On Wed, Aug 20, 2008 at 8:34 PM, Douglas Davidson <[EMAIL PROTECTED]> wrote: > Well, after all, zero is zero, how much difference can it make? Quite a > bit, as it turns out, since in 64-bit one of them is four bytes of zero, and > the other is eight bytes of zero. If you're just comparing against NULL, it > doesn't matter, but if you're using it in something where size counts--say, > a list of vararg arguments--then it matters a lot. It's not easy to debug, > though, because who would think that you need to distinguish one NULL from > another?
It is a little known fact that when passing NULL (and by extension nil or Nil) as a parameter to a vararg function, you *must* cast it to the appropriate pointer type to guarantee correct behavior. Interestingly, Apple's vararg methods which use nil as a terminator (such as dictionaryWithObjectsAndKeys:) make no mention of this in their documentation, and have a great deal of officially sanctioned sample code which doesn't use such a cast. (And none of my code uses it either.) I suppose Apple must be implicitly making a stronger guarantee about the pointer-ness of nil than the C language makes about NULL. Mike _______________________________________________ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the list. Contact the moderators at cocoa-dev-admins(at)lists.apple.com Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/cocoa-dev/archive%40mail-archive.com This email sent to [EMAIL PROTECTED]
