This Week on perl5-porters - 6-12 April 2008

This Week on perl5-porters - 6-12 April 2008

   David Nicol: I have no idea what NaN(Q) is by the way; Google suggests
   it is a furniture store in Japan.

   Jarkko Hietaniemi: It's the strong, silent type of NaN. As opposed to
   the hysteric, screaming type of NaN (aka NaNS).

   -- David N. and Jarkko H., arcing tangents.

Topics of Interest

Make built-in list functions continuous

   David Nicol continued the "unroll map into pushy for loops" thread
   with a decent stab at an implementation using his "Macrame" macro
   processing module.

   Aristotle Pagaltzis stressed the usefulness of having a map block
   producing n elements for each input element, where n could be a fixed
   number greater than 1, an arbitrary number greater than 1, sometimes
   0, and anything in between.

   Some map blocks that use such behaviours lead to remarkably concise
   code that would be very cumbersome to write in any other way.

     http://xrl.us/bje2q

Perl @ 33536

   The perl 5.8.9-tobe thread continued to attract traffic this week. Jan
   Dubois reported back on the problems that the Vista platform was
   causing.

   It boils down to the tradeoff between keeping the binary interface
   stable while preventing people from outside the core build from
   reaching directly into the guts. All you have to do is define
   "PERL_CORE" and you can do whatever you want.

   Jan suggested that one way to do this would be to reorder the struct
   members, on purpose, on each maintenance release. That would quickly
   smoke out poorly-behaved modules and make them play by the rules.

   Not so unsurprisingly, this met with a certain amount of favour with
   the porters; at least, it wasn't dismissed out of hand.

     keep your mits off
     http://xrl.us/bje2u

Saving a pointer in every COP?

   Nicholas Clark had a brainwave, realising that it should be feasible
   to shave off a whole pointer from each COP struct. Sixteen hours
   later, he delivered the patch to do just that.

   He did leave us something to do, though: prove or disprove that it
   made things go faster.

     something to do^W^Wdone
     http://xrl.us/bje2w

   Jerry D. Hedden managed to spot a minor compiler warning, which
   Nicholas promptly fixed.

     but no benchmarks
     http://xrl.us/bje2y

using "-Wall" in modules generate tons of warnings in core files

   Gábor Szabó set about trying to build "Prima" with the 5.10 Strawberry
   Perl distribution, and ran into grief over poorly nested comments (as
   in "/* foo /* bar */").

   Andy Dougherty explained that this problem also arose with fussy
   compilers on Unix platforms, and there the issue was addressed by
   substituting "/ *" (with a space) for the inner opening comment
   marker. It was therefore a simple matter of inspection to figure out
   how config.h was generated by Strawberry.

   Jan Dubois took a look at win32/config_h.PL and found a substitution
   operator that looked like it was to blame. Andy showed how the
   "Configure" process used a "sed" one-liner to work around the damage.

     http://xrl.us/bje22

TODO of the week

   Last week's TODO caught James Bence's attention, so much so that he
   outlined an approach he wanted to try and wondered if it would be
   acceptable. Rafael Garcia-Suarez explained why it wouldn't (as it
   would add to the burden of the pumpking). The primary design
   consideration is that it must be able to go about its business in a
   completely autonomous manner. That is, no sneaky command-line switches
   to spoon-feed it what needs to be done.

     figure out what it should do, then make it do it
     http://xrl.us/bje24

   (I should also mention that this whole TODO idea of the week is not my
   own, bla^Wcredit must be given to Nicholas Clark).

Compressed man pages

   Be able to install them. This would probably need a configure test to
   see how the system does compressed man pages (same directory/different
   directory? Same filename/different filename), as well as tweaking the
   installman script to compress as necessary.

   (I suspect even getting this working for two common platforms, such as
   Linux, *BSD or Solaris, would be a fine start. Other local experts on
   other platforms could piggy-back the work done to hit other targets).

Patches of Interest

Double magic with '\&$x'

   Rafael Garcia-Suarez applied Vincent Pit's patch. Vincent had also
   questioned the wisdom of allowing magic to be triggered merely by the
   gathering of information to produce an error message.

   Rafael commented that while in essence Vincent was correct, the
   unresolved problem about what to do about code in the wild that may
   depend of the precise text of an error message meant that it was
   probably wiser just to let sleeping dogs lie.

     so won't fix
     http://xrl.us/bje26

Make "PL_AMG_names" and "PL_AMG_namelens" static

   Nicholas Clark wrapped up the discussion explaining why these symbols
   that had leaked out accidentally in 5.10 had to stay: some linkers
   might blow up in their subsequent disappearance, even if the client
   code makes no reference to them.

     lazy lazy dynamic loading
     http://xrl.us/bje28

"is_gv_magical" correctly checks "ISA"

   Gerard Goossen, going through the code with a fine-toothed comb for
   his ongoing Kurila project, spotted a mistake due to incorrect
   aliasing of a C array. It could never have worked, but then again
   no-one ever had problems with it. In any event, Rafael applied the
   change since the test suite appears to remain satisfied.

     and it does the right thing
     http://xrl.us/bje3a

changes to perlsec.pod and call for removal of quicksort

   John P. Lindeman offered a patch to clean some of the more glaring
   documentation errors regarding sort in "perlsec", and this was applied
   by Rafael. He also suggested that the sort subsystem based on the
   Quicksort algorithm be removed, since these days the default mergesort
   has much better worst-case characteristics for any pathological set of
   data you care to throw at it.

   Tom Horsley, who wrote the original implementation of quicksort for
   perl, made no impassioned claim to keep it in, admitting that in fact
   he thought the code had been axed years ago.

     out of sorts
     http://xrl.us/bje3c

New and old bugs from RT

regexp: unicode char causes a 'double free corruption' (#48156)

   Niko Tyni identified the changes which had fixed this bug, but noted
   that it is still present in the version of perl shipped with Debian
   stable (no sniggering up in the back row please). Don Armstrong, in
   the Debian bug report, believes that it may allow arbitrary code to be
   executed, which if true, would be very serious indeed.

     http://xrl.us/bje3r

"[[:print:]]" *versus* "\p{Print}" (#49302)

   David Landgren offered a couple of tweaks to Robin Barker's prose.
   Juerd Waalboer also identified a mistake.

     or at least, a counter-example
     http://xrl.us/bje3t

"pack 'A*'" and "pack 'a*'" untaint data in 5.10.0 (#52552)

   Christopher E. Stith was surprised by the fact that in 5.10, the pack
   formats 'a' and 'A' strip tainting off untrusted input, whereas 5.8
   leaves it tainted. Andreas König identified change #24010 as the cause
   for the change in behaviour. Alas, that particular change touched over
   a dozen files (although 4 were POD files, and, surprise pp_pack.c was
   touched)...

     the monks have a go
     http://www.perlmonks.org/?node_id=678463

     I blame Unicode
     http://xrl.us/bje3v

Unwanted warning from XS BOOT (#52572)

     reading the fine documentation leads to resolution
     http://xrl.us/bje3x

"Bizarre copy of ARRAY in sassign at Carp/Heavy.pm" (#52610)

   Chris Heath reported a variation on the bizarre copy theme, seen
   regularly with "Carp". Nicholas Clark thanked him for the report,
   which contained a snippet of code that he was able to shrink down even
   farther.

   This led him to conclude that the heart of the matter is an unwanted
   interaction between Perl's internal stack and lexical pads, but had no
   insight as to what exactly was happening.

     http://xrl.us/bje3z

Perl 5.10 regression bug in match and substitution evaluation in list 
context (#52658)

   Wolf-Dietrich Möller spotted a regression between 5.8 and 5.10
   concerning the use of an "e" modifier on a "s///" operator. Nicholas
   Clark was dismayed to discover that the bug is also in 5.8.9-tobe,
   definitely not good.

   Andreas König fired up his binary search bug finder, and discovered
   that not one, but two separate changes (#26332 and #26334) was at
   fault. The first patch dealt with accelerating "s///e" expressions by
   freeing intermediate temporaries, and the second dealt with "s///e"
   that die in the right hand side result in memory leaks.

     we got oursel's a show-stopper
     http://xrl.us/bje33

regexp failure: "(?=)" turns into OPFAIL (#52672)

   L. Mai reported another failure due to the 5.10 regexp engine
   overhaul: the "match always" "(?=)" idiom flipped over to mean "match
   never". Fortunately Ævar Arnfjörð Bjarmason came to the rescue with a
   short, sharp patch to engine to restore the previous behaviour.

     we do test for this now, right?
     http://xrl.us/bje35

Consistent localization between "foreach (...)" and "while (<fh>)" (#52702)

   Ed Avis wanted to have warnings issued when $_ was modified, due to
   differences in how "while" and "for" behave. Rafael Garcia-Suarez
   thought that using "my $_" in 5.10 was a much better idea.

     http://xrl.us/bje37

crash when localizing a symtab entry (#52740)

   Niko Tyni reported a failure smoking mod_perl2 2.0.4rc1 on 5.10, due
   to the new implementation of constant subroutines, going so far as to
   identify change #29544 as being the (ir)responsible party. No takers.

     http://xrl.us/bje39

Crash perl with "binmode(STDOUT, ':encoding(wildybad)')" (#52786)

   Todd Olson that one can make perl crash and burn on a variety of
   platforms by giving it nothing more than a bogus I/O encoding name.

     http://xrl.us/bje4b

Perl5 Bug Summary

     1811 (+8 -4)
     http://xrl.us/bje4d
     http://rt.perl.org/rt3/NoAuth/perl5/Overview.html

New Core Modules

   Math::BigRat version 0.22
       Tels synched blead with CPAN, applied by Rafael.

         http://xrl.us/bje4f

In Brief

   Nicholas Clark committed change #33657 to split out
   "S_refcounted_he_new_common()" from "Perl_refcounted_he_new_common()"
   after having tested it out on four different machines. Alas, it still
   managed to break the build for Jerry D. Hedden. Fortunately, Nicholas
   was able to commit the subsequent change #33659 that fixed up the
   breakage.

     http://xrl.us/bje4h

   Sérgio Durigan Júnior wondered about the status of the "-m32" flag
   that is planned for 5.12, which would allow a 32-bit perl to be built
   on a 64-bit platform. H.Merijn Brand said that for the moment it was a
   non-starter.

     imagine -Duse64bitall in reverse
     http://xrl.us/bje4j

   The "atan2" thread kicked up far more than you would ever want to know
   about NaNs.

     http://xrl.us/bje4m

   Kurt Starsinic fixed up a long-standing perldata.pod typo.

     http://xrl.us/bje4o

   Alberto Simões took a shot at benchmarking the differences between
   "say" and "print".

     take two
     http://xrl.us/bje4q

   How not to file a bug. (was: "IO::Socket::accept()" doesn't fill
   "io_socket_proto" information in sockets).

     http://xrl.us/bje4s

   Tels wanted to know if a delivery date for perl 5.8.9 had been fixed,
   as this would help him figure out what to do with warnings occurring
   in "Math::BigInt". Yitzchak Scott-Thoennes suggested that it should
   warn at all during normal usage.

     http://xrl.us/bje4u

   Vincent Pit had some "perlclib.pod" tweaks applied.

     memset, strtod and friends
     http://xrl.us/bje4w

   He also made emacs users the world over insanely jealous with a cool
   patch to make "autodoc" generate a Vim XS syntax file. He admitted it
   was slightly frivolous and probably not worth taking, but Vim lovers
   should be happy to know it's out there.

     you also need to love XS
     http://xrl.us/bje4y

   Reini Urban offered an experimental work-in-progress patch for the
   upcoming cygwin-1.7 release with UTF-8 path support.

     oh the pain
     http://xrl.us/bje42

Last week's summary

     30 March-5 April 2008
     http://xrl.us/bje44

About this summary

   This summary was written by David Landgren. I plan to be offline next
   week; there will be no summary for 13-19 April. The summary will
   return the following week, with a bumper fortnight issue.

   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.

• This Week on perl5-porters - 6-12 April 2008 by David Landgren