develooper Front page | perl.perl5.porters | Postings from February 2008

This Week on perl5-porters - 3-10 February 2008

David Landgren
February 14, 2008 14:22
This Week on perl5-porters - 3-10 February 2008
Message ID:
This Week on perl5-porters - 3-10 February 2008

   Ævar Arnfjörð Bjarmason: "It would be a shame if we shipped a perl
   with known segfaults."
   Nicholas Clark (ever the pragmatist): "It wasn't solved in 5.8.8
   so it's not a regression."

Topics of Interest

"pp_const" not that hot?

   Nicholas Clark looked at an execution profile, and saw that in a given
   workset, "pp_const" is called around 200 million times, and in "if"
   statement within is taken only 3000 times. Since the decision to take
   it or not is known at compile time, it could be split into two
   discrete ops which could only be a win.

   No takers, but definitely a nice self-contained project for someone
   who wants to dip their toe in the p5p waters.

     had I infinite tuits

New snapshot for 5.8.9 (Perl @ 33218)

   Last Saturday (the 2nd of February), Nicholas made 65 commits in a row
   to the Perforce repository, thus raising the number of commits in the
   repository to 33218.

   He then posted a snapshot of what will become Perl 5.8.9, alas,
   slightly too late on Saturday afternoon to be included in the previous
   summary (which cuts off at around 16:00 UTC).

   Apart from various known issues like IRIX and C++ compilers, Nicholas
   was very interesting in hearing how it coped on VMS, since he
   integrated lots of changes from 5.10 pertaining to VMS, and wasn't
   sure if his selection was sufficient.

   Jerry D. Hedden pointed out that some of errors on the Cygwin platform
   could be solved by backing out a change dealing with consting.

   Andy Armstrong offered to add "dtrace" support (now that he's an
   expert having already done it for 5.10). Nicholas hoped he could
   backport it from the 5.10 track, assuming it gets into what will be

   Craig Berry promised to review the VMS changes. H.Merijn Brand tweaked
   his 5.8-dor patch to make sure it could still add the "//" defined-or
   operator to 5.8.

     released before christmas

   Jerry asked whether he should try to fix some of the warnings that
   were cropping up in recent builds; Nicholas said he hoped to locate
   the secret patch that, if applied, would make them all go away.

   Jarkko Hietaniemi buzzed Mark Lutz, who works at a large aerospace
   firm and has access to some some serious hardware. He reported success
   on an SGI but gave up on a Cray X1.

   David Cantrell reported compilation success on a Cray YMP, albeit with
   a number of test failures.

   Dave also mentioned that his NetBSD/alpha was perfect barring one
   single failure in POSIX/t/sigaction.t.

Data corruption in CPAN shell?

   H.Merijn Brand reported problems with the CPAN shell. Andreas König
   mentioned that Frank Wiegand had identified the cause as being a
   recent version of "Safe" and that H.Merijn should downgrade to Safe
   version 1.12. (Only 5.8.8 is affected, 5.10 is fine).

   Rafael thought he had fixed it with change #33236, it being something
   to do with version objects being returned from Safe compartments. John
   Peacock identified the interaction problem between "" and
   "Safe", and suggested Rafael release his fix in Safe 1.15 and all
   would be well.

     playing it safe

Possible Y2038 solution

   Michael G. Schwern mentioned a solution he had heard about concerning
   the Y2038 problem, which is bring dates beyond back to before 2038 and
   run it through 64-bit safe routines in order to derive the correct
   time zone and daylight savings information.

     licence-friendly code

   Jesse Vincent pointed out that this approach will fail whenever
   timezones change, the most recent high-visibility exemplar of which
   was the USA's daylight savings changes in 2007.

   Ben Morrow thought that we could only do so much without shipping a
   full timezone database. The conversation continued into excruciating
   detail about the periodicity of calendars and how to deal with
   daylight savings tweakages.

   As part of his research, Michael asked for a table of post-2038 times
   from a 64 bit system. Mark Mielke provided him with enough data to
   keep him going 700 years.

     my 600th birthday is on a Saturday

64 bit "localtime_r()" on 32 bit "time_t" machines

   Michael then delivered some experimental code to provide 64-bit time
   routines suitable for 32-bit hardware. Jan Dubois wondered about the
   licensing issues (since Michael had used code from

   Andy Dougherty explained how to make the code more platform agnostic.
   Michael explained that the code needs quite a bit of work still and
   pointed out the areas where he was not happy. Andy thought that much
   of the problems could be addressed with Configure probes, and promised
   to get a round tuit.

perl compiler, continued

   David Nicol wondered if Reini Urban's compiler work would allow, for
   example, a known IV passed to a function to be passed as a bare "int",
   thereby removing a certain amount of indirection required to get from
   the pointer to an "SV" down to the raw "int".

op/sprintf.t and op/write.t failures with "mingw-runtime-3.14"

   Rob Sisyphus reported that the changes made to the MinGW runtime in
   order to have a C99-compliant "libmingwex", and said he'd file a bug
   with them.

Slowdown in 5.10.0 regexes with atomic patterns

   Dave Mitchell admitted to having chopped some code out of the regexp
   engine that dealt with the super-linear positive cache (no, I don't
   know what it does) on the grounds that he couldn't figure out how it
   could be triggered, nor did anything in the test suite tickle it. And
   it got in the way of making the regexp engine non-recursive.

   Moritz Lenz replied that fixing it up was probably not that important
   since the test case was rather pathological, insofar that if someone
   were to write such a pattern and encounter the slowdown, it would be
   easy to reformulate it to avoid the problem.

     not really a bug

OpenVMS largefile "getpos"/"setpos"

   Hein van den Heuvel was wondering why Perl couldn't deal with large
   files (>2GiB) out of the box, since the information returned by
   "getpos" (a.k.a. "tell") is an opaque cookie that is passed to
   "setpos" (a.k.a. "seek") as required. Therefore perl should just use
   that, and get large file handling for free.

   Craig Berry thought that the interface was cracked open and exposed to
   be compatible with "seek" and "tell". If people didn't really that, he
   proposed a two-line fix that restore the native VMS file positioning

     peeking behind the curtain

Patches of Interest

"win32_async_check()" didn't loop enough

   In the beginning, "win32_async_check()" could interact poorly with
   "win32_msgwait", and the denizens of the Win32::GUI mailing list
   determined that it could go into an infinite loop and consume all
   available CPU. It was subsequently patched to prevent this occurring,
   but the balance swung the other way, and caused 30 second DDE timeouts
   because it didn't loop enough. Robert May provided a patch to find the
   middle ground, and this Rafael applied.

     the goldilocks syndrome

Give Win32 message windows proper window procedures

   Robert May then provided a second patch to improve the "alarm" and
   "kill" implementations on Win32. Rafael applied the patch to blead,
   and if everything checks out correctly, it may be backportable it to

     wake up, time to die

sv.c consting

   Steven Schubiger added some consting goodness to sv.c, which Rafael
   applied. So he did it again, and Rafael applied that too. And then
   again, and still Rafael followed. But then Steven delivered a fourth
   patch of consting goodness, but it didn't get applied.

     repeat as necessary

Extend t/ routine to set subprocess ENV

   Jim Cromie was looking at the XML output from a MAD run, and needed to
   be able to specify an environment variable beforehand, and so set
   about adding a general mechanism to

   Nicholas cautioned about the dangers of being insufficiently
   shell-agnostic, and suggested a hash key/value approach to let each
   platform implement the initialisation of the environment.

Feature bundles are the same across all subversions

   Rafael applied Steffen Müller's patch that ensures that any specific
   feature request (such as "use feature 5.10.3") gets the same set of
   features as "use feature 5.10".

   The result is a little drastic but there doesn't seem a way around the
   possible inconsistencies that may arise. So, for now, the porters
   promise that no new features will be added in 5.10 (that would require
   an extension to the "feature" pragma, other new, non-"feature"
   features are fair game).

     the features remain the same

"mg_magical()" sometimes turns "SvRMAGICAL" on when it shouldn't

   Vincent Pit returned to his magical patch with some test cases that
   demonstrated the problem.

Unwanted warnings from "PerlIO::scalar"

   Hugo van der Sanden explained that his caution regarding the correct
   use of magic in Ben Morrow's patch for "PerlIO::scalar" was not meant
   to kill the patch dead. Ben Morrow responded with what he thought was
   a change that resolved the issue, although he wished there was a
   perlmagic.pod that would explain the finer points of magic.

   Rafael thought that the patch looked good enough to take.

Optimize "OP_IS_(FILETEST|SOCKET)" macros

   Jim Cromie reworked to generate more efficient macros
   written to opcode.h, by relying on the property of consecutive opcode
   numbers. Nicholas was very impressed, as this shaved 300 bytes off the
   size of util.o.

   Jim followed up with another tweak that resulted in a dozen or so
   bytes being saved.

     cache dispenser

Watching the smoke signals

   The most recent 5.8.9-to-be smoke failure on Windows, courtesy of
   Steve Hay.

     Smoke [5.8.8] 33205 FAIL(F) MSWin32 WinXP/.Net SP2 (x86/2 cpu)

   And a series of blead failures, also from Steve, the most recent of
   which is

     Smoke [5.11.0] 33261 FAIL(F) MSWin32 WinXP/.Net SP2 (x86/2 cpu)

New and old bugs from RT

Hints for IRIX (#33849)

   Andy Dougherty wrapped up the compiler issues on IRIX with a patch,
   that Rafael applied. Now to see if it works.

Residual threads crash (#45053)

   Jerry D. Hedden reported that change #31864, designed to resolve bug
   #45053 made a valiant attempt at perfection, but if you run the test
   script repeated, it will emit periodically the message "Bad free()
   ignored (PERL_CORE) during global destruction."

"IO::Handle" method "say" should ignore $\ (#49266)

     "Fixed in bleadperl by change #33258" -- Rafael

"Scalar::Util" - documentation problem (#49434)

   Steve Peters excised the reference to a book mentioned in the
   documentation that will never see the light of day.

Attributes + Unknown Error (#49472)

   Andreas König's binary search revealed that the bug (bad diagnostics)
   was introduced with change #31255. Nicholas helpfully reposted the
   entire patch to the list. Dave Mitchell took one look at it and posted
   change #33265 three hours later to fix it.

Segfault on "perl -e 'split //, unpack "(B)*", "ab"'" (#50256)

   Nicholas got to the bottom of the issue: "split" imposes scalar
   context on "unpack", and parens in unpack templates had, um shall we
   say, undefined behaviour in scalar context.

     behavioural modification

perlop.pod - misnomer in % operator documentation (#50364)

   Martin Becker's documentation tweak regarding modulus and common
   residues was accepted.

"Filter::Util::Call" problem with $_ (#50430)

   Steve Hay twiddled the filter code to make the problem go away and
   also didn't break anything else in the tests, but was hoping someone
   more skilled in the art of filters would care to comment.

     say we just called them a failed experiment?

"keys %+" does not return the correct keys (#50496)

   Jonas Kramer reported a bug with two issues, one of which was due to
   POD formatting issues on his terminal that causes "%-" to be rendered
   as "%?". Don't laugh, people lose satellites for less than this.

   The other issue was confirmed to be a true bug by Abigail, who went on
   to write some TODO tests for t/op/pat.t lest they be forgotten.

Perl 5.10.0 segfaults on "format" with "my" variables (#50528)

   Stephan Springl delivered a delightfully concise test program to show
   how to make 5.10.0 coredump. It turns out that this is actually a
   marginal improvement over 5.8, since the same program will run the
   code without crashing, but will give the wrong results.

   Dave Mitchell figured out what the problem and suggested two lines of
   enquiry to explore. Unfortunately he was waiting for a new delivery of
   tuits and was thus unable to do anything more.

     beware the abominable newATTRSUB

Compiling the latest 5.8 snapshot on QNX (#50530)

   Matt Kraai reported difficulty getting Perl 5.8 up and running on QNX.
   "getcwd" seemed to be giving grief, as do possibly unsigned "time_t"
   data types.

   Nicholas made some suggestions which cleared up some, but not all,

"when( @n && %n )" fails to smart match (#50538)

   brian d foy filed a bug report following his request for comments on
   the behaviour of "&&" in a "when" clause. His argument was that the
   documentation does not coincide with the implementation, but didn't
   know which one needed to be fixed.

     could be a feature

Storable does not store "REGEXP" items (#50608)

   "sand" (who I suspect is really Andreas Köenig's sandbox) filed a
   reminder bug to point out that "Storable" needs to be updated to
   handle the new "REGEXP" datatype in 5.11.

CPAN shell bug on AIX 5.3 (#50612)

   Joachim Görner built a 5.8.8 on AIX. When he tried to run a CPAN
   shell, it appeared to have trouble downloading the CPAN indices,
   trying to rename a file that doesn't exist.

   He pointed out that 5.8.2 works correctly on the same machine.

Perl5 Bug Summary

   289 new + 1494 open = 1783 (10 created, 39 closed)

     ooh, someone's been busy

This is the BBC

   Devel-StackTrace 1.15
       Dave Rolsky announced a fix in the shape of 1.16, available on

New Core Modules

   B::Generate 1.12_04
       Jim Cromie made a new release that works on both 5.10 and 5.8.

   ExtUtils::MakeMaker 6.43_01
       Michael G. Schwern released a development version of the venerable
       ExtUtils::MakeMaker module. Rafael and Steve Peters brought blead
       up to date with the latest goodies.

In Brief

   Moritz Lenz figured out that the weird "__stack_ck_chk_fail_local"
   errors was caused by compiling with "-fstack-protector". Take it out
   and everything is fine. Andy Dougherty said he'd look at providing a
   better test for "Configure".

     back to the drawing board

   Jarkko Hietaniemi revived an two year old message from the depths of
   his outbox regarding the possibility of intercepting a possible
   segmentation fault with "unpack 'P'".

   H.Merijn Brand reported that gcc-4.2.3, HP-UX 11.23 and blead is not a
   recipe for happiness.

     back to 3.4.6

   Jerry D. Hedden asked for, and received, co-maintenance of
   "Thread::Queue". It's now dual-lifed, and so we may expect exciting
   new features on CPAN.

   Yamashina Hio had some more questions about POD's L<> codes but
   received no answers.

   Vincent Pit saw that "mg_copy" ought to take an "I32" instead of an
   "int", and so it was done.

   Alas, Jerry D. Hedden pointed out that this unfortunately causes
   "initialization from incompatible pointer type" warnings in
   "threads::shared". He wondered if there were 32/64-bit issues at hand,
   and if so, what was the best way to resolve them.

   Jim Cromie added some simple tests to validate "-Dx" output saying
   that it wasn't the most important thing in the world, but it might be
   helpful to know if and when the output changes in subtle ways.

     canary in a perl mine

   Jim Cromie thought Nicholas's trick was so useful, he
   gave it the ability to pretty-print the macro expansions.

   Jerry D. Hedden wrote a patch that added a lot of tests for read-only


   José Auguste-Etienne posted a patch to hints/ to allow builds
   on AIX 4.2 to succeed. Applied.

   Slaven Rezic is the current Tk maintainer.

     security patches welcome

About this summary

     last week's news

   This summary was written by David Landgren.

   Weekly summaries are published on and posted on a
   mailing list, (subscription: The
   archive is at Corrections
   and comments are welcome.

   If you found this summary useful, please consider contributing to the
   Perl Foundation to help support the development of Perl. Perl Programming lists via nntp and http.
Comments to Ask Bjørn Hansen at | Group listing | About