Messages in this thread | | | Date | Fri, 25 May 2007 22:36:49 +0100 | From | Al Viro <> | Subject | Re: double exclamation (!!) suckage in the kernel |
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On Fri, May 25, 2007 at 10:32:13PM +0100, Al Viro wrote: > On Sat, May 26, 2007 at 02:26:11AM +0530, Satyam Sharma wrote: > > also be brave enough to take a C quiz here :-) > > > > > what type should x have for !!x to be a valid expression? > > > > Any integer type (includes pointers) > > Er, no... Pointers are not integer types *and* you can use ! on any > scalar type (including floating ones, even though it's not particulary > useful there).
... which means that original question ("what type should x have...") gets the answer "scalars, arrays or functions". The last two variants give you constant 1, though (arrays and functions decay to pointers in such context and that pointer is not going to be different from null pointer of the same type; thus you get !!x => !0 => 1). - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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