Hi,
> as far as i know the compiler does if(!foo) => if(0==foo) =>if(NULL==foo) at
> compile time.
i forgot to say that chapter 6.5.3 (C99) says that the unary operator ! can be
applied to a pointer type; that's the reason why it works although on first
look it seems to work only if the NULL macro is expanded to 0.
> But generally it's not possible to compare a pointer with an integer, because
> they the have diffent type and often do not have the same size. On sparc64
> the user-space pointer have 32 bit while the kernel-space pointers have 64
> bit, so on that platform comparing integers with pointers is a bad idea.
> Therefore gcc generally produces a warning if he finds such ugly code.
>
>
> >> After all, ain't unary logical operations with pointers illegal?
>
> A pointer is an object of size sizeof(pointer); there is no reason why not to
> apply logical operations with that object.
I forgot to say that maybe for some operators (look into the standard) you have
to use a union to apply them (to the other member of the union):
union foo
{
type *p_p;
char a_c[sizeof(type *)];
};
I
If sizeof(int) == sizeof(type *) than you can use int as the second member.
I
Rolf F.
