Re: Large files on 32 and 64 bits ystem

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

On May 25, 9:13 pm, Olivier Scalbert <olivier.scalb...@algosyn.com>
wrote:
> Hello everybody,
>
> Here is my weekly question ....
>
> I need to create a file that has 2540160000 bytes, that is a little more
> than 2**31 bytes.
>
> On a 64 bits linux box, it is ok, but on a 32 bits linux box, I have:
> raised ADA.IO_EXCEPTIONS.DEVICE_ERROR : s-fileio.adb:1135

That line indicates that the GNAT run-time library delegates the write
to fwrite(3), so your question really boils down to whether the C run-
time library has support for large files or not.  What filesystem type
do you use on your machines? (I use XFS which supports files up to 8
exabytes :) )

> The file length is: 2147483647, which is 2**31 - 1

This limitation exists on FAT16 ("msdos" in Linux parlance). Newer
filesystems have higher limits.

> Is it possible to write more than 2**31 bytes with an Ada program on a
> 32 bits linux ?

32-bit Linux has "large file support" using either a dedicated 64-bit
API or the O_LARGEFILE flag supported in open(2) since glibc 2.2. It
might be a good idea to check how GNAT's run-time library deals with
this API but I don't have the time right now. Anyone?

--
Ludovic Brenta.