Perl 5 was released this week, eleven years ago.
sub _ {...} breaks File::Find Jeff "japhy" Pinyan mentioned the Issue That Will Not Die, that if you
define sub _ {...}, then _ as a shorthand for the file most
recently statted stops working. The problem at hand for japhy being
that File::Find fails, and wondered what workarounds were possible.
Mark Jason Dominus was against the idea of teaching File::Find to
work around such damage, because it would probably not be the only
module that breaks under this scenario. The best fix would be to adjust
the parser to prefer string context for _ where it makes sense (and
thus not call sub _). And Rafael Garcia-Suarez did just that with
a quick patch to put more DWIMery into the tokeniser in change #25799.
It turns out that _ is the usual idiom in the gettext world for
dealing with internationalisation (i18n). Yitzchak Scott-Thoennes thought
that a new warning should be generated for attempting to define sub _.
Abigail thought not. The thread then evolved into a discussion about how
and when new warning can, or should, be added to the interpreter.
Earlier thread, summarised here http://dev.perl.org/perl5/list-summaries/2005/20050909.html
This time around http://xrl.us/h5ye
Musing on warnings http://xrl.us/h5yf
Nicholas Clark wants to know how much tweaking to the internals would be
required in order to let perl load different versions of the same module.
Something as mundane as package Alpha using version 1.0 of module Charlie,
and package Bravo using version 2.0 of module Charlie would come in quite
handy. Without getting into the brain-melting complexity of an @array
containing heterogeneously versioned Charlie objects...
The idea sounds quite exciting, sadly, after a few responses the thread flickered out.
http://xrl.us/h5yg
The monster thread of the week, with 44 replies. It starts with a sentence
from perlsub, noted by Xavier Noria: "The return value of a subroutine
is the value of the last expression evaluated by that sub". Pop quiz: what
does the following return?
C<sub f { 1 for 1 }>
Answer: ''. Adriano Ferreira supplied a number of variations on the theme,
with if or while in the place of for, and Abigail pointed out that
do {...} has the same sorts of problems, so it's not only apparent in
subroutines. The problem is that for is a control structure. And the
value of a control structure is unspecified. In fact, it doesn't have one.
Yves Orton noticed that my @b=(0,1); print $b[0+do {1 for 1}] dumps core.
He also wanted to specify the last expression produced by a control structure.
Xavier pointed out that control structure are not expressions. And Rafael
concurred, saying that you can't say my $x = while (...) { ... }. Yves
countered with my $x = do {while (...) { ... }}. Rafael put his foot down
and said that loops are evaluated in void context. To change them now to
be evaluated in scalar or list context (which is what Yves wanted) would
break lots of code.
But the core dump problem remained unresolved.
The beginning http://xrl.us/h5yh
Dave explains exactly what's going on http://xrl.us/h5yi
Rafael explains from the other end http://xrl.us/h5yj
Xavier summarises the current state of play http://xrl.us/h5yk
do { EXPR for EXPR } Robin Houston picked up the core dump noticed by Yves in the above thread and analysed it. And patched the source to fix it.
http://xrl.us/h5ym
Nicholas Clark said that he didn't want to see the new slicing syntax
appearing in maint, and related a horror story of battling with syntax
variants in 5.004, when only 5.004_05 compiles easily on modern platforms
due to compiler evolution (specifically, Configure-back-then gets confused
by what compiler-right-here-right-now says in response to its probes).
If you like this syntax, wait for 5.10. If you can't wait, try and help to make 5.10 get here faster.
http://xrl.us/h5yn
Initially summarised here http://dev.perl.org/perl5/list-summaries/2005/20050915.html
Robin Houston found that using a sort comparison routine that calls itself can cause perl to dump core. Dave Mitchell confirmed that the situation is deeply unsatisfactory. Even if the code base was patched to die gracefully when a recursive sort comparison was found, there are problems with threads that remain in any event. Hugo van der Sanden suggested an approach using attributes. Robin and Dave started to debate a way forward.
The bug report http://xrl.us/h5yo
The trouble with threads http://xrl.us/h5yp
Hugo's suggestion http://xrl.us/h5yq
Robin's way forward http://xrl.us/h5yr
John E. Malmberg got open(FOO, "child.pl foo|") working on VMS, applied by
Craig Berry,
http://xrl.us/h5ys
and synced exit's behaviour with the documentation
http://xrl.us/h5yt
and posted his VMS TODO list
http://xrl.us/h5yu
There's a lot there. And it probably may not be complete.
Jarkko Hietaniemi posted many patches to bring Perl on Symbian up to speed.
http://xrl.us/h5yv http://xrl.us/h5yw http://xrl.us/h5yx http://xrl.us/h5yy http://xrl.us/h5yz
I have the Perl5 bug summary in my spool, but for some reason I cannot find
the message on xray. There were 1507 open tickets as of 2005-10-17.
Nicholas Clark thinks he shook out a reference counting bug with a ponie build:
http://xrl.us/h5y2
Ilya Zakharevich cc'ed p5p about a bug in if and appended a patch.
Some doubts were expressed about the error message (not everyone may
catch the cultural context of "cryptocontext"). Others noted tangentially
that testing for Windows platforms with if ( $^O =~ /Win/i ) will come
to grief on cygwin and Darwin.
http://xrl.us/h5y3
Andy Lester, continuing on his quest to conts, hoisted some repeated code out in av.c and thus shaved a few bytes of the resulting object code.
http://xrl.us/h5y4
Following on from the discussion of manipulating the environment last week,
H.Merijn Brand added a configure probe for clearenv.
http://xrl.us/h5y5
Sébastien Aperghis-Tramoni wrote patch #25802 for autodoc.pl so that it generates the index entries for perlapi.pod and perlintern.pod.
http://xrl.us/h5y6
Gisle Aas fixed up pp_sselect
http://xrl.us/h5y7
Nicholas upgraded ExtUtils::MakeMaker to 6.30 in maint. And wanted to
know what (is)? broke(n)?.
http://xrl.us/h5y8
This summary was written by David Landgren, for once without Immediate Realtime Corrections (IRC), so any typos or wordos are truly my own. I'm offline as of tomorrow morning for a week. Yay!
Information concerning bugs referenced in this summary (as #nnnnn) may be viewed at http://rt.perl.org/rt3/Ticket/Display.html?id=nnnnn
Information concerning patches to maint or blead referenced in this summary (as #nnnnn) may be viewed at http://public.activestate.com/cgi-bin/perlbrowse?patch=nnnnn
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.
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