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SubjectRe: [PATCH 1/6] kernel: add clamp(), clamp_t() and clamp_val() macros
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On Wed, 2008-03-12 at 18:20 +0100, Michael Buesch wrote:
> On Wednesday 12 March 2008 17:54:26 Harvey Harrison wrote:
> > On Wed, 2008-03-12 at 16:13 +0100, Michael Buesch wrote:
> > > So why not call it clamp_const()?
> > > One could even use __builtin_constant_p() and make clamp() use
> > > either clamp_const() or clamp_nonconst() from above automagically.
> > > I'd prefer that.
> >
> > Did you mean something like this? No more clamp_val, just clamp and
> > clamp_t. clamp_t forces all the types, clamp looks at the min and max
> > args, and if they are constants, uses the type of val instead. If not
> > a constant, the strict typechecking is done.
>
> > +#define clamp(val, min, max) ({ \
> > + typeof(val) __val = (val); \
> > + \
> > + if (__builtin_constant_p(min)) { \
> > + typeof(val) __min = (min); \
> > + __val = __val < __min ? __min: __val; \
> > + } else { \
> > + typeof(min) __min = (min); \
> > + (void) (&__val == &__min); \
> > + __val = __val < __min ? __min: __val; \
> > + } \
> > + \
> > + if (__builtin_constant_p(max)) { \
> > + typeof(val) __max = (max); \
> > + __val > __max ? __max: __val; \
> > + } else { \
> > + typeof(max) __max = (max); \
> > + (void) (&__val == &__max); \
> > + __val > __max ? __max: __val; \
> > + } })
>
> Yeah, something like that.
> Does returning of the value work over an indentation level, too?
> I dunno this detail of the language.
> But I'd prefer the following for readability anyway:
>
> + if (__builtin_constant_p(max)) { \
> + typeof(val) __max = (max); \
> + __val = __val > __max ? __max: __val; \
> + } else { \
> + typeof(max) __max = (max); \
> + (void) (&__val == &__max); \
> + __val = __val > __max ? __max: __val; \
> + }
> + __val; })

Yeah, that is better. (and even works).

Harvey



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