linux-kernel - Re: [PATCH] remove abs64()

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Message-Id: <20110412143340.e26fc370.akpm@linux-foundation.org>
Date:	Tue, 12 Apr 2011 14:33:40 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Alexey Dobriyan <adobriyan@...il.com>
Cc:	Randy Dunlap <rdunlap@...otime.net>, linux-kernel@...r.kernel.org,
	behlendorf1@...l.gov, oleg@...hat.com
Subject: Re: [PATCH] remove abs64()

On Wed, 13 Apr 2011 00:16:58 +0300
Alexey Dobriyan <adobriyan@...il.com> wrote:

> On Tue, Apr 12, 2011 at 02:10:40PM -0700, Andrew Morton wrote:
> > On Tue, 12 Apr 2011 14:07:26 -0700
> > Randy Dunlap <rdunlap@...otime.net> wrote:
> > 
> > > > +	__builtin_choose_expr(						\
> > > > +		__builtin_types_compatible_p(typeof(_x), long long),	\
> > > > +		(unsigned long long)({ _x < 0 ? -_x : _x; }),		\
> > > > +	_x)))));							\
> > > > +})
> > > 
> > > that is better?
> > 
> > I think so.
> > 
> > It's a bit concerning that it changes the return type of abs().
> 
> I haven't read every abs() user, but, yes, sizeof(abs()) silently
> changing is the issue.

It changes signedness_of(abs(signed_expr)) as well.  That changes the
signedness of expressions which use abs() and on and on.
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