Re: question about nullptr

scott@slp53.sl.home (Scott Lurndal) writes:

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

scott@slp53.sl.home (Scott Lurndal) writes:
>

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

scott@slp53.sl.home (Scott Lurndal) writes:
>

Janis Papanagnou <janis_papanagnou+ng@hotmail.com> writes:

On 06.07.2024 14:54, Kaz Kylheku wrote:

On 2024-07-06, Thiago Adams <thiago.adams@gmail.com> wrote:

If you were creating C code today and could use a C23 compiler, would
you use nullptr instead of NULL?

 
In greenfield projects under my dictatorship, I use 0, as in:
 
   char *p = 0;
 
I was still 20 something when I (easily) wrapped my head around the 0
null pointer constant, and have not had any problems with it.
Once I learned the standard-defined truth about null pointer constants,
and their relationship to the NULL macro, I dropped NULL like a hot
potato, and didn't look back (except when working in code bases that use
NULL).

>
We also used 0 as "universal" pointer value regularly without
problems.

>
I also like to use 0, but I'm not sure I could say exactly why.  Maybe
because of pre-C exposure (B and BCPL).
>

Whereas I spent 6 years programming on an architecture[*] where a
null pointer was represented in hardware by the value 0xc0eeeeee.  I always
use the NULL macro in both C and C++ code.

>
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.

>
In what sense is using 0 ambiguous?  I can't see it.

>
the digit zero is context dependent, which makes it ambiguous.

Ah.  I thought we were talking about a pointer context so I thought you
meant that using 0 in a pointer context was ambiguous.  In

  char *p = 0;

the 0 is not ambiguous (i.e. open to more than one meaning).  It's open
to being misunderstood by people who don't know C, but that true of the
'char', the '*' and the '=' (and possibly the 'p' and the ';' too).

I.e. it can either be a  null pointer or the value zero
depending on context, which makes it ambiguous to the casual
reader.  Particularly when reading code that someone
else has written.  NULL makes the programmers intent crystal
clear.

That's a rather niche readership -- one that might consider

  char *p = 0;

unclear.  Do you want such people reading your C code with a view to
working on it?

I find myself completely out of step with many posters here about
"explicit code" should look like.  I think

  char *p = 0;

is explicit enough and, in fact, I consider it a plus point if someone
reading it goes "hey, what's going on here?" and ends up learning that 0
is null pointer constant in C.  They may, along the way, learn a few
other things that they should also know before fiddling with the code.
At the very least, they will have learnt that they don't know it all.

--
Ben.