2GB changes file and a pony (was: [squeak-dev] ALL CLEAR (Re: CompiledMethodTrailers ready for use))

David T. Lewis lewis at mail.msen.com
Thu Dec 24 05:54:47 UTC 2009


On Wed, Dec 23, 2009 at 01:19:43AM -0800, John McIntosh wrote:
> It should be 64bit since I made that change years back. However most
> (all?) file systems don't support all 64 bit of space. Still it was
> intersting to learn I could make terabyte sparse file on my freebsd
> system.

Let's see (counting on fingers) I think that a 64 bit address
space is about a trillion times bigger than the current changes
files limit, so that should be sufficient for the next few years.

> 
> So is it 2gb or 4gb? Is that a limit due to 32bit signed numbers?

Various FAT and Linux file systems are limited to 2GB. Very likely
it's due to the use of signed ints for addressing. I'm just guessing
here, but if you use a signed int, you can easily tell if the size
exceeds 2GB by testing for file pointer less than zero. Besides,
who would ever dream of trying to address more than 2GB of space
for a single file? I mean, how may floppy disks is that, anyway?

If we ever get to the point where this matters for a Squeak changes
file, then it will absolutely, positively be time for someone to
burn the disk packs. It will be a very large bonfire, and we can
all roast marshmellows :)

Dave




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