This Week on perl5-porters - 3-9 November 2008
"PS: Hi, guys. Been a while. How you been?" -- Chip Salzenberg, back
on the chain gang.
Topics of Interest
version.pm synopsis thoughts and an additional version.pm affordance
David Golden made good on his promise to write a better synopsis for
version.pm to help steer people out of trouble when dealing with
version numbers and their comparisons.
Michael G. Schwern pointed out a couple of places where things weren't
locked down, but said that he thought David's take was much clearer.
But as usual in matters of versioning, counter examples popped up to
muddy the waters.
http://xrl.us/oxqwy
Should "[:upper:]" match title case?
Karl Williamson read the documentation and saw that "[:upper:]" should
match title case, except that it doesn't, and an undocumented
"\p{IsTitle}" does. What to do?
Tom Christiansen noted that there is still a lot of POSIXy stuff that
Perl doesn't do, but that part of the reason for that is that it's
full of subtlety and traps for the unwary. He would really like to see
a decent collation infrastructure in Perl, but Jarkko Hietaniemi said
that the issues are insanely difficult to resolve.
http://xrl.us/oxqw2
Perl 5.8.8 34711 on AIX 5.3
Rainer Tammer sent in the information he had gleaned from building
what will be 5.8.9 on AIX 5.3. He wondered whether it was worth the
effort to continue to deal with 5.1 since it is no longer supported.
H.Merijn Brand explained that the porters have a long traditional of
continuing to support Perl on orphaned architectures; all that's
really needed is shell access.
H.Merijn and Andy Dougherty offered some suggestions and insights to
help Rainer move forward.
http://xrl.us/oxqw4
In a 64-bit build, Rainer had exactly one failure in
lib/ExtUtils/t/Embed.t.
http://xrl.us/oxqw6
$Config{archname} on AMD64 Windows
Sisyphus had trouble keeping track of the differences between 32-bit
and 64-bit builds on his Vista box. Jan Dubois and Steve Hay provided
the vital clues to help him figure out what he should be doing.
http://xrl.us/oxqw8
Future maintenance plans for 5.8.x
Nicholas Clark added a paragraph to perl589delta explaining that this
release (perl 5.8.9) was likely to be the last of the 5.8 series.
Jan Dubois pointed out that 5.10.0 has a "testing" feel to it, to
which Dave Mitchell stated that his plan was to have 5.10.1 out by the
end of the year as well.
Matt S. Trout mentioned that he had found that users of "DBIx::Class"
do pay attention to EXPERIMENTAL labels, and don't mind as much when
things break. But he'd love to figure out how to get them to take
development snapshots for a spin on a regular basis.
this is the end my friend
http://xrl.us/oxqxa
Change "PREFIX" to "INSTALL_BASE" in perlfaq8 and perlmodinstall
Michael G. Schwern noticed a dead meme still doing the round, on
stackoverflow.com. So went through the documentation and excised
"PREFIX" and replaced it with "INSTALL_BASE", which is the officially
anointed new way of installing modules.
http://xrl.us/oxqxc
That reminded John Siracusa about the problem of sequestered perl
installs.
http://xrl.us/oxqxe
Syntax for macros / function composition at compile time
Erwan Lemonnier asked for some general syntax advice on implementing
Python-style function decorators to Perl. Michael G. Schwern pointed
him at "Method::Signatures" and subroutine attributes.
Matt S. Trout mentioned a secret IRC channel and mailing list where
meddling with syntax takes place.
http://xrl.us/oxqxg
Perl 5.10.x + Tk-804.028-501-12048
The recent tweaks to constant/mutable SV pointers caused Tk to fail
(Tk being the poster child for unexpected consequences from low-level
changes). Marcus Holland-Moritz tweaked thing around to get Tk passing
again.
http://xrl.us/oxqxi
Questions about regcomp.c
Karl Williamson had some very detailed, precise questions to ask
regarding regcomp.c, from which we can conclude that Karl already
knows more about the regular expression than 94% of all Perl 5
Porters. Yves Orton provided the answers and saw that there was a bug
that he needed to fix.
http://xrl.us/oxqxk
#34775 causes run/cloexec.t to hang
Marcus Holland-Moritz uncovered a smoke failure regarding the recent
bug fixes for leaks in PerlIO layers.
Steve Peters confirmed the failure and reverted the change. For Goro,
it's back to the drawing board.
http://xrl.us/oxqxn
"Perl_newSVpvf("%lld")" is broken
Hugo van der Sanden picked up the gauntlet thrown down by Michael G.
Schwern regarding the weird results with printf formats, traced it
down through a dense thicket of #ifdefs, and proposed a patch to tidy
it up.
A long discussion about printf format specifiers and error messages
ensued.
http://xrl.us/oxqxp
Regular expression character classes and unicode.
Yves Orton kicked of a request for comments regarding the
rewrite/revamp of character classes and the breakage that has crept in
since Unicode. He received many comments.
http://xrl.us/oxqxr
Add UPSTREAM flag to Maintainers.pl
Dave Mitchell wanted to gauge the interest in adding some metadata for
dual-lifed modules, to track whether changes to blead should be pushed
upstream to the maintainer first, or whether they were happy to fold
changes back at their own speed. Those who replied were in favour.
Steffen Müller patched all that was necessary in order to implement
the idea.
http://xrl.us/oxqxt
Clone fails to build with [EMAIL PROTECTED]
Michael G. Schwern reported a failure with "Clone", that Marcus
explained was due to the slightly naughty use of an lvalue macro. But
he fixed things anyway.
http://xrl.us/oxqxv
TODO of the week
Here's a biggie for the bored. This task needs C knowledge, and
knowledge of how the interpreter works, or a willingness to learn.
optimize tail-calls
Tail-calls present an opportunity for broadly applicable optimization;
anywhere that "return foo(...)" is called, the outer return can be
replaced by a goto, and foo will return directly to the outer caller,
saving (conservatively) 25% of perl's call&return cost, which is
relatively higher than in C. The scheme language is known to do this
heavily. B::Concise provides good insight into where this optimization
is possible, ie anywhere entersub,leavesub op-sequence occurs.
perl -MO=Concise,-exec,a,b,-main -e 'sub a{ 1 }; sub b {a()}; b(2)'
Bottom line on this is probably a new pp_tailcall function which
combines the code in pp_entersub, pp_leavesub. This should probably be
done 1st in XS, and using B::Generate to patch the new OP into the
optrees.
Patches of Interest
v5.10.0 Pod/Text.pm Can't call method "pod2text" without a package or object
Jari Aalto had a problem using "pod2text" in 5.10 and offered a patch
to reinstate the previous behaviour.
Michael G. Schwern had a closer look at what was going on and
concluded that the real problem was the fact that "Pod::Text" was
using "Pod::Simple" incorrectly. He also pointed out that "pod2text"
as a function has been deprecated for nearly half of Perl 5's
lifetime.
http://xrl.us/oxqxx
Configure/NDBM_File Add prototype detection for NDBM header files
Marcus Holland-Moritz offered a couple of patches to sort out the
problems that have been observed recently with respect to determining
the availability of NDBM. He and H.Merijn Brand had everything settled
down by the end of the week.
http://xrl.us/oxqxz
threads Changes
Nicholas Clark is busy wrapping up 5.8.9, and he noted the fact that
5.8.8 shipped with "threads" 1.07, but 5.8.9 will ship with 1.71. An
amazing amount of work was done, mostly by Jerry D. Hedden, and
Nicholas wanted to know if it was possible to summarise the main
changes in three or fours points.
Jerry responded with a patch that contained what he thought were the
most important improvements, which Nicholas applied with thanks.
http://xrl.us/oxqx3
New and old bugs from RT
"B::Xref" seems to be broken (#18306)
Steve Peters applied a patch from Renée Bäcker, thus closing the
oldest bug closed this week.
ding dong the bug is dead
http://xrl.us/oxqx5
Need to change Cygwin built-in "Cwd::cwd" (#38628)
Steve was able to close this ticket as well, since Jerry D. Hedden
confirmed that its patches have been applied to blead, 5.10 and 5.8.
second verse same as the first
http://xrl.us/oxqx7
filetests sometimes do not set _ (#46463)
Steve said this bug was resolved as well, but Mark Overmeer thought
that documenting sub-optimal behaviour was not the same improving the
behaviour.
http://xrl.us/oxqx9
map leaks memory (#53038)
Marcus Holland-Moritz suggests that this has been fixed by change
#34776 and that bug #48004 is something else altogether (a question of
maps within maps not freeing intermediate temporaries and thus
consuming 300Mb when 9Mb should suffice).
http://xrl.us/oxqyb
perlio.c has a problem (both 5.8 and 5.10) (#54828)
Steve Peters cleared up the question of not all parts of a patch being
applied.
http://xrl.us/oxqyd
h2xs does not handle properly enum constants (#55896)
Back in June, Steve Peters said that he thought fixes applied to
"h2xs" in the meantime should have resolved the problems encountered
in the bug report. Jeremy Ratcliffe replied this week, saying that
only one bug had been fixed in 5.10, all the others remained.
http://blogs.sun.com/akolb/entry/pitfals_of_the_perl_xs
http://xrl.us/oxqyf
Unary minus on 'numeric' inputs like '-1' (#57706)
Renée Bäcker suggested a change to how strings with a leading minus
character are interpreted in the presence of a unary minus.
but the patch has whitespace issues
http://xrl.us/oxqyh
Permission denied when building as non-root user on FreeBSD 6.2+ (#58180)
On FreeBSD (and possibly other Unix variants), you cannot build Perl
if the directory containing your home directory does not have the read
bit set (in order to prevent you from snooping the names of the other
accounts in a shared environment -- which seems pretty dumb if
/etc/passwd is readable, but who am I to argue with an ISP?)
http://xrl.us/oxqyj
"PerlIO::via" leaks memory at a high rate (#59268)
Marcus Holland-Moritz resolved this problem to his satisfaction. If it
summons no black smoke, then a CPAN release of "PerlIO::via" will fix
older Perls as well.
http://xrl.us/oxqym
In regular expressions, "\N{U+...}" doesn't match for ... > 256 (#59328)
Karl Williamson dashed off a quick patch for this, and Yves Orton
applied it.
http://xrl.us/oxqyo
PATCH chr(0400) =~ /\400/ fails for >= 400 (#59342)
Rafaël Garcia-Suarez replied to Yves Orton's comment from last week
where he suggested that octal escapes in regular expression be
outlawed. He agreed that they should be put on board the deprecation
train, but could be retained inside character classes. He also noted
some marvellous inconsistencies in error messages.
Glenn Linderman suggested stealing Python's OoNNN octal notation.
It will take considerable effort on the part of the porters to
convince Tom Christiansen of the need to deprecate octal in regular
expressions. His main argument is that today, the "\g" escape can be
used to disambiguate backreferences from octal. Chip Salzenberg
waltzed in to say that he threw his lot in with Tom.
Undaunted, Glenn replied that there is a definite problem in that
certain octal numbers may not be expressed in a pattern, depending on
the number of backreferences. And when patterns are created by "qr//"
composition, which was Yves Orton's point, this may not even be
evident by casual inspection).
Tom subsequently posed to Andrew Hume, one of the original authors
along with Ken Thompson and Dennis Ritchie, of C, Unix and regular
expression, the question of how they dealt with the octal notation
backreference ambiguity at the very beginning. And provided a whole
pile of links for people who want to know more about the history of
the matter.
http://xrl.us/oxqyq
Inconsistent math with large numbers (#60318)
Andreas König reported on a number of 64-bit perls out in the wild
that consider some ferociously large numbers that end in 89.2 being
larger than the same number ending in 90. Appending a .0 to the latter
makes things work, but is considered distasteful.
http://xrl.us/oxqys
utf8+locale substitution cause the Perl interpreter to hang. (#60326)
Shlomi Fish showed how an "s///" expression containing a particular
UTF-8 character could fall into an endless loop.
http://xrl.us/oxqyu
http://xrl.us/oxqyw
Regexp lookbehind failure after an (if)then|else in perl 5.10 (#60344)
Someone named Adam reported a bug that was introduced at around the
time that Dave Mitchell derecursified the regular expression engine.
Yves Orton took a crack at fixing it and Dave thought his solution was
fine.
http://xrl.us/oxqyy
"local $SIG{FOO} = sub {...}" sets signal handler to SIG_DFL (#60360)
Ian Goodacre posted a problem about localising signal handlers, and
the fact that the default handler is loaded transiently in the switch
from the old handler to the new.
Chip Salzenberg brought the house down with an awesome patch to solve
the problem, which he thought would probably fix up some sub-optimal
behaviour that has probably been around ever since 5.000.
Amid the general applause, Marcus Holland-Moritz expressed concern
Chip's patch alters the signature of a public API. Chip took Marcus's
concerns on board and wanted to know what the current policy was
regarding the modification of a public call.
In a side note, Chip noted why companies like IBM et al invest on
Linux but not FreeBSD, in a sub-thread relating to how difficult it is
to get companies interested in supporting Perl.
Chip came back afterwards with a second iteration of the patch that
Marcus applied with a minor tweak or two.
http://xrl.us/oxqy2
Safe.pm sort {} bug with "-Dusethreads" (#60374)
Alex Hunsaker filed a bug regarding a problem with custom sort
routines in a Safe compartment on a threaded perl. He mentioned that
Andrew Gierth had tracked the problem down to a difference in the
implementation of stashes. In a non-threaded perl, a cop points to the
stash, but in a threaded-perl a level of indirection is introduced and
it points to the name of the stash.
http://xrl.us/oxqy4
"pos()" does not get stored for tainted variables (#60378)
Renée Bäcker, who appears to have memorised the entire set of
unresolved bugs in the RT queue, was quick to point out that the
person submitting this bug submitted the same bug about four years ago
as bug #27344.
but it's still a bug
http://xrl.us/oxqy6
Perl5 Bug Summary
1332 (+7 -20)
http://xrl.us/oxqy8
http://rt.perl.org/rt3/NoAuth/perl5/Overview.html
New Core Modules
"Test::More/Builder/Simple" 0.86
http://xrl.us/oxqza
"Attribute-Handlers" 0.81
http://xrl.us/oxqzc
In Brief
Tom Christiansen wondered about "strange permissions" on files, such
as executable bits of files that would never be executed.
http://xrl.us/oxqze
He'd also like to see a useful "ctags" target in Makefile, which would
probably require some Configure probes.
http://xrl.us/oxqzg
Joshua Hobbit wondered whether replacing "Time::Local" by
"Time::Y2038" (that is, a notorious bug) was particularly wise in
terms of names.
http://xrl.us/oxqzi
Jerry D. Hedden saw that change #34653 breaks DBM functionality, but
Marcus was quick to make a change that he thought would repair it.
http://xrl.us/oxqzk
Yves Orton added some files to .gitignore.
http://xrl.us/oxqzn
PerlIO resource leaks on "open()" and then :pop in :unix and :stdio
(bug #56644). Leaks no longer, thanks to GFUJI's patches, applied by
Steve Peters.
http://xrl.us/oxqzp
And another: "ungetc()" to :scalar might cause problems (bug #57322).
I suspect Steve went through Renée Bäcker's list of bug reports
containing patches.
http://xrl.us/oxqzr
John E. Malmberg began to get POSIX exit mode working/tested on VMS.
Applied by Craig A. Berry.
http://xrl.us/oxqzt
Karl Williamson wanted to use charnames in "Test::More" "like" tests,
and was told to use "qr//" to minimise the pain.
http://xrl.us/oxqzv
And "File::Find" (bug #57926)
http://xrl.us/oxqzx
Last week's summary
This Week on perl5-porters - 20-26 October 2008
http://xrl.us/oxqzz
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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archive is at http://dev.perl.org/perl5/list-summaries/. Corrections
and comments are welcome.
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--
stubborn tiny lights vs. clustering darkness forever ok?
