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SubjectRe: [PATCH] Use NULL instead of integer 0 in security/selinux/
On Thu, 8 Jul 2004, Richard B. Johnson wrote:
> On Thu, 8 Jul 2004, Herbert Xu wrote:
> > What's wrong with using 0 as the NULL pointer?
> Because NULL is a valid pointer value. 0 is not. If you were
> to make 0 valid, you would use "(void *)0", which is what
> NULL just happens to be in all known architectures so far,
> although that could change in an alternate universe.

False. "An integer constant expressions with the value 0, or such an
expression cast to type void *, is called a null pointer constant. If a
null pointer constant is assigned to or compared for equality with a
pointer, the constant is converted to a pointer of that type", and "Any
two null pointers shall compare equal."

In other words, when you use 0 as a null pointer, you really do get a null
pointer. If you are working on an architecture where the bit pattern of
the integer 0 and null pointers are not the same, the compiler will
perform the appropriate conversion for you, so it is always correct to
define NULL as (void *)0.

Personally, I always use 0 and NULL for integers and null pointers
respectively, but that's because of long estalished conventions that make
the code readabile, rather than anything to do with validity of the code.

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