Bug #39403 for forks: maint-perl: 5.8.9-tobe breaks forks in patch 30039

Next release of forks will include the same workaround for patch 30039 as already implemented for perl 5.9.x and later (5.10.x). I wish there were a more elegant way to hook into "reserved word" attributes, other than a source filter. Any suggestions would be appreciated. Used to be trivial to overload when the 'shared' attribute was passed in the handler chain.

I was able to implement an alternative solution using external hooks (overloaded function calls) into Perl's attribute.pm and CPAN Attribute::Handler. This solution is much better than a source filter (and eliminates the requirement for one going forward with perl > 5.8.8), but still feels like a somewhat clunky solution. Having an interface to overload built-in attributes, like 'shared', would be best, if available. This change will be included in the next CPAN release.

In a nutshell, the forks pragma is a drop-in replacement for ithreads, useful primarily for non-threaded perl builds (including Perl 5.6.x) or for scripts that wish to use ithreads but have memory growth/leak issues when using CPAN modules with native ithreads. To accomplish this, one of the features it must support is the 'shared' attribute to emulate threads::shared variable declaration behavior. Attribute declaration is currently handled using CPAN Attribute::Handlers, which in turn depends on Perl core distribution attribute.pm. The issue is that there was a small bug since perl 5.8.0 that allowed the otherwise reserved 'shared' attribute name to "leak" out to custom attribute handlers, as described here: http://www.nntp.perl.org/group/perl.perl5.porters/2006/08/msg115950.html The core patch, already included in Perl 5.10.0, is referenced here: http://archives.devshed.com/forums/perl-102/change-28753-don-t-promulgate-perl- attributes-1951997.html This behavior change "broke" the CPAN forks::shared module on perl 5.10.0 and now also Perl 5.8.8 patched maintenance builds that include this patch (I assume intended to be included in Perl 5.8.9). The initial workaround was to use a source filter to re-write all '$var : shared' as '$var : Forks_shared', such that the attribute could be trapped by a custom attribute handler. Due to the usual dangers & limitations associations with source filters, I've recently rewritten this (not yet released) to override the internal function that Perl depends on to handle reserved attribute names, like the following: { my $old = \&attributes::_modify_attrs; no warnings 'redefine'; *attributes::_modify_attrs = sub { my ($ref, @attr) = @_; return ($old->(@_), (grep(/^shared$/o, @attr) ? 'Forks_shared' : ())); }; } Personally, I wish there were an interface to override the now trapped 'shared' attribute, like what has been available in Perl 5.6 & 5.8. Perhaps some sort of boolean flag interface in attribute.pm, like: attributes::configure(&attributes::ALLOW_RESERVED_ATTR || &attributes::NO_RESERVED_ATTR_WARNINGS) that allows reserved attributes to be returned to custom handlers (and also prevents them from throwing spurious usage warnings throughout user code when use warnings 'reserved' or $^W==1). Regards, Eric On Thu Oct 02 09:41:54 2008, nick@ccl4.org wrote: Show quoted text