BZ#13926: Add __bswap_64 for non-GCC compilers

Andreas Jaeger aj@suse.com
Wed Mar 28 18:12:00 GMT 2012


On 03/28/2012 07:05 PM, Jakub Jelinek wrote:
> On Wed, Mar 28, 2012 at 04:51:00PM +0200, Andreas Jaeger wrote:
>> +#else
>> +# define __bswap_constant_64(x) \
>> +     ((((x)&  0xff00000000000000ul)>>  56)				      \
>> +      | (((x)&  0x00ff000000000000ul)>>   40)				      \
>> +      | (((x)&  0x0000ff0000000000ul)>>  24)				      \
>> +      | (((x)&  0x000000ff00000000ul)>>  8)				      \
>> +      | (((x)&  0x00000000ff000000ul)<<  8)				      \
>> +      | (((x)&  0x0000000000ff0000ul)<<  24)				      \
>> +      | (((x)&  0x000000000000ff00ul)<<  40)				      \
>> +      | (((x)&  0x00000000000000fful)<<  56))
>> +
>> +static __inline unsigned long long int
>> +__bswap_64 (unsigned long long int __bsx)
>> +{
>> +  return __bswap_constant_64 (__bsx);
>> +}
>
> How do you know that the non-GCC compiler in question supports
> unsigned long long type at all?  It is not a standard C89 type...
> Why are you using ul rather than ull suffixed constants?

This is copied from the s390 implementation - which I'll fix if we can 
agree on how to do it.

right now the installed header strings/endian.h contains:
#  define htobe64(x) __bswap_64 (x)
#  define htole64(x) (x)
#  define be64toh(x) __bswap_64 (x)
#  define le64toh(x) (x)

So, IMO we should have a definition for __bswap_64.

Would the patch be ok if do the changes that Roland suggested and use 
ull instead (and fix the s390 version the same)?

I do think we require already that a compiler supports "long long" - 
looking at the installed headers there are many places in installed 
headers that use long long already. But I found  __GLIBC_HAVE_LONG_LONG 
in <features.h>. Should I just guard the definition by this? What shall 
we do if it's false - just fail silently?

Andreas
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