This Week on perl5-porters - 25 September-1 October 2006
"Well not since that time you thought that embedding perl was a good
idea in the first place" -- Johnathon Stowe, commenting on Marc
Lehmann saying that yes, he loved embedding perl in other applications
and that no, he didn't do drugs.
Topics of Interest
Wrapping up EVAL handling in blead's regexp engine
Dave Mitchell checked in a couple of patches to fix the breakage that
had crept in during the recent overhaul to the regexp engine. Yves
Orton liked what he saw, and suggested a few ways to improve the
maintainability.
Dave told him to go for it. And so he did.
Mad scientists at work
http://xrl.us/r4us
pod errors in "perlref.pod"
David Landgren noticed some formatting errors when looking at
"perlref" in blead. Rafael Garcia-Suarez wondered what podlator was
being used, since the pod checked out as valid. The podlator in
question was the bundled "Pod::Perldoc", which led David to wonder why
something like Russ Alberry's podlators code. Russ explained what was
holding this up.
http://xrl.us/r4ut
Nick Ing-Simmons
It was with great sadness that the porters learnt that Nick
Ing-Simmons had died of a heart attack. Nick was one of the longest
serving contributors to Perl's development, and we are all poorer for
his loss. I can recall many a time when people puzzled over things
were done in a particular way in the code, until Nick would chip in
with a a cogent explanation of why. It will be harder without him.
http://xrl.us/r4uu
http://xrl.us/r4uv
The Perl Foundation ran the following obituary
Thanks Nick
http://news.perl-foundation.org/2006/09/thanks_nick.html
Unhandled exceptions in shared libraries
Kalpana Shetty explained a problem with shared libraries throwing an
exception, and the perl program dumping core on a "SIGABRT" signal. No
takers, possibly since the exact nature of the shared library wasn't
specified.
http://xrl.us/r4uw
"reentr" reshuffle
Jarkko Hietaniemi looked at bug #40256 and a few other bits and
pieces, and rejigged reentr.pl to make everyone happy. In fact, Marc
Lehmann was positively ecstatic.
Get down
http://xrl.us/r4ux
seek beyond length
Juerd Waalboer wanted to know whether it was reasonable to seek, upon
a scalar opened for IO, beyond its length. And especially what happens
as a result. Dave Mitchell confirmed that Bad Things were indeed
happening, that probably should be fixed.
oops
http://xrl.us/r4uy
I think that this may be what inspired Jarkko to file cook up the
following patch:
Don't talk to strangers
http://xrl.us/r4uz
Finding the *correct* line number
Curtis "Ovid" Poe wanted to disambiguate two calls to a function on
the same line with "caller". Dave Mitchell mentioned that he had
proposed to spend two bytes per op, which, at the expense of a certain
increase in memory consumption, would clear these sorts of problems
up, once and for all.
http://xrl.us/r4u2
Fixing up "lndir" to improve source tree symlinking
Jim Cromie made a small change to "lndir" to make it behave more
nicely in the presence of modified files (which could other clobber
the pristine base tree). This kicked off a discussion with John
Peacock, Rafael Garcia-Suarez and Andy Dougherty about other tricks
that can be used to deal with similar sorts of home experiments.
http://xrl.us/r4u3
Error message changes in "blead"
Yves Orton mourned the passing of pseudo-hashes, and their attendant
"Can't coerce array into hash" error message. Nicholas Clark reasoned
that it should be possible to change the current "Not a HASH
reference" to something like "can't coerce ARRAY reference to HASH
reference", but wondered if it would break anything.
Yves pointed out that since the message had already changed, the issue
was moot. Nicholas agreed that an error message should explain *why*
something was wrong, rather than just saying that it *was* wrong.
http://xrl.us/r4u4
One may assume that afterwards, Yves went away to see what could be
done to improve the situation, and came back with a new conclusion:
perl's error message suck. They are scattered throughout the source,
which makes maintenance difficult, and localisation impossible. He
proposed changing things like
DIE(aTHX_ "Not a GLOB reference");
to
THROW_ERROR(PERL_ENOTAGLOB);
This way, a message can be changed in one single place, and would
allow commercial vendors to make perl's error message fit in with
their own frameworks (witness the recent z/OS efforts), and finally
allow messages to be translated in to other languages.
Jonathan Stowe wasn't exactly opposed to the idea, but mentioned the
frequent idiom:
eval { somethingnasty() };
$@ and $@ =~ /Some nasty error/ and recover();
Rafael pointed out that there are messages with %s specifiers as well,
but that it would surely benefit the maintenance of "perldiag".
Globales Symbol "x" erfordert ausdrücklichen Paketnamen
http://xrl.us/r4u5
Patches of Interest
What Yves Orton did this week
Nicholas applied Yves's patch from last week, which prompted Yves to
deliver another patch, this time sawing off six thread-shared
variables. The result is that "use re 'debug'" is now lexically
scoped. This latter patch was redone after Rafael had a bit of trouble
with it. Yves also took the opportunity to throw in some tests for
lexically scoped regexp debugging.
Awesome
http://xrl.us/r4u6
On to the main course, Yves then delivered a patch that introduced a
new assertion that allows the writing of elegant expressions to match
arbitrarily deeply nested pairs of tokens. For instance, one could
parse XML documents code with:
/^(<(?:[^<>]+|(?1))*>)$/
(along with the appropriate amount of hand waving). Yves was critical
of the implementation, in that it requires capturing "(...)" to be
used, rather than grouping "(?:...)", but on the other hand it
conforms with what Python and PCRE already do.
Dave Mitchell was most impressed, and quizzed Yves about the
behavioural semantics regarding backtracking. Rafael wanted to know if
it was possible to extend the patch to allow case sensitivity changes
by way of something like "(?i(?1))". (Alas, no).
Robin Houston also expressed his delight at the patch and admitted to
being the party who added this functionality to PCRE since he lacked
the courage to attack Perl's regular expression internals. He too
raised a couple of questions about behaviour in borderline areas.
Yves followed up with another version of the patch that added user
documentation and more tests. He has also been reading Jeffrey
Friedl's *Mastering Regular Expressions*, and has taken up the
challenge to resolve as much as possible the areas in which Jeffrey
finds Perl's regular expressions wanting. He laid out his roadmap in
"perltodo".
All applied.
And the crowd goes wild
http://xrl.us/r4u7
And as Yves was sweeping the floor of the lab clean from his previous
efforts, he bundled up one last patch to tidy the regexp debugging
output somewhat.
http://xrl.us/r4u8
Improving "Exporter" documentation
Smylers caught up on the Exporter thread (thanks to the summary, heh)
and argued in favour of ensuring that code was "strict"-compatible,
even if "use strict" wasn't explicitly mentioned in the snippet. This
means either using package variables or using "our".
http://xrl.us/r4u9
Continuing to deal with some gcc warnings
Sadahiro Tomoyuki figured out why a recent patch of Jarkko's was
causing things to go boom! on a perl compiled with "-Duse64bitint".
Patched.
http://xrl.us/r4va
"File::Temp" doesn't handle "cmp" overloading
Rafael Garcia-Suarez posted a short snippet demonstrating a problem
with "File::Temp" overloading. When stringified (interpolated in a
string), a "File::Temp" object returns the underlying file name.
This works fine until you try to compare the stringified object to a
scalar, at which point perl starts looking for an "eq" operator and
dies. So the fix was to overload "cmp", and all was well, but Rafael
wondered whether "overload" should synthesise a "cmp" from a
stringification override.
Rick Delaney pointed out that it will already do this if you add the
"fallback => 1" attribute. John Peacock didn't like the idea of
generating "cmp" automatically.
http://xrl.us/r4vb
cflags.SH: The Revenge of "gcc -std=c89"
Jarkko, ever the optimist, kicked through the rubble of his previous
C89 configuration patch and worked up a scan to get better results
back to see how "-ansi", "-pedantic" and "-std=c89" behave in the face
of weird system headers and other platform oddities, and asked for
people on proprietary hardware to take it for a spin and see what
comes of it.
Don't take no for an answer
http://xrl.us/r4vc
New and old bugs from RT
threads creation memory leak (#40416)
Santeri Paavolainen posted a short program that demonstrated a fairly
definite leak when creating threads. Dave Mitchell noted that it was
fixed in blead.
Another reason
http://xrl.us/r4vd
"File::Find" has issues with symlinks (#40417)
Ammon posted a very long and detailed report about the problems that
"File::Find" has in relation to symbolic links. Code included.
Warnocked
http://xrl.us/r4ve
Unicode Command Line Arguments (#40418)
Dale Gerdermann wanted to read Unicode arguments from the command line
and it seemed to work in all cases until he hit a regular expression,
and there he had to force a "utf8::upgrade($arg)" for it to work.
Dave Mitchell pointed the "-C" command line switch that takes care of
this issue.
http://xrl.us/r4vf
Dale found similar Unicode problems in conjunction with LWP and
Unicode (#40432)
http://xrl.us/r4vg
"XML-Twig" tests cause "bleadperl" to segfault (#40420)
Shlomi Fish reported that the test suite of "XML-Twig" version 3.26
causes segfaults on "bleadperl", but forgot to say which tests were at
fault.
http://xrl.us/r4vh
Segfault in pack (#40427)
dgay showed how to provoke a core dump with a simple call to "pack"
and provided a simple patch to fix up the problem. Unapplied.
Should have a test, too
http://xrl.us/r4vi
Perl5 Bug Summary
A net increase of ten bugs this week
http://xrl.us/r4vj
Kill a bug today
http://rt.perl.org/rt3/NoAuth/perl5/Overview.html
New Core Modules
* Andreas König released CPAN 1.88_51 to CPAN.
http://xrl.us/r4vk
In Brief
Dave Mitchell applied an expedient hack to allow "\x{NNN}" in
t/op/re_tests.
So there's no excuse now
http://xrl.us/r4vm
Mark Stosberg wanted to clarify the documentation for lib.pm with a
short snippet. H.Merijn Brand golfed it.
And still readable
http://xrl.us/r4vn
David Landgren made a small clarification in "perlref" concerning the
interpolation of scalar references.
http://xrl.us/r4vo
Christian Jaeger made a couple of suggestions to improve the
navigation between "bugs.perl.org", Request Tracker and CPAN.
http://xrl.us/r4vp
Jim Cromie wanted to start cooking with "perl.gcov", so Steve Peters
and Sébastien Aperghis-Tramoni gave him a couple of recipes.
Got you covered
http://xrl.us/r4vq
John E. Malmberg. responsible in large part for brings Perl's VMS
implementation kicking and screaming into the third millennium, had to
say goodbye for now. He's out looking for a new job, and so had to bow
out from the list for the time being.
Thanks, and good luck
http://xrl.us/r4vr
Yves Orton noticed that the ptree constants TODO tests are passing and
wondered if that meant that they could be untodo'ed.
http://xrl.us/r4vs
Jim Cromie proposed a "-U" patch, that stands for Unofficial
Userhacking.
http://xrl.us/r4vt
Jarkko thought that gcc's "-pedantic" should be renamed "-useless".
http://xrl.us/r4vu
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
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--
hope still, a little resistance always maybe stubborn tiny lights vs.
clustering darkness forever ok?
