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Date: Thu, 16 Aug 2001 18:49:58 -0700
From: Andrew Morton <akpm@zip.com.au>
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To: Anton Altaparmakov <aia21@cam.ac.uk>
CC: Jeff Dike <jdike@karaya.com>, Alan Cox <alan@lxorguk.ukuu.org.uk>,
        Daniel Phillips <phillips@bonn-fries.net>,
        "David S. Miller" <davem@redhat.com>, tpepper@vato.org,
        f5ibh@db0bm.ampr.org, linux-kernel@vger.kernel.org
Subject: Re: 2.4.9 does not compile [PATCH]
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		<Your message of "Fri, 17 Aug 2001 00:35:02 +0100." <5.1.0.14.2.20010817002825.00b1e4e0@pop.cus.cam.ac.uk> <5.1.0.14.2.20010817015007.045689b0@pop.cus.cam.ac.uk>
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Anton Altaparmakov wrote:
> 
> #define min(x,y) \
>          ({ typeof(x) __x = (x); typeof(y) __y = (y); __x < __y ? __x : __y; })
> 
> int test(int a, int b, int c)
> {
>          return min(a, min(b, c));
> }

Problems occur if the caller happens to pass in variables whose
names confilct with the ones you chose in the above macro:

laptop:/home/akpm> cat t.c
#define min(x,y) \
         ({ typeof(x) __x = (x); typeof(y) __y = (y); __x < __y ? __x : __y; })

int test(int __x, int __y)
{
        return min(__x, __y);		/* sic */
}

main()
{
        printf("%d\n", test(1, 2));
        printf("%d\n", test(2, 1));
}
laptop:/home/akpm> gcc t.c
laptop:/home/akpm> ./a.out
-1073744344
1074305684


So if you replace "__x" with "__dont_use_this_identifier_its_reserved_for_min"
I don't expect anyone could sensibly complain...

-