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Postings from October 2000
Gurusamy Sarathy wrote:
> I doubt that change#1307 is the problem--we call sv_mortalcopy() in
> lots of other situations.
Yes, but not where tied magic is involved. sv_mortalcopy is recursively
calling the FETCH method when called on a tied hash/array. This is
surely broken?
> IIRC, Chip did the work to support self-ties (prompted by Joshua's
> reports, maybe). I remember thinking at the time that the patch that
> we added might not really support self-referential ties in general
> (as opposed a variable tied to itself, in particular). I'm not sure
> about the details now, but it may have been something to do with
> scenarios like A-tiedto-B-tiedto-C-tiedto...tiedto-A not working.
Shouldn't tie magic be disabled when retrieving from the array
'underneath' a tie? Unless this is done, self-ties cannot ever work.
If self-ties are deemed to be unsupported, then pp_tie should detect and
attemt to do so and croak. That is certainly the easiest option. I'm
happy to have a crack at getting them to work correctly, but I'd need
someone with a sufficiently pointy hat to make some suggestions as to
how to do it.
> Whittling it down to a small test case may prove educational.
I can't get it any simpler than this:
package MyTie;
sub TIEARRAY
{
print ("TIEARRAY @_\n");
bless $_[1], $_[0]
}
sub FETCH
{
print ("FETCH @_\n");
return($_[0]->[$_[1]]);
}
package main;
my (@self, @tie);
tie(@self, "MyTie", \@self);
my $val = $self[0];
Run it and it will recurse like this:
TIEARRAY MyTie ARRAY(0x2f508)
FETCH MyTie=ARRAY(0x2f508) 0
FETCH MyTie=ARRAY(0x2f508) 0
FETCH MyTie=ARRAY(0x2f508) 0
FETCH MyTie=ARRAY(0x2f508) 0
FETCH MyTie=ARRAY(0x2f508) 0
FETCH MyTie=ARRAY(0x2f508) 0
...
until it core dumps.
--
Alan Burlison
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