Peter Seebach and Simon Josefsson wrote:
> > Note that NULL could
> > be the same, or it could be already converted to (void *), so it depends on
> > the implementation whether:
> >
> > printf("%p\n", NULL);
> >
> > is legit. (Which means it's not portable...)
>
> Indeed, and a quite realistic example of where this bug hits in practice
> is with the version-etc module where the final NULL needs to be
> explicitly casted to work properly on all systems, e.g.:
>
> version_etc (stdout, "gsasl", p, gsasl_check_version (NULL),
> "Simon Josefsson", (char *) NULL);
That's true when you consider only ISO C99.
But in POSIX, NULL is required to be (void *) 0. See
<http://www.opengroup.org/onlinepubs/9699919799/basedefs/stddef.h.html>
"The macro shall expand to an integer constant expression with the value 0 cast
to type void *."
Note that this can only for C. Whereas in C++, NULL cannot be (void *) 0,
because
char *p = NULL;
is valid C++, whereas
char *p = (void *) 0;
is invalid (missing a cast). See ISO C++ section [conv.ptr].
Bruno
