Re: [AD] warnings when using VC 7 (.net)

[Robert Ohannessian <ohannessian@xxxxxxxxxx>]

Evert Glebbeek wrote:

> > void pointer arithmetic is undefined so using it for address calculation
> > is painful.
>
> Ok, fair enough.
> I assume using a char* isn't really an option either?
>
> > > Regardless, I *think* using ptrdiff_t instead of unsigned long *should*
> > > fix the problem. (It must be large enough to hold the whole range of
> > > pointer differences, which would be of the order of 2**64 on 64 bit
> > > systems. IIRC, it is defined as (signed) long by DJGPP.)
> >
> > Is it ISO C ?

It's C99 - no clue if it's C89 or not.

Here's what's in my copy of the standard:

"9 When two pointers are subtracted, both shall point to elements of the 
same array object,
or one past the last element of the array object; the result is the 
difference of the
subscripts of the two array elements. The size of the result is 
implementation-defined,
and its type (a signed integer type) is ptrdiff_t defined in the 
<stddef.h> header.
If the result is not representable in an object of that type, the 
behavior is undefined. In
other words, if the expressions P and Q point to, respectively, the i-th 
and j-th elements of
an array object, the expression (P)-(Q) has the value i-j provided the 
value fits in an
object of type ptrdiff_t. Moreover, if the expression P points either to 
an element of
an array object or one past the last element of an array object, and the 
expression Q points
to the last element of the same array object, the expression ((Q)+1)-(P) 
has the same
value as ((Q)-(P))+1 and as -((P)-((Q)+1)), and has the value zero if the
expression P points one past the last element of the array object, even 
though the
expression (Q)+1 does not point to an element of the array object.88)"