value, computed at interpreter startup time.

  This raises two interesting questions : is this a significant threat ?
  And how to enhance the hash function without performance degradation ?
  Hopefully the arguments ended in some interesting benchmarks. To be
  continued.

      http://xrl.us/j7m

Clearing $1
  Dan Kogai thinks that it would be a good idea, if a failing match did
  reset the $<digit> variables to "undef". This opinion is not
  universally shared. SeveralLots of arguments are proposed against this
  change, from backwards compatibility to good coding practices.

      http://xrl.us/j7n

siginfo
  Jarkko Hietaniemi proposed an experimental patch to take advantage of
  the POSIX signal handling feature that goes by the name of "siginfo". It
  enables additional information to be passed to signal handlers : sending
  process id, real user id of sending process, etc. (See your sigaction(2)
  manpage if you have it.)

      http://xrl.us/j7o

Selected bugs
  Perl segfaults during "make install" on Mario A Cruz Gartner's FreeBSD
  4.4 box (bug #22740). That's puzzling because "make" and "make test"
  both succeeded.

  Shlomi Fish and Ton Hospel reported bug #22744, demonstrating an old
  problem with the ".=" operator :

      $b = ($a.="5")."6"; print "$a $b"

  prints "56 56", but it should have been "5 56". Enache Adrian provided a
  fix.

About this summary
  This week's short summary was written by Rafael Garcia-Suarez. Weekly
  summaries are available on http://use.perl.org/ and/or via a mailing
  list, which subscription address is [email protected].
  Comments, corrections, additions, and suggestions are welcome.