Question about sysdeps/unix/sysv/linux/fcntl.c

Question about sysdeps/unix/sysv/linux/fcntl.c

[Hongzhi, Song]

Hi all,

I have a issue on ltp relevant glibc.

https://github.com/linux-test-project/ltp/issues/395


Could someone tell how to fix it?



I also want to know that under what circumstances should we use fcntl 
and fcntl64.


Under what circumstances are the __OFF_T_MATCHES_OFF64_T and 
_FILE_OFFSET_BITS defined?


Why does 32-bit arch calls fcntl64, but 64-bit arch calls fcntl traced 
by strace tool?


Thanks,

Hongzhi

Re: Question about sysdeps/unix/sysv/linux/fcntl.c

[Florian Weimer]

On 09/13/2018 03:57 PM, Hongzhi, Song wrote:
> Hi all,
> 
> I have a issue on ltp relevant glibc.
> 
> https://github.com/linux-test-project/ltp/issues/395
> 
> 
> Could someone tell how to fix it?

See the other thread.  I submitted a reply on Github us well:

`fcntl` always uses `struct flock` arguments. If you use `struct 
flock64`, you should be using `fcntl64`. The issue also goes away if you 
build with `-D_FILE_OFFSET_BITS=64` because then `struct flock` and 
`struct flock64` are basically identical.

The reason for the change was that there is no 32-bit version of the OFD 
locks and no separate `F_OFD_SETLKW` constant, and that `fcntl` 
defaulting to 64-bit in 32-bit mode was just too confusing. The 
previous/non-OFD locks did not do that.

Thanks,
Florian