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Postings from March 2017
On Fri, 10 Mar 2017 07:38:02 -0800, wellnhofer@aevum.de wrote:
> On Fri, 10 Mar 2017 02:16:13 -0800, LeonT wrote:
> > Destructors can and do depend on package variables, this would not
> > solve
> > all non-circular cases.
>
> Right, but it would solve a large class of cases. Also note that Perl
> seems to do the right thing for "my" variables with package scope.
> Only for "our" variables, it seems impossible to get a sane
> destruction order. If you run the program below, $my1 if always
> destroyed before $my2, regardless of initialization order. But "our"
> variables are always destroyed in the DESTRUCT phase without taking
> references between objects into account.
>
> > The proper solution would be to topologically sort the objects and
> > then
> > destroy them in that order (ideally even taking into account that the
> > destruction can add new nodes to the graph), but this is non-trivial
> > to
> > implement and to execute; and obviously would still not solve
> > circular
> > references.
>
> Just because a solution isn't perfect doesn't mean that it shouldn't
> be implemented. Anyway, I'm only asking to acknowledge that this bug
> isn't fixed and to reopen it.
Seems fair enough. I am doing exactly that.
But let me note that simply destroying âourâ variables before the general reference sweep is not so straightforward. If you start by deleting everything stored by globs, then you end up deleting the destructors themselves. Again, deleting everything from globs except subs would only work for some code, and not other code. What Leon Timmermans said about a topological order would probably be the only solution.
> #!/usr/bin/perl
> use strict;
> use warnings;
>
> package TestObj;
>
> sub new {
> my ( $class, $name ) = @_;
> return bless { name => $name }, $class;
> }
>
> sub set_ref {
> my ( $self, $ref ) = @_;
> $self->{ref} = $ref;
> }
>
> sub DESTROY {
> my $self = shift;
> print "Destroying $self->{name}, phase is ${^GLOBAL_PHASE}\n";
> }
>
> my $my1 = TestObj->new('my1');
> my $my2 = TestObj->new('my2');
> $my1->set_ref($my2);
>
> our $our1 = TestObj->new('our1');
> our $our2 = TestObj->new('our2');
> $our1->set_ref($our2);
--
Father Chrysostomos
---
via perlbug: queue: perl5 status: resolved
https://rt.perl.org/Ticket/Display.html?id=32714
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