This Week on perl5-porters - 16-22 March 2008
"I suspect that by now the Parrot code base has moved on sufficiently
that it's faster and cleaner to start from scratch than to try to
merge over that code. I might be wrong, but I'd suggest keeping "redo
from start" as an option." -- Nicholas Clark, not wishing to flog a
dead horse.
Topics of Interest
Lexical "Fatal.pm" and "autodie.pm"
We now return you to last week's discussion about "Fatal" (issuing a
warning become a fatal error that halts execution) and how Paul
Fenwick has begun work to make the effect lexical (that is, scoped to
the current code block).
First off, it appears that "use lethal" has lost out to "use autodie",
which doesn't seem like an improvement, but it has the pumpking's
favour.
As the code was more or less ready to be pulled into the code base,
the question was what to do about dual-lifing the module, since
lexical pragmas aren't available in 5.8 and below. Nonetheless, it
would be nice to get rid of the AUTOLOAD craziness on 5.8 and 5.6.
Further backwards compatibility would not be required as it is
doubtful that anyone stuck on such ancient versions would be using
"Fatal" in the first place.
Aristotle Pagaltzis thought it would be useful to have shorthand
import lists to make warnings from all core functions dealing with,
for instance, I/O, to invoke the Fatal machinery. He was also a little
doubtful about wedging the pragma into the Fatal namespace. It would
be better to have Fatal and the autodie pragma be APIs into the same
underlying code.
There was a certain amount of discussion about what happens when
"Fatal" is used at the package level, and then a "no autodie" pragma
is invoked in a scope. Paul hinted that he'd be happy to implement
whatever the concensus turned out to be, but while there wasn't
exactly disagreement over anything, some of the corner cases had some
pretty horrible choices.
The messages that "Fatal" produces when it does its stuff also came
under fire. Paul said he'd look cleaning that up. Aristotle even
volunteered to chip in with the task if needed.
one thread
http://xrl.us/bh4fn
and another
http://xrl.us/bik25
Wanted: interesting self contained task
Nicholas Clark was a bit sad that the idea of learning about how to
hack on perl's internals attracted so little interest. He concluded
that it would not be worth the effort to write up a conference talk on
the matter if it was likely that no new people became interested in
hacking on perl.
Rick Delaney disagreed and said he that thought the self-contained
task idea was worth pursuing. All that is needed is to find another
task, and set up a mentor.
rewrite the peep-hole optimiser
http://xrl.us/bik27
Perl @ 33536
Nicholas Clark released another snapshot that is asymptotically
approaching 5.8.9. At this point the "ExtUtils::Install" issues
haven't quite settled down on Windows (but subsequent patches to the
list indicate that this is close to being fixed).
Improvements in this snapshot include the quashing of intermittent
threads failures and that it builds out of the box on Stratus VOS.
Steve Hay mentioned that there a couple of his patches that ought to
go in as they quieten a number of compiler warnings on Windows.
http://xrl.us/bik29
"Devel::Size" and bleadperl
Tels noticed (in bug #33530) that "Devel::Size" was no longer
buildable under bleadperl, mainly due to the promotion of regexps to
first-class REGEXP datatypes. Reini Urban fixed it up as best he could
and added an error message that pleased Paul Johnson's sense of
whimsy.
http://xrl.us/bik3b
perl and CPAN distributors
It all started out with the simple wish of Gabor Szabo to hoist the
information about Perl ports from cpan.org out onto the Perl5 wiki in
order to allow many hands keep it up to date.
The thread then developed into a long discussion about how
distributors of operating systems (such as Debian) go about including
Perl in their distribution. There was much talk about the relative
merits of strategies for dealing with architecture-dependant (read:
XS) components, dual-life modules, and fitting in the distribution
packaging schemes.
Rafael Garcia-Suarez hinted that he wanted to take a fresh approach to
these issues in 5.12.
One of the main problems, articulated by Michael G. Schwern, is the
persistent (literally) difficulty in modifying @INC locally, without
resorting to sub-optimal hacks like sitecustomize.pl.
In the final analysis, we need to allow Perl to allow itself to be
driven by the host packaging system whilst retaining the ability for a
local site to include a fresh new Perl module of which the packaging
system has not yet caught up with.
http://xrl.us/bik3d
Is "posix_fallocate()" a possible candidate for POSIX.pm
Joshau Hoblitt wondered if there was any interest in exposing the
"posix_fallocate" function to Perl, which allows one to ask the host
for enough contiguous space in which to write out really huge files,
the idea being to minimise fragmentation as far as possible.
Craig A. Berry replied that any serious patch would be seriously
considered.
http://xrl.us/bik3f
Eliminate cut-n-paste code in dump.c
Jim Cromie spotted a quick way to chop around 150 lines from dump.c.
Reini Urban noted that part of the code in question was duplicated in
various B and Op modules, so it would be nice to expose the underlying
code via an API, which would simplify the task of keeping these
ancillary modules in sync.
http://xrl.us/bik3h
Faster safe signals?
Nicholas Clark wondered if we could have faster safe signals by
pushing the safe signal check down out of the core runloop into a
small number of suitably hot opcodes.
Tim Bunce wondered if adding branch prediction hints in suitable
places might not produce an even greater performance boost.
All of the experiments tended to produce results whose differences
were lost in the noise.
http://xrl.us/bik3j
perl 5.10.1 plan
Dave Mitchell asked what was needed in order to release 5.10.1, such
as outright breakages from 5.8.x and fixes for new things in 5.10.0,
such as some of the quirky edges in "given"/"when", where it is
important to nail them down quickly before too many people get used to
them the way they are now.
Michael G. Schwern mentioned the @_ slowdown (which is no more),
problems with "ExtUtils::Install", making sure things build out of the
box on Vista and a list of issues that have arisen with smart
matching.
http://xrl.us/bik3m
"local $@" has an unwanted side effect
Yuval Kogman described a scenario in which "local $@" doesn't do the
right thing. It boils down to the latter day "DESTROY" method
interfering with the orderly behaviour of unwinding exceptions and
transferring information via [EMAIL PROTECTED]
After a long discussion as to whether it would be possible to fix the
current behaviour, short of introducing a putative "@@" variable,
David Nicol suggested a documentation improvement to describe exactly
how things are now, and that's what made it in.
http://xrl.us/bik3o
Bug tracking system
RT sucks. Bugzilla rulez.
and?
http://xrl.us/bik3q
TODO of the week
(based on a suggestion by Nicholas Clark in private correspondence).
Here's *your* chance to get your name in lights, or at least in the
following section of "This Week on perl5-porters". Take a TODO item,
and... do it! Each week, a random TODO will be featured. To start the
ball rolling, we have:
Merge common code in installperl and installman
There are some common subroutines and a common "BEGIN" block in
installperl and installman. These should probably be merged. It would
also be good to check for duplication in all the utility scripts
supplied in the source tarball. It might be good to move them all to a
subdirectory, but this would require careful checking to find all
places that call them, and change those correctly.
Patches of Interest
"ExtUtils::Install" under Cygwin
Steve Hay thought he had the patch to end all patches to get
"POSIX::access" working sensibly on Cygwin using all the compilers he
could get his hands on. No-one commented on it, apart from Yves Orton
via IRC, so Nicholas Clark committed it.
http://xrl.us/bik3s
New and old bugs from RT
"PERL_NO_SHORT_NAMES" incompatible with perl.h (#51762)
Michael Fowler (of the Debian Project) identified a problem with
"PERL_NO_SHORT_NAMES" which results in undefined symbols occurring at
link time. No answers as yet.
http://xrl.us/bik3u
"open(OUT, ">-")" is not "open(OUT, ">", "-")" (#51842)
Himanshu G. tripped over the 3-arg open and ">-" (STDOUT). Ronald J.
Kimball asked how the documentation could be improved to clarify the
situation.
http://xrl.us/bik3w
Deparse interpolation in regex literal (#51848)
Zsban Ambrus uncovered a deparsing problem in 5.10 (but not 5.8)
whereby "qr/${x}y/" produces "/$xy/", which is definitely wrong.
http://xrl.us/bik3y
UTF-8 non-characters (#51918)
Chris Hall opened a ticket to say that the Encode distribution's
"decode" and "encode" routines only recognise "U+FFFF" as a
non-character, but 65 others, such as "U+FFFE" and "U+10FFFF" and
waved through as being valid characters.
http://xrl.us/bik32
Inconsistent handling of characters with value > 0x7FFF_FFFF and other
issues (#51936)
Even more scary stuff about Unicode non-characters and 13-byte
extended sequences that fairly had my head spinning.
http://xrl.us/bik34
Typo on regular expression at "perlopentut" manual page. (#51964)
Pancho found a very silly typo in a code fragment in the
documentation, so Rafael fixed it.
a patch to remove one character
http://xrl.us/bik36
Document $var, $arg, $type and $ntype XS variables (#51992)
Michael G. Schwern was annoyed at the way perlxs waffles on about
these variables without ever really getting around to explaining what
they are. Michael promised that is someone could explain them to him
then he would make improvements to the documentation.
http://xrl.us/bik38
Warn/abort on attempted perl exit (#52000)
John Gardiner Myers offered a patch (but no tests) to convert an
attempt to call "exit" into a warning. This is a highly desirable
feature to have in a multi-threaded environment where a single "exit"
can really ruin your day (especially when the "exit" comes hidden in
something downloaded from CPAN)...
The patch makes a Perl stack trace available to a "__WARN__" handler
so that the offending code can be tracked down.
http://xrl.us/bik4a
Perl5 Bug Summary
1795 (+9 -6)
http://xrl.us/bik4c
http://rt.perl.org/rt3/NoAuth/perl5/Overview.html
In Brief
Sérgio Durigan Júnior had a few questions about compiling a 64-bit
Perl in a 32-bit system following on from his problems with failed
tests on PPC64. H.Merijn Brand set him straight.
64 bits for all
http://xrl.us/bik4e
Sérgio also asked about make distclean and config.arch but received no
answers.
http://xrl.us/bik4g
But feedback from H.Merijn on how to solve his problem in a better way
led to the resurrection of the rarely used config.over technique for
overwriting Configure behaviour.
http://xrl.us/bik4i
As well as some problems when setting the libraries' installation
path.
http://xrl.us/bik4k
Having pulled the rug up over things long since swept away and
forgotten about, Sérgio added some smarts to "make distclean" remove
config.arch. H.Merijn applied the concept, if not the patch itself, to
Makefile.SH.
http://xrl.us/bik4n
Paul Green reported that a smoke of [EMAIL PROTECTED] on Stratus VOS issued a
number of errors that were all due to Stratus VOS's own take on
reality, and not (or nearly never) Perl's fault. He thus lifted
Stratus's option to stall the release of 5.8.9.
98.68% ok
http://xrl.us/bik4p
Jim Cromie wrote a patch to improve IS_NUM_COMPARE by coalescing all
the opcode numbers involved to be contiguous. He was a bit peeved that
it didn't reduce the resulting assembly code, but figured that at
least it renders the code less sensitive to the ability of the C
compiler to perform sophisticated optimisations.
http://xrl.us/bik4r
Thanks in large part to Eric Wilhelm's tireless efforts, Perl is again
a participant in Google's Summer of Code (at least as far as the
northern hemisphere is concerned).
it's official
http://xrl.us/bik4t
And regarding the GSoC, there is a list of Things To Do.
http://xrl.us/bik4v
Reini Urban uploaded his Mperl compiler and optree debugger. No-one
commented.
http://xrl.us/bik4x
Robin Barker added some optional verbosity to regen.pl and friends.
Unapplied.
http://xrl.us/bik4z
Gerard Goossen stripped out some unnecessarily complex code when
dealing with MAD. Unapplied.
http://xrl.us/bik43
As tweaked the keys for sub and var attributes to avoid clashes with
arrow operators.
http://xrl.us/bik45
Michael G. Schwern reported that the patent for "Software Package
Verification" was nothing to worry about. There had been some concern
in the past that Perl's test infrastructure could have been covered by
its scope.
http://xrl.us/bik47
H.Merijn Brand reported that perl's Configure script had been ported
to "meta-3.5-20".
http://xrl.us/bik49
Vincent Pit went looking for double warnings for single errors, and
found two. "perl -we '\&$x'" used to spit out the same error twice
(along with four others).
http://xrl.us/bik5b
and "perl -we 'my $a; substr $a, 0, 10, "foo"'" did much the same, so
he arranged things to have $a silently upgraded to an empty string
beforehand. Both patches applied.
http://xrl.us/bik5d
Last week's summary
This Week on perl5-porters - 9-15 March 2008
http://xrl.us/bik5f
About this summary
This summary was written by David Landgren. It is hopelessly late; I
crave the indulgence of my readers. It was my birthday this week, or
at least the attendant celebrations, and on top of that, a supermarket
chain obsessed more with profit motives than the well-being of its
clients sold my family beef well past its due date, and, well, I'll
spare you the details...
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 to help support the development of Perl.
