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SubjectRe: [PATCH] remove abs64()
On 04/13, Andrew Morton wrote:
>
> On Wed, 13 Apr 2011 16:27:03 +0200
> Oleg Nesterov <oleg@redhat.com> wrote:
>
> > On 04/13, Alexey Dobriyan wrote:
> > >
> > > +#define abs(x) \
> > > +({ \
> > > + typeof(x) _x = (x); \
> > > + \
> > > + __builtin_choose_expr( \
> > > + __builtin_types_compatible_p(typeof(_x), signed char), \
> > > + (unsigned char)({ _x < 0 ? -_x : _x; }), \
> > > + __builtin_choose_expr( \
> > > + __builtin_types_compatible_p(typeof(_x), short), \
> > > + (unsigned short)({ _x < 0 ? -_x : _x; }), \
> > > + __builtin_choose_expr( \
> > > + __builtin_types_compatible_p(typeof(_x), int), \
> > > + (unsigned int)({ _x < 0 ? -_x : _x; }), \
> > > + __builtin_choose_expr( \
> > > + __builtin_types_compatible_p(typeof(_x), long), \
> > > + (unsigned long)({ _x < 0 ? -_x : _x; }), \
> > > + __builtin_choose_expr( \
> > > + __builtin_types_compatible_p(typeof(_x), long long), \
> > > + (unsigned long long)({ _x < 0 ? -_x : _x; }), \
> > > + _x))))); \
> > > +})
> >
> > Personally I agree.
> >
> > But, we have some stupid users which do something like abs(u32_value)
> > and expecting that abs() should treat this value as "signed".
> >
>
> um, yes, I'd forgotten that one. That's a show-stopper.

May be we can demand to fix them?

I agree with Alexey, it is a bit ugly to have abs() and abs64(), and abs()
itself doesn't look very nice.

What if we simply add

BUILD_BUG_ON( (typeof(_x)-1) > 0 );

into abs()?

After that it would be trivial to find the offenders and fix them,

- abs(unsigned_int)
+ abs((int) unsigned_int)

Oleg.



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