Re: [TUHS] reviving a bit of WWB

Doug McIlroy: To put it more strongly. this is not a legal C source file. char *s = NULL; But this is. char *s = 0; Clem Cole: 67)The macro NULL is defined in <stddef.h> (and other headers) as a null pointer constant; see 7.19. ==== $ cat null.c char *s = NULL; $ cat zero.c char *s = 0; $ zero.c is a legal C program. null.c is not. Create files exactly as shown and compile them if you don't believe me. Prepend `#include <stddef.h>' (or <stdlib.h> or <stdio.h>) to null.c and it becomes legal, but I think that's Doug's point: you need an include file. Personally I prefer to use NULL instead of 0 when spelling out a null pointer, because I think it's clearer: if ((buf = malloc(SIZE)) == NULL) error("dammit andrew"); though I am willing to omit it when there's no confusion about = vs ==: if (*p) dammit(*p, "andrew"); But that's just a question of style, and Doug's is fine too. The language does not require the compiler to pre-define NULL or to recognize it as a keyword; you have to include an appropriate standard header file. Norman Wilson Toronto ON (not 0N nor NULLN)