bug#51857: cross-filesystem copying broken on macOS with coreutils >= 9.0

[Pádraig Brady]

On 15/11/2021 04:02, Sudhip Nashi via GNU coreutils Bug Reports wrote:
> Hello,
>
> Cross-filesystem copying seems to have been broken in the latest coreutils 
> release on macOS. Running a command like ‘cp /usr/bin/clear /tmp/test’ appears 
> to return successfully, but if one analyzes /tmp/test, it’s filled with NULL 
> characters. However, copying works fine when the source and destination file 
> are on the same filesystem. Do you know what might be causing this?
>
> Thanks in advance,
> Sudhip Nashi

What are the source and dest file system types?
Could you send the output of `sudo dtruss cp /usr/bin/clear /tmp/test`?
I suspect SEEK_DATA may have issues on nacOS,
as usage of that is new in coreutils 9.0.

thanks,
Pádraig