On Thu Dec 04 04:35:43 2008, pmichaud wrote:
> On Wed, Dec 03, 2008 at 03:54:16PM -0800, Carl Mäsak wrote:
> > # New Ticket Created by "Carl Mäsak"
> > # Please include the string: [perl #61034]
> > # in the subject line of all future correspondence about this issue.
> > # <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=61034 >
> >
> >
> > Rakudo r33458:
> >
> > $ ./perl6 -e 'my $a = do given 5 {}'
> > Null PMC access in isa()
> > [...]
> > Segmentation fault
> >
> > As soon as the given block contains _something_ (when, default, or
> > just about anything else), the error goes away.
>
> Rakudo probably thinks the {} is an empty hash, and gets all
> confused from there.
>
Turns out not - the problem actually is that for empty blocks with no
statements in, we emitted a:
.return ()
Which meant that the thingy calling it got a Null PMC. infix:= then did
an isa on it, which then gave the error.
Where to fix this takes some care - since a block may get transformed
into a hash composer, we can't just give every block that is empty an
undef in somewhere like, say, the pblock action (well, we can, but only
if it actually has a lambda). Anyway, I wrote a routine to do this and
called it from xblock and in pblock if we have a lambda, which fixes the
original bug, the following:
my $x = -> {}; my $y = $x();
And no doubt a variety of other Null PMC accesses that could have
happened. And of course, it passes the spectests. So, in as git 9a5c690,
and assigning to moritz++ for tests.
Thanks,
Jonathan
