From: Bill Pringlemeir <bpringle@sympatico.ca>
To: ptb@it.uc3m.es
Cc: "Patrick J. LoPresti" <patl@cag.lcs.mit.edu>,
linux-kernel@vger.kernel.org, torvalds@transmeta.com
Subject: Re: [IDEA+RFC] Possible solution for min()/max() war
Date: 06 Sep 2001 20:52:27 -0400 [thread overview]
Message-ID: <m2y9nrn7p0.fsf@sympatico.ca> (raw)
In-Reply-To: <200108302327.f7UNRvl04257@oboe.it.uc3m.es>
In-Reply-To: "Peter T. Breuer"'s message of "Fri, 31 Aug 2001 01:27:57 +0200 (MET DST)"
>>>>> Peter T Breuer <ptb@it.uc3m.es> writes:
> To give you all something definite to look at, here's some test
> code:
> // standard good 'ol faithful version
> #define __MIN(x,y) ({\
> typeof(x) _x = x; \
> typeof(y) _y = y; \
> _x < _y ? _x : _y ; \
> })
> // possible implemetation with type sanity checks - alter to taste
> #define MIN(x,y) ({\
> const typeof(x) _x = ~(typeof(x))0; \
> const typeof(y) _y = ~(typeof(y))0; \
> void MIN_BUG(); \
> if (sizeof(_x) != sizeof(_y)) \
> MIN_BUG(); \
> if ((_x > 0 && _y < 0) || (_x < 0 && _y > 0)) \
> MIN_BUG(); \
> __MIN(x,y); \
> })
[snip]
Sorry, I have been away for a while. I think that I was talking about
a similar approach when Linus was away and David introduced the 3 arg
min/max. I just went through 1800 LKML emails and I am not quite
clear what happened. I have put my code that I posted earlier at the
end of this email. This was the result of someone's `fanciful comment'
`what if gcc could handle "if(strcmp(typeof(a),typeof(b))!=0)"'.
So here is the important part. The code Peter has introduced a cast
in the lines "const typeof(x) _x = ~(typeof(x))0;" etc. I think that
the approach of declaring a variable of the type and initializing to
zero and then comparing "x - 1" _might_ be better.
The version of min() at the end calls the following an error, were
Peter's does not [after removing the sizeof() restriction].
unsigned char Cx = 1; unsigned int Ix = 1; unsigned long Lx = 1;
Ix = min(Cx,Ix); Lx = min(Cx,Lx);
Here the unsigned char is being promoted to int as discussed before.
I think that this is `more faithful' as what we are try to achieve is
to check the sign that will be used in the min comparison; almost
like applying a proper warned signed selectively to the min/max
macros.
Otherwise, I think we have independently came up with the same thing
and the `error' throwing can of course be changed to whatever.
fwiw,
Bill Pringlemeir.
[start code]
#define bug_paste_chain(a,b) a##b
#define bug_paste(a) bug_paste_chain(BUG_AT_LINE_,a)
#define min(x,y) \
\
({extern void bug_paste(__LINE__) (void); \
typeof(x) _x = 0; typeof(y) _y = 0; \
if ((_x-1>0 && _y-1<0) || (_x-1<0 && _y-1>0)) \
bug_paste(__LINE__)(); \
_x = (x), _y = (y); (_x>_y)?_y:_x; \
})
#include <stdio.h>
int main(int argc, char *argv[])
{
signed char cx = 1, cy = 2;
signed short sx = 1, sy = 2;
signed int ix = 1, iy = 2;
signed long lx = 1, ly = 2;
unsigned char Cx = 1, Cy = 2;
unsigned short Sx = 1, Sy = 2;
unsigned int Ix = 1, Iy = 2;
unsigned long Lx = 1, Ly = 2;
cx = min(cx,cy); Cx = min(Cy,Cx); sx = min(sx,sy);
Sx = min(Sx,Sy); ix = min(iy,ix); Ix = min(Iy,Ix);
lx = min(ly,ly); Lx = min(Lx,Ly);
/* No warning. */
/* Lx = (typeof(Lx))min(Lx,&Ly); */
printf("%d %d %hd %hd %d %d %ld %ld\n", cx, Cx,
sx,Sx,ix,Ix,lx,Lx);
cx = -1; Cx = 0;
cx = min(cx,cy); sx = min(cx,sy);
ix = min(cx,ix); lx = min(cx,ly);
Cx = min(Cx,Cx); Sx = min(Cx,Sy);
Ix = min(Ly,Ix); Lx = min(Ix,Ly);
/* correctly gives warning! */
/* Ix = min(Cy,Ix); Lx = min(Cx,Ly); */
printf("%d %d %hd %hd %d %d %ld %ld\n", cx, Cx,
sx,Sx,ix,Ix,lx,Lx);
min((unsigned)ix,sizeof(ix));
/* BUG? printf ("%d\n", min(Iy, 10)); */
printf ("%d\n", min(cx, 20));
printf("min(3,4,5) %d\n", min(min(5,4),3));
return 0;
}
/* gcc -Wall -O2 -o test test.c */
[end code]
next prev parent reply other threads:[~2001-09-07 0:58 UTC|newest]
Thread overview: 159+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-08-24 22:42 [IDEA+RFC] Possible solution for min()/max() war Brad Chapman
2001-08-24 23:21 ` Ben LaHaise
2001-08-24 23:58 ` Brad Chapman
2001-08-25 0:13 ` Alexander Viro
2001-08-25 0:25 ` Brad Chapman
2001-08-25 0:34 ` Alexander Viro
2001-08-25 0:53 ` Brad Chapman
2001-08-25 1:15 ` Alexander Viro
2001-08-25 11:21 ` Brad Chapman
2001-08-27 0:02 ` Rusty Russell
2001-08-28 4:59 ` Linus Torvalds
2001-08-28 5:20 ` Alexander Viro
2001-08-28 5:51 ` Linus Torvalds
2001-08-28 11:10 ` Alan Cox
2001-08-28 14:15 ` Linus Torvalds
2001-08-28 20:06 ` John Alvord
2001-08-28 12:42 ` Roman Zippel
2001-08-28 13:27 ` Linus Torvalds
2001-08-28 14:19 ` Roman Zippel
2001-08-28 15:14 ` Linus Torvalds
2001-08-28 15:44 ` Henning P. Schmiedehausen
2001-08-28 15:55 ` Russell King
2001-08-28 16:05 ` Alan Cox
2001-08-28 16:53 ` Roman Zippel
2001-08-28 16:39 ` Roman Zippel
2001-08-28 21:51 ` Mike Castle
2001-08-29 0:33 ` Daniel Phillips
2001-08-29 1:13 ` Linus Torvalds
2001-08-29 15:42 ` Daniel Phillips
2001-08-29 16:02 ` David Lang
2001-08-29 23:49 ` Daniel Phillips
2001-08-30 2:05 ` Bill Rugolsky Jr.
2001-08-30 3:28 ` Linus Torvalds
2001-08-30 13:10 ` Ion Badulescu
2001-08-30 13:17 ` David Woodhouse
2001-08-30 13:26 ` Ion Badulescu
2001-08-30 16:09 ` Linus Torvalds
2001-08-30 16:28 ` Ion Badulescu
2001-08-31 12:50 ` Jamie Lokier
2001-08-31 13:45 ` Roman Zippel
2001-08-31 16:27 ` Jamie Lokier
2001-08-30 16:31 ` Ben LaHaise
2001-08-30 16:38 ` Peter T. Breuer
2001-08-30 19:51 ` David Weinehall
2001-08-30 20:16 ` Peter T. Breuer
2001-08-30 20:31 ` Daniel Phillips
[not found] ` <mit.lcs.mail.linux-kernel/200108301638.SAA04923@nbd.it.uc3m.es>
2001-08-30 22:42 ` Patrick J. LoPresti
2001-08-30 23:27 ` Peter T. Breuer
2001-08-31 0:55 ` Linus Torvalds
2001-08-31 1:28 ` Peter T. Breuer
2001-08-31 13:22 ` Peter T. Breuer
2001-08-31 14:02 ` Linus Torvalds
2001-08-31 15:34 ` Peter T. Breuer
2001-08-31 22:25 ` [PATCH] i386 SA_INTERRUPT logic Jonathan Lundell
2001-08-31 12:01 ` [IDEA+RFC] Possible solution for min()/max() war Roman Zippel
2001-08-31 12:13 ` Peter T. Breuer
2001-08-31 12:58 ` Roman Zippel
2001-08-31 13:29 ` Peter T. Breuer
2001-08-31 14:12 ` Roman Zippel
2001-08-31 14:28 ` Peter T. Breuer
2001-08-31 16:30 ` Roman Zippel
2001-09-07 0:52 ` Bill Pringlemeir [this message]
2001-09-07 7:26 ` Peter T. Breuer
2001-09-07 12:28 ` Horst von Brand
2001-09-07 18:03 ` Mark H. Wood
2001-09-07 10:58 ` Peter T. Breuer
2001-09-07 14:39 ` Bill Pringlemeir
2001-09-07 15:17 ` Peter T. Breuer
2001-08-30 13:49 ` Roman Zippel
2001-08-30 16:21 ` Linus Torvalds
2001-08-30 16:41 ` Christopher Friesen
2001-08-30 16:50 ` Linus Torvalds
2001-08-30 17:13 ` Roman Zippel
2001-08-31 1:28 ` Ion Badulescu
2001-08-31 5:08 ` Linus Torvalds
2001-08-31 12:37 ` Jamie Lokier
2001-08-31 13:54 ` Linus Torvalds
2001-08-30 17:01 ` Daniel Phillips
2001-08-30 17:03 ` Peter T. Breuer
2001-08-30 17:26 ` Daniel Phillips
2001-08-31 8:04 ` Kai Henningsen
2001-08-30 21:16 ` Graham Murray
2001-08-30 21:47 ` David Weinehall
2001-08-31 10:10 ` Helge Hafting
[not found] ` <mit.lcs.mail.linux-kernel/m266b51c5c.fsf@barnowl.demon.co.uk>
2001-08-30 22:26 ` Patrick J. LoPresti
2001-08-28 16:09 ` Andreas Schwab
2001-08-28 16:47 ` Roman Zippel
2001-08-28 17:12 ` Bill Rugolsky Jr.
2001-08-28 17:28 ` Roman Zippel
2001-08-28 17:29 ` Richard B. Johnson
2001-08-26 17:59 ` Bill Pringlemeir
2001-08-24 23:59 ` Brad Chapman
2001-08-25 0:07 ` David S. Miller
2001-08-25 0:18 ` Brad Chapman
2001-08-25 0:23 ` David S. Miller
[not found] <20010825021651.I8296@router.ranmachan.dyndns.org>
2001-08-25 0:21 ` Brad Chapman
[not found] <20010825024248.J8296@router.ranmachan.dyndns.org>
2001-08-25 0:54 ` Brad Chapman
[not found] <200108281746.f7SHk1O27199@lists.us.dell.com>
2001-08-28 19:33 ` Brad Chapman
2001-08-28 19:02 ` David Lang
2001-08-28 20:38 ` Brad Chapman
2001-08-28 19:25 ` David Lang
2001-08-28 20:34 ` Andreas Schwab
2001-08-28 20:42 ` Brad Chapman
2001-08-28 21:04 ` Christopher Friesen
2001-08-29 9:03 ` Helge Hafting
2001-08-29 1:33 Ignacio Vazquez-Abrams
[not found] <200108291905.f7TJ59T11456@wildsau.idv-edu.uni-linz.ac.at>
2001-08-29 19:11 ` Herbert Rosmanith
2001-08-30 9:56 Herbert Rosmanith
2001-08-30 13:09 ` Helge Hafting
2001-08-30 17:32 mike_phillips
2001-08-30 17:45 ` Ion Badulescu
2001-08-30 20:35 Herbert Rosmanith
2001-08-30 20:44 Herbert Rosmanith
2001-08-30 21:06 ` Peter T. Breuer
2001-08-30 21:14 ` David Woodhouse
2001-08-30 21:32 ` Peter T. Breuer
2001-08-30 21:47 ` David Woodhouse
2001-08-30 21:56 ` Peter T. Breuer
2001-08-30 22:13 ` David Woodhouse
2001-08-30 22:47 ` Peter T. Breuer
2001-08-30 23:02 ` David Woodhouse
2001-08-31 0:08 ` Daniel Phillips
2001-08-30 21:49 ` Mark Zealey
2001-08-30 22:06 ` Peter T. Breuer
2001-08-30 22:14 ` Mark Zealey
2001-08-31 7:04 ` Herbert Rosmanith
2001-08-30 21:17 ` Richard B. Johnson
2001-08-30 21:45 ` Thomas Dodd
2001-08-30 21:46 ` Peter T. Breuer
2001-08-30 23:16 ` David Woodhouse
2001-08-30 23:33 ` David Wagner
2001-08-31 11:18 ` Bernd Schmidt
[not found] <791753058.999219857@[169.254.198.40]>
2001-08-31 0:57 ` Peter T. Breuer
[not found] <20010830174227.A10673@furble>
2001-08-31 1:19 ` Peter T. Breuer
2001-08-31 2:10 ` Peter T. Breuer
2001-08-31 7:43 ` Jonathan Lundell
2001-08-31 8:27 ` Alex Bligh - linux-kernel
2001-08-31 2:34 Andy Chou
2001-08-31 2:48 Rick Hohensee
2001-08-31 14:28 Martin Knoblauch
2001-08-31 14:28 Herbert Rosmanith
2001-08-31 14:37 ` Herbert Rosmanith
[not found] <fa.ehba65v.10i6abc@ifi.uio.no>
[not found] ` <fa.odqvefv.g4k4j6@ifi.uio.no>
2001-08-31 15:45 ` ctm
2001-08-31 16:57 ` Roman Zippel
2001-08-31 17:41 Herbert Rosmanith
2001-08-31 17:57 ` Rik van Riel
2001-08-31 18:13 Herbert Rosmanith
2001-08-31 18:24 Herbert Rosmanith
2001-08-31 18:29 Andy Chou
2001-08-31 18:52 ` Roman Zippel
[not found] <fa.eeq0k8v.1v28iaa@ifi.uio.no>
2001-08-31 18:40 ` Ted Unangst
2001-09-03 20:35 David desJardins
2001-09-04 8:08 ` VDA
2001-09-03 23:16 David desJardins
2001-09-04 9:09 VDA
2001-09-04 13:17 Petr Vandrovec
2001-09-06 1:51 Rick Hohensee
2001-09-06 10:12 ` VDA
[not found] <m2bskndlkt.fsf@sympatico.ca>
2001-09-07 17:39 ` Peter T. Breuer
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