This Week on perl5-porters (26 May / 1 June 2003)
As usual, the weekly summary will try to present a useful or
entertaining cross-section of the perl 5 porters' activity. The various
topics include C-level I/O, scoping, installation layouts, and some
amount of bugs and patches.
setvbuf()
Mark-Jason Dominus tried to use IO::Handle::setvbuf(), and his recent
5.8ish perl complained that it wasn't implemented (bug #22339). In fact,
PerlIO-enabled perls don't support setvbuf() anymore. This was followed
by a small discussion about different methods to do unbuffered I/O at
the C level.
http://xrl.us/ivx
$<digit> scoping
Bug #22369 demonstrates an oddity concerning the lexical scoping of $1
(and other variables that depend on regexps.) Basically, when the same
scope is entered twice, recursively, and when $1 is set by a successful
match inside this scope, the second value obliterates the first one,
even after exiting that scope. Rafael explained what happens behind the
scenes -- $<digit> values are actually associated to regexps, not to
lexical scopes -- and said that this behaviour ought to be better
documented.
http://xrl.us/ivy
@INC setup
There was a small but interesting thread on the default setup of the
@INC path, why it was designed that way, and how OS vendors implement
it. Andy Dougherty summarizes it :
http://xrl.us/ivz
Cygwin and IO layers
Gerrit P. Haase, our Cygwin porter, proposed to make no-CRLF the default
for output on Cygwin. It's still possible to to pull it in every time it
is needed with the environment setting PERLIO=crlf, or on a
per-filehandle basis with "open OUT, '>:crlf', 'text.txt'". Sounds like
a good idea.
Unicode char classes proposal
Jeff Pinyan posted several mails entitled "another attempt at adding
unicode regex support to perl", about designing new Unicode-enabled
character classes. For example, [\p{AtoZ}&&\P{Vowels}] would be
equivalent to [b-df-hj-np-tv-z]. He faced Warnock's dilemma at an
unprecedented level.
http://xrl.us/iv2
In Brief
Joe McMahon is cleaning up and documenting the perl debugger. He says
that "it's about 3000 more lines of POD and comments." And while he's at
it, he fixed a few bugs that were on his way. Impressive.
Alexey Tourbin remarks that a2p, when built, is linked against
libraries that it doesn't actually use (on linux). Andy Dougherty says
it's mostly harmless, at least in the usual cases, and provides a patch
that removes from a2p the libraries that are only needed for
extensions.
A patch that Dave Mitchell sent some time ago, known by the codename of
jumbo closure patch, was applied this week. This is basically a
reimplementation of closures in Perl. Apparently it broke something on
HP-UX 11 + gcc.
Dave Rolsky volunteered to backport Time::Local to the CPAN.
Best of Bugs
Manoj Kumar reports (bug #22329) that perldoc doesn't support
command-line options in the PAGER environment variable.
Enache Adrian fixed bug #22372 : in perl 5.8.0, a format that uses a
foreach loop variable is likely to segfault.
Scott A Crosby reports (bug #22371) a way to produce hash keys that will
collide and that may severely degrade performance of hash lookup. This
can be used against some Perl applications as a denial of service
attack. Nobody commented.
Craig Barratt reports (bug #22395) a regular expression, /(.*)[bc]/
that appears to be much slower in perl 5.8.0 than in perl 5.6.x (it's
apparently O(N^2), versus O(N) previously). It's not clear why.
About this summary
This summary was brought to you by Rafael Garcia-Suarez. Weekly
summaries are available on <http://use.perl.org/> and via a mailing
list, which subscription address is perl5-summary-subscribe@xxxxxxxxx
Feedback appreciated.
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