Re: Pointer usage danger?

["M. Lazarus" <mlazarus@xxxxxxxx>]

Dennis,

 I think you've understood the question.  I wanted to make sure that 
changing the pointer value would not overlay "undefined" memory.

 Note to Chuck: RPG does respect the subscript for the assign:
Array1Ptr = %Addr( Array1( 10 ))

 -mark


At 3/8/2011 01:02 PM, you wrote:
> The right thing to do, is to not DIM the ARRAY2 variable, since you 
> don't know what the individual coming behind you might do.
>
> But the answer to the question I think you asked, is that the mere 
> setting of a pointer does not cause memory to be 
> overlaid.  Something must be done with a variable that's based on 
> the pointer in order for that to happen.
>
> Did I understand the question?
>
> "M. Lazarus" <mlazarus@xxxxxxxx> wrote:
>
> >  Given this code:
> >
> >D Array1       DS              Dim( 10 )
> >D  Field1                2a
> >D  Field2               75a
> >
> >D Array2       DS              Dim( %Elem( Array1 ))
> >D                              Based( Array1Ptr ) Inz( %Addr( Array1 ))
> >D  Field1a                     Like( Field1 )
> >D  Field2a                     Like( Field2 )
> >
> >D Array1Ptr    s          *
> >
> >  /Free
> >      Array1Ptr = %Addr( Array1( 10 )) ;
> >  ...
> >
> >  At this point, the first element of Array2 should be positioned
> >over the last element (#10) of Array1.  Assuming I don't attempt to
> >access element 2 in Array2, is this safe to do or will the shift of
> >Array2, elements 2-10, overlay memory it shouldn't?
> >
> >  -mark