Adding a new imediate type

Bert Freudenberg bert at
Mon Jan 2 16:33:32 UTC 2006

Hans-Martin did that back in 97:

- Bert -

Am 02.01.2006 um 12:51 schrieb Peter Crowther:

>> From: [...] Joerg Beekmann
>> Can anyone comment on how much work would be involved in
>> 1) Adding a new 32bit field to the object header
> Nasty.  I tried it back in the 2.2 days, and failed.  My biggest  
> problem
> was getting the garbage collector stable.
>> 2) Adding a new immediate type like integer, presumable by adding
>> another tag bit.
> Also nasty - there aren't any more tag bits, and tweaking with the
> header format also involves the GC.  If you're going to do this,  
> look at
> the compact classes instead and see whether you can make yours  
> compact.
> Last I looked, I think there were a couple of spares.  Note that  
> changes
> to compact classes did *not* involve image format or VM changes last I
> looked.
>> Do these tasks involve
>> tracking down a bunch of constants and then rebuilding everything,
>> tedious but a with a known path to follow. Or will this
>> involve much more.
> Much, much more.
> 		- Peter

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