This Week on perl5-porters (17-23 May 2004)

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This Week on perl5-porters (17-23 May 2004)

This week, your P5P summary is featuring phases of the moon, and other funny things that always make the day of the average perl hacker.

Shell.pm

Bug #29585 describes how the Shell module fails to handle filenames with spaces in them. Tassilo provided a patch, but Slaven Rezic pointed out that one could argue that rm("my file") should remove two files, my and file: rm("*") does globbing, after all. Moreover, Shell escapes some characters and not some others.

Therefore Tassilo concluded that there are many possible ways of fixing Shell.pm, but each of them leaves quite a lot to be desired, and Rafael commented that Shell was mostly a toy module.

    http://groups.google.com/groups?selm=rt-3.0.9-29585-87427.8.22064370668613%40perl.org

Scoping bug

Jason Rhinelander found a semantic oddity related to scoping of the $<digit> variables (#29701): in the condition of an if() block, the $1 which is set by a regexp match is still seen after the following block; the $1 which is set by a match in the condition of a while() block isn't seen after the said block.

Rafael comments that this may not be a bug, but doesn't remember why exactly. (Thinking about it, probably because if(), unlike while(), can be followed by two blocks).

    http://groups.google.com/groups?selm=rt-3.0.9-29701-87741.16.8398876872253%40perl.org

File::Find and parameters

Roger Yager proposed a patch to File::Find to allow to pass arguments to the callback subroutine. Gisle Aas mentioned the classical alternative solution, to use a closure as a callback; but, as Mark-Jason Dominus pointed out, this solution isn't always convenient. Thus, a documentation patch to File::Find seems to be appropriate.

    http://groups.google.com/groups?selm=auto-000000152005%40eyestreet.com

Thread creation time and phases of the moon

Jamie Lokier remarked submitted a detailed bug report (#29637) about the factors that might influence the creation time of a new thread. It appears that it's highly sensitive to conditions that shouldn't affect the time: for example, changing the name of a subroutine, or even a space in a comment. This seems to be related to the number of mprotect(2) system calls issued during memory allocation. Those calls come from the malloc() implementation used on the system. Jamie provided enough clues to make Dave Mitchell find a solution: the bug was in the function used to clone pointer tables. Thread cloning time is now apparently faster by a 10% factor.

    http://groups.google.com/groups?selm=rt-3.0.9-29637-87553.11.6565004757339%40perl.org

Tainting and UTF-8

Stas Bekman and Rob Mueller found a situation where turning taintedness on a scalar removes its UTF-8 flag. Sadahiro Tomoyuki proposed a patch, that makes the internal routine sv_utf8_upgrade_flags() understand a sufficient amount of magic to handle taintedness. As a side-effect, his patch makes utf8::upgrade() less tolerant to read-only arguments.

    http://groups.google.com/groups?selm=40AC475F.4010208%40stason.org

Autovivification of new lexicals

Shinya Hayakawa proposed a patch to allow lexicals just declared via my to be autovivified, as in :

    (my $x)->{foo}              # creates a hash

Rafael doesn't have a strong opinion about this language feature. Hugo isn't opposed to, but remarks that the patch lacks regression tests.

    http://groups.google.com/groups?selm=200405211244.31291.tetryl%40tokyoprogrammer.com

In brief

Steve Hay found a way to make perl crash with two files, using the autouse module. Nobody commented. (Bug #29708.)

    http://groups.google.com/groups?selm=rt-3.0.9-29708-87779.17.2965328304932%40perl.org

Chip Salzenberg found a bug in the @a = sort(@a) in-place optimization, which was promptly fixed by Dave Mitchell.

    http://groups.google.com/groups?selm=rt-3.0.9-29790-87979.16.2445637115601%40perl.org

Rafiq Ismael found a regular expression and a string against which it should match, that makes a threaded perl segfault, but not a non-threaded perl. (Bug #29650.)

    http://groups.google.com/groups?selm=rt-3.0.9-29650-87589.10.6574674663369%40perl.org

Dave Mitchell fixed a parsing error in the Switch module (bug #28966) by adding case as a keyword in Text::Balanced.

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 perl5-summary-subscribe@perl.org. Comments and corrections welcome.