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

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Message-Id: <20110412144032.1fc09497.rdunlap@xenotime.net>
Date:	Tue, 12 Apr 2011 14:40:32 -0700
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Alexey Dobriyan <adobriyan@...il.com>,
	linux-kernel@...r.kernel.org, behlendorf1@...l.gov, oleg@...hat.com
Subject: Re: [PATCH] remove abs64()

On Tue, 12 Apr 2011 14:33:40 -0700 Andrew Morton wrote:

> 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.
> --

thanks for the further explanations.

---
~Randy
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