Microport Unix -- Large Model Problems

[tony mason]

In article <405 at maynard.UUCP> campbell at maynard.UUCP (Larry Campbell) writes:
>In article <347 at prairie.UUCP> dan at prairie.UUCP (Daniel M. Frank) writes:
>>In article <245 at rabbit1.UUCP> barber at rabbit1.UUCP (Steve Barber) writes:
>>>Another common problem is passing NULL as pointer argument.  NULL is
>>>#defined as 0, which is 2 bytes.  Large model pointers are 4 bytes, so
>>>the stack frame is now basically garbage.
>>
>>   This isn't really true.  Code in stdio.h for the SV/286 release
>>checks your memory model, and if it is large, defines NULL to be 0L,
>>which is the same size as a pointer.  It doesn't please lint, so the
>>best solution is still to cast it as appropriate (like (char *)0),
>>but you ARE generally safe, as long as you include stdio.h.
>
>I wonder why stdio.h doesn't just declare NULL as "(char *) 0", or,
>in the brave new world of ANSI X-whatever, "(void *) 0"?  This should
>do all the right things.

Note that in SCO XENIX (a/k/a MICROSOFT XENIX) they have declared NULL to be
of type (char *)0.  Of course, you always have someone who will abuse this by
doing something stupid such as:

	char	buf[10];

	buf[0] = NULL;

but they will learn!

The best practice is to cast it correctly (it sure makes lint happy!).


Tony Mason				> No opinions expressed here. Only cold hard
University of Chicago   > facts.

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