On Wed, Sep 17, 2008 at 10:01:12AM -0500, Patrick R. Michaud wrote:
> On Tue, Sep 16, 2008 at 09:01:06PM -0700, Stephen Simmons wrote:
> > Using the more elaborate version of the testcase behind #58294, which has a
> > two and a three argument version of max, what use to compile and execute
> > incorrectly before the bug fix now compiles and segfaults. I suspect this
> > has nothing to do with the changes that fixed #58294, and everything to do
> > with recent MMD changes. But that's speculation
> > I've stripped it down to the max(a,b) and max(a,b,c) definitions and one
> > three-arg call, though a two-arg call produces a similar result. The result
> > is:
> >
> > sully:perl6 stephensimmons$ perl6 experiment/max3.p6
> > Null PMC access in invoke()
> > current instr.: '_block11' pc 44 (EVAL_14:19)
>
> I think there's something wrong with Rakudo's code generation
> here; see the --target=pir output for max3.p6. [...]
> ## 2 argument form
> .sub "max" :multi() :lexid("25") :outer("23")
> ## 3 argument form
> .sub "max" :multi() :lexid("33") :outer("23")
>
> Those two empty :multi() declarations look very suspicious to me,
> but I'm not familiar enough with the new MMD implementation to know
> how it's supposed to work.
I just checked with Jonathan on IRC, and he says the empty :multi()
declarations are correct here. So that's not the problem.
Actually, I suspect the problem may be that 'max' is already a
builtin function in Perl, and that the conflict comes because
the builtins (written in PIR) are still using Parrot's MultiSub
while the ones written in Perl 6 are using the new Perl6MultiSub
implementation. If I change the function name in max3.p6 to
be something other than 'max', it appears to work:
$ cat max3.p6
multi sub max3($a, $b) {
if defined $a && defined $b {
if $a >= $b { return $a } else { return $b }
}
elsif defined $a { return $a }
elsif defined $b { return $b }
else { return undef }
}
multi sub max3($a, $b, $c) {
return max3(max3($a, $b), $c);
}
say "6 <" ~ max3(9,2,1) ~ ">";
$ ./parrot perl6.pbc max3.p6
6 <9>
$
So, this problem should be "fixed" when we get the builtins to be
written in Perl 6 (or at least using Perl6MultiSubs).
Pm
