Re: Pointer usage danger?

Hi Mark,


On 3/8/2011 11:13 AM, M. Lazarus wrote:

D Array2 DS Dim( %Elem( Array1 ))
D Based( Array1Ptr ) Inz( %Addr( Array1 ))
D Field1a Like( Field1 )
D Field2a Like( Field2 )

D Array1Ptr s *

The preceding code won't compile. You can't use INZ and BASED on the same variable.

However, assuming I understand the intent of your code, you could do it this way:

D Array2 DS Dim( %Elem( Array1 ))
D Based( Array1Ptr )
D Field1a Like( Field1 )
D Field2a Like( Field2 )

D Array1Ptr s * Inz(%Addr(Array1))

/Free
Array1Ptr = %Addr( Array1( 10 )) ;

At this point, the first element of Array2 should be positioned
over the last element (#10) of Array1.

Correct.

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?

This is safe to do, provided that you don't attempt access elements 2-10. Elements 2-10 do overlay memory that they shouldn't -- but if you don't access them your program will work as expected.

However, I don't understand /why/ you'd do that. It seems silly when you can already access the same data as Array1(10).