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This Week on perl5-porters - 28 April-3 May 2008

David Landgren
May 9, 2008 05:45
This Week on perl5-porters - 28 April-3 May 2008
Message ID:
This Week on perl5-porters - 28 April-3 May 2008

   "I've been playing around with MAD this morning [...] The current
   state of the tests for MAD is a bit sad, though I hope to have
   something that will make interested porters glad in the near future".
   -- Jesse Vincent, not a bad lad to spend a tad on MAD. (gad, Dad! it's
   not a fad).

Topics of Interest

More on tainting

   Nicholas Clark thought that a of points Paul Fenwick made regarding
   late-acting taint weren't borne out by an inspection of what the
   source code actually did.

   Although, looking closely, he found a couple of suspect constructs. He
   thought that one possibility was to alter "$^TAINT" to be "undef" if
   no tainting, 1 (or true) if -T tainting, or 0 for late-acting

   Then again, Paul's idea of deprecating late-acting tainting sounded
   like the path of least resistance.

     better to be safe than sorry

Support mallocs of struct T, which contains struct S[N]

   Nicholas apologised to Jim Cromie for having not applied his patch,
   noting that at the moment Rafael seems to be the only person with
   enough motivation to apply patches.

   He thought that Jim's avenue of research seemed promising and
   suggested he keep slogging on to see whether the rest of it works.

Bug in "if(open(my $fh,...))"

   In a parallel thread (to bug #53504), Matt Sergeant reopened the
   discussion about filehandles persisting past their due date. The
   problem arises when one opens a file as a side effect of a conditional
   in an if statement.

   When Matt learnt that it was sufficient to wrap the "if" block in a
   curly block to force the handle to be closed early, he deemed that it
   was no longer such a problem.

   Hint: if bug reports don't contain the word "perl", they run the risk
   of being filed in a "possible spam" folder for human perusal.

     it's all right

5.6.x in the wild

   A recent change to the GNU "coreutils" package has broken the
   Configure script for 5.6.x (or rather, it's been fixed for more recent
   perls for ages, but hasn't been, and is unlikely to be backported to

   Jesse Vincent asked for a show of hands to see how many porters are
   still using 5.6, to gauge the importance of creating a fix for
   software that was released eight years ago.

   Gabor Szabo won a surprisingly crowded race, by having the courage to
   admit that he has a client still running perl 4.x in a couple of

     an unscientific survey

     GNU coreutils 6.9 breaks F<Configure> (#53446)

Prototypes, parsing and optrees

   Nicholas Clark thought there was a smidgen of performance to be gained
   by figuring out what context a routine needed to used to call a
   function and that maybe a prototype, or its absence, could help. But
   Rafael explained that what he was looking at was actually from
   something completely different, so the question is moot.

Weird kernel failure in t/op/threads.t in blead@33758

   David Landgren related the tale of a test suite falling into an
   infinite loop, spewing out the message

     Fatal error 'Exceeded maximum lock level' at line 199 in file
     /usr/src/lib/libpthread/thread/thr_rtld.c (errno = 136039556)

   and wondered if it was the symptom of some recent change. Nicholas
   Clark thought that the fact that the test was run on a 6-cpu machine
   running FreeBSD 6.0 was probably a better explanation.

   Nicholas also thought it would be slightly more helpful if the "-V"
   switch were able to report the number of CPUs on the machine, at least
   for a subset of platforms where such a test was easy enough to

   Abe Timmerman looked at the code in Test::Smoke::SysInfo and wrote no,
   but I think he meant yes. If so, it should just be a simple matter of

Smoker segfaults on OpenBSD 4.1

   Stephen Schubiger reported that smoke tests of blead had been crashing
   with what turned out to be low-level XS problems. Abe Timmerman had
   heard of the problem also occurring on FreeBSD 7.0.

   In the meantime, Stephen discovered that the latest release of the
   smoker's companion (Test::Smoke 1.32) fixed the problem.

     smokers of the world, upgrade

5.8.9-to-be on Irix

   David Cantrell reported the results of a smoke for the upcoming 5.8
   release on IRIX. Everything was fine except for a couple of failures
   in "Sys::Syslog". One issue involved taint, the other was possibly
   related to CPAN# 30710, but Sébastien Aperghis-Tramoni had no real
   idea about the heart of the problem.

   Similarly, the same problem also occurred with blead, although
   "Time::Piece" and "Archive::Extract" were also giving grief.

     bleeding on Irix

Parameterize "ptr_table_new(table-size)"

   Jim Cromie delivered another fiendishly obscure patch to improve the
   performance of ptr_tables, which serve an important role in
   implementing hashes. Part of the aim was to expose the guts so that
   things like Storable could delve deeper into the core for an increase
   in performance.

   Nicholas Clark was a bit uncomfortable with the idea, expressing the
   wish to see more performance tweaks that don't expand the public API.
   Apart from that, he felt that Jim's research might be help re-tune
   various magic numbers used for sizing things in the core.

   The main sticking point was a useful set of benchmarks to help examine
   the result of changes to the core.

Another perldoc shortcut

   It suddenly dawned on Gisle Aas that instead of typing "perldoc
   perlintro" one could just as easily type "perldoc intro". He wrote a
   patch so that if it failed to find something, it would prepend "perl"
   to the search string and try again. Thus "perldoc re" would continue
   to return the page on the "re" pragma, rather than the "perlre" page.

     all that's lacking is shell auto-completion

   Adriano Ferreira liked the idea so much he pushed "Pod::Perldoc"
   version 3.14_06 out to CPAN and asked for feedback.


Upgrading to "Digest::SHA" 5.47

   The CPAN version has apparently been moving files around in the
   distribution, and this is naughty, since it causes more work when
   integrating into blead. Still not sure if it's all tidied up yet.

     bumping into things in the night

Bug or not? constants warn only once

   Nicholas Clark excoriated the list for wasting time on pointless
   questions (why is Ruby slow?) rather than answering more mundane
   questions which would help things move forward. The issue at hand was
   whether constants should warn once, or as many times as necessary.
   Both outcomes are doable, and feasible, so we just need to decide what
   to do. All he wanted was someone's opinion.

   Aristotle Pagaltzis wanted to be sure that whatever was changed
   wouldn't make things slower than they are now, expressing the opinion
   (yes!) that things had become slower over time (although for the most
   part the price was happily paid). He also took the time to rewrite
   Nicholas's proposed tests into something he felt was easier to read.

   Dave Mitchell was very surprised to learn of 2x slowdowns in the
   regexp engine, and thought that if this was true then it was something
   that needed fixing.

   Aristotle referred him to an article by Ben Tilly.

     Ilya's insight

MAD Dumper - missing encoding of XML-unsafe literals in "pre"

   Jesse Vincent looked at the state of MAD mode in Perl and was dismayed
   by the paucity of tests as well as the way it generated XML. Part of
   the problem was the fact that the test suite relies on "XML::Parser",
   which is a slightly odd state of affairs to have. At least until Dave
   Mitchell gets around to writing an XML parser using /bin/sh.

   Unfortunately Jesse used 5.10.0 as a basis, and significant changes
   have been made in 5.11 and thus the patch could not be applied. Plus
   Gerard Goossen had already fixed it. Nevertheless, had it been
   applicable, it would have leaked a scalar, although fortunately Rick
   Delaney was around to show Jesse how that could have been fixed.

     teacher tell me what's my lesson

TODO of the week

The yada yada yada operators

   Perl 6's Synopsis 3 says:

   *The ... operator is the "yada, yada, yada" list operator, which is
   used as the body in function prototypes. It complains bitterly (by
   calling fail) if it is ever executed. Variant ??? calls warn, and !!!
   calls die.*

   Those would be nice to add to Perl 5. That could be done without new

Patches of Interest


   Alexandr Ciornii offered a patch to allow "Scalar::Util"'s "weaken"
   function to be tested correctly both in the CPAN module and in the
   perl core.

     and strong coffee

Testing $/ with in memory files

   Bram noticed that bug #44833 had been resolved, but no tests were ever
   added to help pin down the issue. There was an issue with the test
   being run by "miniperl", which would possibly give it fits, so Bram
   tweaked it to be skipped if run by "miniperl".

   Rafael applied the patch as it stood, but Ben Morrow thought of a
   tweak for additional robustness. Bram adopted the idea, but it was
   apparently left unapplied.

Extra tests for t/op/tie.t

   As a follow-up to the READONLY bug from last week, Bram added a couple
   of tests to make sure things stayed sane. After have mulled over the
   issue for a while, he returned to it again this week, asking the
   porters whether a deeper overhaul was needed concerning these tests.


Win32 process ids can have more than 16 bits

   Jan Dubois tweaked the Win32 code to return the full 32-bit PID value
   on Windows platforms. He also mentioned that "system" behaves slightly
   differently on Windows, in that it returns the PID and not the exit

   Paul Johnson thought it was high time (since he's been waiting on it
   for ten years) to either document the issue properly, or come up with
   a better interface.

     32 bits ought to be enough for anybody

Two less double magic warnings

   Vincent Pit wrote a patch to kill a redundant warning in the construct
   "binmode $fh, undef"

   as well as "tie $x, $m" when $m is undefined.

   Rafael liked these patches so much, he applied them.

Detab and move POD in Pod/

   In a prelude to major cleanups in "Pod::Html", David Landgren
   submitted a patch to cleanse the whitespace of tabs, and a second
   patch to push the POD down to the end of the file (hint: this comes in
   handy when using "Devel::Cover").

   H.Merijn Brand was loathe to apply the patches, since he remembered
   Tom Christiansen vehemently opposing the change last time someone
   tried to reformat the code for "stylistic" purposes.

     to be continued

   David also noticed that the tests for "Pod::Html" relies on being able
   to find /bin/diff or /usr/bin/diff and wondered if "is()" from
   Test::More wouldn't do just as well.

     evil external OS-dependent dependencies

"~~" with non-overloaded objects

   With a very small dash of C, Vincent Pit tweaked smart matching to
   croak on a non-overloaded object. This made Ricardo Signes, who raised
   the issue in the first place, very happy.

     r e s p e c t (staying out of the living room)

Add some links to external resources

   Shlomi Fish suggested some links to web pages in the documentation,
   but qualified his patch with a complex web of licensing details. This
   prevented the patch from receiving much serious consideration.

     licensed to patch

New and old bugs from RT

"Pod::HTML" generates incorrect HTML for "=item *" (#19655)

   David Landgren went through the open bugs for "Pod::Html" and noticed
   that this one has been fixed as recently as in 5.10.0.


Bug in "File::Find" on Windows when target dir is bare drive letter and 
"no_chdir = 1" (#41555)

   Bram wrote a patch to correct the problem, but wondered how one would
   go about how one could write a test for the behaviour.

Infinite recursion related to "die", overloading, "s///" and "\x{...}" 

   Bram noted that this problem is still around on blead, and was able to
   refine the test cases to show what does and what doesn't cause a

     getting better all the time

Unicode and case insensitive regex (#41664)

   Bram discovered that for some reason the problem goes away if anchors
   are used in the pattern match.

"Carp::croak()" replace user error message by own (#42329)

   Bram wrote a patch to make "croak()" croak with a more useful error
   when there are no file descriptors available to pull in "Carp::Heavy".

     now you know why

"Data::Dumper" ignores "^M" in scalars? (#43617)

   Bram tried to convince the bug reporter that this was more a problem
   of shell interpretation of newlines rather than being the fault of

Missing tests for "sprintf %f" with Nan/+Inf/-Inf (#45383)

   Bram wrote some patches to pin down the behaviour of "sprintf".
   Applied by Rafael Garcia-Suarez.

Clarification about @ISA declaration in perlboot.pod (#45733)

   Bram saw that the patch attached to this bug report had never been
   applied, and asked why. Rafael explained that he never saw it on the
   mailing list the first time around.

     will it be applied this time around?

Split function broken on MacOS (#46073)

   Bram found another patch that had been overlooked and so Rafael
   applied it.

"perl -x" reports incorrect line number for errors or warnings (#46369)

   Anon Sricharoenchai thanked Bram for his followup on how to
   resynchronise perl's concept of line numbers when dealing with files
   that contain Perl and non-Perl chunks.

     or try Inline

Clearing magic (or "length($@)>0" for empty $@ if utf8 is in use) (#51370)

   Animator had opened this can of worms last week on the clearing of
   magic on $@ with an exploration of sorts on how to fix it.

   Rafael Garcia-Suarez commented saying that the results looked
   reasonable, but of course one could only be sure with a series of new
   tests to ensure that nothing had been broken.

   So Bram wrote some code and tests and asked for comments. Nicholas
   Clark thought that the code Bram had written had the freeing and
   clearing of magic the wrong way around. The code also introduced a new
   class of macros to deal with the situation; Nicholas felt this added
   unnecessary complexity.

   Another thing that caught his eye was the fact that one of Bram's
   tests induced a "panic: sv_len_utf8 cache 17 real 0". This will need
   to be looked into. Bram thought that this was probably a side effect
   of the UTF-8 flag not being cleared when it should have been.

   So Nicholas did that, and a after thinking about it for a bit thought
   that "mg_free" might be to blame. He and Bram kicked the idea around a
   bit more and at one point a proposed change might have had the side
   effect of allowing $@ to become tie-able. Nicholas thought that this
   was a bit sick, but then again, hmmm. There has been talk of promoting
   $@ to a first-class object...

perl-5.10.0-33733 assertion with JSON::XS-2.2 (#53244)

   This is the thread with Marc Lehmann discussing the use of "SvCUR".
   The only followup this week was from Sam Vilain, wondering if there
   was a problem or not with "sv_upgrade" and whether Marc might not be
   too liberal in choosing when to access "SvCUR".

Parse problem in "" (#53414)

   Don't use it. Even the author says so.

     when given a real switch

A bug with "Readonly::XS" that might be a guts bug (#53482)

   A change in the core might have been the cause of the problem. Bram
   added some tests to make sure things didn't drift in the future. After
   a couple of idle suggestions, Andreas König came through with the
   patch that seemed to be the root cause.

op/pwent.t should use the DirectoryService on OS X (#53500)

   Jan Dubois outlined the approach that he thought should be taken to
   fix this bug, admitting that he didn't have the time right now to
   pursue the issue.

     feel free to jump in

Some UTF-8 string with CP932 encoding will freeze DOS BOX (#53502)

   Chihiro reported that writing a program in a Japanese environment
   worked, but if the program had a different name, it would freeze
   inside a Windows DOS box. No comments.

     might be a ^S

Bug in "if(open(my $fh,...)) { }" scoping (#53504)

   Matt Sergeant was surprised to discover that $fh was not destroyed
   until the end of the scope encompassing the "if", rather than at the
   end of the "if" block.

   In the subsequent exchange, a work-around was suggested, and the
   usefulness and hatefulness of lexicals "leaking" across if/elsif/elsif
   blocks was debated.

     been there since 5.003

     continued in May

Overload and fallback binary or (|) (#53550)

   Bram opened a ticket related to bug #53482 which showed the overload
   fallback mechanism privileging string context rather than numeric
   context, which, in the context of the bug, would have been more

   Rafael explained that binary or ("|") works on both string and
   numbers, so it would be hard to discern what was needed in a
   systematically correct way. David Nicol speculated on the possibility
   of allowing the author of the overloading to give numeric context the
   first chance and resolving the overload.

     "we travel on the quiet road"

Range operator and magic (#53554)

   Bram opened another ticket regarding the range operator, wondering why
   the interpreter inspects the contents of $x six times in the fragment
   "@y = $x .. $x", where $x was a tied variable (and thus if the magic
   was being used to piggy-back side effects, the double magic would
   throw things out of kilter).

   The prompted Dave Nicol to ask if the range "1..$x" was driving a for
   loop, what would happen if the $x value was modified in the loop. Bram
   thought that it shouldn't be allowed, and promised a TODO test for it.

     magic and loss

Patch for linux LDAP groups (#53560)

   David Dick encountered a test failure regarding groups (as in
   /etc/group) containing spaces in names. This occurred on a Linux box
   using LDAP authentication, and so his expedient fix was to add Linux
   to the list of platforms where group names could be expected to
   contain spaces.

   Rafael applied the patch, but H.Merijn Brand rightfully pointed out
   this scenario would play out the same way on many other Unix-like
   platforms. In which case, a much more robust solution would be to
   determine if LDAP (or in fact any NIS/NSS mechanism, come to think of
   it) was in use, and use that as a basis for the test.

     wanted: finer discriminant

Zero-length regex bug (#53562)

   Another victim failed to notice that "//" has special meaning.

   That the problem comes up so frequently caused David Nicol to conclude
   that the documentation needs a special EMPTY PATTERN section.

     only a wafer-thin documentation patch needed

perl5.10 and blead crash on win32 (#53586)

   Dmitry Karasik uncovered a snippet that runs fine on FreeBSD but
   crashes on Win32. Then again, it does involve "IO::Handle", SIGPIPE
   signals and setting far too many things to "undef".

     bad magic

Perl5 Bug Summary

   All hail Bram, the new Perl5 bug warrior.

     288 new + 1472 open = 1760
     Created this week: 8
     Closed this week: 64

     may his wrangling be long and fruitful

In Brief

   Bram's documentation patch for "perlrun -x" made it in

   as did Vincent Pit's patch for segmentation fault with array ties (bug

   On the Why is Ruby on Rails so darn slow thread, Alberto Simões
   forwarded a message from Leopold Tötsch that gave some Parrot
   benchmarks on crunching Mandelbrot sets.

   John E. Malmberg took a second shot at getting the forked debugger
   working on LINUX/UNIX/CYGWIN/VMS.

   Marc Lehmann read a fascinating paper on heapsort with n log(n) - 0.9n
   comparisons which is interesting because it reduces the number of
   comparisons that need to be performed, which is useful in a language
   where the compares themselves are expensive.

   perl @ 33444 was still having problems in Cygwin due to db-btree.t,
   io_multihomed.t, HiRes.t and op/alarm.t.

   Jesse Vincent found a teeny tiny typo in "Encode" 2.24's Makefile.PL.

Last fortnight's summary

     This Fortnight on perl5-porters - 13-27 April 2008

About this summary

   This summary was written by David Landgren.

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