Xenix286 Wonders, Bugs, and Patches...

[Jonathan W. Krueger]

'#define'ing NULL to be simply 0 (zero) can and will screw up C programs
on the '286 (or '86) which make the assumption that
sizeof(int) == sizeof(int *).  The following exemplefies this:
        baz()
	{
	  ...
	  foo( NULL, more_args_of_various_sizes, ... );
	  ...
	}

	foo( p, more_params_of_various_sizes, ... );
	    struct whatever *p;
	    typeof more_para....;
	{ if ( p == NULL ) /* then */ { ... }
	  ...
	}

The Xenix '286 C compiler generates the call to foo with an "int" 0 (2 bytes),
not a "long" 0 (4 bytes).  foo expects 4 bytes in that position.  This is
partly why on Xenix-286 you find three (or more) packagings of the standard C
library: one for each compiler memory model, small, medium and large.  Another
reason is that larger programs need to use "far jumps" rather than "near
jumps."

Of course, I trust you to tell me if I'm wrong.

			-- Humbly,
			   Jonathan W. Krueger
			...ihnp4!tektronix!tekigm!jonk

			"To change my opinion,
			 you must first change my reality."