Re: question about nullptr

On 2024-07-06, Scott Lurndal <scott@slp53.sl.home> wrote:

Ben Bacarisse <ben@bsb.me.uk> writes:

I'm sure you know (but maybe some other readers might not) that that
does not stop one using 0 in C source code.  Whatever a null pointer
"really" is on some hardware, 0 must work in C, including in comparisons
with == and !=.  You can have

>
Yes.  However, I consider that ambiguous, I prefer to be explicit and
use NULL or nullptr.  Horses for courses.

The thing is that "null" is a word that means "zero".

So it's a bit like saying

#define tri 3

is less ambiguous compared to just using 3.

I get it that 0 is not exclusively a pointer constant, and syntax alone
doesn't indicate which; indeed without type information, we don't know
whether p == 0 is a pointer comparison, floating-point comparison or
integer comparison. Whereas with some other kinds of expressions,
we know more: e.g. p->memb, if correct, tells us that p is a pointer
to a struct or union.

If we have to use someting other than 0 to help us understand p == 0,
maybe the circumstances of the p are not clear enough?

What about "if (p)" and "if (!p)". If 0 is ambiguous, these should
always be written "if (p != nullptr)" and "if (p == nullptr)".
Otherwise p could be a number.

(Indeed, there are coding conventions like that: always use NULL,
and do not test pointers as if they were Booleans.)

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