[Vm-dev] I think I've found a bug in the 64-bit Squeak VM memory compactor

ungar at mac.com ungar at mac.com
Tue Jun 15 06:32:56 UTC 2010


Great story! Creative fix. Just to clarify, I am talking about the part of the image AFTER the header; where the oops start.

Thanks for the smile,

- David

On Jun 14, 2010, at 6:05 PM, Jecel Assumpcao Jr. wrote:

> Dave,
>> The workaround for my VM is simply to skip those first free words, so that the
>> first word in the heap is a non-free object. (The snapshot code does a GC so all
>> real free objects are gone by this time).
> Doesn't the image start with some header bytes (512 in the case of Unix)
> which end up loaded into the start of the heap? Or do these get stripped
> away at some point?
> This reminds me of an OS I created for the iAPX286. I don't know if that
> particular processor was bad or if it was a design flaw, but jumping or
> calling to byte 0 of a segment didn't work in protected mode. So I moved
> the class pointer to the first two bytes of every segment (we had one
> object per segment and the class pointer had previously been a part of
> the object table) and the bug didn't bother us anymore.
> -- Jecel

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