[PATCH xfsprogs 2/2] linux.h: Define xfs_off_t as int64_t

[Felix Janda]

Dave Chinner wrote:
> On Fri, Aug 05, 2016 at 10:02:41AM +0200, Felix Janda wrote:
> > Dave Chinner wrote:
> > > On Mon, Aug 01, 2016 at 08:54:10AM +0200, Felix Janda wrote:
> > > > Christoph Hellwig wrote:
> > > > > On Sat, Jul 30, 2016 at 03:37:37PM +0200, Felix Janda wrote:
> > > > > > int64_t is guaranteed to have the correct size and signedness and is
> > > > > > always avaible because linux.h has a <inttypes.h> include.
> > > > > > 
> > > > > > Fixes compilation error "unkown type name 'off64_t'" on linux when the
> > > > > > public header <xfs.h> is included without _LARGEFILE64_SOURCE or
> > > > > > _GNU_SOURCE defined. This bug was introduced in commit
> > > > > > cb898f157f8410a03cf5f3400baa1df9e5eecd33.
> > > > > 
> > > > > I would much prefer to just define _LARGEFILE64_SOURCE in linux.h..
> > > > 
> > > > Thanks for the suggestion, but that does not work if the system header
> > > > defining (or not) off64_t is included before the xfs headers.
> > > 
> > > Which, to me, is a build bug in whatever code is including the xfs
> > > headers.  Isn't it the responsibility of the build environment to
> > > ensure the dependencies of the libraries being used are correctly
> > > met?
> > 
> > Every program using the xfs header is supposed to know that (only on
> > linux) since commit cb898f157f8410a03cf5f3400baa1df9e5eecd33 it is
> > necessary to define _LARGEFILE64_SOURCE or _GNU_SOURCE?
> 
> Which, I'd say, most already do, because anything trying to use XFS
> ioctls needs to be 64 bit offset clean, even on 32 bit systems.  I
> don't see any problem with requiring it when including a header
> that exposes ioctl interfaces with 64 bit file size/offset fields
> in them....

The easiest way to be 64bit clean is to use _FILEOFFSET_BITS=64. Then
off_t is 64bit on all architectures and it is impossible to use 32bit
interfaces. However the type off64_t will still not be defined...

(On the other hand, when just using _LARGEFILE64_SOURCE it is still
easy to mix 32 and 64bit interfaces.)

Please refer to the "Using LFS Section" of:

http://users.suse.com/~aj/linux_lfs.html

Cheers,
Felix