Re: question about nullptr

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

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

[...]

Do you always cast NULL to a pointer in those (admittedly rare) cases
when one needs to?

>
I may have back in the days when I was using Version 6 C and
AT&T C where
>
$ grep NULL /work/reference/usl/uw2.01/usr/src/common/head/stddef.h
#ifndef NULL
#define NULL       0
>
>
I use gcc today and it defines NULL for C as
>
#define NULL ((void *)0)

Consider a variadic function that uses a null pointer to terminate the
argument list.  Then I always use NULL cast to the appropriate pointer
type.

For example, execl() requires a final argument that should be
`(char*)NULL`.

On the other hand, execl() is specified by POSIX, which also happens to
require NULL to be of type void* -- and you can pretty much get away
with using a void* null pointer where a char* null pointer is expected.

But casting NULL to the appropriate type (checked by reading the man
page) requires less thought.

I just about always use NULL, not 0, when I want a null pointer
constant.  Similarly, I use '\0', not 0, when I want a null character,
0.0 when I want a floating-point zero, and false when I want a Boolean
zero.  I just like being explicit.

In C23, I'll use nullptr rather than NULL *if* I don't care about
portability to pre-C23 compilers.  (I use nullptr in C++.)

--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */