On Thu, 19 Nov 2009, Cameron Simpson wrote:
On 16Nov2009 10:54, Rick Stevens <ricks@xxxxxxxx> wrote: | Another example is that a null pointer (or the value "NUL") is not | necessarily zero, only that it is guaranteed to not point at any valid | datum. Actually, it requires it to behave like 0 in an arithmetic context.
More precisely, it's required to behave like 0 in a boolean context. It's not allowed in any other arithmetic context. 1 + ptr is invalid if ptr is null. 1 + !!ptr is 1 if ptr is null.
But it _doesn't_ require it to be stored as a zero in the machine memory. That's why I cringe whenever I see someone use calloc() or
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