This Week on perl5-porters - 20-26 October 2008
"So we have an existing bug. Sometimes \400 matches \400, and
sometimes it matches \01\00, depending on what I would call spooky
action at a distance. I'm trying to get rid of these inconsistencies.
I think something should be done here, but perhaps its not what I
thought it should be. My patch follows what the code was intending to
do, but perhaps we should change that intention. Please guide me."
-- Karl Williamson, trudging around in the depths of Unicode.
Topics of Interest
Exported symbols: the perl API
H.Merijn Brand shared with us one of the more exciting aspects of
configuring perl. The embed.pl program goes through the source and
pulls out the name of every function marked as public and saves them
in global.sym.
H.Merijn discovered that there's no test to check see if what is found
is truly available. Configure a perl with "-Duseshrplib" for example,
and many are not.
Using some unportable code, he whipped up a program to list everything
that was supposed to be available but wasn't. He wanted to know if a
Windows expert could code up something similar that would work on that
platform.
http://xrl.us/owao2
blead smoke failures for "Module::Build"
Nicholas Clark ran into inconsistencies with $^X (the name of the perl
binary) but got things sorted out. I'm not sure if Ken Williams pushed
the changes upstream to his repository.
http://xrl.us/owao4
"git-info"
Michael G. Schwern lamented the lack of an equivalent command in git
for "svn info", so he wrote an analogue in Perl. Aristotle thought
that he had just reinvented EasyGit. Michael had a look, was
impressed, but decided that the information "eg info" produced wasn't
of vital importance.
http://xrl.us/owao6
FreeBSD 7 "libc_r" detection
Tony Cook supplied a very welcome patch to solve the problem of
configuring perl on FreeBSD 7 with threads, when the threads
compatibility shims are not installed. Chris Williams had a feeling
that this would allow bug #57458 to be closed.
So Chris set about checking the results and confirmed that the patch
was good and the bug was dead.
http://xrl.us/owao8
Problems attempt to load "Storable"
While "Storable" was the symptom, the cause was trying to compile XS
extensions with Sun's C compiler for a perl 5.6.1 compiled with gcc.
Nicholas Clark wrote an elaborate recipe for modifying Config.pm to
make things work. Andy Dougherty thought that it all made sense, but
both were in agreement that the easiest way forward for Tim Smith, who
posed the question initially, would be to recompile everything with
Sun's compiler.
http://xrl.us/owapa
"PL_ors_sv" in "Devel::PPPort"
H.Merijn Brand needed to perform a "local"ised "undef $\", which was
trivial under 5.8.x and beyond, but just about impossible under 5.6
due to radical differences in the underlying implementations.
He wondered if there was a way of pushing the problem off onto
"Devel::PPPort". Marcus Holland-Moritz thought it was pretty much
impossible. H.Merijn contented himself with marking the module as
unsuitable for use with 5.6 and below.
upgrade already
http://xrl.us/owapc
DLL error messages installing "Term::Title" under Cygwin
Ruben Diez asked for help in figuring out a strange error with a fresh
installation of Perl on a fresh copy of Cygwin running on Vista.
Alexandr Ciornii and Reini Urban diagnosed this as a "rebaseall"
problem, and therein lay the solution.
http://xrl.us/ovihr
http://xrl.us/owape
[EMAIL PROTECTED]
Nicholas Clark produced what he fervently hopes is the last snapshot
for perl 5.8.9, with six issues outstanding. If anything else is
broken, it will be for anyone else to fix.
Slaven Rezic posted an impressive list of modules that he had tested
against recent versions of 5.8-maint, and he and Nicholas went through
them. A number of failures were deemed acceptable, since they
represented the nailing down of greyer parts of the implementation.
Other failures were due to relying on implementation bugs that were
also fixed.
Of the six main problems, David Landgren posted updates for
"File::Path" and Ken Williams gave p5p co-maintainer status for
"Pathtools".
Modules were looked at, such as "IO::Mark", "constant" and
"Business::ISBN". SUPER method caching was examined, as were format
references.
http://xrl.us/owapg
Next API question for "Devel::PPPort"
H.Merijn Brand wanted to be able to rely on "Perl_pv_pretty" and
"Perl_pv_escape" in any version of Perl. Marcus Holland-Moritz
initially said that it would be difficult, but went ahead and did it
anyway. This now gives H.Merijn a "pv_display" that does UTF-8 right.
http://xrl.us/owapi
Possible mro bug/change between 5.8.8 and 5.10.0
Michael G. Schwern pinned a problem in "DBIx::Class::CDBICompat" to a
change in behaviour of MRO (method resolution order). Nicholas Clark
hoped that Brandon Black, author of mro.c would be able to shed some
light on the matter.
Matt S. Trout said that Brandon hasn't been available to look at Perl
stuff for months and so he would try and find the time to look at it,
but didn't make any promises as to when that could be.
http://xrl.us/owapk
How to get Test:: to output in utf8
Karl Williamson wanted to get UTF-8 output from "Test::More" but was
stymied by "Wide character in print" warnings. Michael G. Schwern
offered a couple of tips to get it to work.
http://xrl.us/owapn
Change 34559 oddity
Slaven Rezic wondered if the patch for FreeBSD and the legacy thread
library was meant to apply to 6.x or not, since there was a
discrepancy between the log message and code.
Nicholas admitted that the patch was wrong and 6.x was being treated
the same way... but since things continued to work on 6.x, he wasn't
sure whether to take it out or leave it.
http://xrl.us/owapp
TODO of the week
A new task that only need Perl knowledge (and an ability to use "grep"
or "ack").
Parallel testing
(This probably impacts much more than the core: also the Test::Harness
and TAP::* modules on CPAN.)
All of the tests in t/ can now be run in parallel, if $ENV{TEST_JOBS}
is set. However, tests within each directory in ext and lib are still
run in series, with directories run in parallel. This is an adequate
heuristic, but it might be possible to relax it further, and get more
throughput. Specifically, it would be good to audit all of lib/*.t,
and make them use "File::Temp".
Patches of Interest
Revert const'ing in cygwin.c
Changes to blead and backports to 5.10 left some consting problems
that caused the compiler to grumble a bit. This patch was to clean up
the warnings on 5.10, and appears to be Warnocked.
http://xrl.us/owapr
Refactor "Perl_mem_log_*" functions
Marcus Holland-Moritz discovered a nest of duplicate code in various
logging functions, and factored out what he could into a workhorse
function. He hinted that this patch needed to go in, so that he could
deliver a putative "SV allocation tracing" patch.
http://xrl.us/owapt
Add SV allocation tracing to "-Dm" and "PERL_MEM_LOG"
Despite receiving no feedback from the above patch, Marcus went ahead
and applied his SV tracing patch. This works by adding an additional
field in debugging build to SVs, in which a unique serial number can
be stored.
When a leak is spotted, the serial number can be read. The code is run
a second time, this time setting a break-point on new_SV() watching
for the creation of the SV with the same serial number. From there it
usually become a trivial matter to work out who's responsible for
making the mess.
http://xrl.us/owapv
Fix prototype detection for C++
Marcus Holland-Moritz isolated a problem with incorrect function
prototypes for C++ and suggested an improvement. H.Merijn Brand, as
Configure pumpking was a bit concerned since the change would have a
potentially large impact. But as it turned out, the fact that he had
switched Configure over entirely to git simplified the house-keeping
tasks considerably.
http://xrl.us/owapx
Use of freed comppad array during "clear_yystack()"
Marcus Holland-Moritz spotted a bug that using PERL_POISON picked up.
(That is, filling the contents of deallocated pointers with garbage to
trigger segfaults from attempts to dereference said freed pointers).
The problem was that a variable was freed, set to NULL, and freed
again. And in real life this works out nicely.
But for the sake of correctness, Marcus wrote a patch to make things
work correctly, whether PERL_POISON is defined or not.
http://xrl.us/owapz
Not silently casting away constness in SV macros
Marcus also noticed that change #34600 corrected an erroneously
consted SV, and reflected that such problems can lie buried for a long
time since macros like "SvREFCNT_dec" blindly cast away constness,
thus preventing the compiler from doing the job we asked it to do in
the first place.
So he thought about how one might go about fixing it, and came up with
some more preprocessor trickery that would allow the compiler to spot
when constness was being cast away.
Nicholas Clark thought that this was a great idea and committed a
patch to implement it. He then began to start using it, and it allowed
him to fix up some problems straight away.
http://xrl.us/owap3
Watching the smoke signals
Smoke [5.11.0] 34541 FAIL(F) MSWin32 WinXP/.Net SP3 (x86/2 cpu)
Steve Hay's smoke was failing, but Steve wasn't around, so Nicholas
Clark asked for someone else with access to Windows to run the tests
and provide the details to understand what was going wrong. Tony Cook
dug down and found that it was due to an undefined subroutine
&Cwd::getdcwd.
This allowed Nicholas to understand what was going wrong and suggest a
fix, and Tony reported that it was good.
http://xrl.us/owap5
New and old bugs from RT
Threads support in FreeBSD 7.0 (#57458)
Renée Bäcker wanted to know if the recent Configure-fu for FreeBSD
solved this bug.
http://xrl.us/owap7
Feature request: regexp flag to not set $1, $2 etc. (#58072)
Ed Avis asked if it was possible to not set $1, $2 and the like during
a pattern match with captures. He listed three bug reports in the RT
queue about them getting clobbered.
Abigail explained that this was already possible, and showed how.
Norbert Buchmuller mentioned that he had patched "NEXT.pm" using the
same technique (and this was one of the cited bug reports) but was
waiting for someone to review (and apply) the patch.
http://xrl.us/owap9
C coding questions for Unicode problem (#58182)
More bikeshed discussions continued this week on how to name Karl
Williamson's Unicode fixup pragma.
http://xrl.us/owaqb
"PerlIO::via" leaks memory at a high rate (#59268)
Nicholas Clark looked at the problem that Marc Lehmann had uncovered,
and regretted to say he wouldn't be able to fix it properly in time
for 5.8.9. All is not lost though, since he thought it should be
possible to push out a new version via CPAN at some later date.
http://xrl.us/owaqd
"chr(0400) =~ /\400/" fails for >= 400 (#59342)
Karl Williamson produced a one-line fix for this problem, and Tom
Christiansen wondered if this introduced yet another meaning to octal
representations, backslashed or otherwise. Karl responded that it was
already a mess and he just wanted it cleaned up.
Glenn Linderman suggested that a better alternative would be to outlaw
octal escapes larger than \377 on 8-bit-byte platforms (as one can
always work around that by using hex encodings).
Abigail, not usually known to be fond of adding new warnings to old
behaviours thought that in this particular case it might be worth
spitting out a warning if an \NNN octal escape (where NNN is greater
than 0377) is found in a regular expression, on the basis that it
would probably point out buggy assumptions.
All the people who responded were in favour of Karl's patch being
applied.
http://xrl.us/owaqf
"return 0 or die" (#59802)
Dr. Ruud coaxed some examples of this construct from real code via a
web search.
http://xrl.us/owaqh
Core on syntax error! (#59950)
Nick Kostirya stumbled over a coredump when he used a full colon
instead of a semicolon for "use Data::Dumper;". Dave Mitchell replied
that this has been fixed in 5.10.0.
http://xrl.us/owaqj
Typo in perldata (#60022)
Ryan Dilworth pointed out an inconsistency in perldata regarding
arrays, offsets and entries. Daniel Frederick Crisman proposed a patch
to clarify matters and Marcus Holland-Moritz applied it.
http://xrl.us/owaqm
(?>) causes wrongness on long string (#60034)
Zefram pointed out a problem with the "?>" assertion showing up in
5.10.0. Abigail thought that this was due to a variation on the theme
of leaky implementation details, like the way A* is implemented as
A(between 0 and 32767 times). Vincent Pit identified change #29916 as
the cause.
Once Vincent identified the problem, he was able to suggest a few ways
for solving it, each with various costs and benefits. He produced a
patch for 5.8, to get rid of the immediate show-stopper.
5.10/blead will require a different approach and more work.
http://xrl.us/owaqo
CPAN install pauses due to 'ncftp' error on cygwin (#60062)
Arthur Dunham pointed out the futility of asking "ncftpget" to deal
with HTTP resources.
http://xrl.us/owaqq
op/groups.t fails when real group name contains blanks (#60136)
Altblue showed that one the core tests makes an incorrect assumption,
that group names may never contain spaces. If there is one, the test
fails.
http://xrl.us/owaqs
A number of characters match both a posix class and its complement (#60156)
Karl Williamson ran into more pre-existing errors and inconsistencies
in Unicode, this time dealing with POSIX character classes. Yves Orton
dashed off a patch that he expected to work and so was surprised when
in fact it didn't. At the same time he sent out a personal Call For
Papers for the next YAPC::Europe conference: someone ought to put a
"gdb for perl hackers" session together.
http://xrl.us/owaqu
Perl5 Bug Summary
279 new + 1062 open = 1341 (+11 -9)
http://xrl.us/owaqw
http://rt.perl.org/rt3/NoAuth/perl5/Overview.html
New Core Modules
ExtUtils::MakeMaker 6.48
http://xrl.us/owaqy
SelfLoader 1.17
http://xrl.us/owaq2
Test::More/Simple/Builder 0.85_01
cmp_ok() fixage warning
http://xrl.us/owaq4
Attribute-Handlers 0.80
http://xrl.us/owaq6
In Brief
David Golden began cleaning up the task of documenting Perl via git on
the Perl wiki.
http://xrl.us/owaq8
John E. Malmberg ran into a "Module::Build" failure on VMS that he
thought had been fixed at one point by a patch that had been dropped
in the meantime. But then the test succeeded without anything else
happening.
http://xrl.us/owara
John sent in some other patches for VMS, some of which Craig A. Berry
was able to apply. One dealing with "cwd" issues, needs to be
forwarded to the "Pathtools" developers (i.e. Ken Williams).
http://xrl.us/owarc
JCSS suggested that "Storable" could optionally "delete %hash" when
doing "$foo=freeze(\%hash)". Nicholas Clark pointed out that when
error handling is taken into account, this becomes much more difficult
than it would appear at first glance.
http://xrl.us/oware
another Unix platform?
open source BeOS!
one puzzling bug
http://xrl.us/owarg
Last week's summary
This Fortnight on perl5-porters - 28 September-12 October 2008
http://xrl.us/owari
About this summary
This summary was written by David Landgren.
Weekly summaries are published on http://use.perl.org/ and posted on a
mailing list, (subscription: [EMAIL PROTECTED]). 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.
--
stubborn tiny lights vs. clustering darkness forever ok?
