Re: [Xen-devel] [PATCH 1 of 5] blktap: remove HAVE_BYTESWAP_H checking, since it's defined by qemu

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2011-12-19 at 11:46 +0000, Roger Pau Monnà wrote:
> 2011/12/19 Ian Campbell <Ian.Campbell@xxxxxxxxxx>:
> > On Mon, 2011-12-19 at 11:28 +0000, Roger Pau Monnà wrote:
> >> 2011/12/19 Ian Campbell <Ian.Campbell@xxxxxxxxxx>:
> >> > On Mon, 2011-12-19 at 11:26 +0000, Roger Pau Monnà wrote:
> >> >> 2011/12/19 Ian Campbell <Ian.Campbell@xxxxxxxxxx>:
> >> >> > I think this is the correct option. No need to undef stuff. There is
> >> >> > only one other include of byteswap.h in blktap.
> >> >> >
> >> >>
> >> >> On uclibc, byteswap.h gets included by default, because _GNU_SOURCE
> >> >> implies _BSD_SOURCE there. One solution is to add _POSIX_SOURCE, which
> >> >> prevents the addition of _BSD_SOURCE.
> >> >
> >> > What path of includes leads to the inclusion of byteswap.h?
> >>
> >> This one:
> >>
> >> stdlib.h -> sys/types.h -> endian.h -> (becasue __USE_BSD is defined) 
> >> byteswap.h
> >
> > Hrm :-/
> >
> > So on the flip side which platforms don't have this header at all?
> >
> > William suggested BSD doesn't but the use of __USE_BSD seems to suggest
> > otherwise?
> >
> > Does NetBSD have byteswap.h?
> 
> 
> Nope, but NetBSD has it's own preprocessor case:
> 
> #if defined(__NetBSD__)
> #include <sys/endian.h>
> #include <sys/types.h>
> 
> Doesn't have byteswap.h per se, but the functions are there. NetBSD
> and OpenBSD are covered, because they have their specific cases, so
> only Solaris and Linux are left to this case.

Solaris isn't an issue these days.

So, I think the approach used by tools/blktap2/include/libvhd.h should
be used in tools/blktap2/drivers/bswap.h too. i.e. #include byteswap.h
for Linux and remove the local definitions of the swap functions/macros.

Ian.



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