This Week on perl5-porters - 20-26 October 2008

This Week on perl5-porters - 20-26 October 2008

   "So we have an existing bug. Sometimes \400 matches \400, and
   sometimes it matches \01\00, depending on what I would call spooky
   action at a distance. I'm trying to get rid of these inconsistencies.
   I think something should be done here, but perhaps its not what I
   thought it should be. My patch follows what the code was intending to
   do, but perhaps we should change that intention. Please guide me."
   -- Karl Williamson, trudging around in the depths of Unicode.

Topics of Interest

Exported symbols: the perl API

   H.Merijn Brand shared with us one of the more exciting aspects of
   configuring perl. The embed.pl program goes through the source and
   pulls out the name of every function marked as public and saves them
   in global.sym.

   H.Merijn discovered that there's no test to check see if what is found
   is truly available. Configure a perl with "-Duseshrplib" for example,
   and many are not.

   Using some unportable code, he whipped up a program to list everything
   that was supposed to be available but wasn't. He wanted to know if a
   Windows expert could code up something similar that would work on that
   platform.

     http://xrl.us/owao2

blead smoke failures for "Module::Build"

   Nicholas Clark ran into inconsistencies with $^X (the name of the perl
   binary) but got things sorted out. I'm not sure if Ken Williams pushed
   the changes upstream to his repository.

     http://xrl.us/owao4

"git-info"

   Michael G. Schwern lamented the lack of an equivalent command in git
   for "svn info", so he wrote an analogue in Perl. Aristotle thought
   that he had just reinvented EasyGit. Michael had a look, was
   impressed, but decided that the information "eg info" produced wasn't
   of vital importance.

     http://xrl.us/owao6

FreeBSD 7 "libc_r" detection

   Tony Cook supplied a very welcome patch to solve the problem of
   configuring perl on FreeBSD 7 with threads, when the threads
   compatibility shims are not installed. Chris Williams had a feeling
   that this would allow bug #57458 to be closed.

   So Chris set about checking the results and confirmed that the patch
   was good and the bug was dead.

     http://xrl.us/owao8

Problems attempt to load "Storable"

   While "Storable" was the symptom, the cause was trying to compile XS
   extensions with Sun's C compiler for a perl 5.6.1 compiled with gcc.

   Nicholas Clark wrote an elaborate recipe for modifying Config.pm to
   make things work. Andy Dougherty thought that it all made sense, but
   both were in agreement that the easiest way forward for Tim Smith, who
   posed the question initially, would be to recompile everything with
   Sun's compiler.

     http://xrl.us/owapa

"PL_ors_sv" in "Devel::PPPort"

   H.Merijn Brand needed to perform a "local"ised "undef $\", which was
   trivial under 5.8.x and beyond, but just about impossible under 5.6
   due to radical differences in the underlying implementations.

   He wondered if there was a way of pushing the problem off onto
   "Devel::PPPort". Marcus Holland-Moritz thought it was pretty much
   impossible. H.Merijn contented himself with marking the module as
   unsuitable for use with 5.6 and below.

     upgrade already
     http://xrl.us/owapc

DLL error messages installing "Term::Title" under Cygwin

   Ruben Diez asked for help in figuring out a strange error with a fresh
   installation of Perl on a fresh copy of Cygwin running on Vista.

   Alexandr Ciornii and Reini Urban diagnosed this as a "rebaseall"
   problem, and therein lay the solution.

     http://xrl.us/ovihr
     http://xrl.us/owape

perl@34559

   Nicholas Clark produced what he fervently hopes is the last snapshot
   for perl 5.8.9, with six issues outstanding. If anything else is
   broken, it will be for anyone else to fix.

   Slaven Rezic posted an impressive list of modules that he had tested
   against recent versions of 5.8-maint, and he and Nicholas went through
   them. A number of failures were deemed acceptable, since they
   represented the nailing down of greyer parts of the implementation.
   Other failures were due to relying on implementation bugs that were
   also fixed.

   Of the six main problems, David Landgren posted updates for
   "File::Path" and Ken Williams gave p5p co-maintainer status for
   "Pathtools".

   Modules were looked at, such as "IO::Mark", "constant" and
   "Business::ISBN". SUPER method caching was examined, as were format
   references.

     http://xrl.us/owapg

Next API question for "Devel::PPPort"

   H.Merijn Brand wanted to be able to rely on "Perl_pv_pretty" and
   "Perl_pv_escape" in any version of Perl. Marcus Holland-Moritz
   initially said that it would be difficult, but went ahead and did it
   anyway. This now gives H.Merijn a "pv_display" that does UTF-8 right.

     http://xrl.us/owapi

Possible mro bug/change between 5.8.8 and 5.10.0

   Michael G. Schwern pinned a problem in "DBIx::Class::CDBICompat" to a
   change in behaviour of MRO (method resolution order). Nicholas Clark
   hoped that Brandon Black, author of mro.c would be able to shed some
   light on the matter.

   Matt S. Trout said that Brandon hasn't been available to look at Perl
   stuff for months and so he would try and find the time to look at it,
   but didn't make any promises as to when that could be.

     http://xrl.us/owapk

How to get Test:: to output in utf8

   Karl Williamson wanted to get UTF-8 output from "Test::More" but was
   stymied by "Wide character in print" warnings. Michael G. Schwern
   offered a couple of tips to get it to work.

     http://xrl.us/owapn

Change 34559 oddity

   Slaven Rezic wondered if the patch for FreeBSD and the legacy thread
   library was meant to apply to 6.x or not, since there was a
   discrepancy between the log message and code.

   Nicholas admitted that the patch was wrong and 6.x was being treated
   the same way... but since things continued to work on 6.x, he wasn't
   sure whether to take it out or leave it.

     http://xrl.us/owapp

TODO of the week

   A new task that only need Perl knowledge (and an ability to use "grep"
   or "ack").

Parallel testing

   (This probably impacts much more than the core: also the Test::Harness
   and TAP::* modules on CPAN.)

   All of the tests in t/ can now be run in parallel, if $ENV{TEST_JOBS}
   is set. However, tests within each directory in ext and lib are still
   run in series, with directories run in parallel. This is an adequate
   heuristic, but it might be possible to relax it further, and get more
   throughput. Specifically, it would be good to audit all of lib/*.t,
   and make them use "File::Temp".

Patches of Interest

Revert const'ing in cygwin.c

   Changes to blead and backports to 5.10 left some consting problems
   that caused the compiler to grumble a bit. This patch was to clean up
   the warnings on 5.10, and appears to be Warnocked.

     http://xrl.us/owapr

Refactor "Perl_mem_log_*" functions

   Marcus Holland-Moritz discovered a nest of duplicate code in various
   logging functions, and factored out what he could into a workhorse
   function. He hinted that this patch needed to go in, so that he could
   deliver a putative "SV allocation tracing" patch.

     http://xrl.us/owapt

Add SV allocation tracing to "-Dm" and "PERL_MEM_LOG"

   Despite receiving no feedback from the above patch, Marcus went ahead
   and applied his SV tracing patch. This works by adding an additional
   field in debugging build to SVs, in which a unique serial number can
   be stored.

   When a leak is spotted, the serial number can be read. The code is run
   a second time, this time setting a break-point on new_SV() watching
   for the creation of the SV with the same serial number. From there it
   usually become a trivial matter to work out who's responsible for
   making the mess.

     http://xrl.us/owapv

Fix prototype detection for C++

   Marcus Holland-Moritz isolated a problem with incorrect function
   prototypes for C++ and suggested an improvement. H.Merijn Brand, as
   Configure pumpking was a bit concerned since the change would have a
   potentially large impact. But as it turned out, the fact that he had
   switched Configure over entirely to git simplified the house-keeping
   tasks considerably.

     http://xrl.us/owapx

Use of freed comppad array during "clear_yystack()"

   Marcus Holland-Moritz spotted a bug that using PERL_POISON picked up.
   (That is, filling the contents of deallocated pointers with garbage to
   trigger segfaults from attempts to dereference said freed pointers).

   The problem was that a variable was freed, set to NULL, and freed
   again. And in real life this works out nicely.

   But for the sake of correctness, Marcus wrote a patch to make things
   work correctly, whether PERL_POISON is defined or not.

     http://xrl.us/owapz

Not silently casting away constness in SV macros

   Marcus also noticed that change #34600 corrected an erroneously
   consted SV, and reflected that such problems can lie buried for a long
   time since macros like "SvREFCNT_dec" blindly cast away constness,
   thus preventing the compiler from doing the job we asked it to do in
   the first place.

   So he thought about how one might go about fixing it, and came up with
   some more preprocessor trickery that would allow the compiler to spot
   when constness was being cast away.

   Nicholas Clark thought that this was a great idea and committed a
   patch to implement it. He then began to start using it, and it allowed
   him to fix up some problems straight away.

     http://xrl.us/owap3

Watching the smoke signals

Smoke [5.11.0] 34541 FAIL(F) MSWin32 WinXP/.Net SP3 (x86/2 cpu)

   Steve Hay's smoke was failing, but Steve wasn't around, so Nicholas
   Clark asked for someone else with access to Windows to run the tests
   and provide the details to understand what was going wrong. Tony Cook
   dug down and found that it was due to an undefined subroutine
   &Cwd::getdcwd.

   This allowed Nicholas to understand what was going wrong and suggest a
   fix, and Tony reported that it was good.

     http://xrl.us/owap5

New and old bugs from RT

Threads support in FreeBSD 7.0 (#57458)

   Renée Bäcker wanted to know if the recent Configure-fu for FreeBSD
   solved this bug.

     http://xrl.us/owap7

Feature request: regexp flag to not set $1, $2 etc. (#58072)

   Ed Avis asked if it was possible to not set $1, $2 and the like during
   a pattern match with captures. He listed three bug reports in the RT
   queue about them getting clobbered.

   Abigail explained that this was already possible, and showed how.
   Norbert Buchmuller mentioned that he had patched "NEXT.pm" using the
   same technique (and this was one of the cited bug reports) but was
   waiting for someone to review (and apply) the patch.

     http://xrl.us/owap9

C coding questions for Unicode problem (#58182)

   More bikeshed discussions continued this week on how to name Karl
   Williamson's Unicode fixup pragma.

     http://xrl.us/owaqb

"PerlIO::via" leaks memory at a high rate (#59268)

   Nicholas Clark looked at the problem that Marc Lehmann had uncovered,
   and regretted to say he wouldn't be able to fix it properly in time
   for 5.8.9. All is not lost though, since he thought it should be
   possible to push out a new version via CPAN at some later date.

     http://xrl.us/owaqd

"chr(0400) =~ /\400/" fails for >= 400 (#59342)

   Karl Williamson produced a one-line fix for this problem, and Tom
   Christiansen wondered if this introduced yet another meaning to octal
   representations, backslashed or otherwise. Karl responded that it was
   already a mess and he just wanted it cleaned up.

   Glenn Linderman suggested that a better alternative would be to outlaw
   octal escapes larger than \377 on 8-bit-byte platforms (as one can
   always work around that by using hex encodings).

   Abigail, not usually known to be fond of adding new warnings to old
   behaviours thought that in this particular case it might be worth
   spitting out a warning if an \NNN octal escape (where NNN is greater
   than 0377) is found in a regular expression, on the basis that it
   would probably point out buggy assumptions.

   All the people who responded were in favour of Karl's patch being
   applied.

     http://xrl.us/owaqf

"return 0 or die" (#59802)

   Dr. Ruud coaxed some examples of this construct from real code via a
   web search.

     http://xrl.us/owaqh

Core on syntax error! (#59950)

   Nick Kostirya stumbled over a coredump when he used a full colon
   instead of a semicolon for "use Data::Dumper;". Dave Mitchell replied
   that this has been fixed in 5.10.0.

     http://xrl.us/owaqj

Typo in perldata (#60022)

   Ryan Dilworth pointed out an inconsistency in perldata regarding
   arrays, offsets and entries. Daniel Frederick Crisman proposed a patch
   to clarify matters and Marcus Holland-Moritz applied it.

     http://xrl.us/owaqm

(?>) causes wrongness on long string (#60034)

   Zefram pointed out a problem with the "?>" assertion showing up in
   5.10.0. Abigail thought that this was due to a variation on the theme
   of leaky implementation details, like the way A* is implemented as
   A(between 0 and 32767 times). Vincent Pit identified change #29916 as
   the cause.

   Once Vincent identified the problem, he was able to suggest a few ways
   for solving it, each with various costs and benefits. He produced a
   patch for 5.8, to get rid of the immediate show-stopper.

   5.10/blead will require a different approach and more work.

     http://xrl.us/owaqo

CPAN install pauses due to 'ncftp' error on cygwin (#60062)

   Arthur Dunham pointed out the futility of asking "ncftpget" to deal
   with HTTP resources.

     http://xrl.us/owaqq

op/groups.t fails when real group name contains blanks (#60136)

   Altblue showed that one the core tests makes an incorrect assumption,
   that group names may never contain spaces. If there is one, the test
   fails.

     http://xrl.us/owaqs

A number of characters match both a posix class and its complement (#60156)

   Karl Williamson ran into more pre-existing errors and inconsistencies
   in Unicode, this time dealing with POSIX character classes. Yves Orton
   dashed off a patch that he expected to work and so was surprised when
   in fact it didn't. At the same time he sent out a personal Call For
   Papers for the next YAPC::Europe conference: someone ought to put a
   "gdb for perl hackers" session together.

     http://xrl.us/owaqu

Perl5 Bug Summary

     279 new + 1062 open = 1341 (+11 -9)
     http://xrl.us/owaqw
     http://rt.perl.org/rt3/NoAuth/perl5/Overview.html

New Core Modules

   ExtUtils::MakeMaker 6.48
         http://xrl.us/owaqy

   SelfLoader 1.17
         http://xrl.us/owaq2

   Test::More/Simple/Builder 0.85_01
         cmp_ok() fixage warning
         http://xrl.us/owaq4

   Attribute-Handlers 0.80
         http://xrl.us/owaq6

In Brief

   David Golden began cleaning up the task of documenting Perl via git on
   the Perl wiki.

     http://xrl.us/owaq8

   John E. Malmberg ran into a "Module::Build" failure on VMS that he
   thought had been fixed at one point by a patch that had been dropped
   in the meantime. But then the test succeeded without anything else
   happening.

     http://xrl.us/owara

   John sent in some other patches for VMS, some of which Craig A. Berry
   was able to apply. One dealing with "cwd" issues, needs to be
   forwarded to the "Pathtools" developers (i.e. Ken Williams).

     http://xrl.us/owarc

   JCSS suggested that "Storable" could optionally "delete %hash" when
   doing "$foo=freeze(\%hash)". Nicholas Clark pointed out that when
   error handling is taken into account, this becomes much more difficult
   than it would appear at first glance.

     http://xrl.us/oware

     another Unix platform?
     open source BeOS!
     one puzzling bug
     http://xrl.us/owarg

Last week's summary

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

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.

-- 
stubborn tiny lights vs. clustering darkness forever ok?

• This Week on perl5-porters - 20-26 October 2008 by David Landgren