Re: Classpath build process and VM-specific issues

[Archie Cobbs]

Andrew Haley wrote:
>  > > > I would like the vmdata field type then to be VMClass not Object.
>  > > 
>  > > I disagree, as it imposes a restriction on what vmData actually
>  > > is.  The most obvious implementation of vmData is to be a byte[]
>  > > instance holding the byte of a native pointer to an internal VM
>  > > non-moveable data structure.
>  > 
>  > I'm glad to see we agree (although I don't think it's at all obvious
>  > that it should be a byte[], not all VMs use native code).
>
> Eeeh.  I can't imagine that either.  If there's a strong argument for
> holding native pointer in a byte[] ?

Here's my thinking on this topic. Warning: may not apply to you :-)

Object is good because it is automatically the size of a pointer
on any platform. However, it has one significant disadvantage, which
is that you must special case all such fields in your garbage collector
(unless you have a conservative collector). byte[] avoids this problem.

I remember kaffe had a kaffe.util.Pointer reference type that did this,
and was specially recognized by the GC. Slightly better than Object imho.

-Archie

__________________________________________________________________________
Archie Cobbs      *        CTO, Awarix        *      http://www.awarix.com