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

[John M McIntosh]

Oops, didn't see this, but had just sent a note to David Lewis saying I think there is another change needed. 

On 2010-06-15, at 8:52 PM, David T. Lewis wrote:

> 
> On Tue, Jun 15, 2010 at 11:17:48AM -0700, ungar at mac.com wrote:
>> 
>> On Jun 15, 2010, at 1:02 AM, John M McIntosh wrote:
>>> 
>>> PS the reason why David thundered into this is because  
>>> 
>>> (a) on a 32bit system with 32bit image the oops start address is never zero, base is constant 0
>>> (b) on a 64bit system with 64bit image the oops start address is never zero, base is zero
>>> (c) on a 64bit system with 32bit image the oops start address is zero, offset by the mmap as the base
>>> (d) on a 32bit system with 64bit image the oops start address is never zero (and the image size would be less than the 32bit address range), base is constant zero
>>> 
>> 
>> Exactly!
> 
> John,
> 
> Change set attached to the Mantis report, hopefully implementing the
> change as you proposed. I think all that is needed is to use the
> value -1 to represent an invalid object memory pointer, rather than 0.
> This should work for 32-bit and 64-bit object word size.  It limits
> 32 bit address range to 32 bits, but this restriction exists already
> in many places and should cause no additional problems here.
> 
> Dave
> 

--
===========================================================================
John M. McIntosh <johnmci at smalltalkconsulting.com>   Twitter:  squeaker68882
Corporate Smalltalk Consulting Ltd.  http://www.smalltalkconsulting.com
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