OpenEuphoria

Re: Passing NULL to a c function

• Posted by Mathew Hounsell <mfh03 at UOW.EDU.AU> Mar 16, 2000
• 515 views

Hello,
        Here is an explanation of : What is NULL?

It is a symbolic constant (atually it's not, but don't worry) to
        indicate an impossible pointer.

On most machines, and under most OS'es the first word of a processes
        address is part of
reserved memory, therefore a process can never have data there. So address 0 is
an
impossible place to have data.

So C and C++ define an invalid pointer as 0. NULL is just a more
        expressive way of
writing it. For example

        if( avar != NULL ) {

will make most C/C++ programmers think avar is a pointer. Where as with

        if( avar != 0 ) {

avar could be of any type. So I recommend using NULL.

However as NULL is not an official part of C++ Bjarne Stroustop (Spelling?)
recomends you
use 0.

It is defined in the header file <stddef.h>
-------------------------
Sincerely,
Mathew Hounsell

mat.hounsell at excite.com