linux-kernel - Re: Linux Kernel include files

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Date:	Tue, 26 Jun 2007 21:32:39 -0400
From:	Kyle Moffett <mrmacman_g4@....com>
To:	Adrian Bunk <bunk@...sta.de>
Cc:	David Woodhouse <dwmw2@...radead.org>,
	Joerg Schilling <Joerg.Schilling@...us.fraunhofer.de>,
	david@...g.hm, LKML Kernel <linux-kernel@...r.kernel.org>
Subject: Re: Linux Kernel include files

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

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