Re: Does Duff Device break C compilers

>: Better is to rewrite it, like this
>: /* no assumptions made about count */
>: for (n = 0; n < count; n++)
>: to[n] = from[n];
>: which is correct, obvious, maintainable, parallelizable, vectorizable,


>> Better yet, "Krste's Kopy" :-)
>> memcpy(from, to, count*(sizeof *from));


> I wouldn't ordinarily comment on something like this, but I find
>it highly ironic that both of these "obviously correct improvements"
>fail to reimplement the original code, and produce entirely different
>results.


Sorry, this was all my fault. However, it wasn't a misteak (besides
the usual mistake of posting). I read the original code and thought
to my self: "This is stupid. Why didn't he write


*to = from[count -1];


with no loop at all? Oh, he must have left out the ++ when he typed
it in." Hence my trite little comment that my version was "obviously
correct".


As about 75,000 people pointed out, Duff's original code assumed that
*to is a device register (not that the assumption was mentioned
anywhere in the posted code).


Preston Briggs


(All spelling errors added purposely.)
--

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