This Week on perl5-porters (19-25 May 2003)

This Week on perl5-porters (19-25 May 2003)
  Perhaps a bit late, but ready at least, here is your latest P5P summary,
  full of last week's selected threads. Read about I/O problems and other
  language issues.

Stateful PerlIO
  I'm not sure I understand fully the details, but : Dan Kogai, maintainer
  of the "Encode" module, implemented a way to handle internal states, and
  thus BOMs in encoded text. This was a consequence of bug report #22261,
  about "unrecognized BOM when reading a file larger than 1k with
  encoding(UTF-16)".

      The bug : http://xrl.us/inj
      What's a BOM : http://www.unicode.org/unicode/faq/utf_bom.html

What does sysread() do ?
  Nick Ing-Simmons and Gurusamy Sarathy have been working on the semantics
  of the sysread() function and try to reach a consensus. Should it read
  characters, or bytes ? That makes a difference when reading Unicode
  data, or when doing CRLF line-ending translation. Moreover, the third
  edition of the Camel Book and the perlfunc man page don't agree on this
  topic.

  Jarkko Hietaniemi votes for bytes, and for characters when the
  filehandle has been marked as UTF-8. But the common expectation seems to
  be that sysread() should do what the C-level read() does, or, at least,
  that it should always have byte semantics. That's the opinion of Nick,
  Graham Barr, Ton Hospel, and others.

      http://xrl.us/ink

Overloading "="
  John Peacock (still working on version objects!) wants to overload the
  assignment operator. The subsequent thread explores the semantic
  intricacies of this proposal. What happens when both sides of the
  assignment are objects that overload "=" ?

  Dan Sugalski says that overloading "=" is simply a tie, because
  "overloading as it stands now works on the value, while tying works on
  the variable". But, in this case, how would work a tied variable holding
  a blessed value ? Interesting thread.

      http://xrl.us/inl

Constant sub redefined
  Stas Bekman asked for a way to disable the warning "Constant subroutine
  redefined", which is produced by code like

      use constant FOO => 1 ; use constant FOO => 2 ;

  (That's bug id #22291.) This warning can't be disabled via the "no
  warnings" pragma, and that's on purpose, because the FOO constant might
  have been inlined in some code that uses it between the first and the
  second redefinitions, leading to the dangerous situation where "FOO !=
  FOO". However, while developing mod_perl modules under Apache::Reload,
  those warnings can be annoying. In this case the recommended way to shut
  them up is to use a custom $SIG{__WARN__} handler.

      http://xrl.us/inm

In Brief
  Alan Burlison asked for a (usable) general performance benchmark for
  perl. Nicholas Clark, while claiming that "finding a useful benchmark
  seems to be a holy grail", suggests to use SpamAssassin with a fixed
  spam corpus.

  Nicholas reported (as bug #22270) a strange behaviour of the tainting
  mechanism he didn't understand, and Spider Boardman provided a brilliant
  explanation of it, pointing his finger at the right place in the
  documentation.

      http://xrl.us/inn

  As a consequence from a discussion we had last month, Dave Mitchell
  added a new warning, "Useless localization", intended to warn at some
  usages of local() on lvalues, that actually do nothing (e.g. "local($x =
  10)".)

  Jeff 'japhy' Pinyan did submit, a while ago, a patch to add a new
  zero-width assertion "\K" to regular expressions. This was not
  integrated, so he's asking for further advice. Your summarizer pointed
  him at the old thread about this question, where Hugo suggested to turn
  this patch into a built-in optimization.

  A new alpha of MakeMaker, version 6.10_04, was released and integrated.
  Paul Johnson asked for a way to parse correctly a MANIFEST file (esp.
  now that MakeMaker can add a META.yml file to it) ; Michael G Schwern
  pointed him at ExtUtils::Manifest::maniread().

  Jarkko released a new snapshot of maintperl.

About this summary
  This was yet another summary written by Rafael Garcia-Suarez. Weekly
  summaries like this very one are usually available on
  <http://use.perl.org/> and via a mailing list, which subscription
  address is [email protected]. Feedback welcome.