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This Week on perl5-porters (11-17 September 2006)

David Landgren
September 22, 2006 14:28
This Week on perl5-porters (11-17 September 2006)
Message ID:
This Week on perl5-porters - 11-17 September 2006

   "Now to move a huge pile of bugs out of my queue and into
   Randy's. THUD" -- Michael G. Schwern, making "MakeMaker" lighter.

Topics of Interest

Adding macros to Perl5

   Jim Cromie followed up an old message from Salvador Fandiño about
   better assertion support in perl. He went through the repository and
   dug out all the patches, but when he applied them to blead it wouldn't

threads causing smoke trouble on Win32 again

   Steve Hay reported intermittent hangs when smoking threads on Win32.
   He gathered a bit more information by running the tests manually, but
   wasn't able to get things to fail reliably. Dave Mitchell muttered
   something about race conditions in thread finishing, but wasn't able
   to recall precisely what it was that he had noticed.

   Jerry D. Hedden checked in a patch elsewhere to clear this up this

     The race is on

Safe signals and "SIGSEGV"

   Rafael Garcia-Suarez wondered whether "SIGSEGV" should be delivered by
   default in unsafe mode, and pointed to a bug report in Mandriva Linux
   that exposed the problem. Dave Mitchell tended to agree, and suggested
   that "SIGBUS" and "SIGILL" be thrown in as well.

   Mike Guy was in full agreement, and made a list of six points that
   needed to be taken into consideration.

     "This is your Captain. We are about to attempt a crash landing"

Problems with "(??{...})" in blead

   Yves Orton was taking the latest engine for a spin and noticed that
   "Regexp::Common" revealed a problem with how "(??{...})" and
   backtracking no longer play nicely together.

   Dave Mitchell admitted that he must have backed over something in
   "re_eval" and promised to straighten it out when he had a few moments.
   Yves proposed one way of fixing it, after having taken a look at (and
   understood) how it currently works. Dave begged Yves not to go down
   that road, since it would rely on infrastructure that Dave is
   currently in the process of ripping out and replacing.

     I hear shiny

"Acme::Meta" is broken again

   Andreas König noticed that change #26867 in blead resulted in
   "Acme::Meta" becoming unbuildable. Nicholas Clark noted that this was
   the second time that it had been broken, and wondered if the most
   expedient solution was simply to add "Acme::Meta" to the core.

   Seriously though, the question to be asked was is what it does
   considered appropriate behaviour, and thus deserving of proper
   support? In which case regression tests need to be added to the test
   suite ("Acme::Meta" plays fast and loose with stashes -- symbol table
   hashes). Rafael proposed a patch to "Acme::Meta" which restores full
   functionality (?) whilst keeping the the recent speed optimisations
   that have been made in the neighbourhood.

     Acme Development Company

Help me-e-e-e-e

   After a certain Chandra Sekaran posted a vague bug report that
   mentioned PERL, LDAP and the MS Event Viewer, Dominic Dunlop provided
   a detailed response on what steps Chandra should take to get the
   problem fixed, which prompted Andy Dougherty to thank Dominic for his
   kindness and patience over the years when dealing with such reports.

     And he didn't even mention uppercase

   Similarly, Dominic patiently walked a guy named Richard through trying
   to identify why perl was crashing in a SpamAssassin/Mac OS/X

More on trimming OPs

   Dave Mitchell took a look at Jim Cromie's work on combining "op_next"
   and "op_sibling" in the opcode structure, and wanted to obtain better
   figures on what the memory difference would be. Dave thought that the
   massive creation of SVs that come about when one does any sort of work
   would drown out the savings made in shrinking the opcodes.

   As Jim had been encountering difficulties in getting the patch to work
   correctly, he had been asking for help (which then in turn would allow
   such benchmarks to be obtained). Dave Mitchell suggested an elegant
   trick that at least defers having to get it to work.

   Just add an extra dummy field to the structure and see how much the
   overall programs grows. One could then conclude that if Jim were to
   succeed in his efforts, the program would shrink by an equivalent
   amount in the other direction.

   Depending on the code, the change is negligible or significant. More
   real-world code samples will be needed to see whether it is worth
   pursuing. Joshua ben Jore reminded him that "B::Deparse",
   "Data::Dumper" must not be broken because of such changes.

     Union structure blues

   David Nicol set about trying to prod the compiler into producing large
   amounts of code to shed light on Jim's improvements.

Core support for "Data::Bind"

   Chia-liang Kao explained what new core support would be required to
   make "Data::Bind" (which provides Perl6-style semantics for subroutine
   arguments) a little less of a kluge. The main problem is to have a
   read-only lexical alias that points to a regular read-write lexical.

   The easy way out would be to hang the information off the target SV,
   but then the original SV naturally becomes read-only as well, which is
   exactly what we're trying to avoid. Thus some sort of shim layer is
   needed between the alias and the original to get a chance to to the
   deed, which caused chromatic to mutter something out bestowing a new
   vtable upon an SV.

   Rick Delaney and Rafael Garcia-Suarez debated syntax. Nicholas Clark
   and Larry Wall debated implementation issues (with an eye to backwards
   compatibility: any number of suitable solutions exists, but they would
   break existing XS code. Not good).

     ... and in the data bind them

Taint and memory usage

   Xho Jingleheimerschmidt wondered why running a program with taint
   checks appears to double the amount of memory required. This can be a
   problem on lean machines. Xho wanted to know if there is a work-around
   for it, or failing that, an explanation of why it occurs.

   I figured out one part of the problem and will have posted a partial
   reply next week, but you'll have to wait until then and see whether an
   internals guru picks up the ball and runs with it.

     Getting ahead of myself

Dual-lifing "Devel::DProf"

   Andy Lester, evidently having too much spare time on his hands,
   thought it would be a good idea if he were to take care of
   "Devel::DProf". Except that it's noted on CPAN that Ilya Zakharevich
   is already the author. Then again, the version bundled with "blead" is
   different, anyway.

   Ilya was rather non-committal on the idea, citing that while a more
   portable codebase is desirable, the module is too intimately tied to
   perl's internals for it to be easy to make a one-size-fits-all
   distribution. Rafael thought that it might lead to a twisty maze of

   Be that as it may, Andy was most interested in making improvements to
   the "dprofpp" end of things. (Which makes me wonder whether the
   distribution needs to be some dimorphic beast: one side that gathers
   profiling information, and the other side that does the reporting).

     More like dual-heading it

Patches of Interest

Race condition fixes for threads

   Jerry D. Hedden posted a patch to fix what he thought was the cause of
   the race conditions that have been seen (above) with threads. Dave
   Mitchell appreciated the effort, but rebuked Jerry for mixing in
   trivial stylistic changes with serious open-heart surgery on mutexes.

   It becomes difficult to see what is important, makes it harder to
   track changes, and increases the workload of the "maint" pumpking who
   has to try and merge this stuff.

   So Jerry redid the patch to make it easier for people to follow along
   at home. Rafael smoked the patches on a hexaprocessor box, gave them a
   clean bill of health, and so they were applied.

     Flying colours

C++: Solaris CC now compiles "perl"

   Jarkko Hietaniemi sent in an update concerning his work to get the
   perl sources compiling with C++. It caused the Win32 compile to bomb,
   so Yves Orton rewrote the nasty bits and got it to work.

   And then some more from Jarkko:

   Jarkko also rewrote the "Encode"-generated code to make it safe for
   C++ compilers.

How to handle "(?=)" and "(?<=)" properly

   Yves Orton added more shiny goodness to the regular expression engine,
   this time boosting the performance of zero-width lookahead assertions.
   In the benchmarks that Yves had available, this was the last area
   where Python was previously outperforming Perl.

     Getting your bearings

   Elsewhere around the engine, Yves started to add hooks into it to pave
   the way for making a pluggable regular expression engine. (Which may
   lead, for instance, to Yves and Dave Mitchell's work in blead one day
   making it back to maint. Or running the PCRE engine inside Perl).

VMS goodness for the "Module::Build" beta

   Craig Berry sent Ken Williams a patch to reduce the number of failures
   observed when testing "Module::Build". The situation is still not
   perfect, but Craig felt certain that this batch of changes would not
   create problems on other platforms.

Fixing "\N{...}" in regular expressions

   A couple of months back, Sadahiro Tomoyuki showed that "/a\N{PLUS
   SIGN}b/" is parsed as "/a+b/" instead of the more Do-What-I-Meanish
   "/a\+b/". Yves Orton delivered an impressive patch to correct that
   behaviour. Tomoyuki went through the patch with a fine-toothed comb
   and made many suggestions. H.Merijn Brand applied it.

     Unicode unified

Patching win32.c to fix bugs #38723 and #39531

   Andrew Savige mailed in a patch to correct a couple of Windows bugs
   dealing with backticks. In fact, there were two patches, one for maint
   and one for blead. How thoughtful.

   Yves went over it and gave it the thumbs up. Rafael took it for a spin
   on an SMP box but the tests would hang from time to time. But since
   there is a net improvement, it's all gone in, and the test has been
   marked TODO until such time as Yves or someone else can take a closer

Watching the smoke signals

Smoke [5.9.4] 28821 FAIL(XF) OSF1 V5.1 (EV6/4 cpu)

   Jarkko discovered that Finnish locales, threads and regexps was a
   potent brew that caused all sorts of smoke to come flying out of his
   machine. Yves started to sift through the evidence to look for what
   was going wrong.

   After a short while, he hacked up a quick and dirty fix that consisted
   of disabling "study" for UTF-8 strings. And after another look he
   didn't feel so bad about the idea, since the code seemed to indicate
   that it couldn't work anyway.

   Rafael had another look at the patch that had given rise to the
   problems, and noted that it was only the test part of the patch that
   appeared to be in error.

   Yves finally hit paydirt. The test was actually correct. The code was
   wrong. Looking at old patch from Ilya Zakharevich some time last
   century, where a change from double- to single-quoting of some
   embedded Perl code meant that from that time on, the test has been
   patiently studying a stringified reference instead of a reference to a
   string, and that UTF-8 and "study" has been broken forever. Jarkko was
   lost for words. But then quickly recovered and gave Yves his next

   Jarkko and Yves then discussed how Perl should have really implemented
   UTF, properly. Yves hoped that the Perl 6 crowd have learnt their
   lessons well.

     I never liked studying, anyway

Smoke [5.9.4] 28849 FAIL(m) MSWin32 WinXP/.Net SP2 (x86/2 cpu)

   Sadahiro noticed a that a declaration list contained a statement,
   which is a no-no for some compilers. Once that was fixed the smoke
   cleared up.

Smoke [5.9.4] 28848 FAIL(Fm) OSF1 V5.1 (EV6/4 cpu)

   Jarkko noted another failure, that occur when the locale in use uses a
   comma as a decimal point. This reminded H.Merijn Brand of Stupid
   Locale Tricks to try with Windows, and John Peacock wondered how he
   could better test "" to deal with this stuff.

New and old bugs from RT

ref counting bug (#21945)

   Steve Peters thinks this is a heisenbug, so he asked for other people
   to take it for a spin, just in case he was seeing things (or not).

XSUB.h version check may fail due to locale (#37714)

   Rafael hauled out a previously unknown macro into the light to fix up
   this bug. John Peacock was most appreciative, and begin to fold it
   into "", when Rafael came up with an even better patch. So
   John patched Rafael's patch to do some other things he needed it to

-0.0 loses signedness upon numeric comparison (#39875)

   Michael G. Schwern wondered why this bug was still open, since there's
   a patch ready and waiting to be be applied.


Re: File::Spec->case_tolerant() should return true on Cygwin (#40103)

   Michael also wasn't sure what was case tolerant and what wasn't, at
   proposed a simple test to solve the issue.

     A sensitive matter

g++ 2.95.3 on Solaris 8 can't compile perl.h "__attribute__" (#40317)

   Christopher D. Malon was having trouble getting an old GNU C++
   compiler to compile an XS module. No solution appeared to be
   forthcoming immediately.

Question? (#40322)

   A question was asked about how to tell what "nalloc" routine was
   compiled into perl, and an answer was given.

Documentation patch for perlfunc.pod (#40327)

   Merijn B. (the *other* Merijn) noted one passage in "perlfunc"
   concerning "stat" that was less than clear and proposed a fix. Applied
   by Rafael.

overload::Overloaded depends on bad Class->can (#40333)

   Joshua ben Jore wanted to do some really weird stuff to
   "overload::Overloaded", because he was trying to build an instant box
   of death. This would be used to help test to ensure that an
   introspective module doesn't trigger overloading or magic by accident.

"pod2man" output is hyphenated by groff (#40344)

   hjp@yoyo noticed that the nroffish output produced by "pod2man" is
   incorrectly hyphenated by "groff", and added the necessary nroff
   incantation to fix it up. Rafael noted that this is fixed by Russ
   Alberry's latest release of "podlators".

Perl5 Bug Summary

   12 down, 9 up, 1528 total, for an overall week-on-week decline for the
   first time in a while.


     and more stats

New Core Modules

   *   Ken Williams released beta version (0.2805_01) of "Module::Build".

   *   Jos Boumans announced the release to CPAN of CPANPLUS version

   *   Michael G. Schwern released another iteration of
       "ExtUtils::MakeMaker", now standing at version 6.30_04.

   *   Michael also kicked two more kids, "ExtUtils::Command" and
       "ExtUtils::Manifest". out of the MakeMaker menagerie. Randy Kobes
       will take care of them.

   *   Now that Audrey Tang has clarified the licensing issues
       surrounding "Locale::Maketext::Simple", which is a
       dependency"Params::Check", both modules have been added to the

   *   Russ Allbery released the latest version (2.0.5) of "podlators".

In Brief

   Turns out that Perforce does have flexible commit hooks to perform
   actions when a file changes.

   Yet another person wondered how to deal with "Storable" version

   Jerry D. Hedden was looking at threads/shared/typemap. It was removed
   in a patch by accident, and then subsequently reinstated. Jerry
   wondered why, since it is a zero-length file that apparently serves no

   And the patch to reinstate it didn't square with the APC ("Archive of
   Perl Changes") repository, and left the latter in an uncertain state.

   Jonathan Rockway wanted to know whether one could compile Perl 5 for
   Qtopia devices. Paul Johnson provided a couple of tips.

   Gabor Szabo wondered whether errors about the signedness of pointer
   targets in Normalize.xs in 5.9.4 were the same as those in
   "Net::RawIP". Whatever the case, Gabor fixed the problem with a couple
   of casts.

   Yves Orton finally became sufficiently annoyed by the "mktables"
   executes seven time per build mazurka and decided to do something
   about it. So he did. Yay! Rafael applied it. Yay!

   Yitzchak Scott-Thoennes was looking at the ongoing coredumps in Cygwin
   and finally suggested a one-liner involving "sv_setpvn" and "NULL".
   Applied by Rafael.

   We are still looking for a volunteer to work with Klocwork in order to
   perform an analysis of perl code. (At the C side, that is).

   Jarkko removed the probe for "-Wdeclaration-after-statement" from

   Also, if your exotic platform has been having an environmental crisis
   with blead, it may be due to Jarkko's diddling of "Perl_my_setenv()".
   So the diddling was undiddled.

   Premchai noted that "perlsec" talks erroneously about a "Non-Finite
   Automaton" when in fact it should be talking about a Nondeterministic
   Finite Automaton.

   In case you hadn't noticed, JPL (the Java/Perl thing) has been removed
   from "blead" and will not be present in 5.10.

   Ben Morrow showed me a simple of trick to cope with what happens when
   perl headers conflict with systems headers.

   David Nicol added a bit about "B::Deparse"'s failure to grok outer
   lexical scopes in its BUGS section.

About this summary

   This summary was written by David Landgren.

   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:

   Weekly summaries are published on and posted on a
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   archive is at Corrections
   and comments are welcome.

   If you found this summary useful, please consider contributing to the
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