Is #define NULL 0L ok?

[tjt at kobold.UUCP]

Using:

	#include <stdio.h>
	#undef	NULL
	#define	NULL 0L

will fail on a machine with 16 bit pointers, 16 bit int's but 32-bit
longs (the pdp-11, for example).  On the pdp-11, defining NULL as 0L
will cause two words to be pushed on the stack for as a function
argument while the called routine will only be expecting one word for
that argument.

As has been pointed out too many times to count, it is impossible to
define a generic null pointer in C: you have to cast 0 to the pointer
type when passing it as an argument.  You can do this by including the
type cast in each use, or #define a null pointer for each pointer type
you use.
-- 
	Tom Teixeira,  Massachusetts Computer Corporation.  Westford MA
	...!{ihnp4,harpo,decvax}!masscomp!tjt   (617) 692-6200 x275