[Vm-dev] Out of the box primitives for bit in ObjectHeader?

Mariano Martinez Peck marianopeck at gmail.com
Wed Dec 14 12:24:00 UTC 2011

Hi guys. As you may notice, I always try to push in the direction of a VM
where we can have both things: a) a really cooler super fast VM for
production super critical applications  and b)  the most-flexible-possible
VM for doing reasearh and experiment.

Now I was thinking the following:  we have one free bit in the
ObjectHeader. Let's say you are experimenting with something and you would
like to tag objects, such as, "traversed", "processes", "isProxy", etc. To
do that small experiment you need to modify the VM, adapt the bit, code the
primitives, build the VM, put the smalltalk side part etc etc. So I was
thinking why not providing such small functionality out of the box?  the
idea would be not to give semantics to the bit since each user will do
that. So we just provide the VM with 2 primtives, one to get the value
(#getBitValue) and one to set it (#setBitTo:). Choose the names you want.

Then we do not integrate nothing in our images that use such bit, there
won't be colisions. Then each guy who wants to experiments with that, can
use the primitives and do what he wants.

Some people is doing something with its bit: Jean Batiptse is doing XXX, I
am doing YYY, etc. Either in his work or mine, there are much more changes
that just that bit, so in anyway, I will end up needing my own VM.

Finally, I could help in providing the code if it is needed.

So, what do you think?

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