linux-kernel - RE: [PATCH 1/1] minmax.h: Slightly relax the type checking done by min() and max().

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Message-ID: <6fc56385a90742c7ad21a68403dc27df@AcuMS.aculab.com>
Date:   Mon, 28 Nov 2022 09:13:50 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     David Laight <David.Laight@...LAB.COM>,
        LKML <linux-kernel@...r.kernel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>
CC:     Steven Rostedt <rostedt@...dmis.org>,
        'Joe Perches' <joe@...ches.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: RE: [PATCH 1/1] minmax.h: Slightly relax the type checking done by
 min() and max().

From: David Laight
> Sent: 25 November 2022 15:01
> 
> Slightly relax the type checking done by min() and max().
> - Promote signed/unsiged char/short to int prior to the type test.
>   This matches what the compiler does before doing the comparison.
> - Skip the type test if either argument is a positive 'int' constant.
>   Instead cast the constant to 'int', the compiler may promote it
>   back to 'unsigned int' when doing the test.
> 
> Reduces the need to use min_t/max_t() and the possibly unwanted
>   side effects if a type that is too small is specified.
> 
...
> +#define __cmp(x, y, op)	__cmp_maybe_int(__maybe_int_cast(x), __maybe_int_cast(y), op)
> 
>  #define __cmp_once(x, y, unique_x, unique_y, op) ({	\
>  		typeof(x) unique_x = (x);		\

self nak.
That has to be done as:
	typeof(__maybe_int_cast(x)) unique_x = (x);

I will send a V2.

	David

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