Re: Linux Kernel include files

Kyle Moffett
2007-06-27T01:33:14Z

On Jun 22, 2007, at 11:00:38, Adrian Bunk wrote:
> It would certainly help if Joerg would tell what exactly breaks,
> but I spot one likely problem in include/asm-i386/types.h:
>
> #if defined(__GNUC__) && !defined(__STRICT_ANSI__)
> typedef __signed__ long long __s64;
> typedef unsigned long long __u64;
> #endif
>
> It might make sense to remove the #if and simply require that a C
> compiler under Linux must know about the C99 "long long"?

Gah, this particular topic and a few other similar header-
compatibility ones show up once a month on LKML; I should probably
just make a patch to fix all the types.h files and be done with it.
The proper solution is this:

# if __STDC_VERSION__ >= 19901L
typedef signed long long __s64;
typedef unsigned long long __u64;
# elif defined(__GNUC__)
__extension__ typedef signed long long __s64;
__extension__ typedef unsigned long long __u64;
# else
# error "Your compiler doesn't support long long (IOW: It sucks).
Please get a new one"
# endif

That way if you have any kind of vaguely-long-long-compatible
compiler then it will work, and otherwise you'll get a nice useful
error message. It also makes sure that GCC doesn't spew warnings/
errors when in c89-pedantic mode. The "__extension__" keyword is
designed for use in implementation header files which want to use GCC-
isms unconditionally.

Cheers,
Kyle Moffett