linux-kernel - Re: [2.6 patch] asm-generic/int-ll64.h: always provide _

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Date:	Tue, 20 May 2008 12:09:49 +0300
From:	Adrian Bunk <bunk@...sta.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Harvey Harrison <harvey.harrison@...il.com>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [2.6 patch] asm-generic/int-ll64.h: always provide __{s,u}64

On Mon, May 19, 2008 at 06:16:29PM -0700, H. Peter Anvin wrote:
> Adrian Bunk wrote:
>>>>
>>> This is a valid point.  This should be __i486__ for userspace, which 
>>> is  gcc's way to tell you if you're compiling with -march=i486.
>>
>> This doesn't help if you're compiling with e.g. -march=pentium
>
> Yes, it does.  -march=pentium defines __i486__ as well as __i586__, and  
> so on.

$ cat test.c
#include <stdio.h>

int main()
{
#ifdef __i486__
  printf("foobarbaz\n");
#endif

  return 0;
}
$ gcc -O2 -march=i486 -Wall test.c; ./a.out
foobarbaz
$ gcc -O2 -march=pentium -Wall test.c; ./a.out
$ gcc --version
gcc (Debian 4.3.0-4) 4.3.1 20080501 (prerelease)
...
$ /usr/local/DIR/gcc-3.2.3/bin/gcc -O2 -march=i486 -Wall test.c; ./a.out
foobarbaz
$ /usr/local/DIR/gcc-3.2.3/bin/gcc -O2 -march=pentium -Wall test.c; ./a.out
$ /usr/local/DIR/gcc-3.2.3/bin/gcc --version
gcc (GCC) 3.2.3


> 	-hpa

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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