linux-kernel - Re: [PATCH] Make is_signed

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Date:   Mon, 30 Sep 2019 00:09:08 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        jani.nikula@...ux.intel.com, joonas.lahtinen@...ux.intel.com,
        rodrigo.vivi@...el.com, intel-gfx@...ts.freedesktop.org,
        rostedt@...dmis.org, mingo@...hat.com
Subject: Re: [PATCH] Make is_signed_type() simpler

On Sun, Sep 29, 2019 at 10:21:48PM +0200, Rasmus Villemoes wrote:
> On 29/09/2019 22.06, Alexey Dobriyan wrote:
> > * Simply compare -1 with 0,
> > * Drop unnecessary parenthesis sets
> > 
> > -#define is_signed_type(type)       (((type)(-1)) < (type)1)
> > +#define is_signed_type(type)       ((type)-1 < 0)
> 
> NAK. I wrote it that way to avoid -Wtautological-compare when type is
> unsigned.

Was is W=1?

godbolt doesn't show it with just -Wall

	https://godbolt.org/z/kCA7mm

And the warning which found i915 case is -Wextra not -Wtautological-compare.