This Week on perl5-porters (27 February-5 March 2006)

This Week on perl5-porters - 27 February-5 March 2006

   "Module::Build" achieves core status, VMS improvements, and the usual
   bunch of bug fixes and enhancements.

Topics of Interest

Function prototyping and op/utftaint.t failures in "blead" in "Win32"

   Yves Orton first starting looking at smoke failures on Win32, and
   wondered why he was seeing redefined subroutines in "Getopt::Long",
   but Nicholas Clark stepped up and said that Yves had been caught out
   by a glitch that had since been fixed in the source code.

   Steve Hay and Nicholas worked through the failure, which was a problem
   of taintedness when "." (dot) appears in the "PATH" environment
   variable. A fine example of how hard it is to get cross-platform
   platform-dependent code correct.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00939.html

"Term::ReadLine", "CON:" and "Term::ReadKey" on "Win32" (cpan #17773)

   Johnathon Stowe mentioned the issues he had uncovered with CPAN bug
   reports filed against "Term::ReadKey". He had traced the problem to
   "Term::ReadLine" using the special device "CON:" (as in *console*) on
   "Win32". One may open such a file directly, and things will work
   correctly, but open the file and pass it as a handle to
   "Term::ReadLine" and things start to fall apart, which is in fact what
   happens at the moment. Johnathon thought that the best approach would
   be to fix "Term::ReadLine".

     Somebody else's bug
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg01018.html

DBD::Oracle 1.17 and 64-bit perl on AIX 5.1

   John L. Allen was failing miserably at getting Oracle and 64-bit perl
   on AIX to talk to each other, and asked for help. H.Merijn Brand
   thought that the combination was "like voluntarily having someone tie
   you down on a bed of nails, and then being whipped with a bunch of
   rusty barbed wire." Dave Mitchell considered it highly doubtful that
   one would be able to connect a 32-bit Oracle library to a 64-bit perl.

   After trying out different long integer and long double Perl
   compilations, John succeeded in building a perl with 32-bit integers,
   long doubles (128 bits) and Oracle all playing nicely.

   Alan Olsen, speaking from experience, recommended that John go either
   full 32-bit, or full 64-bit. Choosing the middle ground just leads to
   pain and unhappiness.

     It can be done
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00008.html

"pow" failures on AIX with "uselongdouble"

   After having done battle with Oracle on AIX, John L. Allen turned his
   attention to failures in the test suite, and noticed some misbehaviour
   with the "pow" function. Dominic Dunlop confirmed that something
   strange was indeed occurring.

   After a bit of detective work, John realised that the problem was not
   with perl, but AIX's underlying math libraries. He wrote a small C
   program to demonstrate the error, which should allow someone with the
   necessary "Configure"-fu to write the probe to work around the
   breakage.

     The library and the damage done
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00105.html

Detecting @ISA cache invalidation

   Caching in which package a method is found ensures decent run-time
   performance. That is, if an object calls a method unknown to the
   current package, it consults @ISA to look for other packages that may
   have a suitable method. Once it succeeds in finding it the first time,
   it caches the information so that subsequent method calls can avoid
   paying the cost of the search. That works fine until @ISA is modified,
   in which case the cache has to be invalidated, which in turn means
   that objects need to take a fresh look through the @ISA chain to
   locate their methods again.

   Usually you don't have to care about this at all, it just works. But
   some modules extremely tricky things, and can get thrown by changes to
   @ISA, and worse, up until now there was no easy way of determining
   when it happens.

   So Joshua ben Jore wrote "B::sub_generation", which provides a handy
   technique for letting user code know when cache invalidation occurs.
   When asked to explain what this all meant, Joshua provided a short
   snippet of code, showing how things can get derailed if code doesn't
   realise that @ISA changed. Rafael thought that Joshua's exposé should
   be saved somewhere in "perlguts".

     Talkin' about my B::sub_generation
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00021.html

Small bug fixed in "Module::Build" passthrough Makefile.PL

   Ken Williams made a change to "Module::Build::Compat" to deal with the
   fact that the method call "CPAN::Shell->install()" doesn't appear to
   return anything useful.

   Yitzchak Scott-Thoennes wanted to know how one could reliably test to
   see whether the install did in fact succeed. Andreas Koenig
   recommended using the "$module->uptodate" method as a suitable
   work-around.

   Ken planned to use that approach soon.

     Look for a new version of Module::Build soon
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00031.html

Tracking down leaks in "XS" "SV"s

   Tracking down leaking scalars in "XS" code is hard.

   Andy Armstrong has started to work on "Devel::LeakTrace", which uses a
   custom run loop, and was having trouble determining the relationship
   between where "SV"s are created, and where perl reports that they were
   created.

   Dave Mitchell pointed out that since 5.8.1 it has been possible to
   compile a perl executable with "-DDEBUG_LEAKING_SCALARS", which adds
   extra information to "SV"s, which in turn can be picked up by
   something like "Devel::Peek". On the other hand, Andy's approach has
   the benefit of not requiring a specially prepared perl.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00066.html
     http://search.cpan.org/dist/Devel-LeakTrace/

Understanding "ext" and testing

   Adam Kennedy is working on the Vanilla Perl 5.8.8 distribution, and
   was having trouble with some of the tests in the "IO::" packages. He
   didn't understand how the tests could succeed at all, and wondered how
   long they had been failing.

   Steve Hay had a look, and saw that the behaviour is dependent on
   whether the "fork" emulation code is used or not. And that some of the
   tests to see whether "fork" is defined or not are quite bizarre.

   Nick Ing-Simmons came to the rescue, giving an explanation for why
   some of the things are the way they are. All in all, it's an area that
   Needs Work.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00078.html

Making "File::Find" Iterative

   The venerable "File::Find" module uses a callback scheme, something
   beginners to Perl may find a bit unusual. Shlomi Fish looked at
   extending it to provide an iterative interface similar to Shlomi's own
   "File::FTS" module.

   Randal Schwartz pointed to an article he had written that dealt with
   the same issue. Steve Peters noted that the main criterion for judging
   patches to "File::Find" is that they should incur no speed penalty,
   thus, for a patch to be accepted, it would need solid benchmarking.

   Nick Ing-Simmons explained that the question of speed was one of
   system calls. Make one unnecessary call, and the difference would show
   up for people scanning deep and wide directory trees.

   In the end, Shlomi decided to concentrate on "File::Find::Object", as
   it appeared to be closer to suiting his needs. David Nicol wondered
   whether "File::Find" was thread-safe, and Tels made a plug for his own
   "File::Walker"

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00047.html

     File::FTS
     http://search.cpan.org/dist/File-FTS/

     File::Walker
     http://search.cpan.org/dist/File-Walker/

Will someone please fix "Devel::DProf"?

   Jarkko Hietaniemi made a plea for someone with too much spare time on
   their hands to please take a look at "Devel::DProf" and fix some its
   worst bugs. Andy Lester wanted some test cases.

   Jarkko countered with:

     $ perl -d:DProf -e 'sub foo { next } for (1) { foo }'
     $ perl -d:DProf -e 'use autouse qw(Pod::Usage pod2usage); pod2usage'

   Tels searched the RT queue:

     http://rt.perl.org/rt3/Ticket/Display.html?id=24058

     The bug stops here
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00152.html

"Module::Build" 0.27_08 added to the standard distribution

   A first attempt was made to add "Module::Build" to the core. This was
   perhaps the largest thread of the week. It appears the graft has
   succeeded, but more work is required.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00167.html

The continuing saga of "*a=$a=*b;${"a"}=*a;"

   Nicholas returned to the "*a=$a=*b;${"a"}=*a;"-perl-go-boom bug and
   couldn't see a easy way out, short of cheating and getting the
   optimiser to spot the sequence and thereby emit a different op-tree to
   make the problem go away.

   David Nicol wondered whether it was a case of worrying too much about
   a construct that doesn't come up in practice. chromatic thought that a
   tool simply should not crash on invalid input.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00169.html

Some more VMS goodness

   Peter Prymmer sent in a patch for some VMS-specific issues, which
   Craig Berry applied partially. Peter was lacking a bit of context to
   understand the reason why Craig did not apply the rest of it, and John
   E. Malmberg summarised the issue nicely for the vmsperl readership who
   don't follow p5p, and thus also saved the p5p summariser from having
   to do so:

     Peter's patch
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00170.html

     John's summary
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00186.html

Matching dynamic Unicode properties

   Dan "Mr. Encode" Kogai related something he'd heard about non-existent
   Unicode properties (like "\p{IsBogus}") in pattern matches. Sometimes
   perl spits out an error... but not always. Yitzchak was quick to that
   the results depended on whether the match had failed or not before the
   scanner reached the location of "\p" property in the target string.

   Hugo van der Sanden wasn't even sure one could call it a bug (which
   Dan did not say either), but thought that perhaps the "utf8" module
   could offer something to check for this situation, since, as
   Sadahiro-san pointed out, it could be hard to check for user-defined
   properties sufficiently early in the general case.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00189.html

What Andy Lester did this week

     Removed a redundant o->op_type
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg01001.html
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00000.html

     Non-null optimizations for SvREFCNT_inc
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00032.html

     Initialising all of mgvtbl
 
http://www.xray.mpe.mpg.de/maIling-lists/perl5-porters/2006-03/msg00033.html

Patches of Interest

"PERL_TRACK_MEMPOOL" cripples environment after "exit()"

   Marcus Holland-Moritz uses "blead" for his daily work, which leads to
   some interesting discoveries. He had wanted to run "gcov" coverage
   analysis of one of his XS modules, and became distracted by strange
   failures, probably best attributed to the environment variable code
   clean out that took place a few months ago. Evidently there are still
   demons lurking in that code. Marcus supplied a patch to nail one of
   them, applied by Rafael Garcia-Suarez.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00940.html

Silence useless errors in "B::Lint" for "grep"

   Joshua ben Jore offered a patch to silent what he perceived to be a
   useless warning emitted by "B::Lint", concerning implicit matches with
   "grep". Since "grep{ /pattern/ }" is such a frequent idiom (and
   insofar as $_ is topicalised (the New way of referring to what used to
   be known as "local"ised) within the "grep" code block), it's a rather
   stupid warning. Rafael agreed with Joshua and applied the patch,
   saying that he'd be happy to accept similar patches for postfix "for"
   and "map".

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00002.html

Long pathnames on VMS and sundry fixes

   John E. Malmberg sent in a patch for VMS builds and long pathname
   handling. Abe Timmerman reported that results looked good.

     The patch
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00122.html

     The smoke results
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00127.html

Watching the smoke signals

   Smoke [5.9.4] 27358 FAIL(F) hp-ux 11.11/64 (PA-2.0/64/2 cpu)

   H.Merijn Brand poked around in "test.pl" to try and cope with change
   #27345 and problems with tainting. He made the appropriate changes to
   get things to work on HP-UX but wondered whether the patch would work
   on other systems like "VMS" or "Win32". Steve Hay found problems with
   the latter, and proposed an alternative.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00041.html

New and old bugs from RT

Lexical variables in regexp "?{}" assertions (#38639)

   Richard Clayton identified a problem with lexicals defined within a
   "for" and being set within a "?{}" assertion of a pattern match. It
   gets set the first time through the loop, but not on subsequent
   iterations. The work-around is to declare the lexical in a scope
   further out from the "for" block. No takers.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00941.html

"Configure -des" stops waiting for "<CR>" (#38642)

   Anton Koinov ran into problems configuring perl on Gentoo. Andy
   Dougherty was intrigued, and tried to guess what was going wrong, and
   suggested Anton run the following command

     sh -x ./Configure -S 2>&1 | tee Configure.out

   ... in order to capture all of the text generated during the run (as
   "-des" discards certain output deemed to be mostly harmless). No news
   back from Anton as of yet.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00944.html

MULTICALL causes segfaults with very large return stacks (#38644)

   Tassilo von Parseval has been working with the new "MULTICALL"
   interface and noticed problems when the return stack is very large.
   This shows up as segfaults in XS code, such as "List::Util".

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00958.html

Long file names on Stratus VOS (#38645 and #38646)

   Paul Green uses Perl on Stratus VOS, whose file system limits file
   names to no more than 32 characters. This poses a problem when he
   tries to run the test suite of a module like "Pod::Simple", which
   contains a test name search_25_glob_squaa_coloncolon_kleene.t. At 40
   characters long, that's more than Stratus can bear.

   Similarly, there's another file, _white_with_navy_blue_on_black.css
   that is also a bit too long. Nicholas Clark wondered whether 32 was
   some sort of POSIX minimum, and recalled that some tests had already
   been renamed to deal with characters in file names that VMS had
   trouble processing. Joshua Juran noted that traditional Mac-based
   platforms ("MacOS" and "Lamp") are limited to 31 characters. (MacOS X
   does not have this limitation).

   (The Summariser wishes to point out the existence of Sébastien
   Aperghis-Tramoni's "Test::Portablility::Files" to module authors).

     One file
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg01003.html

     And then another
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg01004.html

     No more excuses
     http://search.cpan.org/dist/Test-Portability-Files/

64-bit (non-)builds on Solaris 8 (#38664)

   James Overly had problems building a 64-bit perl on Solaris 8.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00058.html

Debugger Loses Names for Anonymous Subroutines (#38673)

   chromatic showed how the trick of assigning to the "__ANON__" typeglob
   to name an anonymous subroutine doesn't work in the debugger.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00147.html

"O::Deparse" not working as expected (#38684)

   "harleypig" was having trouble with "split". I tried to pay attention,
   but Stephen McCamant supplied a patch to fix the behaviour (which was
   apparently broken), which was applied by Rafael. The end.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00202.html

Perl5 Bug Summary

     1548 open items
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00193.html

     in all their glory
     http://rt.perl.org/rt3/NoAuth/perl5/Overview.html

New Core Modules

   *       "CPAN" version 1.87 uploaded by Andreas Koenig.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00949.html

   *       "Archive::Tar" version 1.29 uploaded by Jos I. Boumans.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00074.html

In Brief

   Seung-Ho Han wanted to know how make sense of what "B::Xref::compile"
   produces. Joshua ben Jore explained what was going on, and that more
   clues can be found by studying O.pm.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg00952.html

   Jerry Hedden started to extract threads.pm from the core in order to
   make it available on CPAN. This would permit enhancements to be made
   to the threads implementation faster than the current "blead" to
   "maint" to "release" cycle.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-02/msg01013.html

   Jim Cromie continued to refine his self-described hare-brained
   "op-next"/"op-sibling"optimisation scheme, defending it against the
   critics, but ran into trouble somewhere deep down in the guts. In
   doing so, he came up with a new presentation scheme for "B::Concise".

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00001.html

   Anton Berezin caught and eliminated an extraneous "#endif" in
   fakesdio.h.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00010.html

   Jarkko Hietaniemi discovered that "-d:Foo=bar" no longer works in the
   current Perl release (bug report #38657). Rafael traced the problem
   down to the fact that "\0" (NUL) was no longer allowed in environment
   variables, and fixed things up as change #27359. Jarkko also supplied
   another patch for the same thing, which Rafael also applied.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00025.html
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00052.html

   Getting back to last week's thread on unwanted auto-vivification with
   "foreach", David Nicol showed a snippet of code that offers a way of
   working around the problem, and wondered whether the documentation
   should record it somewhere. Graham Barr noted that using "reverse"
   also suppresses the auto-vivification behaviour. And that if you
   didn't want a slice reversed, you needed to "reverse reverse".

     There's at least one way to do it
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00044.html

   Jarkko added a test to "Data::Dumper"'s test suite to ensure that the
   bug #38612 that was fixed in 5.8.7 never returns.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00049.html

   H.Merijn added "Configure" support for the GCC compiler options
   "__builtin_expect" and "__builtin_choose_expr".

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00063.html

   Paul Marquess delivered a patch for "Compress::Zlib", following on
   from his recent work to add compression plugins.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00064.html

   Joshua start to have a look at the new smart match operator "~~" and
   found a discrepancy between its behaviour and that of Pugs/Perl6.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00081.html

   Abe Timmerman patched Porting/checkcfgvar.pl to pick up configure.com
   and plunged unwittingly into the wonderful and frightening world of
   VMS symbols. John E. Malmberg and Craig A. Berry were sent in to
   rescue him.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00090.html

   Abe then thought it would be a good idea to see what happens when one
   builds a threaded perl on VMS. In the process he uncovered a couple of
   problems that John and Craig sorted out.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00139.html

   Dave Rolsky wanted to know if nested closures still leak memory. Dave
   Mitchell thought that no closure leakage bugs remained in "blead", but
   pointed out that not all of the new code had made it back into
   "maint".

     Until proven otherwise
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00103.html

   Randy W. Sims want to install an older perl on his Ubuntu linux
   distribution, but the install began to create an infinitely deep
   directory tree.

     On and on and on
 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00148.html

   Linda W gave a report on the effects of configuration options on the
   resulting perl binary.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00161.html

   Perl can no longer be compiled with a K&R compiler.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00160.html

   David Nicol posted his thought on what he would like to see in the way
   of plug-in optimisers. A optimistic optimiser could optimise a section
   of code, and then, if some assumption failed to hold true, it could
   de-optimise the code back to the initial state. I think some
   proof-of-concept code will be required.

 
http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/2006-03/msg00174.html

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

   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/

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