[Mesa-dev] [PATCH] mesa: Fix test for big-endian architecture in compiler.h

[Oded Gabbay]

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On Sat, Feb 13, 2016 at 2:39 AM, Roland Scheidegger <sroland at vmware.com> wrote:
>
> Am 12.02.2016 um 10:01 schrieb Jochen Rollwagen:
> > Hi,
> >
> > i think i found & fixed a bug in mesa concerning tests for big-endian
> > machines. The defines tested don't exist or are wrongly defined so the
> > test (probably) never fires. The gcc defines on my machine concerning
> > big-endian are
> >
> > jochen at mac-mini:~/sources/mesa$ gcc -dM -E - < /dev/null | grep BIG
> > #define __BIGGEST_ALIGNMENT__ 16
> > #define __BIG_ENDIAN__ 1
> > #define __FLOAT_WORD_ORDER__ __ORDER_BIG_ENDIAN__
> > #define _BIG_ENDIAN 1
> > #define __ORDER_BIG_ENDIAN__ 4321
> > #define __BYTE_ORDER__ __ORDER_BIG_ENDIAN__
> >
> > The tested values in current mesa are quite different :-)
> >
> > The following patch fixes this.
> >
> > diff --git a/src/mesa/main/compiler.h b/src/mesa/main/compiler.h
> > index c5ee741..99c63cb 100644
> > --- a/src/mesa/main/compiler.h
> > +++ b/src/mesa/main/compiler.h
> > @@ -52,7 +52,7 @@ extern "C" {
> >   * Try to use a runtime test instead.
> >   * For now, only used by some DRI hardware drivers for color/texel
> > packing.
> >   */
> > -#if defined(BYTE_ORDER) && defined(BIG_ENDIAN) && BYTE_ORDER == BIG_ENDIAN
> > +#if defined(__BYTE_ORDER__) && defined(__BIG_ENDIAN__) &&
> > __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
> >  #if defined(__linux__)
> >  #include <byteswap.h>
> >  #define CPU_TO_LE32( x )       bswap_32( x )
> >
>
> Note that on some platforms this file would include endian.h - which
> defines those BYTE_ORDER etc. values. Albeit it includes this _after_
> these ifdefs...
> But don't ask me how this is really supposed to work...
>
> Roland

<stdlib.h> includes <bits/waitstatus.h> which includes <endian.h>

However, this depends on the c/h files to include <stdlib.h> before
including "compiler.h", which doesn't always happen (e.g
dummy_errors.c) and it is a very fragile situation.

So I think this is a good fix and this patch is:
Reviewed-by: Oded Gabbay <oded.gabbay at gmail.com>

Jochen,

Note that I downloaded this patch from pw and it was malformed. I
don't know if its a pw problem or a problem in how you sent the patch
to the ml.

    Oded


>
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