On 04/26/2012 11:32 AM, Richard Henderson wrote:
> On 04/26/12 08:25, Jes Sorensen wrote:
>> Just checking mdadm.h and bswap32() is defined like this:
>>
>> #define bswap_32(x) (((x) & 0x000000ffU) << 24 | \
>> ((x) & 0xff000000U) >> 24 | \
>> ((x) & 0x0000ff00U) << 8 | \
>> ((x) & 0x00ff0000U) >> 8)
>>
>> so I am not 100% sure just swapping to an s32 in the struct will work on
>> big endian systems? Will the 0x000000ffU not force the conversion back
>> to unsigned or what happens in this case?
>
> This is actually semi-complicated. c89 or c99 rules? X already of a
> type larger than unsigned int?
>
> But if X is signed int, this entire expression will always be unsigned.
>
> You're certainly better off with a cast as we discussed on irc.
Answering this question is beyond my bitfield/bigendian/littleendian
foo. So nice to have Richard around ;-)
--
Doug Ledford <dledford@xxxxxxxxxx>
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http://people.redhat.com/dledford
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