This Week on perl5-porters (30 January-5 February 2006)

This Week on perl5-porters - 30 January-5 February 2006

   Perl 5.8.8 was released this week.

perlvar.pod: $^X isn't necessarily "argv[0]"

   Yitzchak Scott-Thoennes patched perlvar.pod to point out that $^X
   could contain information from /proc/self/exe, on platforms that
   supported it. But even on platforms that do support it, such as Linux,
   you can still run into grief with "chroot"ed environments.
   Nevertheless, Rafael Garcia-Suarez liked the patch enough to accept
   it. Nicholas Clark pointed out that the name is different on FreeBSD
   and Solaris.

   Alan Burlison showed how to find the name of executable on Solaris
   without having to rely on access to /proc, which interested Rafael.
   Gisle Aas was unable to compile Alan's snippet, and it turned out that
   the technique Alan was relying on was only fairly recently made
   available on Solaris. So he coded another approach.

     An improvement to $^X
     http://xrl.us/jxs7

     An earlier, similar attempt
     http://xrl.us/jxs8

$^E and Borland on Win32

   Steve Hay wondered about the differences between

     # borland
     perl -e "open F, 'nothere' or die $^E"
     Died at -e line 1.

     # MSVC
     perl -e "open F, 'nothere' or die $^E"
     The system cannot find the file specified at -e line 1.

   so he wrote some code to find out what was going on. And afterwards he
   still couldn't figure out where and when the Windows "GetLastError"
   was being called. Jan Dubois clarified the issue concerning whether
   what "GetLastError" returns is relevant or not. And I think the
   discussion stopped there.

arenaroots patch

   Jim Cromie sent in a consolidated patch that implements putting all
   the arenas into a singly-linked list. He then sent in a patch to
   implement meta-arenas, which allow perl to separate the
   meta-information about the arena from the arena itself, which results
   in some small savings of memory.

     Consolidation
     http://xrl.us/jxs9

     Separation of meta-data
     http://xrl.us/jxta
     http://xrl.us/jxtb
     http://xrl.us/jxtc

Segmentation fault when matching regexps

   Lukasz Debowski filed bug #38379 that showed how to make perl dump
   core when trying to match a string against a particularly arduous
   regular expression. Yves Orton explained that the problem came from
   excessive back-tracking that the pattern forced the regexp engine to
   undertake, and offered a couple of ideas about how to rewrite the
   pattern in question to make it more efficient.

   Lukasz thought that it should be possible to get the regexp engine to
   bail out gracefully under such circumstances and provide a more
   informative error message about the problem.

     Patches, as they say, are welcome.
     http://xrl.us/jxtd

Typo in perlfunc.pod

   Eagle-eyed "p.boven" spotted a documentation error in "perlfunc.pod",
   filed as bug #38380. Trying to find the error by reading the patch
   alone is just about impossible, fortunately a description of the
   problem was included in the report. Nicholas applied the patch.

     Try and spot the difference by reading the patch
     http://xrl.us/jxte

Exhausting memory when printing large, deep hashes

   Paul Boutros filed bug #38384, wherein traversing a large hash of
   hashes uses a phenomenal amount of memory. Gisle Aas realised that the
   problem was merely an issue of numbers being interpreted as strings,
   thus causing the hashes' "SvIV" structures to be upgraded to the
   larger "SvPV" structures.

   (The trick is to use "0+$foo{bar}" to force numeric context).

     http://xrl.us/jxtf

5.8.8

   With the lyrics from Bein' Green, by Joe Raposo, Nicholas Clark
   released the long-awaited Perl version 5.8.8 to the world.

     It's out there
     http://xrl.us/jxtg

     Alternate lyrics
     http://members.tripod.com/Tiny_Dancer/green.html

Camelpacks and Activestate

   There is an issue or two surrounding Camelpack, which is bundle of
   Activestate and MingW. One issue being that it might be violating
   Activestate's license terms, and/or the O'Reilly camel trademark, and
   even possibly R. J. Reynolds as well.

     http://xrl.us/jxth

XS::Connect, or making C/Perl thunk faster

   Chase Venters has problems with DateTime, in that it is too slow. He
   thought about recasting some of the code into C, but learnt that the
   authors had already tried that, and noticed an overall slowdown,
   because of the cost of thunking (crossing between Perl and C). And
   wondered whether there was a way of reducing the cost, and put forward
   a couple of ideas. Glenn Linderman came up with a pretty good
   refinement.

   Tony Cook mentioned something called "Imager" that already lets one do
   something along those lines (or at least, the next release will).

   Nick Ing-Simmons suggested Chase take a look at both "Tk" and and
   "DBI", which have been refining this concept for a decade. "Tk", in
   particular, uses Perl to generate (print) C code, which helps cut down
   on typos.

     http://xrl.us/jxti

"autouse" noisy with 5.8.8

   Rafael noticed that "autouse" may now produce warnings of the form

     Prototype mismatch: sub main::bar: none vs ($) at
     /usr/lib/perl5/5.8.8/autouse.pm line 57

   and fixed it with change #27034. Nicholas wondered whether Rafael's
   change was a fix, or just sweeping a problem under the carpet. Because
   autouse is pretty hairy anyway, Rafael figured that it was all right.

     http://xrl.us/jxtj

$, is undefined by default

   In bug #38398, Roderick Schertler raised the point that it would be
   nice if $, (the separator when printing in list context), was an empty
   string rather than "undef", since that would allow

     print join $,, @foo;

   rather than

     print join defined $, ? $, : '', @foo;

   Abigail agreed, but thought that the proper way to fix the problem was
   with a pragma:

     no warnings;
     print join $,, @_;

   Jim Cromie suggested

     local $, = '';

   ... but that only works if $, hasn't already been set. H.Merijn Brand
   (implicitly) suggested recompiling Perl with his "dor" patch:

     print join $,//'', @foo

     http://xrl.us/jxtk

No more "Null(av|ch|cv|hv|sv)"

   Steven Schubiger grepped through the code base and pinpointed a number
   of places where "Nullav", "Nullsv" and the like continue to lurk, and
   wondered whether they could be replaced by "NULL", and whether
   "perlapi.pod" should note that they are deprecated.

   Andy Lester pointed out some even more dubious code constructed that
   need to be NULLified, and Nicholas admitted to being happy to see them
   all go.

   So Steven tackled "Nullav" and "Nullch" first, except that he also
   deleted the definitions themselves, which would destroy backwards
   compatibility, so he re-did the patch to keep them.

   And then followed up with "Nullcv", "Nullsv" and the rest of the gang.
   There followed a discussion about the possibly apocryphal hardware
   whose null pointer bits are not all zero.

     http://xrl.us/jxtm

Doing proper UTF-9 hash lookups

   Nicholas proposed a patch to make the tokeniser itself UTF-8 aware.
   This makes two TODO tests pass, but alas another test starts to fail.
   A code audit is needed to make sure UTF-8-flagged keys are dealt with
   correctly everywhere. And then the same thing needs to be done to the
   pad code (the code that deals with lexicals).

     http://xrl.us/jxtn

Unicode slowdown 5.8.6 "->" 5.8.7

   Nicholas also revisited the Unicode slowdown and proposed an API
   enhancement in order to minimise data copying. Sadahiro Tomoyuki (who
   is the expert in these matters) came up with a better solution.

   Nicholas implemented Tomoyuki's idea, and saw a fourfold improvement
   in speed. Phil Pennock took the code for a spin, and sadly noted that
   it shaved only two seconds off a forty-odd seconds run time.

     Unicode melts my brain, again
     http://xrl.us/jxto

Make parallel "make test" work

   Nicholas Clark continued on a roll, trying to track down parallel
   testing failures, and isolated a race condition between "List::Util"
   and "Math::BigInt::Fastcalc". It looks as if the Makefile.PL for
   "Math::BigInt::FastCalc" is being executed at precisely the same
   moment that "List::Util" is being copied to ".../lib". Which is of
   course extremely difficult to reproduce.

   Steve Peters was able to identify that the real culprit was in fact
   "overload.pm" and not "Math::BigInt::FastCalc".

     http://xrl.us/jxtp

   Nicholas found another parallel build race failure, which prompted
   Alan Burlison to reminisce on problems he had encountered with
   parallel tests at Sun.

     http://xrl.us/jxtq

Trouble ahead for "nmake" on Vista?

   Adam Kennedy heard that "nmake" (the aging version that can be legally
   distributed) no longer runs on Vista (or at least, a current beta),
   and wondered what the solution was. Apparently, there's a "dmake"
   floating around that seems to have everyone's favour.

     http://xrl.us/jxtr

Files in use in Windows and Cwd.pm

   There was a really long thread to do with Window,
   "ExtUtils::MakeMaker" and "Cwd.pm", but it came across badly threaded
   on Xray and I had a hard time following it all. The pointers are:

     Someone's MUA is playing silly buggers here
     http://xrl.us/jxts
     http://xrl.us/jxtt
     http://xrl.us/jxtu

blead @ 27028 OpenVMS Alpha 8.2 - All tests pass

   John E. Malmberg reported a perfect compile on VMS -- yay!

     http://xrl.us/jxtv

5.8.8-RC1 on Cray

   H.Merijn Brand gave perl a smoke test on Cray hardware. Oddly enough,
   it appears to have about the same performance as a TRS-80. Just
   running "Configure" alone took over 24 hours...

     http://xrl.us/jxtw

Label optimised away when it shouldn't

   Gisle noticed that

     $ perl -le 'goto foo; if (0) { foo: print "hi" }'

   produces

     Can't find label foo at -e line 1.

   Not that anyone should want to code like that, nor should it be fixed,
   but that maybe the behaviour be noted somewhere in case someone comes
   to grief over it. Paul Johnson pointed out the relevant part of
   "perlfunc" that does in fact explain it.

     http://xrl.us/jxtx

A good p5p mailing list archive

   Steve Hay was looking for a good archive of the p5p mailing list. It
   seems that xray had been down for a while, and so he looked at the
   alternatives.

     http://xrl.us/jxty

Enhancing "PERL_TRACK_MEMPOOL"

   Nicholas took Jan Dubois's "PERL_TRACK_MEMPOOL" code and added some
   functionality to it to improve the feedback when running under
   "valgrind", and also added a "PERL_POISON" switch to improve the
   chances of dying a quick death when buggy code tries to access memory
   it no longer owns.

     http://xrl.us/jxtz

Perl5 Bug Summary

   1543 open issues.

     http://xrl.us/jxt2

New Core Modules

CPAN-1.83_64

   Andreas Koenig uploaded CPAN-1.83_64, which, if nothing goes wrong,
   will become the 1.84 official release soonish.

     http://xrl.us/jxt3

About this summary

   This summary was written by David Landgren. I wasn't able to start
   this until Thursday night, due to various constraints in Real Life
   (such as drinking beer with the local Perl mongers last night). As a
   result (of the late start, not the beer) the threshold for
   interesting-enough-to-summarise threads was higher than usual. Also, I
   didn't have the time for the witty URL titles. Sorry about that, but a
   brief summary is better than no summary at all.

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

   Information concerning patches to maint or blead referenced in this
   summary (as #nnnnn) may be viewed at
   http://public.activestate.com/cgi-bin/perlbrowse?patch=nnnnn

   If you want a bookmarklet approach to viewing bugs and change reports,
   there are a couple of bookmarklets that you might find useful on my
   page of Perl stuff:

     http://www.landgren.net/perl/

   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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   Perl.

-- 
"It's overkill of course, but you can never have too much overkill."