[LTP] [PATCH] fcntl.2: F_OFD_XXX needs flock64

[Cyril Hrubis]

Hi!
> Thanks, I think I understand now. I think there are a couple of
> potential fixes...
> 
> The simplest thing is to do what you're suggesting and simply document
> that F_OFD_* locks require large file offsets. If we do that though,
> then I think we also ought to do something to ensure that the build
> breaks if you try to use F_OFD_* commands without large offsets.
> 
> The simplest way would be to put the F_OFD_* constant definitions under
> "#ifdef??__USE_FILE_OFFSET64", but I'm open to suggestions that would
> make the compiler error out with a more helpful error message.

Hmm, I do not think that this is a good idea. The usuall way how to
handle missing constants are fallback definitions such as:

#ifndef F_OFD_FOO
# define F_OFD_FOO xyz
#endif

This wouldn't do much.

Also these should be only disable on 32bit if __USE_FILE_OFFSET64 is not
defined. But you likely meant that here.

> The other option would be to fix glibc and the kernel to handle legacy
> struct flock with F_OFD_ cmd values. That would mean adding F_OFD_*64
> command values and fixing glibc to swap them in appropriately. That's
> doable, but I'm not sure it's really worth it. We'd also have to think
> about how to handle the old kernel/new glibc case (and vice versa), and
> that probably won't be trivial.

I do not think that this is worth the work either.

-- 
Cyril Hrubis
chrubis@suse.cz