Re: [PATCH] xfsprogs: fix crc32 build on big endian

[Dave Chinner <david@fromorbit.com>]

On Fri, Oct 04, 2013 at 09:20:03PM -0500, Eric Sandeen wrote:
> While kernelspace can test #ifdef __LITTLE_ENDIAN, this
> doesn't work in userspace.  __LITTLE_ENDIAN is defined -
> as is __BIG_ENDIAN.
> 
> So we build on all boxes as __LITTLE_ENDIAN, and the
> self-test (thankfully!) fails on big endian boxes.

I'm glad I put that self test into the build now. :)

> Fix this by testing __BYTE_ORDER values.
> 
> And add an else which should never be hit, but just in case...
> 
> Signed-off-by: Eric Sandeen <sandeen@redhat.com>
> ---
> 
> diff --git a/libxfs/crc32.c b/libxfs/crc32.c
> index 1c0d958..0f847d2 100644
> --- a/libxfs/crc32.c
> +++ b/libxfs/crc32.c
> @@ -63,18 +63,20 @@ typedef __u32	u64;
>  static inline u32
>  crc32_body(u32 crc, unsigned char const *buf, size_t len, const u32 (*tab)[256])
>  {
> -# ifdef __LITTLE_ENDIAN
> +#if __BYTE_ORDER == __LITTLE_ENDIAN
>  #  define DO_CRC(x) crc = t0[(crc ^ (x)) & 255] ^ (crc >> 8)
>  #  define DO_CRC4 (t3[(q) & 255] ^ t2[(q >> 8) & 255] ^ \
>  		   t1[(q >> 16) & 255] ^ t0[(q >> 24) & 255])
>  #  define DO_CRC8 (t7[(q) & 255] ^ t6[(q >> 8) & 255] ^ \
>  		   t5[(q >> 16) & 255] ^ t4[(q >> 24) & 255])
> -# else
> +# elif __BYTE_ORDER == __BIG_ENDIAN
>  #  define DO_CRC(x) crc = t0[((crc >> 24) ^ (x)) & 255] ^ (crc << 8)
>  #  define DO_CRC4 (t0[(q) & 255] ^ t1[(q >> 8) & 255] ^ \
>  		   t2[(q >> 16) & 255] ^ t3[(q >> 24) & 255])
>  #  define DO_CRC8 (t4[(q) & 255] ^ t5[(q >> 8) & 255] ^ \
>  		   t6[(q >> 16) & 255] ^ t7[(q >> 24) & 255])
> +# else
> +#  error What endian are you?
>  # endif
>  	const u32 *b;
>  	size_t    rem_len;

Looks good - it matches the other endian checks in the code.

Reviewed-by: Dave Chinner <dchinner@redhat.com>

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

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