[RFC] 4950302: (fs spec) Random write produces different results on Linux vs Windows from same .class

[David Lloyd]

On Thu, Nov 21, 2019 at 12:39 PM Brian Burkhalter
<brian.burkhalter at oracle.com> wrote:
>
>
> On Nov 19, 2019, at 4:52 PM, David Lloyd <david.lloyd at redhat.com> wrote:
>
> What if, on Linux (newer kernels only unfortunately), instead of using
> O_APPEND at open, instead use pwritev2() and pass RWF_APPEND when
> writing if the channel was opened for append?  This would eliminate
> the extra system calls.  If you pass a -1 as the offset to that call
> with that flag set, then the file's offset is updated.
>
>
> With respect to pwritev2(), the RWF_APPEND flag curiously does not appear in Ubuntu 18.04.3 LTS despite this being on a Linux 5 kernel:
>
> $ uname -s -r -v
> Linux 5.0.0-36-generic #39~18.04.1-Ubuntu SMP Tue Nov 12 11:09:50 UTC 2019
>
> According to [1] RWF_APPEND is supposed to be since Linux 4.16. Am I missing something?
>
> Thanks,
>
> Brian
>
> [1] https://manpages.debian.org/testing/manpages-dev/preadv2.2.en.html

It probably has more to do with the glibc (and associated header
files) in use.  You consider directly defining the symbols if a
feature test macro check doesn't satisfy?

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- DML