Today, I was doing some mucking about with class data, generated
packages, and Class::ISA, and I started to wail and gnash my
teeth. I cried, "Why can't I just replace the darn object system?"
-- Ricardo Signes, a man with a method.
Last week, Marc Lehmann had tossed out a link to an interesting paper he had read on heapsorts, with a new implementation that purported to require fewer comparisons.
This week John P. Lindeman wrote a very thoughtful reply that's worth reading in its own right. In essence, one of the fundamental problems facing heapsort these days is that it is very cache-unfriendly.
Quicksort and mergesort tend to process data sequentially, and that plays nicely with how caches behave. Heapsort, on the other hand, tends to skip around all over the place, and that leaves the cache lines cold and unloved. And so John feels that heapsort will be unlikely to beat the other algorithms consistently, especially when large datasets are processed, which is where the correct use of cache comes into play.
welcome to the real world http://xrl.us/bkkda
Nicholas Clark asked for some volunteers to help with the mundane pumpking tasks that need doing when a new release goes out the door. Such things as checking author/email names, module versioning, dual-life synchronisations and making suggestions for perl589delta.pod.
Yitzchak Scott-Thoennes checked out most of the CPAN/core discrepancies. Steffen Müller did the author names.
out-sourcing pumpkingship http://xrl.us/bkkdc
Jim Cromie started to play around with git, and the more he looked at it, the more he liked it. He proposed a script to deal with ignoring files not under revision control, but Rafael thought that he had the logic completely backwards.
git down http://xrl.us/bkkde
Simon Wistow, in a flash of inspiration, realised that it would
be fun to dive into the guts and figure out how to add a new
keyword to the language, such as method, which would start out
being a simple alias for sub. He was quite surprised at how easy
it was, and on which side things that can be implemented both inside
or outside the core should be.
Jonathan Rockway muttered about Devel::Declare and
Method::Signatures. Jesse Vincent revealed that Chia-liang Kao
and Yuval Kogman were working on Perl6-Declare that was much
more robust and flexible than Method::Signatures.
Matt S. Trout thought that Jesse's recent work on MAD and Yuval's
start on B::Simple should be a big help in making the perl5
syntax more malleable.
anyone for "with" http://xrl.us/bkkdg
Bram saw what he thought was a flaw in the infrastructure for dealing with TODO tests. Imagine a function that should return 1. Except it doesn't, because a bug that no-one understands makes it return 2.
So we write a TODO test to say "this should return 1". Now imagine that the bug was tickled, and now the function returns 3. Currently there's no way of detecting that the value, while still incorrect, has changed. Some people were dubious about the value of detecting this.
different kinds of wrong http://xrl.us/bkkdi
Sébastien Aperghis-Tramoni had a couple of questions about the new 5.10 regexp extensions (or rather, the documentation that explains their behaviour). After a couple of porters worked the the problems in the wording, Aristotle Pagaltzis wrote up a new description, that Yves Orton thought was a good description.
http://xrl.us/bkkdk
Simon Wistow was looking at Devel::Gladiator, a module that
examines memory allocations in arenas (geddit?), and wondered
why, given two nearly identical snippets, one leaked massively
while the other didn't.
Naturally, Dave Mitchell gave a cogent explanation as to why, and demonstrated a simpler case in a couple of lines of Perl, no modules needed.
http://xrl.us/bkkdn
Ricardo Signes want to do some exotic things with classes, objects and overloading. Aristotle Pagaltzis admitted to having wanted to do as much in the past. Ævar Arnfjörð Bjarmason had thought of doing even more bizarre things, and I would say more, but alas this paragraph is too small for it to fit.
The thread is well worth reading in its entirety, for a view on the current thinking on allowing more flexible syntaxes.
http://xrl.us/bkkdp
Lyle ran into a problem with recursive inheritance and wondered why things didn't work in a way that would make it possible.
Nicholas Clark explained that the code that looks after this was heavily rewritten thanks to Brandon Black and his MRO work. He also thought that it should be possible to plug in a custom MRO handler that would do what Lyle wanted.
http://xrl.us/bkkdr
File::Path::mkpath() incompatibility in perl-5.10 Gisle Aas demonstrated a problem in the 2.x version of
File::Path's mkpath creating unwanted directories.
David Landgren offered a work-around, and began to
work a better solution.
the right path http://xrl.us/bkkdt
Following up on Andy Lester's blog about the grief caused by
BEGIN: { }, which is a labelled lexical scope rather than
a BEGIN block, there was a tentative suggestion to make
such things warn.
Most people weren't too comfortable with the idea, suggesting that if it was really a problem then it would have wound up on the TODO list at some point.
JFDDI http://xrl.us/bkkdv
In playing around with BEGIN blocks while researching things from the above thread, Aristotle Pagaltzis came across some some strange behaviour with a BEGIN block within a subroutine.
Nicholas explained how it was quite consistent given the rules concerning compile-time and run-time effects, and Jan Dubois wrapped out the remaining doubts.
http://xrl.us/bkkdx
Marc Lehmann had raised the problem of char * as an interface to
character strings in XS last week. Yves Orton pointed out that this
is used internally by the core, and thus faces the same issues. Win32
is particularly sensitive to the issue.
http://xrl.us/bkkdz
chromatic proposed a patch for the TODO from last week. Yay!
the yada yada yada operator http://xrl.us/bkkd3
and a revised patch to add the ..., !!!, and ??? operators
the yada yada yada trinity http://xrl.us/bkkd5
system() accepts a LIST syntax (and a PROGRAM LIST syntax) to
avoid running a shell. readpipe() (the function behind qx//)
could be similarly extended.
David Landgren thought that the patch to add web page links to the Perl documentation should be refused on the grounds of the likelihood of them becoming obsolete and therefore contributing to the maintenance burden.
looked at your 1996 bookmarks recently? http://xrl.us/bkkd7
Jesse Vincent moved MAD's libraries under lib/ and placed them
under the MAD:: namespace. Other than that he tidied up Gerrard
Goossen's work on the test suite and generally brought the bitrot
level down close to zero.
Gerrard wondered whether, because of the dependency on XML::Parser,
if it wouldn't be better to spin the libraried out completely as
CPAN modules. Jesse felt that pulling MAD too far away from the
core would all but ensure its demise.
what, me worry? http://xrl.us/bkkd9
Florian Ragwitz suggested a documentation patch for MRO but it was ignored.
the next self can http://xrl.us/bkkeb
SvMAGICAL_off in mg_free In the ongoing saga concerning mg_free and mg_clear, Bram
identified only one other place in the core where SV*MAGICAL_off()
was called after mg_free. So he cleaned things up, and Rafael
Garcia-Suarez applied his patch.
http://xrl.us/bkked
In the process of working with magic, Bram wanted to know how
to downgrade a PVMG to a PV. John Peacock wondered why on
earth someone would want to do such a thing, to which Bram replied
that it would make testing easier. John suggested a different
approach that, while more work for Bram, better reflected what
was going on under the hood.
got magic? http://xrl.us/bkkef
SvMORTAL to check if a SV is mortalized Claes Jakobsson was grovelling deep in XS code, trying to figure out whether SV were mortal or not, and was surprised to discover that there was no simple check available. So he wrote a macro to allow SVs to be tested as such.
Rafael wondered whether it would be more interesting to wrap it up as a module so that older perls could use it. In turn, Claes wondered if the hassle of setting up the module and having the XS author bring it in and use it was worth it.
Nicholas was hesitant to load up the core with yet another addition to the API, and when Claes thought about writing regression tests for it, he realised that the best place for it would be on CPAN.
mortal combat http://xrl.us/bkkeh
File::Find on Windows when target dir is bare drive letter and no_chdir = 1 (#41555) Last week, Bram fixed this bug, but wondered how one could write some tests for it. This week, David Landgren sketched out an approach, but no-one commented on its viability.
http://xrl.us/bkkej
Stefan Schlotterbeck-Macht filed a bug back in January concerning a
cross-compilation failure, the exact problem being a make target
<command-line> not having a rule in the Makefile. Andy
Dougherty noticed it this week, and suggested that it was quite
possible that just deleting the target in the Makefile would be
sufficient.
http://xrl.us/bkkem
NDBM_File fails to build (#50180) Also back in January, Devogon filed a report with NDBM_File not
being built on 5.10.0 under Debian. Andy had a look at things, and
saw that they had changed both the name of the header file (now
called gdbm-ndbm.h) and the library file (gdbm-compat).
Andy wanted to patch Configure to do the right thing and so made a request for comments. Currently there are three different header files to search, as well as three different library names. The question was whether there were any other possibilities lurking about on other platforms.
speak up http://xrl.us/bkkeo
In April, Niko Tyni wrote a very detailed bug report concerning a segfault in a mod_perl environment. This provided sufficient information to Rafael Garcia-Suarez to make a small change to sv.c, which was later officialised as change #33807.
one good turn deserves another http://xrl.us/bkkeq
This is the thread about the correct use of SvCUR. Nicholas Clark
revived the thread when he explained that one of the reasons the
code broke was that because when gcc is instructed to add the
-g compiler switch for debugging purposes, Configure
piggybacks this and enables a raft of code assertions, and JSON::XS
was tripping over one of them.
Many new assertions had been added to the code by Nicholas when he worked on slimming down the SV bodies, and he needed to be sure that nothing broke out in the wild (due to a cavalier approach to the internals). Andreas König's long BBC smoke campaign showed that by and large Nicolas's changes were completely transparent.
Marc Lehmann compared 5.8.8 and 5.10.0, running bare, or with POSIX loaded, and noticed that while the bare binary was smaller, the size when POSIX was loaded showed a larger increase on 5.10 compared to 5.8. This appeared to contradict the statement in perldelta, and this left Marc feeling a bit confused.
http://xrl.us/bkkes
if(open(my $fh,...)) { } scoping (#53504) Aristotle Pagaltzis showed how Perl 6 deals with the problem of scoping lexicals to blocks, and that the rules there are much simpler.
http://xrl.us/bkkeu
index() matching beyond end of string when \0 bytes are involved (#53746) Giuseppe Insana filed a fairly comprehensive report detailing his surprise
at some results with index when NUL bytes appear in the string.
Bram simplified matters, which made it clear to see what the problem was.
Abigail wrote a series of TODO tests so that some budding internals
hacker who wanted to take a stab at fixing pp_index in pp.c
would know if their efforts were successful or not.
hint hint http://xrl.us/bkkew
Chris Hall ran into difficulties with the results of large integer divisions being upgraded to floating point, with the loss of accuracy that that implies. He and Dominic Dunlop kicked the problem around a bit but were not able to come up with an explanation for what they were seeing.
but -Mbigint ok http://xrl.us/bkkey
Ronald Fischer complained thusly when bitten by print merrily
accepting a bareword as its first argument and silently stringifying
it. Bram promised some TODO tests for this.
Something tells me this is not going to be simple to fix.
the magic of print http://xrl.us/bkke4
Kevin Ryde found an instance of Encoding::Supported that he
suspected should read Encode::Supported. And indeed it should.
Patched by H.Merijn Brand.
http://xrl.us/bkke6
pod2man loses =head2 starting [with] ' or . (#53910) Kevin also discovered that Pod::Man failed to properly escape
POD headings that begin with a quote or period, letting them be
interpreted by *roff and thus ignored. He proposed a simple
patch that should be enough to resolve the issue.
more POD love http://xrl.us/bkke8
http://xrl.us/bkkfa http://rt.perl.org/rt3/NoAuth/perl5/Overview.html
Released by Dan "the Encode maintainer" Kogai.
http://xrl.us/bkkfc
Paul Marquess synched blead with the current CPAN release, which should make things play more nicely on 5.10
http://xrl.us/bkkfe
Jerry D. Hedden pushed the latest threads::shared out the
door. The main change is saner semantics for ref() on
shared objects.
http://xrl.us/bkkfg
The above module in turn allowed Jerry to release a version of
Thread::Queue that allows one to enqueue structures with
circular references.
http://xrl.us/bkkfi
Bhavna Yadav wondered how to port a Perl script on Vxworks. Dominic Dunlop pointed out that Wind River ported Perl independently to their Vxworks operating system... seven years ago, and as far as Dominic was aware, no porter had any technical knowledge of the platform.
http://xrl.us/bkkfk
Thanks to Reini Urban, one can build a static perl on Cygwin.
no shared libraries http://xrl.us/bkkfn
Alexandr Ciornii pinged the list with an 18 month old Net::SMTP
documentation patch that had never been applied.
http://xrl.us/bkkfp
In the Taint (PL_tainting, SvTAINTED_on, SvTAINTED_off, SvTAINT)
thread, Paul Fenwick explained that late-acting tainting left
PERL5LIB wide open.
this is a problem http://xrl.us/bkkfr
Vadim Konovalov cross-posted a question regarding Perl cross-compilation on arm-linux but no-one took him up on it.
http://xrl.us/bkkft
Abigail tweaked File::Copy to use the 3-arg open instead of
a slightly crufty and vaguely deprecated 2-arg form.
http://xrl.us/bkkfv
Abigail also wrote an initial cut to teach File::Copy to
respect permission bits. This caused problems on Cygwin, so,
for want of a better solution, Jerry D. Hedden changed some
of the failing tests into TODO tests for that platform.
http://xrl.us/bkkfx
Alexandr Ciornii supplied a Data::Dumper patch to make the latest
blead version compile on older perls.
http://xrl.us/bkkfz
Ricardo Signes fixed up a POD link for perlunitut .
http://xrl.us/bkkf3
David Nicol wrote a wafer thin patch to underscore the semantic
importance of the empty pattern (//).
http://xrl.us/bkkf5
This Week on perl5-porters - 28 April-3 May 2008 http://xrl.us/bkkf7
This summary was written by David Landgren.
Weekly summaries are published on http://use.perl.org/ and posted on a mailing list, (subscription: perl5-summary-subscribe@perl.org ). The archive is at http://dev.perl.org/perl5/list-summaries/ . Corrections and comments are welcome.
If you found this summary useful, please consider contributing to the Perl Foundation or attending a YAPC to help support the development of Perl.