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From: Christoph Egger <Christoph.Egger@amd.com>
Subject: Re: [Qemu-devel] [PATCH] build fix: xen on NetBSD/amd64
Date: Fri, 10 Jul 2009 14:36:58 +0200
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To: malc <av1474@comtv.ru>
Cc: qemu-devel@nongnu.org

On Friday 10 July 2009 12:18:39 malc wrote:
> 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.

Well, across different compilers, they are.


> > 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).

sys/cdefs.h is included implicitely by any libc standard header on NetBSD.
No need for an #ifdef __NetBSD__ ... #endif for this.

> Few more points:
>
>  a. the file in question already uses aligned attribute _inside_ the
>     structures without any macros

So the pragmas have no effect then ? If so, then just remove them.

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

Easy to fix. Will you do or should I send a diff ?

Christoph

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