This Week on perl5-porters (16-22 February 2004)
This week is to be filed in the categpry "busy" for the Perl 5 porters.
Read about new optimisations, new ideas, new warnings, bugs, fixes, and
other future plans for the next major version of Per 5.
A couple of optimisations
Paul Johnson revamped the internal OP structure so that optrees now take
less memory (while the speed impact is not mesureable.) This is going
only in bleadperl, because, obviously, it breaks binary compatibility.
http://groups.google.com/groups?selm=20040221174213.5c39a8b5.rgarciasuarez%40free.fr
Dave Mitchell continues his series of impressive patches by extending
the AELEMFAST optimisation to lexical arrays. This optimisation was
already in place for global arrays, to access an element where the index
is an integer constant between 0 and 255. As a result, access to fixed
elements of lexical arrays seems to be faster by a factor of 50%.
http://groups.google.com/groups?selm=20040222160435.GA20408%40fdisolutions.com
read() return value and EOF
Michael Bell reports (as bug #26787) that read() can return 0 on Linux
even when not at end-of-file, when under a high system load. It is a bug
in perl, or a misfeature, or a bug in Linux? Should read() return
undef on EOF?
http://groups.google.com/groups?selm=rt-3.0.8-26787-78336.2.2498005290219%40perl.org
Reopening a STD filehandle
Stas Bekman reports (bug #26670) that perl (with the PerlIO
implementation, default since 5.8.0) seems to handle dup(2) badly when
some STD streams are closed, emitting an obscure warning "Filehandle
STDOUT reopened only for input" (or the inverse). Nick Ing-Simmons
points out that this is in fact expected behaviour: since STDOUT was
closed, the next open() reuses filehandle number 1, which is, by
definition, STDOUT (in perl and in C); so perl, here, warns about a
potential bogus situation. Nick's advice is to reopen a closed STD
handle to /dev/null.
http://groups.google.com/groups?selm=rt-3.0.8-26670-78082.19.4315995467592%40perl.org
Autovivification of an assignment
Ton Hospel notices (bug #26866) that the autovivification of hash and
array references does not seem to happen consistently. For example, this
is valid:
$u = undef; $x = $u->{foo}
but this dies with a fatal error:
$x = ($u=undef)->{foo}
Nicholas Clark points out that this is probably the same problem that
was reported as bug #18635.
http://groups.google.com/groups?selm=c101e9$jf8$1%40post.home.lunix
A prototype for defaulting to $_
Continuing a thread from last week, a proposal to extend the prototype
syntax was discussed: a new prototype character, "_", could stand for
"optional value that defaults to $_". For example, a function that takes
a list as a parameter, but that uses $_ if passed the empty list, could
have the prototype "sub mychomp(_@)". However, this implies that the
prototypes of built-ins would change.
The complete thread:
http://groups.google.com/groups?selm=20040206164438.GK19932%40c3.convolution.nl
New warning
The dubious construct
my $foo = $bar if $condition;
(and other equivalent ones) now produces a deprecation warning, thanks
to Dave Mitchell. (See our previous episodes for details).
Miscellaneous Bugs
Jamie Lokier reports (bug #26909) that in a (?{...}) regular
expression block, lexical variables are captured, just like in closures,
but without warning the user as of 5.8.0. This lack of warning is fixed
in recent perls.
He also reported (as bug #26910) that "use strict 'vars'" doesn't seem
to be active in (?{...}) blocks.
Sean O'Rourke reported that calling a subroutine f() recursively with
"goto &f" leaks memory, and suggests that it may come from lexicals not
being freed. (Bug #26959.)
In Brief
Rafael announced that he plans to make a new developement release of
perl, 5.9.1, in March.
Meanwhile, Leon Brocard released perl 5.005_04 RC2.
http://groups.google.com/groups?selm=20040219142651.GA31294%40kanga.astray.com
Brendan O'Dea sent a batch of patches that he applied to the Debian
5.8.3-2 release of perl.
http://groups.google.com/groups?selm=20040215122717.GA26812%40londo.c47.org
Russ Allbery released Term::ANSIColor 1.08. MIME::Base64 3.00, which was
released a while ago, was also integrated into the perl distribution.
About this summary
This summary was written by Rafael Garcia-Suarez. Weekly summaries are
published on http://use.perl.org/ and posted on a mailing list, which
subscription address is [EMAIL PROTECTED] (I've been
trying to use gmane (http://news.gmane.org/) as a message archive, but
it's horribly slow.) Corrections and comments are welcome.
