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

This Week on perl5-porters - 17-23 February 2008

Thread Next
David Landgren
February 28, 2008 15:29
This Week on perl5-porters - 17-23 February 2008
Message ID:
This Week on perl5-porters - 17-23 February 2008

   Nicholas: So, it seems that constant folding runs in "compile time",
   which scares me somewhat. Surely it should be running in run time?

   Rafael: The whole point of compile time optimisation is that it runs
   at compile time, isn't it?

   Nicholas: Runs *at* compile time, but (I assume should) run under run
   time rules. There appear to be special exceptions scattered throughout
   the code that certain things aren't fatal if compilation is in

   (debating the elegant simplicity of the Perl 5 internals).

Topics of Interest

"pp_const" cools off

   Nicholas Clark applied Vincent Pit's patch from last week to slim down
   "pp_const" by splitting the op into two, which eliminates a costly

   Sébastien Aperghis-Tramoni reported that his web service that showed
   the gcov output of the Perl codebase had gone belly up (it was by
   poring over a gcov run that Nicholas spotted the original opportunity
   to optimise).

   Abe Timmerman said that a similar offering of his own was still up,
   except that the perl.gcov target was currently broken, so there was
   nothing to show.

     paths not taken

To B or not to B

   Jim Cromie and Reini Urban discussed the finer points of testing the
   "B" modules.

   Reini posted some "B::Debug" enhancements.

   Reini finished up with the delivery the delightfully named "B::MAD"
   module. He wasn't sure of the usefulness, but reasoned that some mad
   hacker might be able to put it to use.

     don't worry B::Happy

extending t/ to set the subprocess ENV

   Jim Cromie found a simpler way to set up the environment of a test
   requiring a fresh perl to be launched. This was to allow
   "PERL_XMLDUMP" to be specified, in order to verify MAD output.

   Nicholas wondered if Jim's hack was VMS-compatible. Craig A. Berry
   suggested that all that was needed was the correct use of "local".
   Hilarity ensued as Yitzchak Scott-Thoennes shot down each of Jim's
   attempts to effect the change in a loop, which had the result of the
   localness (locality?) evaporating at the end of the block.

     need a hash slice to go

   Somewhere along the way, Jim noticed a couple of warnings about unused
   variables when MAD is enabled.

You can't always optimise what you want

   Nicholas Clark continued with his interesting self-contained task from
   last week that dealt with constant optimisations and thought it should
   be possible to unroll constant "pack"s. (like "$var = pack("a2",
   "xyz")" being replaced by "$var = "xy""). He had the source code that
   could more or less do it, but ran all around the codebase trying to
   find a place to lodge it so that it would be acted upon at the right
   time. He finally wound up where he started from, and realised that it
   wasn't possible.

     nor do you always get what you need

Assistance with IPC modules and perl 5.10

   Nicholas Clark and Andy Armstrong came through with the goods to
   figure out what was going wrong with "IPC::Shareable" and
   "IPC::ShareLite" on the upcoming Fedora release. So Fedorans will soon
   be able use 5.10 straight out of the box.

Modulo operator and floating point numbers

   Ken Williams considered the recent change to the documentation
   concerning the modulo operator and suggested some further tweaks that
   Rafael applied.

   He then started thinking about moduli of floating point numbers and
   was surprised by the results of the current implementation. Zefram
   pointed out that the same issue is described in his bug #41215.

   Ken would have liked to make things behave in a more logical manner,
   but Rafael was happy to let sleeping dogs lie.

Perl on Symbian OS

   Gowtham wanted to know if the perl port that ran on Symbian 8 was
   usable on Symbian 9. Jarkko Hietaniemi, author of the the original
   port, was sceptical, given that the platform had been locked down.
   This might mean that Perl (as an "unauthorised application") would not
   have the privilege of opening a TCP connection.

   If the build toolchain has changed significantly then major work will
   be required to bring the port up to speed. In any event, Jarkko said
   that he had no more time to take care of it.

     sounds like no

"PERL_RUNTIME", or, adventures in "sprintf" ops

   Having discovered the nifty f flag and its positive impact on
   "length", Nicholas reasoned that "sprintf" was a likely candidate for
   more of the same. Except things went wrong, and had him diving all the
   way back to Malcolm Beattie's change #44 from 1997. He managed to sort
   things out and wrapped it up in change #33369.

"use encoding 'utf8'" bug for Latin-1 range

   Jarkko Hietaniemi kicked off a long thread last week, and was still
   bubbling along nicely as I summarised it. So the executive summary
   (subject to change, next week) is that "use encoding" is broken and
   its use should be discouraged.

UTF-8 problem with Perl 5.10.0

   More UTF fun this week. Phil Harvey wrote to explain how he had been
   burnt by the changes to "U0" and "C0" flags for "unpack", that used to
   allow one to sneak past the abstraction model and poke at the
   implementation details. This caused a number of mutually
   irreconcilable problems, and so the decision was made during 5.9 to
   make a clean break with the past.

     it /was/ noted as an Incompatible Change


   Tels discovered ohloh, and its spectacularly out-of-date idea of
   activity on the Perl codebase. It was slurping the contents of Sam
   Vilain's git repository, and choking on the complex history of the
   codebase. This meant that it looked as if development stopped years
   ago. Andy Armstrong fixed up the summary info to indicate that Perl 5
   is still alive and kicking.

Patches of Interest

Installing threads files on non-threaded Perls

   Michael G. Schwern questioned the desire to exclude threads modules
   from being installed on non-threaded builds. His contention being that
   if someone uses the module on a non-threaded build, they get a nice,
   informative error message as to why things don't work.

   If they are removed, then only a basic "module not found in any of
   these zillion directories" message is issued instead. Michael was
   worried that some people might go to all the effort of trying to
   download the threads package from CPAN, only to find out that it
   *still* doesn't work, and in fact cannot unless perl itself is

   Jerry D. Hedden saw the logic in this line of reasoning, and reversed
   his stance.

     helpful errors

     back they go

   Elsewhere on planet threads, Jerry pushed some more updates out.

     threads 1.69

     threads::shared 1.17

     Thread::Semaphore 2.07

     Thread::Queue 2.06

"perl -M:Foo -we 1"

   Robin Barker related a discussion (and curiously, the
   discussion was about Perl) relating to "perl -M:DProf -we 1" not
   generating a warning. So he tweaked the getopty code in perl.c to make
   it do so. Jim Cromie thought that the proposed warning, so worded, was
   not particularly helpful.

     -M doesn't get the colon

Convert Changes file to UTF-8

   Brendan O'Dea converted Changes to UTF-8. I don't know what happened
   in transit, but the result was a mess by the time the message hit my

no archlib in otherlibdirs

   Reini Urban proposed a change to the various lib paths. Rafael
   admitted the current mechanism was a bit ad-hoc and it reminded him
   that he needed to work on a 5.12 roadmap.

   Andy Dougherty explained how things are supposed to behave currently. bug within overloaded stringification

   Nicholas Clark tried to apply Marcel Grünauer's fix to "NEXT" but
   "patch" failed miserably in the attempt. Nicholas blamed Apple's

New and old bugs from RT

threads still crashing (#45053)

   Jerry D. Hedden discovered that his thread segfaults would occur
   regularly on a machine with 4Gb of RAM, but not on another that had
   only 1Gb. He wondered if it could be the symptom of some bad
   signed/unsigned voodoo.

   Tels replied that he was unable to provoke any crashes on his own

QNX Test failures (#49818)

   Matt Kraai diagnosed a series of test failures he was having on QNX.
   Two could be traced to tests building a ".pbc" file and then trying to
   overwrite it after it had been loaded. His brutal fix for that problem
   was to delete the file before overwriting it, but suspected there was
   a better approach to the problem.

   The second series of tests were due to bugs in QNX's "atof". So the
   fix here would be to tweak Configure to use Perl's own implementation.

bug in regcomp code leading to panic (#50114)

   Yves Orton stopped and suggested a couple of source code changes to
   try and regretted that he didn't have more time to devote to the
   issue. He nevertheless found the time to commit change #33324 that he
   hoped would resolve the problem.

   Apparently, it did.

   In other news, Michael Schroeder (reporter of the bug) asked why
   "$r=qr{^bar}; "foo\nbar" =~ /$r/m or die" dies on blead, but not on
   5.8. He tracked down where in the regexp engine things had changed (no
   mean feat) and wondered what the reasoning was.

   Rick Delaney explained that he had made the change to fix a related
   matching problem, and had not thought to add a regression test that
   would have caught the change that Michael tripped over.

   Yves felt that it could be fixed for 5.10.1.

modified hints for Darwin x86 64bit (#50946)

   Daniel Quinlan supplied a patch to the Darwin hints file to allow a
   64-bit perl build. Rafael applied the patch but Nicholas warned that
   there may be problems, since the 64-bitness of the build would not be
   reflected in machine/architecture pathnames. This could lead to all
   sort of mixed-bitness nightmares if different builds coexisted on the
   machine. Unless of course Darwin just does the right thing.

"pod2man" needs to translate some ASCII characters (#50950)

   Mike Ward complained that backticks and dashes were being incorrectly
   translated by "Pod::Man".

Install Perl-5.8.7 source on Solaris 10 Sparc (#50960)

   Elad Dotan reported having trouble building Perl on Solaris, but
   provided so little information that diagnosis was difficult. Andy
   Dougherty tried, though.

Method dispatch breaks with "defined(\&sub)" (#51072)

   Dagfinn Ilmari Mannsåker discovered that trying to call "->next::can"
   on a package that has not (yet) been defined will cause a segfault.
   Rafael wrote a nifty patch to autovivify it as an empty package.

Perl5 Bug Summary

     288 new + 1499 open = 1787 (6 more, 4 less)

This is the BBC

       Andreas König was surprised to discover that "Devel::LeakTrace"
       was broken, and in fact had been so since change #17968 from 2002.
       He wasn't sure on which side the fault lay.

In Brief

   Robin Barker discovered some C files in the test suite that needed
   some consting goodness applied.

   The recent change #33291 had VMS falling off the wall, so John E.
   Malmberg and Craig A. Berry put it back together again.

     the king's men

   Reini Urban gave the Cygwin hints a little TLC. Applied.

   Steve Hay revived the discussion about automated generation on Win32
   configuration information, saying that he had improved the situation
   with some Makefile trickery, but full automation remained elusive.

     bespoke configuration

   Porting/ really does indenting now. (Change #33352).

   Jim Cromie tweaked his recent opcode generator tweaks, shaving a few
   more bytes from op.c.

About this summary

   This summary was written by David Landgren.

   Last week's is here

     This Week on perl5-porters - 10-16 February 2008

   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.

Thread Next Perl Programming lists via nntp and http.
Comments to Ask Bjørn Hansen at | Group listing | About