Re: %Addr & Passing Parameter

[Scott Klement <klemscot@xxxxxxxxxxxx>]

Hi Jean,

On Tue, 28 Oct 2003, Jean Reksodiputro wrote:
[SNIP]
> I have a wrapper CLP, where I declared this vars:
>    Dcl  &ArrWhs      *Char     1
>    Dcl  &NbrWhs      *Dec     (3 0)   0
>    Dcl  &OkFlag      *Char     1
[SNIP]
> Divspwhchkr     PI
>
> D  p1_AuthWhs                    2  0 dim(99)
> D  p1_NbrWhs                     3


It's very important to understand that when you pass a parameter by
reference (which is what you're doing here -- and is the default method
of passing parms) the parameter utilizes the same space in memory as the
calling program's variable.

It is, therefore, very important that whichever program originally
declares the variable declares as much memory, or more, as will be needed
by each program that receives these parameters.

If I understand correctly, your CL program is the "originator" of that
variable.  It allocates space for a TYPE(*CHAR) LEN(1) variable (1 byte)
and then passes it as a parameter to each RPGLE in turn.

Now consider what happens...   Your first RPG program reads that parm as
a 198 byte long array!   There's only 1 byte allocated by the CL program,
but the RPG is trying to access 198 bytes!  Whatever data happened to be
in the next 197 bytes of memory after &ArrWhs will be overwritten by
your array.   This could be harmless, but more likely, you're going to
overwrite something important!

Instead, you need to make sure you allocate space for the entire array.
The easiest way to do this would be to declare &ArrWhs as TYPE(*CHAR)
LEN(198)  That way, you've declared the entire 198 bytes that you need.

The only time that you could get away with declaring only 1 byte would
be if the array was an input parameter to the CL, and you were just
passing it through to another program.   In this case (unless I
misundersand you) you're not just passing it through, it's originating
from the CL program.

Good Luck