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SubjectRe: [PATCH] Use NULL instead of integer 0 in security/selinux/

On Fri, 9 Jul 2004, Eric W. Biederman wrote:
> Does this mean constructs like:
> ``if (pointer)'' and ``if (!pointer)'' are also outlawed.

Of course not.

Why should they be?

What's considered bad form is:
- assignments in boolean context (because of the confusion of "=" and
- thinking the constant "0" is a pointer.

There's no reason why "if (!ptr)" would be wrong. That has zero confusion
about 0 vs NULL.

The confusion about "0" is that in traditional C it means two things: it
can either be an integer (the common case) or it can sometimes be a
pointer. That kind of semantic confusion is bad.

But it has nothing to do with the _value_ zero, or testing pointers for
being non-NULL. The value zero is not about semantic confusion, it's just
a bit pattern. And testing pointers is not ambiguous: when you test a
pointer, it's _un_ambigiously checking that pointer for NULL.

Problems arise when there is room for confusion, and that's when the
compiler should (and does) warn. If something is unambiguous, it's not


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