[Vm-dev] Re: Numbered primitives in images

[David T. Lewis]

On Sun, Jan 17, 2010 at 08:43:37PM +0530, K. K. Subramaniam wrote:
> On Sunday 17 January 2010 12:50:17 am David T. Lewis wrote:
> > Doing it automatically based on imageFormatVersion would probably
> > work, but has a catch-22 for someone adding closures to an older
> > image (e.g. adding the closure support to Etoys). For that situation
> > you want to be able to turn on closure support even though the image
> > does not yet need them, so perhaps e.g. a "-closures" command line
> > option turn on closure support in that case.
> > 
> > Any other ideas?
> An image may run on a VM on multiple platforms and not all may be at the same 
> rev, breaking backward compatibility between 3.10 and 3.11 may cause more 
> grief than necessary.
> 
> How about patching the VM to check for env variable (say SQUEAK_PRIM311) in 
> addition to checking for -closures?

I guess we're still looking for ideas at this point. As Eliot points
out, rewriting the primitive table (which is probably what we would
do based on s SQUEAK_PRIM311 flag) is a messy hack, and it would be
best not to put that sort of thing into the VM.

Perhaps a BackwardCompatibilityHacksPlugin to keep the messy stuff
out of the main VM would be possible. To extend the challenge a bit
further, it would be interesting to see how far back in time we could
go with a single VM. The ftp.squeak.org site has images going all the
way back to Squeak 1.1.

Dave