This Week on perl5-porters (28 June / 4 July 2004)
This was a week rich in discussion. Read about programming with threads,
UTF-8 crashes and leaks (and fixes), parsing, globbing, deparsing, and
other things.
Destructors and ithreads
Eric Garland shares his thoughts about how destructors work with
ithreads. Destructors are mostly used to free some external resources
(managed by a library) and thus should be run in most cases at
application exit time (and not at thread destruction time). Thus, with
the current implementation of desctructors (where objects are cloned
among threads and destroyed when the thread ends), destructors should
refcount external resources by hand and free them only at appropriately
late times.
Elizabeth Mattijsen submits a pure perl solution, that uses CLONE() (and
says that it's probably too late to change the meaning of destructors in
perl.) Eric proposes to make variables selectively cloneable. Dave
Mitchell points out that it would be impractical.
http://groups.google.com/groups?selm=40E31208.5020506%40ericgarland.com
Stas Bekman wishes that, in addition of being a class method, CLONE()
could be also called on each object that can() CLONE() at thread
creation time. This would be easier than maintaining by hand a list of
weak references to each object created. Nicholas Clark proposes to call
the class method CLONE() with all objects into @_, which could be
cumbersome if there are lots of objects. Dave wonders about the
potential problems that would be caused by inheritance.
http://groups.google.com/groups?selm=40E5A3BE.30302%40stason.org
B::Deparse and postponed for() scoping
Torsten Hofmann reports that the following construct is not handled
correctly by B::Deparse, due to the scoping of the lexicals : (bug
#30504)
do_something() for my ($foo, $bar, $baz);
Stephen McCamant sent a proof-of-concept patch. Yves Orton asked about
the deparsing of "my $foo if 0", to which Rafael answered that
B::Deparse had no easy way to reconstruct the original code -- which
corresponds to a deprecated construct anyway.
http://groups.google.com/groups?selm=rt-3.0.11-30504-91514.16.8566653002298%40perl.org
Memory leak with "eq" and UTF-8
Bug #30509, about the string comparison operator "eq" leaking memory
with UTF-8 strings in a function defined before the encoding module is
loaded, was promptly fixed by Dave Mitchell.
UTF8 stack crash in Safe compartments
Dave also fixed bug #30258, which was reported a couple of weeks ago:
perl panics when one tries to use split() on an UTF-8 string from an
Safe compartment.
http://groups.google.com/groups?selm=20040702022315.GD1941%40iabyn.com
Parser corruption
Andrew Pimlott produced a malformed program that causes memory
corruption in the parser. This doesn't happen in bleadperl, since byacc
has been replaced by bison in it. (Bug #30518.)
More parsing
Peter Dintelmann finds out that "keys %!" produces a warning, "Use of
"keys" without parentheses is ambiguous". Rafael says that this kind of
warning is implemented by heuristics that only try to be accurate in
most cases. Nicholas finds that the "%" is optional for the argument of
keys().
http://groups.google.com/groups?selm=8FD9B6A658383E468B55D364D1A99516018571F1%40ffz00zm6.ffz00e.mail.dresdner.net
File::Glob and shell idioms
Jaap Karssenberg reports (bug #30553) some oddities about the behavior
of File::Glob regarding brace expansion (th{is,at}), existing files,
and options; notably when there is only one item between the braces.
Rafael points out that the underlying implementation conforms to BSD
standards (in fact it's ripped from OpenBSD) and that he's not very
surprised by the current behaviour (see the mails for details.)
http://groups.google.com/groups?selm=rt-3.0.11-30553-91751.1.29752801968813%40perl.org
Magic and lvalues
Bug #30582 demonstrates that you can't return an hash element from an
lvalue subroutine when the hash has magic attached to it.
http://groups.google.com/groups?selm=rt-3.0.11-30582-91886.18.5112021131844%40perl.org
Splicing oneself
Glenn Linderman provided an example of splice() that doesn't produce the
intuitive result (bug #30568) :
@stk = ( 1, 2, 3 ); splice @stk, -2, 2, $stk[ -2 ];
Dave Mitchell explains what happens behind the scenes. Ton Hospel
comments that it maybe hasn't to be fixed, "since strictly speaking it's
like using $i + $i++". Wolfgang Laun tweaks the above code so that it
produces a segfault.
http://groups.google.com/groups?selm=rt-3.0.11-30568-91811.14.57126175291%40perl.org
Dup'ing PerlIO handles between different layers
Stas Bekman says that he's "unable to convert an existing perlio handle
into one that is handled by a different perlio layer which requires
extra arguments to open." More precisely,
open my $fh2, "<&:crlf", $fh or die $!;
works, whereas
open my $fh2, "<&:APR", $fh, $p;
doesn't (note the extra argument.) Nick Ing-Simmons suggests another way
to do it, more correct regarding the language, but this other way is yet
to be implemented.
http://groups.google.com/groups?selm=40E4A33A.3010406%40stason.org
Stabilisation
Nicholas Clark posted a first draft of the perldelta for perl 5.8.5.
Rafael uploaded a new version of Safe to the CPAN, incorporating the
latest fixes in bleadperl.
Marcus Holland-Moritz glanced at microperl.
http://groups.google.com/groups?selm=20040702052538.7286dd33%40r2d2
Uri Azoulay is trying to build perl on some more or less exotic systems
(HP-UX 11.00, AIX, OSF).
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] Comments and
corrections welcome.
