short pointers (32 bit) in 64 bit apps

[Nicholas Sherlock]

On 19/05/2010 8:54 p.m., Reza Roboubi wrote:
> Nicholas Sherlock wrote:
>> On 19/05/2010 3:58 p.m., Reza Roboubi wrote:
>>> Do you know what it takes to do it? How much work for a newcomer to get
>>> up to speed with gcc? (Maybe this should go to the developer list?)
>>
>> You would need to write a memory allocator which divides the address
>> space into 4GB (32-bit pages). Then you could create a new malloc
>> routine which has an extra argument to allow you to allocate memory
>> from within a specified 4GB page. That way you can make all of your
>> allocations for a given data structure lie within the same region.
>
> Since we are trying to _compress_ these structs in the first place
> malloc'ing them individually is pointless anyway. We should probably
> have some sort of custom (fixed size) allocator.

If the pointers only have to refer to memory within the same memory 
allocation, and that allocation is smaller than 4GB, that's a 
significantly more restricted problem. You wouldn't need a custom memory 
allocator, you could just store the difference between the pointer 
target and the pointer's location instead of an absolute pointer. That 
sounds doable.

Cheers,
Nicholas Sherlock