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Advancing past the last element of an array

 
 
Tim Rentsch
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      01-13-2010
Kaz Kylheku <(E-Mail Removed)> writes:

> On 2009-12-28, Johannes Schaub (litb) <(E-Mail Removed)> wrote:
>>> When you're dealing with multidimensional arrays, the compiler can
>>> genearate code which assumes that no bounds are violated.
>>>
>>> So for instance if you have some machine instruction with, say, a 12 bit
>>> displacement field, and in the given situation, that bit field is wide
>>> enough to address a dimension of the array, then the compiler can just
>>> blindly generate that instrution, even if your program overflows the 12
>>> bit width.

>>
>> There are exactly two valid values of object pointers: Either a byte in
>> memory, or a null pointer value - there is no dedicated past-the-end value.

>
> In C, there is a concept of pointer validity which takes into account
> /how/ that pointer was obtained. That information is not necessarily
> encoded in the pointer's run time value. (Remember, in C, type
> information is not also encoded in run-time values; that doesn't mean
> you can violate the type system and still have a well-defined program).
>
> Since the validity of a pointer includes how it was obtained,
> merely knowing where that pointer points is not enough of an assurance
> of correctness. [...]


Perhaps you would be so good as to tell the group in
which section(s) of which ISO document(s) this concept
is explained or described?
 
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