Messages in this thread | | | Subject | Re: [PATCH 1/6] kernel: add clamp(), clamp_t() and clamp_val() macros | From | Harvey Harrison <> | Date | Wed, 12 Mar 2008 10:34:09 -0700 |
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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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