This Week on perl5-porters (5-11 September 2005)

This Week on perl5-porters (5-11 September 2005)

The Return of the perl5-porters Summaries

   Sébastien Aperghis-Tramoni, Adriano Ferreira and David Landgren have
   stepped up to the plate to bring you the weekly p5p summaries. We make
   no promises as to how long we can keep this up, but we'll give it a go
   for as long as we can.

   There has been a lot of action happening in Perl 5 land, and we hope
   that these messages will help people keep abreast of the latest
   developments.

   Onto last week's traffic:

sub _ { ... } and -X _

   Peter Dintelmann pondered over the meaning of "-X _" when "sub _ { ...
   }" defined, as it can lead to some surprising behaviour. Mark-Jason
   Dominus pointed to http://hop.perl.plover.com/errata/byid.cgi/131 and
   http://hop.perl.plover.com/~alias/list.cgi?2:mss:264 for more
   information on the matter.

     http://xrl.us/hkyk

VMS Issues

   John E. Malmberg asked for advice on how to deal with File::Copy on
   VMS. The library test fails because the copied file ends up with a
   timestamp of 'now', which is consistent with the way things are done
   in the DCL command shell. Part of the problem was that the test suite
   failure message was misleading. John fixed things up as best he could.

     http://xrl.us/hkym

   He also landed a patch for ExtUtils::CBuilder. After a bit of work, he
   and Ken Williams got it working correctly.

     http://xrl.us/hkyn

   In other VMS news, the current bleadperl is testing fairly well. The
   main show-stopper being problems with Compress::Zlib.

     http://xrl.us/hkyo

Eliminating arenaroots

   Internally, perl uses arenas of memory to allocate fixed-length
   objects quickly and efficiently. The current plan is the shrink the
   number of roots down to one. Jim Cromie supplied a patch. The test
   smokes produced a number of odd results that had people scratching
   their heads, until it was realised that the problem was a single
   statement "if" that lost its braces.

     http://xrl.us/hkyp

Dying in a grep

   Chris Heath noted the following:

     $ perl -e 'for ("foo") { grep(die, "bar") }'
     Died at -e line 1.
     Attempt to free unreferenced scalar: SV 0x96c61dc, Perl interpreter:
     0x96ae008.

   Normally, the third line shouldn't appear. And "map" will do the same
   thing. Salvador Fandiño noted that this had already been recorded as
   bug #24254.

     http://xrl.us/hkyq

eg should be e.g. in the documentation

   David Landgren was peeved that *exempli gratia* is often abbreviated
   to "eg" in the documentation, rather than "e.g.". Mark-Jason Dominus
   wondered why it was not abbreviated to "for example". Michael Schwern
   brought the discussion to a close by performing a simple cost/benefit
   analysis.

     http://xrl.us/hkyr

Math::Complex atan2 bug

   Steffen Müller observed the following

     [...] in the complex plane, we get:
     perl -MMath::Complex -e "print atan2(0,i)"
     i/0: Division by zero.
     Died at c:/perl/perl58/lib/Math/Complex.pm line 1284.

     This is not correct.
     Obviously, 0/i is the same as 0/1 which is 0.
     Thus atan2(0,i) == atan2(0,1) == atan(0) == 0

   Jarkko Hietaniemi said that he'd cook up a patch, but that he had
   other outstanding things to do with Math::Complex and Math::Trig.

     http://xrl.us/hkys

undefing *foo{CODE}

   Ben Tilly reported that undef'ing the CODE slot of a typeglob doesn't
   quite work well enough to be useful, and supplied a short snippet of
   code showing the problem.

     http://xrl.us/hkyt

   Dave Mitchell shed some light on what was going on under the covers
   "the thing continues to exist, but has no useful 'value'", and Rafael
   Garcia-Suarez noted that

      delete &mysub

   is on the TODO list, but getting it right in all cases is extremely
   tricky.

tr// on EBCDIC platforms

   Sadahiro Tomoyuki found problems with transliterating Unicode
   characters. I can only offer my deepest sympathy.

     http://xrl.us/hkyu

New core module releases

   Graham Barr released IO version 1.22. There was concern about what the
   impact would be on the 5.6 series.

     http://search.cpan.org/dist/IO/

   Dan Kogai released Encode 2.12...

     http://search.cpan.org/dist/Encode/

   ... and Ruslan U. Zakirov spotted a problem with an example in the
   documentation.

The return value of SvUTF8()

   In December 2004, Ton Hospel raised bug #32884. The internal perl API
   defines SvUTF8() as taking a pointer to an SV, and returning a boolean
   value indicating whether the SV contains utf-8 encoded data.
   Compilers, casting between chars and ints, can arrive at the situation
   whereby...

     if (SvUTF8(sv)) { ... }

   ... and ...

     bool utf8 = SvUTF8(sv);
     if (utf8) { ... }

   ... don't behave in the same way. Steve Peters revived interest in the
   bug, by asking whether returning a U32 value instead of a bool would
   fix matters.

     http://xrl.us/hmtr

In Brief

   Rajarshi Das found a problem with Encode on EBCDIC. Dan Kogai noted
   that the code is not well tested on EBCDIC. There was another thread
   on the matter:

     http://xrl.us/hkyv

   Robert Spier released the latest version of the Perl5 bug summary

     http://rt.perl.org/rt3/NoAuth/perl5/Overview.html

   Summary of the summary: there are 1500 open tickets.

   "brucer" filed a bug report for "my $var if 0". Michael Schwern
   demonstrated that this now produces a warning in bleadperl.

     $ bleadperl -wle 'my $v if 0;'
     Deprecated use of my() in false conditional at -e line 1.

   Ikegami reported bug #37076, a snippet involving threads and 'require
   IO'. Using 'use IO' makes the bug go away. Nicholas Clark suggested
   that this is caused by threads scribbling over memory that doesn't
   belong to them.

   "sgromoll" reported #37133, a crash related to threads and lock().
   Nicholas thought this was could be a deadlock in the threads
   implementation.

   Michael Schwern noted that #7615 "if (local $a = 1){ ... }" is still a
   problem:

     $ bleadperl -wle '$a = 10;  if( local $a = 1 ) {}  print $a'
     Found = in conditional, should be == at -e line 1.
     1
     $ bleadperl -wle '$a = 10;  if( my $a = 1 ) {}  print $a'
     Found = in conditional, should be == at -e line 1.
     10

   Michael Schwern also followed up on the test suite of PathTools 3.10,
   which was released some time ago.

     http://xrl.us/hkyw

   In bug #36075, Nicholas Clark wants to get "malloc_size" and
   "malloc_good_size" into "Configure", because this would help perl on
   Darwin. Steve Peters and H.Merijn Brand discussed various schemes for
   doing this

   Garry reported a memory leak with threads in #37134. Dave Mitchell
   managed to come up with some remarkably concise code that demonstrates
   the bug:

     use threads;
     sub ThreadRoutine {}
     while (1) {
       $thread = threads->new(\&ThreadRoutine);
       $thread->join;
     }

   Brendan O'Dea supplied a few tweaks for "a2p", thereby closing a
   couple of Debian bugs, and wondered if anyone still uses it ("a2p",
   that is).

About this summary

   This summary was written by David Landgren.

   Information concerning bugs referenced in this summary (as #nnnnn) may
   be viewed at http://rt.perl.org/rt3/Ticket/Display.html?id=nnnnn

   Weekly summaries are published on http://use.perl.org/ and posted on a
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   archive is at http://dev.perl.org/perl5/list-summaries/. Corrections
   and comments are welcome.

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