Messages in this thread | | | Date | Sat, 10 Jul 2004 08:58:47 +0200 | From | Andrea Arcangeli <> | Subject | Re: [PATCH] Use NULL instead of integer 0 in security/selinux/ |
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On Fri, Jul 09, 2004 at 11:23:52PM -0700, Linus Torvalds wrote: > I really don't see the point of complaining about the fixes. There's just > _no_ way to say that "0" is more readable than "NULL" in any of the cases. > I dare you - show _one_ case where a 0/NULL patch was wrong or even > remotely debatable. I dare you.
I definitely agree.
Several years ago I once wrote a singificant piece of code for a projet with #define NULL -1UL, this actually wasn't my choice but a requirement of the project (the headers were pre-defined) but it worked perfectly since we never did '!ptr' we always did 'ptr == NULL' instead (etc..). So at runtime it has never been a problem because we coded with NULL != 0 in mind. Of course I known normally NULL is always equal to 0 but I didn't realize that defining NULL !=0 wasn't exactly the C language (I learnt it later on the hard way in some mailing list, I believe at some point I did patches like the one in this thread but claiming it to be a bugfix, and not just a cleanup ;).
IIRC my argument about these patches being bugfixes, was about an architecture with a valid page mapped at address 0, that wouldn't generate a segfault. This is incidentally why we had to use NULL = -1 instead of NULL = 0. The answer I got at that time form some C guru is that I would need to hack the compiler specifically for such achitecture to accomodate for NULL = -1, so that '!ptr' will be the same as 'ptr == -1UL' (for pointers). In practice I think it has been a lot easier for us to avoid using '!ptr' than to hack gcc... - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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