[chuck-users] push but no pop?

Kassen signal.automatique at gmail.com
Sun Apr 12 18:30:34 EDT 2009


> As written, array's popBack() function has a void return.  It would be nice
> if popBack() returned the element it removed, so we could write the code
> like this:

I agree with this, it's not clear to me why it doesn't do this already.
Actually I thought it did but only worked correctly for primitives. I just
tested and that turns out to be a mistake.

I think it's clear that we need this and I hope it'll be addressed one when
somebody goes over the series of bugs related to arrays and type; it can't
be very hard, assuming the other existing issues will be addressed. Our
arrays need some loving care.

> This may be operator error rather than a bug, but the following code:
>        fun Element allocateElement() {
>            if ((_pool.size() => int size) > 0) {
>                _pool[size-1] @=> Element @ element;
>                size-1 => _pool.size;
>                return element;
>            }
>            return new Element;
>        }
> reports:
>        chuck(20184,0xa018a830) malloc: *** error for object 0x5eb6e0:
> double free
>        *** set a breakpoint in malloc_error_break to debug
> I think the problem may be in "return new Element" -- it may be trying to
> return the Element itself, rather than a reference to the Element.  If
> that's the case, though, it seems like something that should be caught at
> compile time.

I suspect this is another case of the bits of the GC that are are already in
there and occasionally collect things before they need to be collected.
Until there is a new version I'm inclined to categorise anything related to
more advanced operations on arrays involving no-primitive types on the
"Clemow's bane" pile. First of all there is the issue that I think we are
seeing here which involves the over-collection of things that aren't (yet)
garbage, secondly there is the issue that if you do manage to get a item out
of a array in a way like this ChucK will somehow lose track of what type it
is at which point there will be issues of a extremely headache-inducing

Mike may be able to help you; I seem to remember him&me got something quite
similar to this to work for some of his code but I forgot the details. The
one thing my memory hasn't repressed is that the solution involved
sprinkling the code with magical "@" signs, more or less at random :¬). I
love ChucK but here be dragons.

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