Re: [Qemu-devel] [PATCH] build fix: xen on NetBSD/amd64

[malc <av1474@comtv.ru>]

On Fri, 10 Jul 2009, Christoph Egger wrote:

> On Thursday 09 July 2009 21:21:06 Anthony Liguori wrote:
> > Christoph Egger wrote:
> > > Hi!
> > >
> > > Attached patch fixes this build error on NetBSD/amd64:
> > >
> > > hw/xen_blkif.h:20: warning: #pragma pack(psuh[, id], <n>) is not
> > > supported on this target
> > > hw/xen_blkif.h:36: warning: #pragma pack(pop[, id], <n>) is not supported
> > > on this target
> > >
> > > Signed-off-by: Christoph Egger <Christoph.Egger@amd.com>
> >
> > You'll invoke the fury of malc for introducing an identifier that begins
> > with '__' :-)
> 
> In NetBSD, there is this in <sys/cdefs.h> :
> 
> #if __GNUC_PREREQ__(2, 7)
> #define __packed        __attribute__((__packed__))
> #define __aligned(x)    __attribute__((__aligned__(x)))
> #define __section(x)    __attribute__((__section__(x)))
> #elif defined(__PCC__)
> #define __packed        _Pragma("packed 1")
> #define __aligned(x)    _Pragma("aligned " __STRING(x))
> #define __section(x)    _Pragma("section " ## x)
> #elif defined(__lint__)
> #define __packed        /* delete */
> #define __aligned(x)    /* delete */
> #define __section(x)    /* delete */
> #else
> #define __packed        error: no __packed for this compiler
> #define __aligned(x)    error: no __aligned for this compiler
> #define __section(x)    error: no __section for this compiler
> #endif
> 
> 
> > There really isn't pragma pack on NetBSD?  That's ashame.
> 
> No. Above defines are sufficient and portable.

Above defines are sufficient but not anywhere near portable.

> Now you know where the __aligned define in my patch comes from. :-)

You should conditionally include include sys/cdefs.h on NetBSD and not
defining your own version of __aligned (which is forbidden by the
standard).

Few more points:

 a. the file in question already uses aligned attribute _inside_ the
    structures without any macros

 b. unlike all other xen* files the header guard is __XEN_BLKIF_H__
    and not QEMU_XEN_BLKIF_H (that should be fixed too)

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