Re: Weirdest thing ever

[Paul Crawford <psc@sat.dundee.ac.uk>]

Dear Xavier,
> While it is conceivable that a DOS program could read beyond 2GB, it is
> very unlikely it could seek to those positions, and very certain it
> could not do so beyond 4GB.

Just to say that in the course of other testing here, I looked to see 
what the Microsoft C6.0 library calls for filelength() did with 64-bit 
dosemu. What I found was:

With 32-bit Linux/dosemu it can't open files >2GB.

With 64-bit it can open files >2GB but sees the length incorrectly:

For <4GB it is correct if you treat the returned value as unsigned. This 
may be the case in some software, but it is unlikely to be universal.

For files >4GB it seems to only get the lower 32-bits of the size, so 
the file appears (incorrectly) to be less than 4GB in size. I would have 
prefered the system to return (4GB-1) as at least you know the file is 
very big in this case!

However, I have not tested to see if useful data access is possible >2GB 
as I don't have any DOS applications that use very large files.

Regards,
Paul
-- 
Dr. Paul S. Crawford
Satellite Station
Dundee University
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