Re: Re[2]: [RFA]: BOOL coding standards (Was: Problem with +numberWithBool: ?)

[Helge Hess]

On Feb 2, 2004, at 6:01 AM, Leigh Smith wrote:
> > Hm, well, actually I do prefer "if (ptr == NULL)" over "if (!ptr)". 
> > Not sure why.
>
> Implicit is the assumption that NULL is always 0, which isn't actually 
> a specification, merely a convention of the compiler that NULL is 
> actually something like:
>
> #define NULL (void *) 0
>
> While unusual for a compiler to declare NULL to be something other 
> than 0, it would be legal C, depending on the processor architecture. 
> I'd definitely favour the more explicit ptr == NULL since you are then 
> articulating that you are checking against a NULL pointer, rather than 
> doing an implicit cast to an integer before then inverting the 
> implicit comparison against 0.

Good point! Just checked the C99 draft:
  http://www.vmunix.com/~gabor/c/draft.html#7.1.6

which indeed proves you right :-) NULL is not required to be defined as 
0.

On the other side - a ptr used in a boolean expression might be 
specified to test against "!= NULL" - not sure, need to read that up, 
but would make sense and sounds likely.

Greets
  Helge
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