>I strongly agree with the general direction of adding some 'harmless' binary
>header. And, while we're talking about it, why not adding the 'expected file
>size' in it?! This way the image could check immediately if something's
>obviously broken.

Indeed, we might consider a number of things to put in that header.

For example, it would be nice to control the allocation of memory 
between object memory and system "slop," so that large plugins with 
substantial memory space can be accomodated on sufficiently large 
machines without recompiling the VM.  Presently, the MacOS VM appears 
to allocate a fixed (and constant in the VM) amount of slop (0.5M 
when last seen).  It would be nice if this could be placed in a file 
somewhere so that the VM can allocate memory differently, if need be, 
on bootup.