This Week on perl5-porters - 13-19 October 2008

This Week on perl5-porters - 13-19 October 2008

   "It's far from being a critical issue, and I'm not saying that magic
   shouldn't be enabled there. But I'd really like to see magic behave in
   the most predictable possible way." -- Vincent Pit, inventing a new
   meaning for "predictable".

Topics of Interest

use bytes pragma

   Karl Williamson, in his ongoing overhaul of Unicode handling,
   discovered some inconsistencies between the documentation for and
   implementation of the "bytes" pragma. As such, he wasn't willing to
   hazard a change, but wondered how often it was used in real life.

     http://xrl.us/ovbq2

PATL/autorequire-0.08.tar.gz broken since perl5.8.8@30113

   Slaven Rezic noted that refactoring in DynaLoader had caused this
   module to fail, and traced it down to some hairy .PL template code.
   Vadim Konovalov admitted guilt over the template syntax and offered to
   atone for his sins by writing the machinery that would allow nicer
   templating during the build.

     http://xrl.us/ovbq4

ties and other filehandle bondage

   Ricardo Signes uncovered an ugly problem with opening a file handle to
   a reference of a tied scalar. And while this was probably not the
   wisest thing to do in the first place, any error message would be
   better than none.

   Vincent Pit reasoned that the best way to solve this would be to have
   magic triggered on every "print" argument, but that might be woefully
   expensive. Nicholas Clark thought that correctness was better than
   speed, and if you're into magic you probably don't care about
   efficiency.

     http://xrl.us/ovbq6

blead and Glib's lazy-loader

   Torsten Schönfeld reported a problem with "av_clear" on @ISA not doing
   the right thing, and having to call "av_shift" repeatedly instead. (I
   seem to remember summarising a similar issue a couple of weeks ago).

     http://xrl.us/ovbq8

Change 32016 breaks a test in "MPEG::Audio::Frame"

   Slaven Rezic uncovered a bug in "MPEG::Audio::Frame". Nicholas Clark
   noted that this was because Yuval Kogman was a wicked man who peeked,
   and relied upon the implementation. Yuval admitted that the module
   ought to be fixed up (rather than perl), but confessed to low amounts
   of tuits.

   Nicholas was also in awe of the amount of testing Slaven was doing in
   tracking the changes for 5.8.9.

     http://xrl.us/ovbra

TODO of the week

Add a code coverage target to the Makefile

   Make it easy for anyone to run "Devel::Cover" on the core's tests. The
   steps to do this manually are roughly

   *   do a normal "Configure", but include "Devel::Cover" as a module to
       install (see INSTALL for how to do this)

   *     make perl

   *     cd t; HARNESS_PERL_SWITCHES=-MDevel::Cover ./perl -I../lib
         harness

   *   Process the resulting Devel::Cover database

   This just give you the coverage of the .pms. To also get the C level
   coverage you need to

   *   Additionally tell "Configure" to use the appropriate C compiler
       flags for "gcov"

   *   make perl.gcov

       (instead of "make perl")

   *   After running the tests run "gcov" to generate all the .gcov
       files. (Including down in the subdirectories of ext/

   *   (From the top level perl directory) run "gcov2perl" on all the
       ".gcov" files to get their stats into the cover_db directory.

   *   Then process the Devel::Cover database.

   It would be good to add a single switch to "Configure" to specify that
   you wanted to perform perl level coverage, and another to specify C
   level coverage, and have "Configure" and the Makefile do all the right
   things automatically.

New and old bugs from RT

"File::Copy" module (#32135)

   Nicholas Clark disagreed with Adriano Ferreira's comment of what was
   the underlying problem in this bug report. He wondered if the real
   problem did not in fact lie with "IO::Scalar".

     http://xrl.us/ovbrc

   In a related report ("File::Copy" does not handle file objects sanely
   (bug #59650)), a rabbit supplied a patch to deal with "IO::Scalar"
   objects (which is probably why Nicholas revived the preceding bug.
   Nicholas had a minor quibble over the use of "xor" rather than "ne",
   and wondered if there were any corner cases where they would behave
   differently.

     http://xrl.us/ovbre

Unicode problem (#58182)

   Karl Williamson reported back on his progress in dealing with Unicode
   in Perl. He now has a good idea of what he wants to do, but had some
   questions of a practical nature regarding C coding standards. He asked
   a very interesting question: what is the feeling regarding the use of
   lookup table to push design decisions into data, rather than code.

   Another crucial design assumption was that "uc" tries to convert in
   place if possible. Karl wondered if it would reasonable to always
   return a new SV regardless of whether the original container would
   fit, as it would simplify the code. To this latter point, Rafaël
   Garcia-Suarez told him to go ahead with whatever was easiest; there
   would always be time to optimise it later on, should the need arise.

   In another subthread, Karl pointed people at the bikeshed and asked
   for colour schemes. That is, this new Unicode functionality will be
   enabled via a pragma in 5.10 (becoming the default behaviour in 5.12).
   What, then, should be the name of the pragma? Karl had a number of
   ideas, but was dissatisfied with all of them.

     http://xrl.us/ovbrg

Memory leak with regex in 5.10.0 (#59516)

   Marcus Holland-Moritz plugged the leak with a well-placed
   "SvREFCNT_dec".

     http://xrl.us/ovbri

bun in perl 5.8.8 on AIX 5.3 (#59866)

   Rainer Tammer noted a perfect 64-bit build on AIX 5.2, but *ceteris
   paribus* a failure AIX 5.3. A 32-bit build was fine. H.Merijn Brand
   was able to repeat the failure.

     http://xrl.us/ovbrk

Variable falls out of scope but is not garbage-collected (#59882)

   Frédéric Brière reported a problem of a variable with no remaining
   references not being garbage collected. Dave Mitchell explained that
   method lookup caching was interfering with things and suggested an
   alternate syntax to Do The Right Thing.

   Nicholas Clark thought that caching should only improve performance,
   not require people to jump through hoops to avoid side effects. He
   proposed a change to the implementation but wondered if there were any
   corner cases that might be affected. Dave Mitchell was reluctant to
   entertain any changes, since the GV implementation has not been widely
   studied.

     the cold light of day
     http://xrl.us/ovbrn

"x" forces scalar context on array variables (#59884)

   James Schneider stumbled over an edge case with "x", the replication
   operator. Much discussion about context, parentheses and "qw()"
   followed.

     http://xrl.us/ovbrp

"\x", "\0", and "\N{}" not ok in double-quotish when followed by > \x100 
(#59908)

   Karl Williamson needs someone to tell him where to look in the source
   to track down the problem he summarised in this bug report.

     help, I need somebody
     http://xrl.us/ovbrr

tainted values in ternary conditional (#59916)

   Dean wanted the propagation of tainted values with ternary expressions
   to change, and wrote some tests to describe the behaviour he sought.

     http://xrl.us/ovbrt

Errors in compilation (#59922)

   Rajini S was encountering difficulties in testing a 32-bit build on
   HP-UX. H.Merijn Brand and Andy Dougherty thought that the new build
   was getting mixed up with parts of the system perl.

     http://xrl.us/ovbrv

Memory leak when accessing "%+" (#59942)

   Marc Lehmann reported a problem with "%+", but Renée Bäcker thought it
   had already been solved in blead by change #34151, and suggested
   looking at bug #57024.

     http://xrl.us/ovbrx

"Modification of read-only value" in grep (#59956)

   Ed Avis set up a construct that produced a misleading error message.
   Eric Brine explained that the so-called modification error was due to
   autovivification, and suggested that it would be nice to have a better
   error message.

     http://xrl.us/ovbrz

Bug in threads / perl 5.8.8 on AIX 5.2 / 5.3 (#59960)

   Rainer Tammer found, and solved, a bug in threads on AIX. H.Merijn
   Brand suggested that at the very least, a maintainer for README.aix
   would be a great idea, should Rainer feel like volunteering.

     http://xrl.us/ovbr3

Memory leak when using the "qr" operator (#59994)

   Roland Illig independently (re-)discovered the "qr//" leak, only to
   learn it had been fixed. Marcus Holland-Moritz suggested what he hoped
   was an appropriate patch for Roland's 5.10.0 installation since 5.10.1
   is not yet shipping.

     http://xrl.us/ovbr5

"crypt()" returns tainted data even when input strings are detainted 
(#59998)

   Frédéric Buclin uncovered some inconsistencies with tainted data when
   "crypt" is involved.

     http://xrl.us/ovbr7

Perl5 Bug Summary

     279 new + 1054 open = 1333 (+15 -5)
     http://xrl.us/oudz6
     http://rt.perl.org/rt3/NoAuth/perl5/Overview.html

New Core Modules

   Archive::Tar 1.40
         http://xrl.us/ovbr9

   CPAN.pm 1.9301
         http://xrl.us/ovbsb

   ExtUtils::MakeMaker 6.47_01
         http://xrl.us/ovbsd

   ExtUtils::MakeMaker 6.47_02
         http://xrl.us/ovbsf

   Test::More/Simple/Builder 0.82
         http://xrl.us/ovbsh

   Test::More/Simple/Builder 0.84
         http://xrl.us/ovbsj

In Brief

   Yamashina Hio found that "Storable::thaw" segfaults on blessed
   reference to overloaded object and supplied a patch that Nicholas
   Clark was happy to apply.

     http://xrl.us/ovbsm

   Jerry D. Hedden saw some problems arising following change #33119 that
   integrated some consting goodness to cygwin.c.

     http://xrl.us/ovbso

   Jerry then suggested a small lib/DB.t fix, and Nicholas Clark fixed
   the problem with change #34554.

     applied
     http://xrl.us/ovbsq

   Karl Williamson wondered if there was a document that helped porters
   come to grips with the use of git. The answer was to note things on
   the wiki. This could then be folded into perlhack at a later date.

     http://xrl.us/ovbss
     http://xrl.us/ovbsu

   Niko Tyni pushed a Debian patch to fix "h2xs" enum handling with C++
   comments

     unapplied
     http://xrl.us/ovbsw

   Niko also posted a patch because "h2xs" incorrectly treats enum values
   like macros.

     also unapplied
     http://xrl.us/ovbsy

   While discussing the (im?)possibility of prototype-based polymorphism,
   Michael G. Schwern thought that "Method::Signatures" was probably the
   way to go.

     just a smop
     http://xrl.us/ovbs2

Last week's summary

     This Fortnight on perl5-porters - 28 September-12 October 2008
     http://xrl.us/ovbs4

About this summary

   This summary was written by David Landgren.

   Weekly summaries are published on http://use.perl.org/ and posted on a
   mailing list, (subscription: perl5-summary-subscribe@perl.org). The
   archive is at http://dev.perl.org/perl5/list-summaries/. Corrections
   and comments are welcome.

   If you found this summary useful, please consider contributing to the
   Perl Foundation or attending a YAPC to help support the development of
   Perl.

• This Week on perl5-porters - 13-19 October 2008 by David Landgren