To anyone out there who is thinking of a Grand Unified Infant
Mortality Solution, here's another thing that vastly complicates
things, and that we don't yet have a workable solution for yet: prompt
finalization.
my %x;
{ # start scope
my $timer1 = Timer->new();
my $timer2 = Timer->new();
$x{timer} = $timer2;
...
} # $timer1->DESTROY should be called
# $timer2->DESTROY should NOT be called
Right now, the only correct implementation of this that has been
proposed is to do a full DOD run at the end of every single scope. We
can do minor optimizations of that, by for example suppressing the DOD
if no object that implements a DESTROY method is live, but that's it.
At the moment, this threatens to make perl6 the *slowest* language
hosted by Parrot! (Since we haven't implemented any other languages
yet that need this.) It is possible that this problem will be fixed by
weakening the finalization guarantees in the language definition, but
it's definitely something to worry about.
The connection to the infant mortality problem is just that some
solutions might make this easier. Or harder. For example, the current
conservative stackwalk breaks even the painfully slow solution: there
might be a stale pointer somewhere on the C stack (or in a register,
or a saved register window) that keeps the DESTROYable object alive
unnaturally.
