Does GCC really recognize __attribute__ ((bitwise))?

Ian Lance Taylor iant@google.com
Thu Mar 27 17:40:00 GMT 2008


Eus <eus@member.fsf.org> writes:

> When browsing the Linux kernel 2.6.21.5's source code, I noticed a variable
> definition like:
>
> typedef __u64 __bitwise __be64;
>
> Being curious about __bitwise, I found it out to be:
>
> #define __bitwise __bitwise__
>
> that finally turned out to be:
>
> #define __bitwise__ __attribute__((bitwise))
>
> Since it was __attribute__, I tried to find its documentation in GCC texinfo
> file. But, I couldn't find one. Even I have tried to find it out in the Internet.
> But, I still couldn't find one.

There is no "bitwise" attribute in standard gcc.

Looking at the Linux 2.6.24 sources, I see that it is defined as an
attribute only when __CHECKER__ is defined.  This has something to do
with sparse--see Documentation/sparse.txt.  I don't know the details.

Ian



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