This Week on perl5-porters (6-12 November 2006)

This Week on perl5-porters - 6-12 November 2006

   "*This is like sitting your mother down to teach her computers and
   beginning by explaining little endian vs big endian and the intimate
   details of protected mode memory*" -- Michael G. Schwern, firmly
   believing that there must be a better way of installing perl.

Topics of Interest

INC handlers and "__FILE__"

   (I didn't get around to summarising this thread last week).

   Ron Isaacson had reported that he used code references in @INC, to
   great effect, but regretted that the modules loaded no longer really
   knew where they came from, "__FILE__" and related things would refer
   to the module loader module, rather than their own paths.

   Rafaél Garcia-Suarez concocted a quick fix in pp_ctl.c for "blead",
   which improves the situation considerably. Glenn Linderman wondered if
   a cheap and nasty hack, a "#line" directive at the top of each file,
   could do as a temporary work-around.

   Nicholas Clark suggested Ron take a look at an Acme module of his,
   that might do more or less what he needed (see, sometimes Acme modules
   *are* useful).

     http://xrl.us/s5f7

Failures in /run/cloexec.t on Solaris and Tru64

   The new t/run/cloexec.t test blew a bit of smoke out the O-rings. It
   could mean that this is testing the operating system, rather than
   perl, in which case it might wind up being removed. Andrew Savige,
   father of the original patch, tried to teach it some manners.

     http://xrl.us/tart

Building perl with VC++ 2005 (VC8)

   Steve Hay, Steve Peters and Jan Dubois continued to work this week on
   getting Visual C++ from Microsoft to compile the perl source, and had
   lots of fun, or not, playing around with I/O, DLLs and the C runtime
   library. By the end of the week all appeared to have been straightened
   out.

     http://xrl.us/taru

   Later on in the week, Steve Hay started having problems with test
   failures on a VC8 build. These were apparently due to problems in
   interacting with (or rather, finding) the C runtime library.

   After a bit of a discussion Steve was moving in the right direction.

     http://xrl.us/tarw

Installing Perl shouldn't feel like a rite of passage

   Michael G. Schwern felt that the Configure process was a bit too
   verbose, asked to many questions, and sometimes gave some very scary
   replies. He felt that it would be a good idea to be able to reduce the
   verbosity level. Some way down in the thread, he showed the README
   from Ruby, which, it must be said, is short, sharp, and to the point.

   Andy Dougherty noted that the INSTALL file had amassed considerable
   cruft over the years, due to various stupid bug reports that had
   wasted considerable time of those doing front-line support at the
   time.

   Nonetheless, as Michael pointed out, the perl install process is
   geared to catering for people with weird system setups, are in the
   business of packaging Perl for distributions or are using it on
   non-mainstream systems. The README and the Configure step reflect
   this: it's hard to know what's important, and what's noise.

   H.Merijn Brand felt that it might be worthwhile to put more emphasis
   on Policy.sh, the idea being that if you've sweated out a
   configuration trial-by-fire once, you can at least save that file away
   in a safe place, and reuse it next time you build a perl.

   At the end of a fairly long, but always interesting thread (lots of
   good stuff from chromatic), Jarkko Hietaniemi injected a dose of
   reality into the discussion, pointing out that "Configure" is not
   going to be redesigned any time soon, it's hard to produce an
   interface to it that makes end-user programmers and system
   administrators happy, and so yes, to a certain extent it *will* be
   difficult to avoid building perl from being a rite of passage.

     655000 lines of C can't be wrong
     http://xrl.us/tarx

   Andy Dougherty produced an initial tweak to Configure to tone down the
   *** WHOA THERE!!! *** messages to something a bit more laid back.

     goodness gracious
     http://xrl.us/tary

   Jesse Vincent updated README to make it a little friendlier, and
   feared that the resulting discussion would evolve into a discussion of
   the colour of the bikeshed. Rafaël JFDI'ed the patch.

   There were a number of useful suggestions made, and Michael reported
   back that the target guinea pig for installing Perl liked the new
   version.

     http://xrl.us/tarz

Failures while attempting to install "Plagger" with bleadperl

   Steve Peters was delighted to discover that Plagger has even more CPAN
   dependencies than Catalyst or Jifty. Therefore, installing that one
   module causes a large slab of CPAN to be pulled down and tested, which
   is just the ticket when you're taking "blead" for a spin.

   Alas, twenty eight modules failed their test suite, and three more
   failed to build altogether.

     Uh, could you run prove -vb on that, please?
     http://xrl.us/tar2

Taking a look at the OS X hintfile for 10.4

   Michael G. Schwern also thought that the hintfile for OS/X was rather
   dusty, especially in terms of the 10.4 release, and thought that a
   touch of spring cleaning was in order.

   Andy Dougherty, Dominic Dunlop, Bo Lindbergh and Edward Moy had a look
   at the issues, and it appears that the main ones are locales and
   "poll()". Considerable head scratching and archive diving was
   observed, and Andy hoped that the patch file would be commented with
   pointers to this and other discussions, so that when the problem is
   revisited, say, in 2011, it will be easy to zoom in on the previous
   debate.

     those who do not learn from history
     http://xrl.us/tar3

Warnings from Pod/t/man.t in blead

   It seems that "Pod::Man" is also falling foul of the new "Variable
   length character upgraded in print" diagnostic. Rafaël fixed the
   problem in "blead", but Russ Allbery noted that it wouldn't work for
   "maint", as it uses modern "blead"ing features. He suggested a
   possible "maint"-compatible technique, and wanted to know if it would
   fly.

   As proposed, the technique caused the tests on "blead" to fail, but
   Rafaël produced a variant that should work on both codebases. It did
   lead him to doubt whether the warning was actually useful in general.

     Modern man
     http://xrl.us/tar4

Chatting about sort sanity checking

   David Nicol began to see how easy it would be to add warnings to catch
   custom sort comparison functions that don't fulfill the contract of
   what such a function is supposed to do (return a negative or positive
   value, or zero). The low-hanging fruit would be to check for "<", ">"
   operators and the like.

   John P. Linderman thought this would be a good idea, but found it
   difficult to reconcile with the constraint that there should be no
   runtime penalty.

     Out of sorts
     http://xrl.us/tar5

MRO, sub_generation and so on

   Brandon Black wrote "Class::C3", which provides an alternate technique
   for method lookups, and he had come to the conclusion that for best
   results, it needed to be more tightly integrated into the core (or
   rather, the core needed to expose some aspects to the outside, that
   his module could tap into).

   Specifically, he had problems with the fact that a single change
   somewhere can blow away the entire method name cache. What would be
   nice would be to a way to blow away the methods on a per-package
   basis, as it would less the cost of method cache invalidations.

   Hugo van der Sanden was extremely interested in the approach, since he
   has lots of code that creates methods on the fly, and this winds up
   continually trashing the cache. Joshua ben Jore thought that "Moose"
   and "Class::Trait" would benefit from the concept.

   Nicholas Clark was somewhat sceptical, wondering how often people run
   around adding new methods to code (once it's up and running, after
   some preliminary initialisation phase). Be that as it may, he wasn't
   particularly familiar with that part of the codebase, and suggested
   looking through the lens of "perlbrowse", to find out *who* has been
   working on that code in the recent past.

   He did just that, and discovered that most of the code dates back to
   beginning of the revision history, and thus the details are literally
   lost in the mists of time. After taking another, closer look, Nicholas
   was able to give Brandon some reasonable directions on how to proceed.

     A new order
     http://xrl.us/tar6

Perl Debugger resets the $main::{"_<$filename"} upon eval with a "#line 
$filename" directive

   Shlomi Fish found a problem with the debugger, that only showed up in
   non-threaded 5.8.8 builds. After poring over the changes in
   "perlbrowse", he was able to pin-point the likely culprits. Once this
   legwork was done, it was a small matter for Rafaël to come up with a
   fix.

   Shlomi was most impressed, and asked if Rafaël had come up with a
   test, to ensure that the bug didn't come back again. Rafaël admitted
   to not being sure how to go about that, and Shlomi said that he had an
   idea for one. So he produced a stand-alone test that did the deed, and
   again it was a small matter for Rafaël to recast it in terms of a test
   for the test suite.

     debugging the bug in the debugger
     http://xrl.us/tar7

24714 broke "Term::ReadLine::Gnu"

   Andreas König discovered that a recent change to optimise lazy copying
   in "sv_setsv()" caused "Term::ReadLine::Gnu" to go belly up. Nicholas
   Clark rejigged the patch to restore the old behaviour to callers
   outside the core, but Andreas still wasn't getting satisfaction.

     http://xrl.us/tar8

Patches of Interest

New regexp syntax omnibus

   Yves has been speaking with Larry Wall about the work on the regular
   expression engine. Since all the new "(?..)" verbs do something quite
   different to the older zero-width assertions, it makes sense to make
   them look different. So now they are introduced by "(*...)". (Makes me
   glad I haven't been writing code that uses them).

   Anyway, the plot is beginning to be revealed at last. Yves wants to
   build Perl 6 rules on Perl 5. This is going to be interesting.

   Additional changes followed, and all of it wound up being landed in
   "blead".

     http://xrl.us/tar9

   Joshua ben Jore was having trouble keeping Yves Orton's new regular
   expression control verbs straight, since he kept getting mixed up with
   Prolog. He also had trouble keeping up with the current thread dealing
   with these matters, since he replied to a previous thread on the
   subject. He thought that ERROR should become CUT, and CUT become
   something else. Either that, or use whatever Perl 6 uses.

     the hobgoblin of little minds
     http://xrl.us/tasa

Static linkage for "perl.exe" for win32

   Vadim Konovalov added a new target and few small tweaks to the Win32
   Makefile, to allow a static perl.exe to be built (no more perl.dlls).
   Steve Hay suggested better names for the resulting executable.

     No more DLL hell
     http://xrl.us/tasb

   Vadim would really like to know how to push this patch forward, since
   it would make his life a lot easier.

     http://xrl.us/tasc

Make "s?printf" reject tainted formats

   A few months ago, the idea was put forward that "printf"y format
   strings should be subject to taint checks. Rafaël wrote the code to
   implement this, and then stood back to see what people thought of the
   concept. Dave Mitchell warmed to the concept and Johnathon Stowe
   suggested that "strftime" ought to receive similar treatment.

   Rafaél couldn't see how to abuse "strftime" effectively, so that was
   left alone, but the code for the "printf" family went in.

     taint fair
     http://xrl.us/tasd

"Perl_die()" / "Perl_croak()"

   Philip M. Gollucci finally scratched his itch and fixed up the
   "printf" compiler attribute checks, by disabling them. This allows
   modperl 2 to be built under "blead" again.

   Robin Barker was under the impression that it is distressingly easy to
   break modperl when working with "blead", and wondered if there was
   some way of capturing in core tests the assumptions that modperl
   relies upon.

     http://xrl.us/tase

Make "if (%hash) {}" act the same as "if (keys %hash) {}"

   Yves Orton noticed that, while semantically equivalent, testing for
   %hash or "keys %hash" to see if a hash contains something do not run
   at the same speed. He patched the core to make the former become about
   as fast as the latter.

   Rick Delaney reminded Yves to watch out for tied hashes, in case his
   patch changed existing behaviour. Worse, using "if (%hash)" now resets
   the iterator, which was more or less the final nail in the coffin for
   the idea.

   Yves then took a different approach, and created a new opcode
   "boolkeys" to be used in this "if (%hash)" context, made it do the
   right thing in the face of tied hashes, and as a result made it even
   faster than using "if (keys %hash)".

     faster %pussycat
     http://xrl.us/tasf

New and old bugs from RT

localtime(3) calls tzset(3), but localtime_r(3) may not. (#26136)

   Back in July, Benjamin Holzman supplied a patch to fix up the mess
   when playing around with "tzset" and the "TZ" environment variable.
   H.Merijn Brand dusted it off and applied it to blead as change #29209.

   Yves Orton wondered whether it was good for Windows, since it caused a
   number of tests to fail. Furthermore, it was unlikely to work in any
   event, since recent overhauls to the environment variable handling on
   Windows has decoupled the changing of environment variables within
   Perl space from affecting the underlying C runtime library's notion of
   the environment.

   Sadahiro Tomoyuki suggested that the safest course of action was to
   leave the code, and skip the tests on Windows, and supplied a patch to
   do just that.

     time on my side
     http://xrl.us/tasg

"/^/m" doesn't match after a newline at the end of the string (#27053)

   Yves then responded to a February 2004 bug filed by zefram, who didn't
   like the behaviour of "^" in a certain context. He thought that while
   it could be construed as a bug, it has since managed to become
   sufficiently widespread to have evolved into a feature. While fixing
   it would be theoretically good, it would cause a lot of existing code
   to fail, starting with important pieces of the "Test::" namespace
   itself.

   This made Steve Peters ponder the idea of adding a "Won't fix" bug
   status, which would allow bugs like this to be no longer counted
   towards the open bugs total. Steve thought that a number of
   auto-vivification feature-bugs could go this way as well.

     sort of like unemployment statistics
     http://xrl.us/tash

"Cwd::chdir()" and handles (#38466)

   Steve Peters pinged Ken Williams on a patch for "PathTools".

     http://xrl.us/tasi

"Data::Dumper" fails to dump all hash keys when iterator is not at start 
(#40668)

   Jerry D. Hedden fixed this bug, bumped the version, and Rafaël applied
   it.

     http://xrl.us/tasj

Bleadperl crash in Perl_pp_entersub() (#40681)

   Steve Hay and Nicholas Clark got to the heart of the matter caused by
   modperl 1.x blowing up on "blead". And when Nicholas finally came face
   to face with the bug, he didn't know what the best way to solve it
   would be.

     http://xrl.us/task

Different behaviour of precompiled regular expression (#40684)

   Claus Fischer reported a bug that Yves noted was already fixed in
   "blead".

     http://xrl.us/tasm

"Attribute::Handlers" not fully functional at runtime (#40695)

   Johnpc discovered that attribute handlers don't work quite perfectly
   for routines that are pulled in dynamically, via "require". His
   work-around was to place the "require" in a "BEGIN" block. Rafaël
   suggested trying a different approach, and asked if that would work
   instead.

     http://xrl.us/tasn

Weird behaviour in tainted hash with large integer, "SvIV/SvPV" mismatch 
(#40708)

   payerle wasn't sure, but he thought he had encountered a bug in Perl,
   and so he filed a slightly apologetic bug report. Dave Mitchell
   cheerfully confirmed that it was in fact really and truly a bug in
   Perl. He simplified the code, and showed that 5.8.7 and blead gets it
   wrong, but, somewhat miraculously, 5.8.8 gets right.

   At this point, Dave punted, and asked Nicholas to take a look.

     http://xrl.us/taso

perl parser bug leading to memory corruption/segmentation fault or 
simply parse errors (#40718)

   Dave Mitchell fixed the parser so that it no longer lost its mind.

     http://xrl.us/tasp

Perl5 Bug Summary

     22 up, 18 down, now 1539
     http://xrl.us/tasq

     http://rt.perl.org/rt3/NoAuth/perl5/Overview.html

New Core Modules

   *   Test::More/Simple/Builder 0.65

         http://xrl.us/tasr

In Brief

   Nicholas Clark uses an Intel-based Macintosh.

     http://xrl.us/tass

   Mike Schilli fixed a bug in SelfLoader.pm. Applied.

     http://xrl.us/tast

   Robin Barker worked on suppressing the "df" warning in stat.t on OS X
   but Rafaël beat him to it.

     http://xrl.us/tasu

   But he was first to fix t/op/inccode.t failing under "minitest".

     http://xrl.us/tasv

   and silenced a signed/unsigned mismatch warning,

     http://xrl.us/tasw

   not once, but twice,

     http://xrl.us/tasx

   Rafaël made "Text::Wrap" warn less aggressively.

     http://xrl.us/tasy

   he also added a whole lotta goodness to "Attribute::Handlers", based
   on last week's discussion.

     http://xrl.us/tasz

   Jarkko Hietaniemi made a couple of small tweaks based on smoke signs,
   that is, errors produced in daily stream of smoke tests.

     http://xrl.us/tas2

   Michael G. Schwern uncovered a "blead" configuration that prevented
   "strict" from being installed.

     Not a feature
     http://xrl.us/tas3

About this summary

   This summary was written by David Landgren.

   Weekly summaries are published on http://use.perl.org/ and posted on a
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-- 
Much of the propaganda that passes for news in our own society is given 
to immobilising and pacifying people and diverting them from the idea 
that they can confront power. -- John Pilger

• This Week on perl5-porters (6-12 November 2006) by David Landgren