Uninitialized externals and statics

[Henry Spencer]

In article <4700042 at m.cs.uiuc.edu> kenny at m.cs.uiuc.edu writes:
>... When a pointer is compared with an integer, it is
>implicitly promoted to an integer.  Saying
>	if (foo == NULL)
>means EXACTLY the same thing as saying
>	if (foo == (char *) NULL)
>and if the NULL pointer doesn't have an all-zero representation, the
>compiler is responsible for promoting it...

Right conclusion, seriously wrong reasons.  Comparing a pointer to an
integer is *illegal* in general.  There is one, repeat one, special
case:  an integer constant expression of value zero -- repeat, an
integer CONSTANT expression of value ZERO -- gets turned into a NULL
pointer of the appropriate type when compared to a pointer.  Note that
it is the integer, not the pointer, that is converted.  Note that no
such conversion is done on integer variables, integer constant expressions
with non-zero values, or general integer expressions.
-- 
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